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Crew Training Department
WIZZ AIR
COLD WEATHER OPERATIONS MANUAL (T RAINING)
Revision Re vision 0/05-2012 | Wizz Air
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© Wizz Air 2004-2012. All rights rights reserved.
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© Wizz Air 2004-2012. All rights rights reserved.
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T able able of content: 0.
PREFACE GLOSSARY/DEFINITIONS ABBREVIATIONS
Page: 5 7 12
PART I – GENERAL 1. OVERVIEW
17
1.1. 1.2. 1.3. 1.4. 1.5. 2. 2.1. 2.2. 2.3. 2.4. 3. 3.1. 3.2. 3.3. 3.4. 4.
17 17 18 20 20 21 21 27 27 29 31 31 32 32 43 48
4.1. 4.2. 4.3. 4.4. 4.5. 4.6. 5. 5.1. 5.2. 5.3. 6. 6.1. 6.2.
AIRCRAFT AIRCRAFT CONTAMI CONTAMINA NATI TION ON IN FLIGHT FLIGHT AIRCRAFT AIRCRAFT DE/ANTI-ICIN G ON THE GROUND PERFORMA PERFORMA NCE NCE ON CO NTAMINATE NTAMINATE D RUNWAYS RUNWAYS FUEL F REEZI NG LIMITATIONS LOW TEMPERATU RE EFFECT ON ALTIMETRY
AIRCR AIRCRAF AFT T CONTAMIN C ONTAMINATION ATION IN FLIGHT ICING PRINCIPLES ICING CERTIF CERTIF ICATION ICATION IN-FLIGHT ICE PROTECTION AIRBUS AIRBUS PROCEDURE FOR FLIGH FLI GHT T IN ICING CONDITIO N
AIRCR AIRCRAF AFT T DE-ICING DE- ICING / ANT ANT I-ICING I-ICING ON O N THE T HE GROUND GENERAL DE-/ANTIDE-/ANTI-ICING ICING AWA RENESS RENESS CHECKLIST DE-/ANTIDE-/ANTI-ICING ICING AI RCRAFT RCRAFT ON THE GROUN GROUND D FLUID CHARACTERISTICS CHARACTERISTICS AND HANDLING AN DLING
PERFORMANCE ON CONTAMINATED CONTAMINATED RUNWAYS RUNW AYS CONTAMINATED RUNWAY RUNWAY AIRCRAFT AIRCRAFT BRAKI BRAKING NG BRAKING PE RFORMA NCE AIRCRAFT AIRCRAFT DIRECTIONAL CO NTROL CROSSWIN CROSSWIND D PERFORMA PERFORMA NCE NCE OPT IMIZATIO IMIZATIO N AND AN D DETERMINATION
FUEL FREEZ FREEZIN ING G L IMITATIONS IMITATIONS INTRODUCTION DIFFERENT DIFFERENT TY PES OF FUEL MINIMUM ALLOWED F UEL TEMPERATU TEMPERATURE RE
LOW TEMPERA T EMPERAT T URE EFFECT ON O N ALTIMETER ALTIMETER INDICATION INDICATION GENERAL CORRECTIONS CORRECTIONS
48 49 54 60 63 64 66 66 67 68 70 70 71
Part II – A 320 TYPE SPECIFFIC. EQUIPEMENT and PROCEDURES 7. AERODROME
77
7.1. 7.2. 8.
77 80 86
8.1. 8.2. 9. 9.1. 9.2. 9.3. 9.4.
RWY CONTAMINATION, BRAKIN BRAKING G CO NDITIONS AND REPORTS REPORTS SNOWTAM AND MOT NE DE-CO DING
A 320 AIRCRAFT A IRCRAFT ICE ICE AND AN D RAIN PROTECTION PERFORMA PERFORMA NCE NCE
FLIGHT CREW PROCEDURES LIMIT LIMITATIONS ATIONS OPERATIO OPERATIO N IN ICING CONDITIONS ON GROUND DE-ICING/ANTI ICING FLIGHT –PHASES RELATE RELATED D PROCEDURES
86 98 100 100 101 101 106
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0.
PREFACE
0.1
Wizz Air Cold Weather Operations Manual is an explanatory reference for cold weather operations concepts and procedures for daily operation in cold weather conditions and should be used in conjunction of Wizz Air Operation Manual.
0.2
The manual is voluntary limited to types of operations authorised by Wizz Air and operated by Wizz Air type of aircraft (A320).
0.3
This manual c onsist of two parts: Part I – “General” - The purpose of this part of the manual is to provide crew with an understanding of Airbus aircraft operations in cold weather conditions, and address such aspects as aircraft contamination, performance on contaminated runways, fuel freezing limitations and altimeter corrections. This part is based on Airbus brochure “Getting to grips with Cold Weather Operations”, summarizes information contained in several Airbus Industrie documents and p rovides related rec ommendations. Part II – “A 320 T ype specific equipment and procedures” – This part of the manual represents A 320 aircraft specific equipment and procedures for daily operation in cold weather conditions defined in Airbus and Wizz Air manuals, such as: AFM, FCOM, MEL, ERM, EFRAS, OM etc.
0.4
The manual is p ublished under t he responsibility of Wizz Air Training Department. It‟s content is approved by Fl ight Ops Depart ment and is compliant with Wizz Air Operating Manual. Should any deviation or discrepancy appear between the information provided in this manual and that published in the applicable Airbus and/or Wizz Air manual/s/ the latter shall prevail at all times, considering the rule of priorities as defined in OM B 1.2.
0.5
The manual will be amended according further changes in Wizz Air SOPs, regulations and aircraft c ertification.
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GLOSSARY/DEFINITIONS Anti-icing is a precautionary procedure, which provides protection against the formation of frost or ice and the accumulation of snow on treated surfaces of the aircraft, for a limited period of t ime (holdover time). Anti icing code describes the quality of the treatment the aircraft has received and provides information for determining t he holdover time. Aquaplaning or hydroplaning is a situation where the tires of the aircraft are, to a large extent, separated from the runway surface by a t hin fluid fil m. Braking action is a report on the conditions of the airport movement areas, providing pilots the quality or degree of braking that may be expected. Braking action is reported in terms of: good, medium to good, medium, medium to poor, poor, nil or unreliable. Clear ice is a coating of ice, generally clear and smooth, but with some air pockets. It is formed on exposed objects at temperatures below, or slightly above, freezing temperature, with the freezing of super-cooled drizzle, droplets or raindrops. See a lso «cold soak». Cold soak: Even in ambient temperature between -2°C and at least +15°C, ice or frost can form in the presence of visible moisture or high humidity if the aircraft structure remains at 0°C or below. Anytime precipitation falls on a cold-soaked aircraft, while on the ground, clear icing may occur. This is most likely to occur on aircraft with integral fuel tanks, after a long flight at high altitude. Clear ice is very difficult to visually detect and may break loose during or after takeoff. The following can have an effect on cold soaked wings: Temperature of fuel in fuel cells, type and location of fuel cells, length of time at high altitude flights, quantity of fuel in fuel cells, temperature of refueled fuel and time since refueling. Contaminated runway: A runway is considered to be contaminated when more than 25% of the runway surface area (whether in isolated areas or not) within the required length and width being used is covered by the following: -
Surface water more than 3 mm (0.125 in) deep, or slush, or loose snow, equivalent to more than 3 mm (0.125 in) of water; or
-
Snow which has been compressed into a solid mass which resists further compression and will hold together or break into lumps if picked up (co mpact ed snow); or
-
Ice, including wet ice
Damp runway: A runway is considered damp when the surface is not dry, but when the moisture on it does not give it a shiny appearance. De-icing is a procedure by which frost, ice, slush or snow is removed from the aircraft in order to provide clean surfaces. This may be accomplished by mechanical methods, pneumatic methods, or the use of heate d fluids. De/Anti-icing is a combination of the two procedures, de-icing and anti-icing, performed in one or two steps. A de-/anti-icing fluid, applied prior to the onset of freezing conditions, protects against the build up of frozen deposits for a certain period of time, depending on the fluid used and the intensity of precipitation.
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With continuing precipitation, holdover time will eventually run out and deposits will start to build up on exposed surfaces. However, the fluid film present will minimize the likelihood of t hese frozen deposits bonding to the st ruct ure, making subsequent de-icing much easier. Dew point is the t emperature at which water vapor starts to condense. Dry runway: A dry runway is one which is neither wet nor contaminated, and includes those paved runways which have been specially prepared with grooves or porous pavement and maintained to retain «effectively dry» braking action, even when moisture is present. Fluids (de-icing and anti-icing) De-icing fluids are: a. Heated w ater b. Newtonian fluid (ISO or SAE or AEA Type I in accordance with ISO 11075 specification) c. Mixtures of water and Type I fluid d. Non-Newtonian fluid (ISO or SAE or AEA Type II or IV in accordance with ISO 11078 specification) e. Mixtures of w ater and Type II or IV fluid De-icing fluid is normally applied heated to ensure maximum efficiency Anti-icing fluids are: a. Newtonian fluid (ISO or SAE or AEA Type I in accordance with ISO 11075 specification) b. Mixtures of water and Type I fluid c. Non-Newtonian fluid (ISO or SAE or AEA Type II or IV in accordance with ISO 11078 specification) d. Mixtures of w ater and Type II or IV fluid Anti-icing fluid is nor mally a pplied unheated on c lean aircraft surfaces. Freezing conditions are conditions in which the outside air temperature is below +3°C (37.4F) and visible moisture in any form (such as fog with visibility below 1.5 km, rain, snow, sleet or ice crystals) or standing water, slush, ice or snow is present on the runway. Freezing fog (Metar code: FZFG) is a suspension of numerous tiny supercooled water droplets which freeze upon impact with ground or other exposed objects, generally reduc ing the horizontal visibility at t he earth‟s surface to less than 1 km (5/8 mile). Freezing drizzle (Metar code: FZDZ) is a fairly uniform precipitation composed exclusively of fine drops - diameter less than 0.5 mm (0.02 inch) very close together which freeze upon impact with the ground or other objects. Freezing rain (Metar code: FZRA) is a precipitation of liquid water particles which freezes upon impact with the ground or other exposed objects, either in the form
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of drops of more than 0.5 mm (0.02 inch) diameter or smaller drops which, in contrast to drizzle, are widely separated. Friction coefficient is the relationship between the friction force acting on the wheel and the normal force on the wheel. The normal force depends on the weight of the aircraft and the lift of the wings. Frost is a deposit of ice crystals that form from ice-saturated air at temperatures below 0°C (32°F) by direct sublimation on the ground or other exposed objects. Hoar frost (a rough white deposit of crystalline appearance formed at temperatures below freezing point) usually occurs on exposed surfaces on a cold and cloudless night. It frequently melts after sunrise; if it does not, an approved de-icing fluid should be applied in sufficient quantities to remove the deposit. Generally, hoar frost cannot be cleared by b rushing alone. Thin hoar frost is a uniform white deposit of fine crystalline texture, which is thin enough to distinguish surface features underneath, such as paint lines, markings, or lettering. Glaze ice or rain ice is a smooth coating of clear ice formed when the temperature is below freezing and freezing rain contacts a solid surface. It can only be removed by de- icing fluid; hard or sharp tools should not be used to scrape or chip the ice off as this can result in damage to the aircraft. Grooved runway: see dry runway. Ground visibility: The visibility at an aerodrome, as reported by an accredited observer. Hail (Metar code: GR) is a precipitation of small balls or pieces of ice, with a diameter ranging from 5 to 50 mm (0.2 to 2.0 inches), falling either separately or agglomerated. Holdover time is the estimated time anti-icing fluid will prevent the formation of frost or ice and the accumulation of snow on the protected surfaces of an aircraft, under (average) weather conditions mentioned in the guidelines for holdover time. The ISO/SAE specification states that the start of the holdover time is from the beginning of the anti-icing treatment. Ice Pellets (Metar code PE) is a precipitation of transparent (sleet or grains of ice) or translucent (small hail) pellets of ice, which are spherical or irregular, and which have a diameter of 5 mm (0.2 inch) or less. The pellets of ice usually bounce when hitting hard ground. Icing conditions may be expected when the OAT (on the ground and for takeoff) or when TAT (in flight) is at or below 10°C, and there is v isible moisture in the air (such as clouds, fog with low visibility of one mile or less, rain, snow, sleet, ice crystals) or standing water, slush, ice or snow is present on the taxiways or runways. (AFM definition) Icy runway: A runway is considered icy when its friction coefficient is 0.05 or below. Light freezing rain is a precipitation of liquid water particles which freezes upon impact with exposed objects, in the form of drops of more than 0.5 mm (0.02 inch) which, in contrast to drizzle, are widely separated. Measured intensity of liquid water particles are up to 2.5mm/hour (0.10 inch/hour) or 25 grams/dm2/ho ur with a maximum of 2.5 mm (0.10 inc h) in 6 minut es.
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Non-Newtonian fluids have characteristics that are dependent upon an applied force. In this instance it is the viscosity of Type II and IV fluids which reduces with increasing shear force. The viscosity of Newtonian fluids depends on temperature only. NOTAM is notice containing information c oncerning t he establish ment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel conc erned with flight operations. One step de-/anti-icing is carried out with an anti- icing fluid, typically heate d. The fluid used to de-ice the aircraft remains on aircraft surfaces to provide limited a nti-ice c apability. Precipitation: Liquid or frozen water that falls from clouds as rain, drizzle, snow, hail, or sleet. Continuous: Intensity changes gradually, if at all. Intermittent: Intensity changes gradually, if at all, but precipitation stops and starts at least once within the hour preceding the observation. Prec ipitation intensity is an indication of the amount of precipitation falling at the time of observation. It is expressed as light, moderate or heavy. Each intensity is defined with respect to the type of precipitation occurring, based either on rate of fall for rain and ice pellets or visibi lity for snow a nd drizzle. The rate of fall criteria is based on time and does not accurately describe the intensity at the t ime of observation. Rain (Metar code: RA) is a precipitation of liquid water particles either in the form of drops of more than 0.5 mm (0.02 inch) diameter or of smaller widely scattered drops. Rime (a rough white covering of ice deposited from fog at temperature below freezing). As the fog usually consists of super-cooled water drops, which only solidify o n contact with a solid object , rime may form only on the windwa rd side or edges and not on the surfaces. It can generally be removed by brushing, but when surfaces, as well as edges, are covered it will be necessary to use an approved de-ic ing fluid. Saturation is the maximum amount of water vapor allowable in the air. It is about 0.5 g/m3 at - 30°C and 5 g/m3 at 0°C for moderate altitudes. Shear force is a force applied laterally on an anti-icing fluid. When applied to a Type II or IV fluid, the shear force will reduce the viscosity of the fluid; when the shear force is no longer applied, the anti-icing fluid should recover its viscosity. For instance, shear forces are applied whenever the fluid is pumped, forced through an orifice or when subjected to airflow. If excessive shear force is applied, the thickener system could be permanently degraded and the anti-icing fluid viscosity may not recover and may be at an unacceptable level. SIGMET is an information issued by a meteorological watch office concerning the occurrence, or expected occurrence, of specified en-route weather phenomena which may affect the safety of aircraft operations. Sleet is a precipitation in the form of a mixture of rain and snow. For operation in light sleet treat as light freezing rain. Slush is water saturated with snow, which spatters when stepping firmly on it. It is encountered at temperature around 5° C. Snow (Metar code SN): Precipitation of ice crystals, most of which are branched, star- shaped, or mixed with unbranched crystals. At temperatures
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higher than about -5°C (23°F), the crystals are generally agglomerated into snowflakes. Dry snow: Snow which can be blown if loose or, if compacted by hand, will fall apart upon release; specific gravity: up to but not including 0.35. Dry snow is normally experienced when temperature is below freezing and can be brushed off easily from t he aircraft. Wet snow: Snow which, if compacted by hand, will stick together and tend to or form a snowball. Specific gravity: 0.35 up to but not including 0.5. Wet snow is normally experienced when temperature is above freezing and is more difficult to remove from the aircraft structure than dry snow being sufficiently wet to adhere. Compacted snow: Snow which has been compressed into a solid mass that resists further compression and will hold together or break up into chunks if picked up. Specific gravity: 0.5 and over. Snow grains (Metar code: SG) is a precipitation of very small white and opaque grains of ice. These grains are fairly flat or elongated. Their diameter is less than 1 mm (0.04 inch). When the grains hit hard ground, they do not bounce or shatter. Snow pellets (Metar code: GS) is a precipitation of white and opaque grains of ice. These grains are spherical or sometimes conical. Their diameter is about 2 to 5 mm (0.1 to 0.2 inch). Grains are brittle, easily crushed; they bounce and break on hard ground. Supercooled water droplets is a condition where water remains liquid at negative Celsius temperature. Supercooled drops and droplets are unstable and freeze upon impact. Two step de-icing/anti-icing consists of two distinct steps. The first step (deicing) is followed by the second step (anti-icing) as a separate fluid application. After de-icing a separate overspray of anti-icing fluid is applied to protect the relevant surfaces, t hus providing maximum possible anti- ice capability. Visibility: The abi lity, as det ermined by at mospheric c onditions and expressed in units of distance, to see and identify prominent unlit objects by day and prominent lit objects by night. Visible moisture: Fog, rain, snow, sleet, high humidity (condensation on surfaces), ice crystals or when taxiways and/or runways are contaminated by water, slush or snow. Visual meteorological conditions: Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling, equal to or better than specified minima. Wet runway: A runway is considered wet when the runway surface is covered with water, or equivalent, less than or equal to 3 mm or when there is sufficient moisture on the runway surface to cause it to appear reflective, but without significant areas of standing water.
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ABBREVIATIONS AAL
Above Aerodrome Level
AC
Advisory Circular
A/C
Aircraft
ACARS
ARINC Commun ication Addressing and Reporting Syste m
AEA
Association of European Airlines
AFM
Airplane Flight Manual
AGL
Above Ground Level
AIP
Aeronautical Information Publicat ion
ALT
Altitude
ALTN
Alternate
AMM
Aircraft Maintenance Manual
AMSL
Above Mean Sea Level
AoA
Angle of Attack
AOC
Air Operator Certif icate
AOT
All Operators Telex
APU
Auxiliary Power Unit
ASD
Accelerate- Stop Distance
ASTM
American Society for Test ing and Materials
ATA
Aeronautical Transport Association
ATC
Air Traffic Control
ATIS
Automatic Terminal Information Service
ATS
Air Traffic Service
AWO
All Weather Operations
C
Celsius, Centigrade
CAPT
Captain
CAS
Calibrated Airspeed
CAT
Clear Air Turbulence
CAT I
Landing Category I (II or III)
CAVOC
Ceiling and Visibility OK
CFDIU
Centralized Fault Data Interfac e Unit
CFDS
Centralized Fault Data System
CFP
Computerized Flight Plan
CG
Center of Gravity
C/L
Check List
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cm
Centimeter
CMC
Centralized Maintenance Co mputer
CM1/2
Crew Me mber 1 (LH) / 2 (RH)
CRT
Cathode Ray T ube
DA
Decision altitude
DBV
Diagonal Braked Vehicle
DFDR
Digital Flight Data Recorder
DET
Detection/Detector
DH
Dec ision Height
ECAM
Electronic Centralized A ircraft Monitoring
ENG
Engine
ETA
Estimated Time of Arrival
ETD
Estimated Time of Departure
E/WD
Engine / Warning Display
F
Fahrenheit
FAA
Federal Av iation Administration
FAF
Final Approach Fix
FAR
Federal Aviation Regulations
FBW
Fly By Wire
FCOM
Flight Crew Operating Manual
FL
Flight Level
FLT
Flight
FM
Flight Manual
FMGS
Flight Management Guidance System
FMS
Flight Management System
F/O
First Officer
FOD
Foreign Object Damage
F-PLN
Flight Plan
ft
Foot (Feet)
FWC
Flight Warning Co mputer
GA
Go Around
GMT
Greenwic h Mean Ti me
GPS
Global Positioning System
GPWS
Ground P roximity Wa rning System
GS
Ground Speed
G/S
Glide Slope
H
Hour
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hPa
hect o Pascal
Hz
Hertz (cycles per second)
IAS
Indicat ed Air Speed
IATA
International Air T ransport Assoc iation
ICAO
International Civil Aviation Organization
IFR
Instrument Flight Rules
ILS
Instrument Landing Syste m
IMC
Instrumental Meteorological Conditions
in
inch(es)
INOP
Inoperative
ISA
International St andard At mosphere
ISO
International St andard Organization
JAA
Joint Aviation A uthorities
JAR
Joint Aviation Regulations
K
Kelvin
kg
kilogram
kHz
kilohertz
km
kilometer
kt
knot
lb
pounds (weight)
LDA
Landing Distance Available
LDG
Landing
LPC
Less Paper in the Coc kpit
M
Mach
m
meter
MAPT
Missed Approach PoinT
MAX
Maximum
mb
Millibar
MDA/H
Minimum Descent Altitude / Height
MIN
Minimum
MLW
Maximum Landing weight
mm
Millimeter
MOCA
Minimum Obstruct ion Clearance Altitude
MORA
Minimum Off- Route Altitude
ms
Millisecond
MSA
Minimum Safe (or Sect or) Altitude
MSL
Mean Sea Level
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MTOW
Maximum Take Off Weight
NA
Not Applicable
NAI
Nacelle Anti Ice
NAV
Navigation
NIL
No Ite m Listed (Nothing)
NM
Nautical Miles
NOTAM
Notice To Airmen
OAT
Outside A ir Te mperature
OCA/H
Obstacle Clearance Altitude / Height
OM
Outer Marker
PANS
Procedures for Air Navigation Services
PAX
Passenger
PERF
Performance
PIREP
Pilot Report
PSI
Pounds per Square Inch
QFE
Actual atmosphe re pressure at airport elevation
QNE
Sea level standard atmosphere (1013 hPa or 29.92» Hg)
QNH
Actual atmosphe re pressure at sea level based on local station pressure
QRH
Quick Reference Handbook
RA
Radio Altitude/ Radio Altimeter
REF
Reference
RTO
Rejected Take Off
RTOW
Regulatory Take Off Weight
RVR
Runway Visua l Range
RWY
Runway
SAE
Society of Automotive Engineers
SAT
Static Air Temperature
SB
Service Bullet in
SFT
Saab Frict ion Test er
SID
Standard Instrument Departure
SOP
Standard Operating Procedures
STD
Standard
SYS
System
t
ton, tonne
T
Temperature
TAF
Terminal Aerodrome Forecast
TAS
True Air Speed
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TAT
Total Air Temperature
TBC
To Be Confirmed
TBD
To Be Determined
TEMP
Temperature
T/O
Take-Off
TOD
Take-Off Distance
TOGA
Take-Off/Go-Around
TOGW
Take-Off Gross Weight
TOR
Take-off Run
TOW
Take-Off Weight
UTC
Coordinat ed Universal Ti me
V1
Critical engine failure speed
V2
T/O safety speed
VAPP
Final approac h speed
VFR
Visual Flight Rules
VHF
Very High Frequency (30 – 300 MHz)
VLS
Lowest selectable speed
VMC
Minimum control speed
VMU
Minimum unstick speed
VOR
VHF Omnidirectional Range
VR
Rotat ion speed
VREF
Landing reference speed
VS
Stalling speed (=VS1g for Airbus F BW aircraft)
WAI
Wing Anti Ice
WPT
Waypoint
WX
Weather
WXR
Weather Radar
Z
Zulu time (UTC)
ZFW
Zero Fuel Weight
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PART I – GENERAL 1.
OVERVIEW
1.1.
AIRC RAFT CO NTAMINATION IN FLIGHT
Atmospheric physics and meteorology define t hat icing c onditions gene rally occur from slightly positive temperature °C down to -40 °C and are most likely around FL100. Nevertheless, it should be understood that if severe icing rarely occurs below -12 °C, slightly positive OATs do not protect from icing and that icing conditions can be potentially met at any FL.
High accretion rates are not systematically associated with Cumulonimbus; stratiform clouds can ice intensively! Icing conditions are far most frequent than effective ice accretion. Icing conditions do not systematically lead to ice accretion. Should the pilot encounter icing conditions in flight, some recommendations are: - in addition to using ENG ANTI ICE and WING ANTI ICE according to procedures, the pilot should keep an eye on the icing process: accretion rate, type of cloud. - when rapid icing is encountered in a stratiform cloud, a moderate change of altitude will significantly reduce the rate. It is an obligation for the AT C controller to acc ept altitude change. - if icing conditions prevail on the approach, keep speed as high as permitted, delay flap extension as much as possible, and do not retract flaps after landing.
Ice and snow due to ground precipitation, or overnight stay, should be totally cleared before takeoff, regardless of the t hickness. Ot herwise aircraft is not c ertified for flying. 1.2.
AIRCRAFT DE/ANTI- IC ING ON THE GROUND
Aircraft contamination endangers takeoff safety and must be avoided. The aircraft must be c leaned. To ensure t hat t akeoff is performed with a c lean aircraft, an external i nspection has to be carried-out, bearing in mind that such phenomenon as clear-ice cannot be visually detect ed. Strict procedures and chec ks apply. In addition, responsibilities in acc epting the aircraft status are c learly defined. If the aircraft is not clean prior t o t akeoff it has to be de-iced. De-icing procedures ensure that all the contaminants are removed fro m aircraft surfaces. If the outside conditions may lead to an accumulation of precipitation before takeoff, the aircraft must be anti-iced. Anti-icing procedures provide protection against the accumulation of c ontaminants during a limited timeframe, referred to as holdover time. The most important aspect of anti-icing procedures is the associated holdover time. This describes the protected time period. The holdover time depends on the weather conditions (precipitat ion and OAT) and the t ype of fluids used to anti- ice the aircraft.
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Different types of fluids are available (Type I, II, and IV). They differ by their chemical compounds, their viscosity (capacity to adhere to the aircraft skin) and their thickness (capacity to absorb higher quantities of contaminants) thus providing variable holdover times. Published tables should be used as guidance only, as many parameters may influence their efficiency - like severe weather conditions, high wind velocity, jet blast... - and considerably shorten t he protect ion time. 1.3.
PERFORMANCE ON CONTAMINATED RUNWAYS
1.3.1. AIRCRAFT BRAKING There are three ways of decelerating an aircraft: The primary way is with t he wheel brakes. Wheel brakes stopping performance depends on the load app lied on the wheels and on the slip ratio. T he efficiency of the brakes can be improved by increasing the load on the wheels and by maintaining the slip ratio at its optimum (anti-skid system). Secondary, ground spoiler decelerates the aircraft by increasing the drag and, most importantly, improves the brake efficiency by adding load on the wheels. Thirdly, t hrust reversers decelerate t he aircraft by creating a force opposite to the aircraft ‟s motion regardless of the runway‟s condition. The use of thrust reversers is essential on cont aminated runways.
1.3.2. BRAKING PERFORMANCE The presence of c ontaminants on the runway affect s the performanc e by: A reduct ion of the f riction forces (µ) between the t ire and t he runway surface, An additional drag due t o c ontaminant spray impingement and c ontaminant displace ment drag, Aquaplaning (hydroplaning) pheno menon. There is a clear distinction between the effect of fluid contaminants and hard contaminants: Hard c ontaminants (c ompact ed snow and ice) reduce t he friction forces. Fluid contaminants (water, slush, and loose snow) reduce the friction forces, create an additional drag and may lead to aquaplaning. To develop a model of the reduced µ according to the type of contaminant is a difficult issue. Nevertheless, recent studies and tests have improved the model of µ for wet and contaminated runways, which are no longer derived from µ dry. The certification of the most recent aircraft already incorporates t hese improvements.
1.3.3. CORRELATIO N BETWEEN REPORTE D µ AND BRAKING PERF ORMANCE Airports release a friction coefficient derived from a measuring vehicle. This friction coefficient is termed as “reported µ”. The actual friction coefficient, termed as “effective µ” is the result of the interaction between tire/runway and depends on the tire pressure, tire wear, aircraft speed, aircraft weight and anti-skid system efficiency. To date, there is no way to establish a clear correlation between the “reported µ” and the “effective µ”. There is even a poor correlation between the “reported µ” of the different measuring
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vehicles. It is then very difficult to link the published performance on a contaminated runway to a “reported µ” only. The presence of fluid contaminants (water, slush and loose snow) on the runway surface reduces the friction coefficient, may lead to aquaplaning (also called hydroplaning) and creates an additional drag. This additional drag is due to the precipitation of the contaminant onto the landing gear and the airframe, and to the displacement of the fluid from the path of the tire. Consequently, braking and accelerating performance are affected. The impact on the accelerating performance leads to a limitation in the depth of the cont aminant for takeoff. Airbus Industrie publishes the takeoff and la nding performa nce according to the type of contaminant, and to the depth of fluid contaminants. Hard contaminants (compacted snow and ice) only affect the braking performance of the aircraft by a reduction of the f rict ion coefficient.
1.3.4. AIRCRAFT DIRECTIONAL C ONTROL When the wheel is yawed, a side-friction force appears. The total friction force is then divided into the braking force (component opposite to the aircraft motion) and the cornering force (side-frict ion). The sharing between cornering and braking is dependent on the slip ratio, that is, on the anti-skid syste m. Cornering capability is usually not a problem on a dry runway, nevertheless when the total friction force is significantly reduced by the presence of a contaminant on the runway, in crosswind conditions, the pilot may have to choose between braking or controlling the airc raft.
1.3.5. CROSSWIND Airbus Industrie provides a maximum demonstrated c rosswind for dry and wet runways. This value is not a limitation. This shows the maximum crosswind obtained during the flight test campaign at which the aircraft was actually landed. Operators have to use this information in order to est ablish their own li mitat ion. The maxi mum crosswind for automatic landing is a li mitat ion. Airbus Industrie provides as well some recommendations concerning maximum crosswind for contaminated runways. These conservative values have been established from calculations and operational e xperience.
1.3.6. PERFORMANCE OPTIMAZATION AND DETERMINATION The presence of a contaminant on the runway leads to an increased accelerate-stop distance, as well as an increased accelerate-go distance (due to the precipitation drag). This results in a lower takeoff weight which can be significantly impacted when the runway is short.
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To minimize the loss, fla p setting and ta keoff speeds s hould be o ptimized. Increasing the flap and slats extension results in better runway performance. Both the accelerate-stop and accelerate-go distances are reduced. A short and contaminated runway naturally calls for a high flap setting. Nevertheless, one should bear in mind that the presence of an obstacle in the takeoff flight path could still require a lower flap setting as it provides better climb performance. An optimum should be determined. This optimum is usually found manually by a quick comparison of the different takeoff charts. The Airbus LPC (Less Paper in the Cockpit) enables an automatic computerized selection of the optimum flap. The takeoff speeds, namely V1, VR and V2 also have a significant impact the takeoff performance. High speeds generate good climb performance. The price to pay for obtaining high speeds is to spend a long time on the runway. Consequently, takeoff distances are increased and the runway performance is degraded. Thus, a contaminated runway calls for lower speeds . Once again, the presence of an obstacle may limit the speed reduction and the right balance must be found . Airbus performance programs, used to generate takeoff charts, take advantage of the so- called “speed opti mization”. The process will always provide the optimum speeds. In a situation where the runway is conta minated, t hat means as low as possible. 1.4.
FUEL FREEZING LIMITATIONS
The minimum allowed fuel temperature may either be limited by: The fuel freezing point to prevent fuel lines and filters from becoming blocked by waxy fuel (variable with the fuel being used) or The engine fuel heat manageme nt syst em to prevent ic e cryst als, contained in the fuel, from blocking the fuel filte r (fixed te mperature). The latt er is often outside t he flight envelope and, thus, t ransparent t o the pilot. Different fuel types having variable freezing points may be used as mentioned in the FCOM. When the actual freezing point of the fuel being used is unknown, the limitation is given by the minimum fuel specification values. In addition, a margin for the engine is sometimes required. The resulting limitation may be penalizing under certain temperature conditions especially when JET A is used (maximum freezing point -40°C). In such cases, knowledge of the actual freezing point of the fuel being used generally provides a large operational benefit. Although t he fuel freezing limitation should not be deliberately exceeded, it should be known that it ensures a significant safety m argin. When mixing fuel types, operators should set t heir own rules with regard to the resulting freezing point, as it is not really possible to predict it. When a mixture of JET A/JETA1 contains less than 10% of JETA, considering the whole fuel as JETA1, with respect to the freezing point, is considered to be a pragmatic approach by Airbus Industrie when associated with recommended fuel transfer. 1.5.
LOW TEMPERATURE EFFECT ON A LTIMETRY
Temperature below ISA: Aircraft true altitude below ind icated altitude Very low temperature may: Create a potent ial terrain hazard Be t he origin of an altitude/position error.
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Corrections have to be applied on the height above the elevation of the altimeter setting source by: Increasing the height of t he obstacles, or Decreasing the aircraft indicated altitude/height. Minimum OAT should be established and specified for using approach and takeoff procedures if FINAL APPR mode (V-NAV in approach) use is intended.
2.
AIRCRAFT CONTAMINATION IN FLIGHT
The objective of this chapter is to explain some of the difficulties encountered by flight crews in winter time or cold/wet air. Many forms of ice may deposit or accrete on the airframe, in flight or on ground, and that will affect aircraft performance. It is difficult to determine how much the performance is affected. There are cases when the amount of ice looks insignificant and proves to produce large performance degradation. The opposite case may also be true. 2.1.
ICING PRINCIPLES
2.1.1. ATMOSPHERIC PHYSICS AT A GLANCE Water is a well-know n co mponent of at mos pheric air. Clear air includes water vapo r in very variable proportions according to air temperature (SAT or OAT). The maxi mu m a mount of water vapor allowable in t he air is about 0.5 g/ m3 at - 30°C and 5 g/m3 at 0°C for moderate altitudes. These limiting conditions are called saturation. Any a mount of wate r in excess of the saturation condit ions will sh ow under t he form of wate r drops or ice c rysta ls. T hese form c louds. Saturation conditions may be exceeded by two processes: First, is the lifting of warm air. Air lifting may be produced by meteorological instability or orography. Instability is associated with weather systems, perturbations or large amounts of clouds. Orographic effect is due to wind blowing ont o a mountain, henc e lifting on the exposed side. Second is the rapid cooling of the lower air layer during a night with clear sky. In both of these conditions, the amount of water initially present in the air mass may become in exce ss of t he saturation condit ions at the new (lower) te mperature. Exce ss wate r precipitates in t he form of drops, droplets o r ice c rysta ls. The icing phenomenon is due to the fact that water does not necessarily turn into ice just at, or below 0°C. Water at negative Celsius temperature may remain liquid; then, it is called supercooled. But supercooled drops and droplets are unstable. This means that they can freeze all of a sudden if they are hit by an object, especially if the object is at negative te mpe rature. That is the basic mechanism fo r aircraft icing. Consequences of the above are the following:
The range of OAT for icing is: slightly positive °C, down to -40°C; but severe icing rarely occurs below -12°C. This can be translated into altitudes: at mid
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latitudes, altitudes where severe icing is most likely to occur are around FL 100 down t o the ground. Due to varying temperature conditions around the airframe, a slightly positive OAT does not protect fro m severe icing. Accumulation of ice (icing) occurs on the «penetrating» or protruding parts of the airframe: nose, wing or fin, or tailplane leading edges, engine intakes, antennas, hinges, etc . On ground, in addition to all types of precipitat ion (all types of snow, freezing rain), the full airframe may get covered with frost. That almost systematically occurs overnight, if the sky is clear and temperature gets around 0° C or below.
Most of the time, icing conditions do not last for long in the sky. This is why it is unsafe to rely only on pilot reporting (PIREP or absence of PIREP) to detect icing conditions.
2.1.2. METEOROLOGY AT A GLANCE Supercooled wate r ca n be found in many c louds in the at mosphe re, p rov ided t he te mpe ratu re is below and not too far from freezing. Largely conv ective clouds like big Cumulus or Cumulonimbus are good suppliers. Apart from the possible effects of hail, Cumulonimbus are a spec ial icing t hreat, beca use, co ntrary t o all other icing clouds, ic ing condit ions can b e met o utside the c loud body, for example under the anvil. Anvils often generate freezing drizzle or freezing rain. The precipitation under an anvil can lead to seve re icin g. Layers of st ratifo rm c louds, absolutely rega rdless of t heir t hickness, ca n exhibit high quantities of freezing drops, including freezing drizzle. That is because, in spite of the ir stratus appearance, they include some li mite d but co ntinuous convective act ivity, which makes it an ideal locat ion for generat ing freezing drizzle. Meteorology provides a classification of supercooled water drops according to their dia mete r in micro ns or drop size (o ne mic ron = 1 µm = on e thousa ndt h of a millimeter): 0 to 50 µm: standard supercooled droplets. They stay aloft and make clouds. 50 to 500 µm: freezing drizzle. They sink extremely slowly and generate curious ice shapes. 500 to 2000µm: freezing rain. Fall down and lead t o clear ice. Cloud physics show that no cloud is ever made of a single drop size. One cloud can be unequivocally described by its spect rum of droplets. It is co nsidere d that most common supercooled clouds contain a spectrum of droplets between 0 and 50µm, whic h cul minates around 20µ m. When freezing drizzle is present, t he spectru m is not deeply changed, but another peak, smaller, shows at about 200µm, with very few drops in between. However, the large majority of the water content remains within t he lower part of the spectru m (i.e. la rge droplets are muc h fewer tha n t he 20µm ones).
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This situation is prone to icing. Low level clouds and ot her grey clouds may have a high water content.
This type of cumulus congestus may hide severe intermitt ent icing.
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Although t he grey c louds cont ain supercooled liquid water, t he situation is too windy to be a big icing threat except inside the CB
This type of thick stratus looking like heavy soup with a mountain blockage, may be a t hreat for icing.
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2.1.3. ICE SHAPES ACCRETED IN FL IGHT In-flight ic ing experience shows a very large variety of ice acc retion shapes and textures. Some are flat, some look like lace, some are like a hedgehog or a sea urchin. Others are single or double bumps, running along the leading edge, surprisingly pointing forward. There is a very large number of parameters which may influence the icing process. A non-limiting list can be:
Air te mperature: OAT or SAT Aircraft speed or tot al air te mperature: TAT Aircraft size Type of c loud Type of precipitation Liquid wat er cont ent of the air mass Liquid water drop size distribution (see: c ertificat ion) Possible presenc e of ice c rystals Tot al water content of the air mass Aircraft skin local temperature and heat capacity Type and extent of the de-icing or anti-icing system.
The individual influe nce of each para meter noted above present a very difficult theoretical problem. The various influences are not at all additive. Shapes can range from a pure moon arc adhering on the leading edge, to a double horn, or a flat, grooved plate, downst ream of the lea ding edge itself (which is ca lled runback ice), or even shark teeth, pointing towards the airflow and randomly distributed aft of the leadin g edge. Mo on arc is gene rally made of pure ice (ca lled blac k ice or clear ice, as both mean the same); double horn is often made of white, rough ice, called rime ice. At temperatures around 0 °C, rime ice is full of air bubbles and/or water flow ing through. The innumerable va riety of ice shapes, partic ularly of those made of rime ice, reveals how complex the ice accretion process may be. Due to historical and technica l reaso ns, a fu lly co mpreh ensive study is virt ually impossible. For example, in reviewing the influence of flying speed: Speed has an effect on several characteristics of the ice which accretes. The best known effect is kinetic heating (KH). Kinetic heating is the difference between TAT and SAT. For example, at 250 kt, KH is about + 10°C. Those 10° show in a te mpe rat ure inc rease of t he leading edge relative to the rest of the airframe. KH is sometimes called temperature recovery, because it naturally heats the leading edge and therefore somew hat protects it from ic ing, as long as the outs ide air is above - 10°C.
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The following graph gives an idea of the variety of shapes that could be enco untere d in a variety of clouds, whic h would offer ic ing conditions at all temperatures, from 0 °C down to -40 °C.
This figure shows: 1- the envelope of conditions, which are prone to icing, as a function of outside air temperature and aircraft speed. Only negative temperatures should be considered, but kinetic heating (KH, or ram effect) moves the maximum temperature for icing towards more negative values when speed is high. Limit is the red curve, based on the law of temperature recovery for altitudes around FL 100. However, conditions around the red curve may be those where the most difficult ice accretion cases can be met. Yellow sector is icing free. Blue sector is where icing may be encountered. Blue and yellow sectors are limited around -40°C, because practically no supercooled water might be present at colder temperatures. 2- the graph tends also to show how icing conditions may affect the ice accretion shape. Variability of shapes is great around the red curve, as shown by an example of speed effect around - 10°C. In such a regime, shapes do vary very rapidly. In general, some runback ice accretion may be met just above the red curve at intermediate speeds. At lower temperatures, which means farther under the red curve, accretions are much whiter and tend to be of a pointed shape.
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Observation of ice accreting in flight strongly suggests that the ice which effectively accretes is the differe ntial result of inco ming su perco oled water (plus possible ice cryst als) and out going amount of wat er due to a mix of eros ion, evapo ration and sublimation. The combined effect of those three is never negligible and, sometimes, one of the m is so do mina nt in the ove rall ic ing proce ss that no significa nt ice is accreting. In that cont ext, it is ve ry diffic ult to desc ribe, c lassify and predict ice shapes. Therefore, meas ures taken for airc raft protection against ic ing nee d to be based on some sort of definition of a «worst case» or an «envelope case» scenario. Such cases will be used in ice p rotection syste ms design and in certification. Consequences of t he above, include t he follow ing rules of thu mb:
Icing conditions are far more frequent than effective ice accretion for a given aircraft. It is not bec ause icing has been reported ahead of you that y our aircraft will also ice. Increase of speed decreases t he amount of ice accreted.
If rapid ice accretion is met, a moderate change of altitude is normally enough to decrease or sto p the ice to accrete. The ATC controlle rs must immediately acc ept suc h a pilot request.
2.1.4. OTHER TYPES OF CONTAMINATION On ground, aircraft parked outside collect all ty pes of precipit ation which do not flow off: frost, condensation, freezing drizzle, freezing rain, slush, sleet, wet and dry snow. It would be useless to enumerate differences between those different cases. Very often, wings are covered with a mixture of different things. That, in itself, has two causes:
Wing thermal characteristics vary, due to the possible presence of cold fuel and associated metal/co mposite st ructure. Normal weather evolution calls for precipitation, which vary against time due to temperatu re change. Snow often hides underneath ice, etc...
In all cases, a wing must have been cleaned prior to takeoff, regardless of the kind of contamination. To further complete the picture, taking off, landing and taxiing in slush may lead to projection of large amounts of wet snow whic h may f reez e upon impact on sensit ive part s of th e airframe: flaps, slats an d landing gear.
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ICING CERTIFICATION
Aircraft designers do their best to ensure airframes have smooth surfaces to ease the surrounding airflow. This rule is applied with special care to the wing leading edge and upper surface, because smoothness in these areas produces the best lift force. Any type of ice accretion is an obstacle to smooth airflow. Any obstacle will slow the airflow down and introduce turbulence. That will degrade the lifting pe rformanc e of t he wing. The execution of an icing certification test in natural icing is difficult. Finding 3 inches of ice, a number of times, in the real at mosphere, regardless of the season, is an impossible challenge. Furthermore, after accreting such an ice, by the time the pilot exits the cloud and executes t he certification maneuvers, most of the ice will be gone by co mbined effects of buffet during stalls, erosion, evaporation and sublimation. This is why natural ice shapes, once identified, are reproduced in shapes of plastic foam and glued to aircraft leading edges. Handling and performance tests are performed in that configuration. Flight tests in natural icing are still done to demonstrate the efficiency of the de-icing systems, including failure cases. This is necessary because no plastic foam would ever reproduce the intense thermodynamic process which develops between the ice and the airframe. As the c ertification method is overprotective for large jets, so me reasonable assumpt ions have been made. One is very important and often unknown by pilots: Aircraft are not certified for sustained icing in configurations with slats and flaps out. Aircraft behavior was thoroughly checked with foam ice shapes, as picked up in the clean configuration. Then, as stated, slats and flaps were deflected and all reference speeds for take off and landing verified. It is assumed that an aircraft w ouldn‟t stay long enough in icing conditions with slats/flaps extended to pick up such an amount of ice that performance would be modified. The certification rule has proved to be more than adequate for large jets, as no accident or significant incident has ever occurred in the category due to in-flight icing. However, it should not be interpreted as a total protection against unlimited icing. Unlimited icing is tot ally unlikely to occ ur, but pilots must remain conscious that there is a limit somewhere, which could be given in terms of exposure time, coupled with ice accretion rate. Again, that limit has never proved to be encountered in 30 years of large jet transport. 2.3.
IN-FLIGHT ICE PROTECTION
There are three principle methods of protecting the airframe from ice accretion. Namely, mechanical, electrical heating or hot bleed air are used to de-ice and/or anti-ice the critical surfaces of the aircraft.
2.3.1. HOT BLEED AIR Hot air is usually used on aircraft with jet engines. These systems are referred to as antiice systems, as they run continuously and are usually switched on before ice accretes. The heated surfac es thus prevent ic ing. Bleed air ice protection systems c an also be used to remove light accumulations of ice. However, the amount of energy to evaporate accreted ice being very high, bleed air ice protection systems cannot be considered as
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fully effective de-icing systems. All Airbus wing and nacelle (engine intake) ice protection systems use hot bleed air type anti- icing. Wing leading edges: Such large aircraft as the Airbuses are significantly more icing resistant than smaller aircraft. This is due to the size and thickness of their wing. It was found that thick wings collect less ice than thin ones. The de-iced part is heated so as to be evaporative, which means that the heat flux is so high as to melt the ice when it is accreting and the remaining water evaporates. Then, the heated part of the leading edge remains clean under icing conditions. But that heat flux has a drawback. As it must keep the leading edges at highly positive temperature in flight, it needs to be computed so as to: -
First, compensate for outside a ir cooling (called forced convection),
-
Second, melt the possible ice (compensate for the change of phase from ice to water).
The addition of both represents a high demand on the energy supply. That is the reason why it is inhibited on ground. In the absenc e of a rapid cooling due to airspeed, heat flux would damage the slats by overheating. It should be noted t hat t he tailplane and the fin also have leading edges t hat c an pick up ice, but they are not de-iced. This is because it has been proven they both have large margins relative to their maximum needed efficiency. Tailplane maximum efficiency is needed in forward CG maneuvering and fin maximum efficiency is needed in single engine operation. Both are demonstrated to meet the certification targets with ice shapes. Engine intake leading edges These are the most carefully de-iced, because the engine fan should be best protected. Hot air is bled from the engine compressor and heats the whole of the nacelle leading edge.
The standard procedures call for greater use of the nacelle anti-ice (NAI) than of the wing anti-ice system (WAI). This is due to a special feature of air intakes. In certain flight conditions, the tempe rature may drop by several degrees inside the intake («sucking» effect). Therefore, inside icing may occur at slightly positive outside air temperatures, whilst the wing itself wouldn‟t. The NAI is never inhibited, because the air is forced through at all speeds by the engine.
2.3.2. ELECTRICAL HEATING Electrical heating is typically used where small amounts of ice are encountered or on small surfaces like turboprop air intake. This method can be found on probes protruding into the airflow. On Airbus aircraft sensors, static ports, pitot tubes, TAT and Angle of Attack (AoA) probes, flight compart ment windows and waste -water drain masts are elect rically antiiced.
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For these items, the same problem of overheating exists as for the wing leading edge. It is solved automatically by air/ground logic, so that the pilot does not need to be concerned. Electrical heating can also be found on turboprop aircraft to heat the inner part of the propeller blades. For the outer parts of the propeller, the centrifugal forces provide a socalled self-shedding effect, whereby any forming piece of ice is thrown away. On Airbus aircraft, the Ram Air Turbine (RAT) is driven by a two-blade propeller with a selfshedding design.
2.3.3. MECHANICAL DE-ICING BOOTS They are typically used for propeller aircraft. The boots are rubber tubes, which are installed on the leading edges of the wing. As soon as ice accretes, the boots are inflated by pressurized air. The change of their shape breaks the ice layers. Mechanical boots ice protection systems are de-icing systems designed to remove already accreted ice. De-icing boots are not used on Airbus aircraft. 2.4.
AIRBUS PROCEDURE FOR FLIGHT IN ICING CONDITION
The AFM/FCOM states that icing conditions may be expected when the OAT (on the ground and for takeoff) or when TAT (in flight) is at or below 10°C, and there is visible moisture in the air (such as clouds, fog with low visibility of one mile or less, rain, snow, sleet, ice crystals) or standing water, slush, ice or snow is present on the taxiways or runways. These are conservative limits defined by airworthiness authorities to guide pilots in selecting anti-ice systems without necessarily guaranteeing that t hey will encounter icing conditions. The engine ice protection system ( Nacelle A nti- Ice: NA I) must be immediately activated when encountering the above-noted icing condition. This procedure prevents any ice accretion (anti-icing) on the air intakes of the engines, thus protecting the fan blades from damage due to ingested ice plates (FOD). When the Static Air Temperature (SAT) is below -40°C the NAI must only be „ON‟ when the aircraft enters cumulonimbus clouds, or when the Advisory Ice Detect ion Syste m - if installed - annunciates ICE DETECTED. As stated above, the w ings are more t olerant to ice accu mulation. The FCOM requires the activation of Wing Anti-Ice System (WA I) whenever there is an indication of airframe ice accumulation. The activation of the WAI system can be used to prevent any ice formation (anti-ice) or to remove an ice accumulation from the wing leading edges. Ice accumulation on the airframe can be evident either from an ice buildup on the windshield wipers or on the ice detector pin (visual cue), located between the two front windshields. The AFM recommends avoiding e xtended fl ight in icing c onditions with extended slats and flaps, as accreted ice may block the retraction of the high lift devices causing mechanical damage to the slat / flap system.
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If the pilot suspects that ice is accumulating on the protected surfaces (WAI inoperative), or if t he pilot suspects that a signif icant amount of ice is accumulating on the un protec ted parts of the wing, VLS must be increased as specified in the AFM/FCOM. In all cases the decision to activate and de-activate the Nacelle and Wing Anti-ice systems is in the responsibility of the flight c rew, based on the above F COM criteria.
2.4.1. ICE DETECTION The definition of icing conditions, as «visible moisture and less than 10°C TAT» has proven to be rather conservative. As already stated, when icing conditions are present (as per the definition), it does not necessarily mean that ice accretes on the aircraft. On the ot her hand, there are s ituations where the icing c onditions, as per t he AFM, are difficult for the f light c rew to identify, e.g. during flight at night-t ime. Although at night it is possible to check visibility with the headlights on, or to estimate the visible length of the wing, visibility depends only on the size of the particles, not on the encountered liquid water content, which is important for ice accretion. For instance, big ice crystals do not harm the wing but they reduce visibility more than water droplet s. Therefore, the pilot is provided with visual cues (specific or not specific) to decipher the icing conditions that are encountered. The following information can be e xtracted fro m these c ues: Beginning of ice accretion; Type of icing encountered (rime, glaze and mixed); Ice thickness; Accretion rate; End of ice acc retion, if t he cue is periodically de- iced. Potential use: To determine the icing conditions, in order to apply the AFM/FCOM procedures (for activating the various ice protect ion systems), Last element to be free of ice, indicating the end of the specific icing procedures, if any. To detect particular icing conditions (supercooled large droplets, or ground icing).
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AIRCRAFT CONTAMINATION IN FLIGHT Please, bear i n mind:
Atmospheric physics and meteorology define that icing conditions generally occur from slightly positive temperature °C down to -40 °C and are most likely around FL100. Nevertheless, it should be understood that if severe icing rarely occurs below -12 °C, slightly positive OATs do not protect from icing and that icing conditions can be potentially met at any FL. High accretion rates are not systematically associated with Cumulonimbus; stratiform clouds can ice intensively! Icing conditions are far most frequent than effective ice accretion. Icing conditions do not systematically lead to ice accretion. Should the pilot encounter icing conditions in flight, some reco mmendations are: - In addition to using NAI and WAI according to procedures, the pilot should kee p an eye on t he icing process: Accretion rate, type of cloud. - When rapid icing is encountered in a stratiform cloud, a moderate change of altitude will significantly reduce the rate. It is an obligation for the ATC controller to acc ept altitude change. - If icing conditions prevail on the approach, keep speed as high as permitted, delay flap extension as much as possible, and do not retract flaps after landing. Ice and snow due to ground precipitation, or overnight stay, should be tot ally c leared before ta keoff, regardless of t he thickness. Otherwise aircraft is not c ertified for flying. Optional ice detector systems available on Airbus aircraft are advisory systems and do not replace AFM procedures. For the time being, Airbus Industrie is not convinced of the benefits of a primary ice det ection system.
3.
AIRCRAFT DE-ICING / ANTI- ICING ON T HE GROUND
3.1.
GENERAL
Safe aircraft operation in cold weather conditions raises specific problems: Aircraft downtime and delays in flight schedules. These can be minimized by a program of preventive c old weather servicing. The operator must develop procedures for cold weather servicing during cold weather. This servicing must meet their specific requirements, based on: Their cold weather experience; The available equipment and material; The climatic conditions e xisting at their destinations.
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DE-/ANTI- IC ING A WARENESS CHEC KLIST
3.2.1. THE BASIC REQUIREMENTS 1. Respons ibility The person technically releasing the aircraft is responsible for the performance and verification of the results of the de-/anti-icing treatment. The responsibility of accepting the performed t reatment lies, however, with the Commander. The transf er of responsibility t akes place at t he moment t he aircraft starts moving under its own power. 2. Necessity Icing conditions on g round can be expected when air te mperatu res approach or fall below freezing and w hen moisture or ice occurs in the for m of eit her precipitation or condensation. Aircraft-related circumstances could also result in ice accretion, when humid air at temperatu res above freezing c omes in contact with cold structure. 3.Clean aircraft concept Any contamination of aircraft surfaces can lead to handling and control difficulties, performance losses and/or mechanical da mage. 4. De-Icing Are the conditions of frost, ice, snow or slush such that de-icing is required to provide clean surfaces at engine start? 5. Anti-icing Is the risk of precipitation such that anti-icing is required to ensure clean surfaces at lift off? 6. Checks Do you have enough information and adequate knowledge to dispatc h the aircraft? 3.3.
DE-/ANTI-ICING AIRCRAFT ON THE GROUND
3.3.1. COMMUNICATION To obtain the highest possible visibility concerning de-/anti-icing, a good level of communicat ion between ground and flight c rews is necessary. Any observations or points significant to the flight or ground crew should be mutually communicated. These observations may concern the weather or aircraft-related circumstances or other factors important for the dispatch of the aircraft. The minimum communication requirements must comprise the details of when the aircraft was de- iced and the quality of t reatment (t ype of fluid). This is summarized by the anti-icing code.
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Remember: Uncertainty should not be resolved by transferring responsibility. The only satisfact ory answer is c lear communication. Don’t rely on someone else to have done the job, unless it is clearly reported as having been d one.
3.3.2. CONDITIONS W HICH CAUSE AIRCRAFT ICING WEATHER - RELATED CONDITIONS Weather conditions dictate the «when» of the «when, why and how» of aircraft de-/antiicing on the ground. Icing conditions on t he ground can be expect ed when air te mperatures f all below freezing and when moisture or ice occurs in the form of either precipitation or condensation. Precipitation may be rain, sleet or snow. Frost can occur due to the condensation of fog or mist. Frost occurs systematically when OAT is negative and sky is clear overnight. To these weather conditions must be added further phenomena that can also result in aircraft ice accretion on the ground: AIRCRAFT - RELATED CONDITIONS The conc ept of icing is commonly associated only with exposure t o inclement w eather. However, even if the OAT is above freezing point, ice or frost can form if the aircraft structure temperature is below 0° C (32° F) and moisture or relatively high humidity is present. With rain or drizzle falling on sub-zero structure, a clear ice layer can form on the wing upper surfaces when the aircraft is on the ground. In most cases this is accompanied by frost on t he underwing surface.
3.3.3. CHECKS TO DETERMINE THE NEED TO DE-ICE/ANTI-ICE THE CLEAN AIRCRAFT CONCEPT Why de-ice/anti-ice on ground? The aircraft performance is certified based upon an uncontaminated or clean structure. If the clean aircraft concept were not applied, ice, snow or frost accumulations would disturb the airflow, affect lift and drag, increase weight and result in deterioration Aircraft preparation for service begins and ends with a thorough inspection of the aircraft exterior. The aircraft, and especially its surfaces providing lift, controllability and stability, must be aerodynamically clean. Otherwise, safe operation is not possible. An aircraft ready for flight must not have ice, snow, slush or frost adhering to its critical flight surfaces (wings, vertic al and horizontal stabilizers and rudder). Nevertheless, a frost layer less than 3mm (1/8 inch) on the underside of the wings, in the area of fuel tanks, has been accepted by the Airworthiness Authorities without effect on takeoff perfo rmance, if it is caused by cold fuel (low fuel te mperatu re, OAT more t han
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freezing and high humidity). Also a thin layer of rime (thin hoar-frost) or a light coating of powdery (loose) snow is acc eptable on the upper surface of the fuselage.
EXTERNAL INSPECTION An inspection of the aircraft must visually cover all critical parts of the aircraft and be performed fro m points offering a c lear view of t hese parts. In particular, these parts include:
Wing surfaces including leading edges, Horizontal stabilizer upper and lowe r surface, Vertical stabilizer and rudde r, Fuselage, Air data probes, Static vents, Angle-of-attack sensors, Control surface c avities, Engines, General ly inta kes and outlets, Landing gear and wheel bays.
C LEAR ICE PHENOMENON Under certain conditions, a clear ice layer or frost can form on the wing upper surfaces when the aircraft is on the ground. In most cases, this is accompanied by frost on the underwing surface. Severe conditions occur with precipitation, when sub-zero fuel is in
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contact with the wing upper surface skin panels. The clear ice accumulations are very difficult to detect from ahead of the wing or behind during walk-around, especially in poor lighting and when the wing is wet. The leading edge may not feel particularly cold. The clear ice may not be detected from the cabin either because wing surface details show through. The following factors contribute to the formation intensity and the final thickness of the clear ice layer: Low temperature of fuel that was added to the aircraft during the previous ground stop and/or the long airborne time of the previous flight, resulting in a situation that the remaining fuel in the wing tanks is below 0° C. Abnormally large amount of remaining cold fuel in wing tanks causing the fuel level to be in contact with the wing upper surface panels as well as the lower surface, especially in the wing tan k area. Temperature of fuel added to the aircraft during the current ground stop, adding (relatively) warm fuel can melt dry, falling snow with the possibility of re-freezing. Drizzle/rain and ambient temperatures around 0°C on the ground is very critical. Heavy freezing has been reported during drizzle/rain even at temperatu res of 8 to 14°C (46 to 57°F). The areas most vulnerable to freezing are:
The wing root area between the front and rear spars, Any part of t he wing that c ontains unused fuel aft er flight, The areas where different wing structures are concentrated (a lot of cold metal), such as areas above the spars and the main landing gear doubler plate.
GENERAL CHECKS A reco mmended proc edure to c heck the wing upper surface is to place high enough steps as close as possible to the leading edge and near the fuselage, and climb the steps so that you can touch a wide sector of the tank area by hand. If clear ice is detected, the wing upper surface should be de-iced and then re-checked to ensure that all ice deposits have been removed. It must always be remembered that below a snow / slush / anti-icing fluid layer there can be clear ice. During checks on ground, electrical or mechanical ice detectors should only be used as a back-up advisory. They are not a primary system and are not intended to replace physical checks. Ice can build up on aircraft surfaces when descending through dense clouds or precipitation during an approach. When ground temperatures at the destination are low, it is possible that, when flaps are retracted, accumulations of ice may remain undetect ed between stationary and moveable surfaces. It is, therefore, important that these areas are checked prior to departure and any frozen deposits removed. Under freezing fog conditions, it is necessary for the rear side of the fan blades to be checked for ice build-up prior to start-up. Any discovered deposits should be removed by directing air from a low flow hot air source, such as a cabin heater, onto the affected areas.
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When slush is present on runways, inspect the aircraft when it arrives at the ramp for slush/ice accumulations. If the aircraft arrives at the gate with flaps in a position other than fully retract ed, those flaps which are extended must be inspect ed and, if necessary, de-iced before retraction. As mentioned above, the Flight Crew Operating Manual allows takeoff with a certain amount of frost on certain parts of t he aircraft (a frost layer less t han 3mm (1/8 inch) on the underside of the wings, in the area of fuel tanks and a thin layer of rime or a light coating of powdery (loose) snow on the upper surface of t he fuselage.) This allowance exists to cope mainly with cold fuel, and humid conditions not necessarily linked to winter operations. However, when the aircraft need to be de-iced, these areas must be also de-iced. It is important to note that the rate of ice formation is considerably increased by the presence of an initial depth of ice. Therefore, if icing conditions are expected to occur along the taxi and takeoff path, it is neces sary to ensure that all ice and frost is re moved before flight. This consideration must increase flight crew awareness to include the condition of the taxiway, runway and adjacent areas, since surface contamination and blown snow are potential causes for ic e accretion equal to natural precipitat ion.
3.3.4. RESPONSIBILITY . THE DE-ICING/ANTI-ICING DECISIO N Maintenance responsibility: The information report (de-icing/anti-icing code) given to the cockpit is a part of the tec hnical airworth iness of t he aircraft. T he person releasing the aircraft is responsible for the performance and verification of the results of the de/anti-icing treat ment. T he responsibility of accept ing the performed treatment lies, however, with t he Commande r. Operational responsibility: The general transfer of operational responsibility takes place at the moment the a ircraft starts moving by its o wn power. MAINTENANCE / GROUND CREW DECISION The responsible ground crew member should be clearly nominated. He should check the aircraft for the need to de-ice. He will, based on his own judgement, initiate de-/antiicing, if required, and he is responsible for the c orrect and co mplete de- icing and/or antiicing of the aircraft. C OMMANDER ’S DECISION As the final decision rests with the Commander, his request will supersede the ground crew member‟s judgement to not de-ice. As the Co mmander is responsible for the anti-ic ing condition of t he aircraft during ground maneuvering prior to takeoff, he can request another anti-icing application with a different mixture ratio to have the aircraft protected for a longer period against accumulation of precipitation. Equally, he c an simply request a repeat application. Therefore, the Commander should take into account forecasted or expected weather conditions, taxi conditions, taxi times, holdover time and other relevant factors. The Commander must, when in doubt about the aerodynamic cleanliness of the aircraft, perform (or have pe rformed) an inspec tion or simply request a further de -/anti- icing.
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Even when responsibilities are clearly defined and understood, sufficient communication between flight and ground crews is necessary. Any observation considered valuable should be mentioned to the other party to have redundancy in the process of decisionmaking.
3.3.5. THE PROCEDURES TO DE-ICE AN D ANTI- ICE AN AIRCRAFT When aircraft surfaces are contaminated by frozen moistu re, they must be de -iced prior to dispatch. When freezing precipitation exists and there is a risk of precipitation adhering to the surface at the time of dispatch, aircraft surfaces must be anti-iced. If both anti-icing and de-icing are required, the procedure may be performed in one or two steps. The selection of a one or two step process depends upon weather conditions, available eq uipment, available fluids and the holdover ti me required to be ac hieved. When a large holdover time is expected or needed, recommended, using undiluted f luid for the sec ond step.
a
two-step
procedure
is
DE - ICING Ice, snow, slush or frost may be removed from aircraft surfaces by heated fluids or mechanical methods. For maxi mum effect, f luids shall be applied close to t he aircraft surfaces to minimize heat loss. Different methods to efficiently remove frost, snow, and ice are described in detail in the ISO method specificat ion. Refer also to t he Aircraft Maintenance Manual (AMM). Gene ral de-icing fluid application strategy The following guidelines describe effect ive ways to remove snow and ic e : Wings/horizontal stabilizers: Spray from the tip towards the root, from the highest point of the surface camber to t he lowest. Vertical s urfaces: Start at the t op and work downward. Fuselage: Spray along the top centerline and then outboard; avoid spraying directly onto windows. Landing gear and wheel bays: Keep applic ation of de-ic ing fluid in this area to a minimum. It may be possible to mechanically remove accumulations such as blown snow. However, where deposits have bonded to surfaces they can be removed using hot air or by carefully spraying with hot de-icing fluids. It is not recommended to use a high-pressure spray. Engines: Deposits of snow should be mechanically removed (for example using a broom or brush) from engine intakes prior to departure. Any frozen deposits, that may have bonded to either the lower surface of the intake or the fan blades, may be removed by hot air or other means recommended by the engine manufacturer. ANTI- ICING Applying anti-icing protection means that ice, snow or frost will, for a period of time, be prevented from adhering to, or accumulating on, aircraft surfaces. This is done by the applicat ion of anti-ic ing fluids.
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Anti-icing fluid should be applied to the aircraft surfaces when freezing rain, snow or other freezing precipitat precipitat ion is is falling and adhering at the time time of ai rcraft dispatch. dispatch. For effective anti-icing protection, an even film of undiluted fluid is required over the aircraft aircraft surfac surfaces es whic whic h are are c lean or which have been de- iced. For maximum anti-icing protection undiluted, unheated Type II or IV fluid should be used. The high fluid pressures and flow rates normally associated with de-icing are not required for this operation and, where possible, pump speeds should be reduced accordingly. The nozzle of the spray gun should be adjusted to give a medium spray. The anti-icing fluid application process should be as continuous and as short as possible. Anti-icing should should be c arried arried o ut as near to t he departure departure ti me as is operational operational ly possible, possible, in order to maintain holdover time. In order to control the uniformity, all horizontal aircraft surfaces must be visually checked during application of the fluid. The required amount will be a visual indication of fluid just beginning to drip off the leading and trailing edges. Most effect effect ive results results are obtained by commencing on the highest part of the wing wing section and covering from there towards the leading and trailing edges. On vertical surfac surfaces, es, start at the t op and work down. The f ollowing ollowing surfaces should should be protec protec ted by antianti- icing: icing: Wing uppe uppe r surface, Horizontal st abilizer abilizer upper su rface, Vertic Vertical al stabilizer stabilizer and rudde r, Fuselage Fuselage depending upon amount and type of precipitation. precipitation. Type I fluids fluids have li mited mited ef fectiveness when used for anti anti-ic -ic ing ing pu rposes. rposes. Litt le benefit benefit is gained gained f rom the mini mal holdover ti me gene gene rated. LIMITS AND PRECAUTIONS Application limits: Under no circumstances can an aircraft that has been antiiced receive a further coating of anti-icing fluid directly on top of the existing film. In continuing precipitation, the original anti-icing coating will be diluted at the end of the holdover time and re-freezing could begin. Also a double anti-ice coating should not be applied applied bec ause the flow-off characteristics characteristics during takeoff may be c ompromised. ompromised. Some Some T ype IV IV fluids may, over a period of t ime ime u nder certain low low humidity c onditions onditions,, thicken and affect the aerodynami aerodynamic c perfo performan rmanc c e of the fluid fluid during subsequent takeoff. If gel residues of Type IV fluids are found at departure, the surface must be cleaned and re- protect ed as necessary. Should it be necessary for an aircraft to be re-protected prior to the next flight, the external external su rfaces must first be de- iced with a hot fluid mix befo re a furthe furthe r application of anti-icing fluid is made. The aircraft must always be treated symmetrically - the left hand and right hand sides (e.g. left wing/rig wing/right ht wing) must must receive the same same and c omplete t reatment. reatment.
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Engines are Engines are usually not running running o r are are at idle during treatment. treatment. Air c onditioning should be selected OFF. The APU may be run for electrical supply but the bleed air valve should be closed. All reasonable precautions must be taken to minimize fluid entry into engines, other intakes intakes / outlets and control surfac surface e c avities. Do not spray de-icing / anti-icing fluids directly onto exhausts or thrust reversers. De-icing / anti-icing fluid should not be directed into the orifices of pitot heads, static vents or direc directly tly onto angleangle- of-a of- attack sensors. sensors. Do not direct fluids onto flight deck or cabin windows because this can cause cracking of acrylics acrylics or penetration penetration of t he window window sealing. All doors and windows must must be c losed to preven prevent: t: Galley al ley floor areas being conta minated with slippery de- icing/ant icing/ant i-icing fluids fluids Upholstery Upholstery bec oming oming soiled. Any forward area from which fluid may blow back onto windscreens during taxi or subsequent takeoff should be free of fluid residues prior to departure. If Type II or IV fluids are used, all traces of the fluid on flight deck windows should be removed prior to departu departu re, with partic particul ular ar at tent ion bein being g paid to windows windows fitt ed with wipers. wipers. De-icing/anti-icing fluid can be removed by rinsing with clear water and wiping with a soft cloth. Do not use the windscreen wipers for this purpose. This will cause smearing and loss loss of transparency. transparency. Landing gear and wheel bays must be kept free from build-up of slush, ice or accumulations accumulations of blown blown s now. Do not spray de-icing fluid directly onto hot wheels or brakes. When removing ice, snow or slush from aircraft surfaces, care must be taken to prevent it entering and acc umulating umulating in aux iliary iliary intakes or c ontrol surface hinge hinge a reas, i.e. remove snow from wings and stabilizer surfaces forward towards the leading edge and remove from ailer ai lerons ons and e levators back towards towards t he trailing trailing edge. Do not close any door until all ice has been removed from the surrounding area. A functional flight control check using an external observer may be required after deicing / anti-icing. This is particularly important in the case of an aircraft that has been subjec subjected ted t o an extrem extreme e ice or snow c overing. overing. C HECKS Final check before aircraft dispatch No aircraft should be dispatched for departure under icing conditions or after a de-icing / anti-icing operation unless the aircraft has received a final check by a responsible authorized authorized pe rson. rson.
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The inspection must visually cover all critical parts of the aircraft and be performed from points offering sufficient visibility on these parts (e.g. from the de-icer itself or another elevated piece of equipment). It may be necessary to gain direct access to physically c heck heck (e.g. by touch) to ensure ensure t hat there is no c lear ice ice on suspect areas. areas. Pre take-off check When freezing precipitation exists, it may be appropriate to check aerodynamic surfaces just prior t o the airc airc raft taki ta king ng the active ac tive runway runway or initiatin in itiating g the takeoff roll roll i n order to confirm that they are free of all forms of frost, ice and snow. This is particularly important when severe conditions conditions a re experienced, or when the publ ished ished holdover times ti mes have either been been e xceeded or are are about to run run out. When deposits are in evidence, it will be necessary for the de-icing operation to be repeated. If the takeoff location cannot be reached within a reasonable time, and/or a reliable c heck heck of the wing uppe r surfac surface e status cannot be made f rom inside the aircraft aircraft , consi c onsider der a repeat aircraft treatme treatme nt. If aircraft surfaces cannot adequately adequately be inspec inspec ted f rom inside the aircraft , it is desirable to provide a means of assisting the flight crew in determining the condition of the aircraft. The inspection should be conducted as near as practical to the beginning of the departure runway. When airport configuration allows, it is desirable to provide de-icing/anti-icing and inspection of aircraft near the beginning of departure runways to minimize the time interval between aircraft de-icing / anti-icing and takeoff, under conditions of freezing precipitation. F LIGHT CREW INFORMATION / COMMUNICATION No aircraft should be dispatched for departure after a de-icing / anti-icing operation unless the flight crew has been notified of the type of de-icing / anti-icing operation performed. performed. T he ground ground c rew must make sure t hat t he flight flight c rew has been inform informe e d. The T he flight flight c rew should should make make sure t hat t hey have the information. information. This information includes the results of the final inspection by qualified personnel, indicating that the aircraft critical parts are free of ice, frost and snow. It also includes the nec essary anti-ic anti-icin ing g c odes to allow allow t he flight flight c rew to estimate estimate the holdover ti me t o be expect expect ed under the prevailing weather c onditions. onditions. Anti-ic Anti-icing ing codes It is essential that the flight crew receive clear information from ground personnel c oncerning oncerning the t reatment reatment app lie lie d to the aircraft. The AEA (Association of European Airlines) recommendations and the SAE and ISO specifications specifications promote t he standardized standardized use of a four- eleme eleme nt code. This gives flight flight crew the minimu m detail det ails s to assess asses s holdove holdove r ti mes. T he use of loc local al time time is prefe rre rre d but, in any case, statement of the reference is essential. This information must be recorded and c ommunicat ommunicat ed to the flight flight c rew by referring referring to t he last step of the procedure. procedure. Examples Examples of anti-icing codes: AEA Type II/75/16.43 local TLS / 19 Dec 99 AEA Type II:
Type of fluid fluid used
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75:
Percentage of fluid/water mixtu res by volume 75% f luid / 25% water
16.43:
Local time of start of last application
19 Dec 99:
Date
ISO Type I/50:50/06.30 UTC/ 19 Dec 99 50:50:
50% f luid / 50 % water
06.30:
Time (UTC) of start of last application
Fluid application and holdover time guidelines Holdover protection is achieved by anti-icing fluids remaining on and protecting aircraft surfaces for a period of time. With a one- step de/anti-icing operation, holdover begins at the start of the operation. With a t wo-step operation, holdover begins at the start of the second (anti-icing) step. Holdover time will have effectively form/accumulate on aircraft surfaces.
run
out,
when
frozen
deposits
start
to
Due to its properties Type I fluid forms a thin liquid-wetting film, which gives a rather limited holdover time, depending on weather conditions. With this type of fluid, increasing the concentration of fluid in the fluid/water mix would provide no additional holdover time. Type II and Type IV fluids contain a thickener which enables the fluid to form a thicker liquid-wetting film on external surfaces. This film provides a longer holdover time, especially in conditions of freezing precipitation. With this type of fluid, additional holdover time will be provided by increasing the concentration of fluid in the fluid/water mix, with maximum holdover time avai lable from undiluted fluid. Holdover Time Tables are Information" pages 6.2-6.5.
published
in
EAG
documentation
under
"Operations
However, due to the many variables that can influence holdover times, these times should not be considered as minimum or maximum, since t he actual time of protec tion may be extended or reduced, depending upon the particular conditions existing at the time The lower limit of the published time span is used to indicate the estimated time of protection during heavy precipitation and the upper limit, the estimated time of protec tion during light precipitation. The protection time will be shortened in severe weather conditions. Heavy precipitation rates or high moisture content, high wind velocity and jet blast may cause a degradation of the protective film. If these conditions occur, the protection time may be shortened considerably. This is also the case when the aircraft skin temperature is significantly lower than the out side air te mperature. The indicated times should, therefore, only be used in conjunction with a pre- takeoff check.
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All de/anti-icing fluids following the specifications mentioned below are approved for all Airbus aircraft: Type I: Type II: Type IV:
SAE AMS 1424 standard SAE AMS 1428 standard SAE AMS 1428C standard
The list of approved fluids is given in AMM 12.31
3.3.6. PILOT TECHNIQUES This section addresses the issue of ground de-icing/anti- icing from the pilot‟s point of view. The topic is covered in the order it appears on cockpit checklists and is followed through, step-by-step, from flight preparation to takeoff. The focus is on the main points of dec ision- making, flight procedures and pilot t echniques. R ECEIVING AIRCRAFT When arriving at the aircraft, local advice from ground maintenance staff may be considered, because they may be more familiar with local weather conditions. If there is nobody available, or if t here is any doubt about their knowledge c oncerning de -ic ing/antiicing aspects, pilots have to det ermine the need for de- icing/anti-icing by the mselves. If the prevailing weather conditions call for protection during taxi, pilots should try to determine «off block time» to be in a position to get sufficient anti-icing protection regarding holdover time. This message should be passed on to the de-icing/anti-icing units, the ground maintenance, the boarding st aff, the dispatch offic e and all other units involved. C OCKPIT PREPARATION Before treat ment, avoid pressurizing or test ing flight control systems. Try to make sure that all flight support services are completed prior to treatment, to avoid any delay between t reatment and st art of taxiing. During treatment observe that: Engines are shut down or at idle, APU may be used for electrical supply, All air bleeds should be OFF, All external lights of treated areas should be OFF. Consider whether communication and information with the ground staff is/has been adequate. A specific item included in the normal c ockpit preparation procedures is reco mmended. The minimum requirement is to receive the anti-icing code in order to figure out the available p rotect ion time from t he holdover timetable. Do not consider the information given in the holdover timetables as precise. There are several parameters influenc ing holdover t ime.
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The timeframes given in the holdover timetables consider the very different weather situations worldwide. The view of the weat her is rather subject ive; experience has shown that a certain snowfall can be judged as light, medium or heavy by different people. If in doubt, a pre-takeoff check should be c onsidered. As soon as the treatment of the aircraft is completed, proceed to engine starting. TAXIING During taxiing, the flight crew should observe the intensity of precipitation and keep an eye on the aircraft surfaces visible from the cockpit. Ice warning systems of engines and wings or ot her additional ice warning syste ms must be c onsidered. Sufficient distance from the preceding aircraft must be maintained, as blowing snow or jetblast s c an degrade the anti-icing protec tion of the aircraft. The extension of slats and flaps should be delayed, especially when operating on slushy areas. However, in this c ase slat/flap extension should be verified prior t o takeoff. TAKEOFF Recommendations provided in the aircraft-specific FCOM, regarding performance corrections or procedures applied when operating in icing conditions should be considered. GENERAL REMARKS In special situations, flight crews must be encouraged not to allow operational or commercial pressures to influence decisions. The minimum requirements have been presented he re, as well as the various precautions. If there is any doubt as to whether the aircraft is contaminated - do NOT takeoff. As in any other business, the key factors to ensuring efficient and safe procedures are: Awareness, understanding and co mmunication. If there is any doubt or question at all, ground and flight crews must communicate with each other. 3.4.
FLUID CHARACTERISTICS A ND HA NDLING
3.4.1. DE-ICING/ANTI-ICING FLUIDS - CHARACTERISTICS Although numerous fluids are offered by several manufacturers worldwide, fluids can be principally divided into two classes, Type I and T ype II/IV fluids. TYPE I F LUID CHARACTERISTICS
No thickener system Minimum 80% glycol content Newtonian fluid: Viscosity depends on te mperature Relatively short holdover time
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Depending on the respective specification, they contain at least 80 percent per volume of either monoethylene-, diethylene- or monopropyleneglycol or a mixture of these glycols. The rest comprises water, inhibitors and wetting agents. The inhibitors act to restrict corrosion, to increase the flash point or to comply with other requirements regarding materials‟ compatibility and handling. The wetting agents allow the fluid to form a uniform film over the aircraft‟ s surfaces. Type I fluids show a relatively low viscosity which only changes depending on temperature. Glycols can be well-diluted with water. The freezing point of a water/glycol mixture varies with the content of water, whereas the concentrated glycol does not show the lowest freezing point: This is achieved with a mixture of approximately 60% glycol and 40% water (freezing point below -50°C). The freezing point of the concentrated monoethylene, d iethylene or propyleneglycol is in the range of - 10°C. Therefore Type I fluids are normally diluted with water of the same volume. This 50/50 mixture has a lower freezing point than the concentrated fluid and, due to the lower viscosity, it flows off the wing much bet ter. TYPE II/IV FLUID CHARACTERISTICS
With thickener syste m Minimum 50 percent glycolPseudo-plastic or non Newtonian fluid: Viscosity depends on temperature and shear forces t o which the fluid is e xposed Relatively long holdover time
Type II/IV fluids contain at least 50% per volume monoethylene-, diethylene- or propyleneglycol, different inhibitors, wetting agents and a thickener system giving the fluid a high viscosity. T he rest is wat er. Although the thickener content is less than 1%, it gives the fluid particular properties. The viscosity of the fluid and the wetting agents causes the fluid to disperse onto the sprayed aircraft surface, and acts like a protect ive cover. The fundamental idea is a lowering of the freezing point. Due to precipitation such as snow, freezing rain or any other moisture, there is a dilution effect on the applied fluid. This leads to a gradual increase of the freezing point until the diluted fluid layer is frozen due to the low ambient temperature. By increasing the viscosity, a higher film thickness exists having a higher volume which can therefore absorb more water before freezing point is reached. In this way, t he holdover time is inc reased. The following summarizes the properties of particular constituents of Type II and IV fluids:
The glycol in the fluid reduces the freezing point to negative ambient temperatures. The wetting agent allows the fluid to form a uniform film over the aircraft‟s surfaces. The thickening agent in Type II and IV fluids enables the film to remain on the aircraft‟s surfaces for longer periods.
Type II and IV fluids can be diluted with water. Because of the lower glycol content, compared to the Type I fluids, the freezing point rises all the time as water is added. The viscosity of Type II and IV fluids is a function of the existing shear forces. Fluids showing
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decreasing viscosity at increasing shear forces have pseudo-plastic or non- Newtonian flow properties. During aircraft take-off, shear forces emerge parallel to the airflow at the fluid and aircraft surface. With increasing speed the viscosity decreases drastically and the fluid flows off the wing. The protective effect of the Type II and IV fluids is much better when compared to the Type I fluids. Therefore they are most efficient when applied during snowfall, freezing rain and/or with long t axiways before t ake- off. Type II/IV and Type I fluids can all be diluted with wat er. This may be done if due to weather conditions, no long conservation time is needed or higher freezing points are sufficient. All above types of fluid have to meet the specified anti-icing performance and aerodynamic performance requirements as established in the respective specifications (ISO, SAE, AEA). This has to be demonstrated by the fluid manufacturer. Anti-icing process
The anti-icing fluid which freezes at a very low temperature (e.g. -30°C), is applied on a clean surface. It forms a protective layer.
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This fluid layer absorbs the frozen precipitation. It keeps the freezing temperature of the diluted fluid well below OAT or aircraft skin temperature, thus preventing frozen precipitation to accumulate.
Then the layer becomes more and more diluted by the melted precipitation; its freezing temperature increases. When it reaches OAT or the aircraft skin temperature, anti-icing fluid fails a nd the frozen precipitat ion accumulates. Exceeding the holdover time means that the anti-icing fluid has failed and lost its effectiveness, i.e. frozen precipitation is no longer absorbed by the diluted anti-icing fl uid, ma king the protection ineffective.
3.4.2. FLUID HANDLING De-icing/anti-icing fluids are chemical products with an environmental impact. During fluid handling, avoid any unnecessary spillage, comply with local environmental and health laws and the manufacturer‟s safety data sheet. Mixing of products from different suppliers is generally not allowed and needs extra qualification test ing.
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Slippery conditions due t o the presence of fluid may exist on t he ground or on eq uipment following the de-icing/anti-icing procedure. Caution should be exercised due to increased slipperiness, particularly under low h umidity or non- precipitating weather conditions.
3.4.3. DE-ANTI/ANTI-ICING EQUIPMENT De-icing/anti-icing t rucks Most of today‟s equipment consists of trucks with a chassis on which the fluid tanks, pumps, heating and lifting co mponents are installed. Although centrifugal pumps are installed in older equipment, more modern equipment is fitted with cavity pumps or diaphragm pumps showing very low degradation of Type II and IV fluids. Most of the trucks have an open basket from which the operator de-/anti-ices the aircraft. Closed cabins are also available, offering more comfort to the operator in a severe environment. Stationary equipment Stationary de-/anti-icing facilities, currently available at a limited number of airports, consist of a gantry with spraying nozzles moving over the a ircraft, similar in c oncept to a car wash.
AIRCRAFT DE-IC ING / ANTI-ICING O N THE GROUND Please, bear in mind:
Aircraft contamination endangers takeoff safety and must be avoided. The aircraft must be c leaned. To ensure t hat takeoff is performed with a c lean aircraft, an external inspect ion has to be carried-out, bearing in mind that such phenomenon as clear-ice cannot be visually detected. Strict procedures and checks apply. In addition, responsibilities in accepting the aircraft status are clearly defined. If the aircraft is not clean prior to takeoff it has to be de-iced. De-icing procedures ensure that all the contaminants are removed from airc raft surfaces. If the outside conditions may lead to an accumulation of precipitation before takeoff, the aircraft must be anti-iced. Anti-icing procedures provide protection against the accumulation of contaminants during a limited timeframe, referred to as holdover time. The most important aspect of anti-icing procedures is the associated holdovertime. This describes the protected time period. The holdover time depends on the weather conditions (precipitation and OAT) and the type of fluids used to anti-ice the aircraft. Different types of fluids are available (Type I, II, and IV). They differ by their chemical compounds, their viscosity (capacity to adhere to the aircraft skin) and their thickness (capac ity to absorb higher quantities of c ontaminants) t hus providing va riable ho ldover times. Published tables should be used as guidance only, as many parameters may influence their efficiency - like severe weather conditions, high wind velocity, jet blast... - and considerably shorten the protec tion time.
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PERFORMANCE ON CONTAMINATED RUNWAYS
Operations on fluid contaminated runways raise numerous questions from operators. Airlines which often operate under cold or inclement conditions are generally concerned in obtaining a better understanding of the numerous factors influencing aircraft braking performance: On one hand, how to minimize the payload loss, and on the other, how to maintain a high level of safety. It is evident that the braking performance is strongly affected by a slippery runway, however, one should also consider the loss in acceleration performance and in aircraft lateral controllability. Once the different aspects of the impact of a contaminated runway are explained, it is quite necessary to review the operational information provided to the pilots. This information mainly contains some penalties (e.g. weight penalty or maxi mum crosswind reduction) but as well some indications on the runway condition provided as a «friction coefficient». All th is information sho uld be readily unde rstood so as to jeopardize neither airline safet y nor airline ec onomics. 4.1.
CONTAMINATE D RUNWAY
A runway is considered contaminated when more than 25% of the surface is covered with a c ontaminant. Contaminants are: water, slush, snow and ice. The SPECIAL OPERATIO NS chapter of t he FCOM, provides t he following def initions:
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If the layer of contaminant on the runway is thin enough, the runway is not considered contaminated, but only wet . FLEX takeoff is not allowed from a c ontaminated runway. As far as performance determination is concerned, the following guidelines should be considered, as mentioned in the FCOM: WET RUNWAY and EQUIVALENT Equivalent of a wet runway is a runway covered with or less than: 2 mm (0.08 inch) slush 3 mm (0.12 inch) water 4 mm (0.16 inch) wet snow 15 mm (0.59 inch) dry snow CONTAMINATED RUNWAY An equivalence bet ween depth of slush and snow has been defined: 12.7 mm (1/2 inch) wet snow is equivalent t o 6.3 mm (1/4 inch) slush 25.4 mm (1 inch) wet snow is equivalent to 12.7 mm (1/2 inch) slush 50.8 mm (2 inches) dry snow is equivalent t o 6.3 mm (1/4 inch) slush 101.6 mm (4 inches) dry snow is equivalent to 12.7 mm (1/2 inch) slush Contaminated runway parameters c an include t he following data: Runway fric tion coefficient; Braking action; Conta mination c haract eristics and measurements. 4.2.
AIRC RAFT BRAKING
Aircraft braking performance, in other words, aircraft «stopping capability», depends on many parameters. Aircraft deceleration is obtained by means of: Wheel brakes, aerodynamic drag, air brakes (spoilers) a nd thrust reversers.
4.2.1. WHEEL BRAKES Brakes are the primary means of stopping an aircraft, particularly on a dry runway. Deceleration of the aircraft is obtained via the creation of a friction force between the runway and the t ire. This frict ion appears at t he area of c ontact t ire/runway. By applying the brakes, the wheel is slowed down and, therefore creates a force opposite to the aircraft motion. This force depends on the wheel speed and the load applied on the wheel. WHEEL LOAD A load must be placed on the wheel to increase the contact surface between the tire and the runway, and to create a braking/frict ion force. There is no optimum on the load to be placed on the wheels. The greater the load, the higher the fr iction, the bett er the braking ac tion.
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The FRICTION COEFFICIE NT is defined as the ratio of the maximum available tire fric tion force and the vertical load act ing on a tire. This coefficient is named MU or µ.
WHEEL SPEED The area of tire/runway contact has its own speed, which can vary between two extremes: Free rolling speed, which is equal to the aircraft speed. Lock-up speed, which is zero. Any intermediate speed causes the t ire to slip over the runway surfac e with a speed equal to: Aircraft speed - Speed of t ire at point of c ontact. The slipping is oft en expressed in terms of percentage to the aircraft speed. Refer to the next figure.
The friction force depends on the slip percentage. It is easily understood that a free rolling wheel (in other words, zero % slip) does not resist aircraft motion, therefore does not create a friction force; so, in theory, there is no b raking ac tion.
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It is a well-known fact that a locked-up wheel simply «skidding» over the runway has a bad braking performance. Hence, the advent of the so-called «anti-skid» systems on modern aircraft.brake releasing in order to maintain t he brake s lip at that value. Somewhere in bet ween these two extremes, lies t he best braking performance. The following figure shows that the maximum friction force, leading to the maximum braking performance, is obtained for a slip ratio a round 12%.
Tests have demonstrated that the friction force on a dry runway varies with the aircraft speed as per the following graph:
4.2.2. GROUND SPOILERS Ground spoiler extension increases the aerodynamic drag and leads to deceleration. Extending the ground spoiler also significantly degrades the lift, thereby increasing the load on the wheels and brake eff iciency.
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4.2.3. THRUST REVERSERS Similar to ground spoiler extension, reversers create a force opposite to the aircraft‟s motion, inducing a significant decelerating force which is independent of the runway contaminant. Regulations do not allow crediting reversers‟ effect on performance on a dry runway. However, regulations presently allow crediting reversers‟ effect on takeoff performance for wet and contaminated runways. The situation is a bit different for landing performance where regulations allow crediting the effect of reversers only for c ontaminated runways, and not f or dry and wet runways. Remark: This may lead to a performance-limited weight on a wet or contaminated runway being greater than the performance-limited weight on a dry runway. It is compulsory to restrict the performance-limited weight on a wet/contaminated runway to that of a dry runway. As illustrated by the following graphs, reversers proportionally have a more significant effect on contaminated runways than on dry runways, since only low deceleration rates can be achieved on c ontaminated or slippery runways.
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AIRCRAFT BRAKING Please, bear i n mind:
There are three ways of decelerating an aircraft: The primary way is with the wheel brakes. Wheel brakes stopping performance depends on the load applied on the wheels and on the slip ratio. The efficiency of the brakes can be improved by increasing the load on the wheels and by maintaining the slip ratio at its optimum (anti-skid system). Secondary, ground spoiler decelerates the aircraft by increasing the drag and, most importantly, improves the brake efficiency by adding load on the wheels. Thirdly, thrust reversers decelerate the aircraft by creating a force opposite to the aircraft‟s motion regardless of the runway‟s condition. The use of thrust reversers is indispensable on c ontaminated runways.
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BRAKING PERFORMANCE
The presence of contaminants on the runway surface affects the braking performance in various ways. The first obvious consequence of the presence of contaminants between the tire and the runway surface is a loss of fr iction force, henc e a reduced µ. If this phenomenon is quite natural to understand, it is difficult to convert it to useable figures. That is why the mathematical model is still evolving and is monitored by regulations. The presence of a fluid contaminant like water or slush can also lead to a phenomenon known as aquaplaning or hydroplaning. In such a configuration, there is a loss of contact, therefore of friction, between t he tire and t he runway surface . Fluid contaminants produce a lot of precipitation on the airframe and landing gears, causing additional d rag.
4.3.1. REDUCTION OF THE FRICTI ON COEFFICIE NT µ Friction force reduction is due to the interaction of the contaminant with the tire and the runway surface. One can easily understand that this reduction depends directly on the contaminant. Let us review t he µ reduction by c ontaminant. WET RUNWAY The following text is extracted from the ICAO Airport Services Manual, Part 2. „«Normal» wet frict ion is the c ondition where, due to t he presenc e of wat er on a runway, the available friction coefficient is reduced below that available on the runway when it is
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dry. This is because water cannot be completely squeezed out from between the tire and the runway and, as a result, there is only partial contact with the runway by the tire. There is consequently a marked reduction in the forc e opposing the relative mot ion of the tire and runway because the remainder of the contacts is between tire and water. To obtain a high coefficient of friction on a wet or water-covered runway, it is, therefore, necessary for the intervening water film to be displaced or broken through during the time each element of tire and runway are in contact. As the speed rises, the time of contact is reduced and there is less time for the process to be completed; thus, friction coefficient on wet surfaces tend to fall as the speed is raised, i.e. the conditions in effect become more slippery.” In other words, we expect µWet to be less than µDry, and to diminish as speed increases. Until recently, regulations stated that a good representation of the surface of the wet runway condition is obtained when considering µDry divided by two. For example, for the A320 aircraft µWet= µDry/2. As of today, a new method has been developed accounting for: Tire wear state Type of runway Tire inf lation pressure Anti-skid effec t demonstrated t hrough flight t ests on wet runways. In any cases, the braking friction coefficient diminishes (non-linearly) with the aircraft ground speed. F LUID CONTAMINATED RUNWAY: WATER , SLUSH AND LOOSE SNOW The reason for friction force reduction on a runway contaminated by water or slush is similar to the one on a wet runway. The loss in friction is due to the presence of a contaminant film between the runway and the tire resulting in a reduced area of tire/runway dry contact. As for the µwet, µcont is often derived from µdry. Again, until recently, regulations stated that µcont = µdry /4. As for the wet condition, a new model has been developed to take into account tire wear state, type of runway, t ire inflation pressure and anti-skid effect. HARD CONTAMINATED RUNWAY: C OMPACTED SNOW AND ICE These two types of contaminants differ from water and slush, as they are hard. The wheels just roll over it, as they do on a dry runway surface but with reduced friction forces. As no rolling resistance or precipitant drag is involved, the a mount of contaminant on the runway surface is of no consequence. Assuming an extreme and non-operational situation, it would be possible to t akeoff f rom a runway cove red with a h igh laye r of hard compacted snow, while it would not be possible to takeoff from a runway covered with 10 inch of slush. One can easily imagine that the rolling resistance and precipitation drag would be way t oo important. The model of t he frict ion forces on a as defined in the FCOM, leads to t he Compacted snow: µ Icy runway: µ
runway covered by co mpact ed snow and icy runway following µ: = 0.2 = 0.05
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4.3.2. PRECIPITATION DRAG Regulation requires, e.g. AMJ 25x1591: «During take-off acceleration, account should be taken of precipitation drag. During accelerate-stop deceleration and at landing, c redit may be taken for precipitat ion drag.» Precipitat ion drag is co mposed of the two f ollowing drags: 1. Displacement drag Drag produc ed by t he displace ment of the contaminant fluid from the path of t he tire. Increases with speed up to a value close to aquaplaning speed.
It is proportional to t he density of the contaminant, to the frontal area of t ire in the co ntaminant and to t he geometry of t he landing gear. 2. Spray impingement drag Additiona l drag produced by t he spray thrown up by the wheels (mainly t hose of t he nose gear) onto the fuselage.
4.3.3. AQUAPLANING As previously e xplained, t he presence of water on t he runway c reates an intervening water film between the tire and the runway leading to a reduction of the dry area. This phenomenon gets more critical at higher speeds, where the water cannot be squeezed out from between the tire and the runway. The aquaplaning is a situation where «the tires of the aircraft are, to a large extent, separated from the runway surface by a thin fluid film. Under these conditions, tire traction drops to almost negligible values and aircraft wheels braking as well as wheel steering for directional control is, therefore, virtually ineffect ive.» ICAO Airport Services Manual, Part 2. Aquaplaning speed depends on the tire pressure and on the specific gravity of the contaminant (i.e. How dense is t he c ontaminant). In other words, the aquaplaning speed is a threshold from which friction forces diminish severely.
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BRAKING PERFORMANCE Please, bear in mind:
The presence of c ontaminants on the runway affects t he performanc e by: - A reduct ion of the friction forces (µ) bet ween the tire and the runway surface . - An additional drag due to contaminant spray impingement and contaminant displace ment drag. - Aquaplaning (hydroplaning) pheno menon. There is a clear distinction between the effect of fluid contaminants and hard contaminants: - Hard c ontaminants (c ompact ed snow and ice) reduce the frict ion forces . - Fluid contaminants (water, slush, and loose snow) reduce the friction forces, create an additional drag and may lead t o aquaplaning. To develop a model of the reduced µ according to the type of contaminant is a difficult issue. Until recently, regulations stated t hat µwet and µcont can be deriv ed from the µ observed on a dry runway (µdry/2 for wet runway, µdry/4 for water and slush). Nevertheless, recent studies and tests have improved the model of µ for wet and contaminated runways, which are no longer derived from µdry. The certification of the most recent aircraft already incorporates these i mprovements.
4.3.4. CORRELATIO N BETWEEN REPORTE D µ AND BRAKING PERF ORMANCE INFORMATION PROVIDED BY THE AIRPORT AUTHORITIES A SNOWTAM contains: The type of contaminant, Mean depth for each t hird of tot al runway length, Estimated braking ac tion, Reported µ. Some operators have requested that Airbus provide contaminated runway performance data with Reported µ or Estimated Braking Action as an entry, in lieu of the type and depth of contaminant.
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REPORTED MU
EST IM A TE D BRAKING ACTION
SIGN
0.4 and above
GOOD
5
0.39 to 0.36
MEDIUM/GOOD
4
0.35 to 0.30
MEDIUM
3
0.29 to 0.26
MEDIUM/POOR
2
0.25 and below
POOR
1
9 - unreliable
UNRELIABLE
9
DIFFICULTIES IN ASSESSING THE EFFECTIVE µ The two major problems introduced by the airport authorities evaluation of the runway characteristics are: The correlation between test devices, even though some correlation charts have been established. The correlation between measurements made with test devices or friction measuring vehicles and aircraft performance. These measurements are made with a great variety of measuring vehicles, such as: Skidometer, Saab Friction Tester (SFT), MU-Meter, James Brake Decelerometer (JDB), Tapley meter, Diagonal Braked Vehicle (DBV). Refer to ICAO, Airport Services Manual, Part 2 for further information on these measuring vehicles. The main difficulty in assessing the braking action on a contaminated runway is that it does not depend solely on r unway surface adherence c haract eristics. What must be found is the resulting loss of friction due to the interaction tire/runway. Moreover, the resulting friction forces depend on the load, i.e. the aircraft weight, tire wear, tire pressure and anti-skid syst em efficiency. The only way out is to use some smaller vehicles. These vehicles operate at much lower speeds and weights than an aircraft. Then comes the problem of correlating the figures obtained from these measuring vehicles and the actual braking performance of an aircraft. The adopted method was to conduct some tests with real aircraft and to compare the results with t hose obtained from measuring vehicles. Results demonstrated poor correlation. For instanc e, when a Tapley meter reads 0.36, a M U- meter reads 0.4, a SFT reads 0.43, a JBD 12... To date, scientists have been unsuccessful in providing the industry with reliable and universal values. Test s and studies are still in progress. As it is quite difficult to correlate the measured µ with the actual µ, termed as effective µ, the measured µ is te rmed as «reported µ«. In other words, one should not get confused between:
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coefficient
induced
from
the
tire/runway surface interaction between a given aircraft and a given runway, for the conditions of the day. 2. Reported µ: Frict ion coefficient measured by the measuring vehicle.
Particularit ies of fluid contam ina nts Moreover, the aircraft braking performance on a runway c overed by a fluid c ontaminant (water, slush and loose snow) does not depend only on the friction coef ficient µ. As presented in chapters C2.2 and C2.3, the model of the aircraft braking performance (takeoff and landing) on a contaminated runway takes into account not only the reduct ion of a f rict ion coefficient but also: The displacement drag The impingement drag These two additional drags (required to be taken into account by regulations) require knowing the t ype and depth of the contaminant. In other words, even assu ming the advent of a new measuring friction device providing a reported µ equal to the effective µ, it would be impossible to provide takeoff and landing performance only as a function of the reported µ. Airbus Industrie would still require information regarding the depth of fluid c ontaminants. DATA PROVIDED BY AIRBUS INDUSTRIE Hard contaminants For hard contaminants, namely compacted snow and ice, Airbus Industrie provides the aircraft performance independently of the amount of contaminants on the runway. Behind these ter ms are some effect ive µ. These t wo sets of data are certified. Fluid contaminants Airbus Industrie provides takeoff and landing performance on a runway contaminated by a fluid contaminant (water, slush and loose snow) as a function of the depth of contaminants on t he runway. For instance, takeoff or landing charts are published for «1/4 inch slush», «1/2 inch slush», «1/4 inch water» and «1/2 inch water». For loose snow, a linear variation has been established with slush. In other words, pilots cannot get the performance from reported µ or Braking Action. Pilots need t he type and depth of c ontaminant on t he runway.
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CORRELATION BETWEEN REPORTED µ AND BRAKING PERFORMANCE Please, bear i n mind:
4.4.
Airports release a f rict ion coefficient derived f rom a measuring vehic le. This friction coefficient is termed as «reported µ». The actual friction coefficient, termed as «effective µ» is the result of the interaction tire/runway and depends on the tire pressure, tire wear, aircraft speed, aircraft weight nd anti-skid system efficiency. To date, there is no way to establish a clear correlation between the «reported µ» and the «effective µ». There is even a poor correlation between the «reported µ» of the different measuring vehicles. It is then very difficult t o link the publ ished performanc e on a contaminated runway to a «reported µ« only. The presence of fluid contaminants (water, slush and loose snow) on the runway surface reduces the friction coefficient, may lead to aquaplaning (also called hydroplan ing) and c reates an additional drag. This additional drag is due t o the precipitation of the contaminant onto the landing gear and the airframe, and to the displacement of the fluid from the path of the tire. Consequently, braking and accelerating performance are affected. The impact on the accelerating performance leads to a limitation in the depth of the contaminant for takeoff. Hard contaminants (compacted snow and ice) only affect the braking performance of t he aircraft by a reduct ion of the f rict ion coefficient. Airbus Industrie publishes the takeoff and landing performance according to the type of c ontaminant, and to the depth of fluid contaminants.
AIRCRAFT DIRECTIONAL CONTROL
The previous section analyzes the impact of the reduct ion of the frict ion forces on aircraft braking performance. The reduction of friction forces also significantly reduces aircraft directional c ontrol. One should also c onsider the effect of the crosswind component on a slippery runway.
4.4.1. INFLUENCE OF SLIP RATI O When a rolling wheel is yawed, the f orce on the wheel can be resolved in two direct ions: One in the direction of wheel motion, The ot her perpendicular to the motion. The force in direction of the motion is the well-known braking force.
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The force perpendicular to the motion is known as the «side-friction force» or «cornering force». Steering c apability is obtained via the c ornering force.
Maximum cornering effect is obtained from a free-rolling wheel, whereas a locked wheel produces zero c ornering effect . With respect to braking performance, we can recall that a free-rolling wheel produces no braking. In other words, maximum steering control is obtained when brakes are not applied. One realizes that there must be some compromise between cornering and braking. The following figure illustrates t his principle:
The above figure shows that when maximum braking efficiency is reached (i.e. 12% slippage), a signific ant part of t he steering capability is lost. This is not a problem on a dry runway, where the total friction force, split in braking and cornering, is high enough. It may however be a problem on a slippery runway, where the total friction force is significantly reduced. In some critical situations, the pilot may have to choose between braking or controlling the aircraft. It may not have both at the same time.
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4.4.2. INFLUENCE OF WHEEL YAW ANGLE The cornering force also depends on the wheel yaw angle. The wheel yaw angle is defined as the angle between the wheel and its direction of motion. The cornering force increases with the yaw angle, however if the wheel is yawed too much, the cornering force rapidly decreases. The wheel yaw angle providing the maximum cornering force depends on the runway condition and diminishes when the runway is very slippery. It is around 8° on a dry runway, 5° on a slippery runway and 3° on an icy runway.
4.4.3. GROUND CONTROLLABILITY During a crosswind landing, or aborted takeoff, cornering force is the primary way of maintaining t he aircraft within the runway width. In a crosswind situation, the airc raft crabs. That is, the aircraft‟s nose is not al igned with the runway centerline. The wind component can be resolved into two directions: crosswind and head/ tail wind. Similarly, thrust reverse component is resolved both in a component parallel to the runway centerline, actually stopping the aircraft, and in a component perpendicular to the runway. For the purpose of this example, let‟s refer to it as «cross -reverse». These two forces, crosswind and «cross-reverse» try to push the aircraft off the runway. The cornering forces induced by the main wheel and the nose wheel must balance this effect.
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In such a situation, releasing the b rakes would act ually allow a greater c ornering force t o be developed, thus, regaining aircraft directional control. When using autobrake, LOW mode provides more cornering forc e than MED mode.
AIRC RAFT DIRECTIONAL CO NTROL Please, bear in mind:
4.5.
When the wheel is yawed, a side-friction force appears. The total friction force is then divided into t he braking force (component opposite t o the aircraft motion) and the cornering force (side-f rict ion). The maximum cornering force (i.e. directional control) is obtained when the braking force is nil, while a maximum braking force mea ns no cornering. The sharing between cornering and braking is dependent on the slip ratio, that is, on the anti-skid system. Cornering capability is usually not a problem on a dry runway, nevertheless when the tot al frict ion force is significantly reduc ed by the presence of a cont aminant on the runway, in crosswind conditions, the pilot may have to c hoose between braking or controlling t he aircraft .
CROSSWIND
4.5.1. DEMONSTRATED CROSSWIND A demonst rated crosswind is given in the Aircraft Flight Manual (AF M). The words
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«demonstrated crosswind» have been intentionally selected to express that this is not necessarily the maximum crosswind that the aircraft is able to cope. It refers to the maximum crosswind that was experienced during the flight test campaign, and for which sufficient recorded data is available. It is also intentional that demonstrated crosswind is not given in the limitation section, but is in the performance section of the AFM. Demonstration of crosswind capability is made on dry or wet runways and it is usually considered that the given figures are equally applicable t o dry or wet runways. In fact the information given by the AFM is an indication of what was experienced during certification flight tests to provide guidance to operators for establishing their own limitatio ns. FAR/JAR 25 requires this information to be given. The maximum crosswind for automatic landing is defined in the limitation section of the AFM. In this case, it has to be understood as a limitation. That is the limitation of the system.
4.5.2. EFFECT OF RUNWAY CONTAMINATION It is a matter of fact that a poor runway friction coefficient will affect both braking action and the capability to sustain high crosswind components. Airbus Industrie issued recommendations based on c alculations and operational e xperience in order t o develop guidelines on the maximum crosswind for such runway c onditions. The FCOM - Special Operations - indicates the maximum recommended crosswinds related t o estimated runway b raking act ion.
CROSSWIND Please, bear in mind:
4.6.
Airbus Industrie provides a maximum demonstrated crosswind for dry and wet runways. This value is not a limitation. This shows the maximum crosswind obtained during the flight test campaign at which the aircraft was actually landed. Operato rs have to use this information in order to establish their own limitation. The maxi mum crosswind for auto matic landing is a limitat ion. Airbus Industrie provides as well some recommendations concerning maximum crosswind for contaminated runways. These conservative values have been established from calculations and ope rational experience.
PERFORMANCE OPTIMIZATION AND DETERMINATION
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4.6.1. PERFORMANCE OPTIMIZATION A contaminated runway impacts runway related performance. The accelerate-go distance is increased due to the precipitation drag, and the accelerate-stop distance is increased due to t he reduction in the f riction forces. The natural loss of payload, resulting from lower takeoff weight, can be minimized by different means. Optimization of flap setting, takeoff speeds and derated takeoff thrust are the main ways of limiting a loss in takeoff weight. F LAP SETTING Three different flap settings are proposed for takeoff. The name of these flap/slat position, it has been standardized to 1+F, 2 and 3 for the A320 family. Of course, the actual flap/slat deflect ion differs for each aircraft. The influence of the flap setting on the takeoff performance is well-known. Low flap settings (e.g. Conf1+F) provide good climb performance (good lift to drag ratio) while the t akeoff distance is longer (in other words bad runway pe rformanc e). A higher flap setting (e.g. Conf3) helps reduce the takeoff distance (improvement of the runway performance) at the expense of the climb performance (degradation of the lift to drag ratio). Most of t he time, a c ontaminated runway calls for higher flap set ting. T he accelerate- go and the acc elerate-st op distances are then reduced. Yet , the presence of an obstacle may still require a minimum climb gradient calling for a lower flap setting. The right balance must be found. The choice of the optimum flap setting is usually done manually. A quick comparison of the performance for the t hree different flap settings reveals which one is best. The LPC (Less Paper in the Cockpit) allows for an automatic selection of the optimum configuration. TAKE - OFF SPEEDS An improvement of runway performance can be achieved by reducing the takeoff speeds. A reduced V2 generates a reduced accelerate-go distance, while a reduced V1 generates a reduced acc elerate-st op distance. Regulations are helpful in this matter, as the 35ft screen-height is reduced to 15 ft should the runway be contaminated. For a given set of conditions, the V2 speed is lower at 15 ft than at 35 ft. In other words, the screen-height reduction allows for lower speeds. Remark: Just like the effect of thrust reverse, the screen-height reduction may lead to a performance-limited weight on a wet or contaminated runway being greater than the performance-limited weight on a dry runway. It is compulsory to restrict the performance-limited weight on a wet/contaminated runway to that of a dry runway. Nevertheless, the determination of takeoff speeds must always account for the runway condition.
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Moreover, Airbus takeoff charts take advantage of the so-called «optimized speeds». That is, speeds are increased, to meet a climb limitation or reduced to meet a runway limitation, accordingly. In the case of a short and contaminated runway, the optimization process automatically selects lower speeds - yet, speeds are high enough t o clear an obstac le, if any. Though, the speed reduction gets its own limitation. The speeds must have some safety margins to t he stall speed, minimum unstick speed (VMU) and minimum control speeds VMCA (Minimum Control Speed in the Air) and VMCG (Minimum Control Speed on the Ground) Regulations require t he following: V1 ≥ V1 limited by VMCG VR ≥ 1.05 VMCA and V2 ≥ 1.1 VMCA V2 ≥ 1.13 Vs1g for Fly-By-Wire aircraft, V2 ≥ 1.2 Vs for other aircraft. Remark: Other conditions exist, e .g. conditions on VMU. The first condition affects the accelerate-stop distance. The last two conditions affect the accelerate-go distance.
PERFORMANCE OPTIMIZATION AND DETERMINATION Please, bear i n mind:
The presence of a contaminant on the runway leads to an increased acceleratestop distance, as well as an increased accelerate-go distance (due to the precipitation drag). This results in a lower takeoff weight which can be significantly impacted w hen the runway is short. To minimize the loss, flap setting and takeoff speeds should be optimized. Increasing the flap and slats extension results in better runway performance. Both the accelerate-stop and accelerate-go distances are reduced. A short and contaminated runway naturally calls for a high flap setting. Nevertheless, one should bear in mind that the presence of an obstacle in the takeoff flight path could still require a lower flap setting as it provides better climb performance. An optimum should be determined. This optimum is usually found manually by a quick comparison of the different takeoff charts. The Airbus LPC (Less Paper in the Cockpit) enables an automatic computerized selection of the optimum flap. The takeoff speeds, namely V1, VR and V2 also have a significant impact the takeoff performance. High speeds generate good climb performance. The price to pay for obtaining high speeds is to spend a long time on the runway. Consequently, takeoff distances are increased and the runway performance is degraded. Thus, a contaminated runway calls for lower speeds. Once again, the presence of an obstacle may limit the speed reduction and the right balance must be found. Airbus performance programs, used to generate takeoff charts, take advantage of the socalled «speed optimization». The process will always provide the optimum speeds. In a situation where the runway is contaminated, t hat means as low as possible. The FLEXIBLE THRUST principle, used to save engine life by reducing the thrust to the necessary amount, is not allowed when the runway is contaminated. Different methods are proposed by Airbus Industrie to determine the performance on a contaminated runway. The methods differ by their medium (paper or elect ic) and the level of conservatism and details they provide.
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5.
FUEL FREEZING LIMITATIONS
5.1.
INTRODUCTION
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On some particular routes, fuel freezing limitations may be a concern. When very low temperatures are expected, the dispatch or flight plan may be affected, and have economical implications. Some routes may not be flown under severe temperature conditions with any fuel type. Similarly, when ve ry low t emperatures are encountered in flight, specific crew procedures may be necessary. This chapter reviews various aspect s associated with fuel freezing limitat ions.
5.2.
DIFFERENT TYPES OF FUEL
For commercial fuel requirements, (excluding North America, Russia and China), it is primarily the petroleum companies who dictate turbine fuel specifications, due to the variations in national spec ificat ions. The Aviation Fuel Quality Requirements for Jointly Operated Systems is a petroleum industry st andard which e mbodies the most st ringent requirements of the UK DEF STAN 91/92 and USA ASTM D1655 fuel specifications to produce a kerosene fuel designated JET A1. It is known as the Joint Fuelling System Checklist (JFSCL) and is used by eleven major aviation fuel suppliers for virtually all civil aviation fuel supplies outside of North America, Russia and China. All civil jet fuels in USA are manufactured to specifications defined by the American Society for Testing and Materials (ASTM). These civil fuels are designated by ASTM as D1655 JET A and JET A1, high and low freeze point kerosene type fuels, and D1655 JET B, wide cut low flash point type fuel. JET A is the principle fuel available in the USA. Jet fuels for use by the U.S. military services are controlled by an U.S. government specification and are given t he prefix «JP». International Air Transport Association (IATA) issued a «guideline jet fuel specification», the main purpose of which is to make specification comparison of jet fuels produced in various countries. The IATA Guidance Material presently defines suitable characteristics for four grades of aviation turbine fuels: JET A, JET A1, TS-1 (kerosene-type fuels) and JETB (wide-cut fuel). These fuels meet the requirements of t he following specifications: JET A ASTM D1655- 98b (JETA) JET A1 JFSCL (JET A1) TS-1 GOST 10227-86 (TS- 1)
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CAN/C GSB-3.22.97 (Wide cut type)
The following fuel types are approved for use on Airbus Industrie aircraft. Some of them are approved for ce rtain models only ( refer to FCOM and AFM limitat ions). Kerosene: This is an aviation turbine fuel type obtained from di rect distillation. Generally, the term «kerosene» is employed to describe a wide range of petroleum, defined only by a minimu m f lash point of 38°C and an end point of no more than 300°C. Flash point is the fuel temperature at which sufficient vapor forms at the surface of the liquid for the vapor to ignite in air when t he flame is applied. End point or final point is the fuel temperature at which all of the liquid will distill over into vapor. «JET A1» is by far the most frequently used fuel in civil aviation, (except in the USA and Russia), and has a maximum freezing point of -47°C and a mandatory requirement for a st atic dissipator additive. «JET A» is similar to JET A1 but has a higher maximum freezing point of -40°C, with an option for a stat ic dissipator additive. It is primarily available in the USA. JP8 is similar t o JET A1. It c ontains additives required by military users. TS1 is a Russian fuel similar to JET A1. RT (Russian) and TH (Romanian) are other commonly available kerosenes in Eastern Europe. These three fuels can be used if the individual fuel batches are re-qualified to JET A1 or JET A fuel specification. Alternatively, specific flight test or in-service evaluation before approval on Airbus aircraft can be considered. 5.3.
MINIMUM ALLOWED FUEL TEMPERATURE
The minimum fuel t emperature, published in t he operational docu mentat ion, may be more restrictive than the certified aircraft environmental envelope. It includes two different limitations both linked to engine operation: Fuel freezing point limitation, and Fuel heat management syst em limitation. a) Fuel freezing point limitation This limitation provides an operating margin to prohibit operations under fuel temperatu re conditions t hat c ould result in the precipitation of waxy product s in the fuel. The presence of wax crystals in the fuel is undesirable because of the risk of fuel lines and filters becoming blocked, with consequential effects on engine operation (instability, power loss or flame-out). The resulting limitat ion varies with the freezing point of t he fuel being used. Aside from t his, engines have a fuel warming (oil cooling) syste m at their inlet. Because of the architect ure of this system and the fact t hat the fuel inlet hardware va ries from one engine type t o another, the spec ification of what fuel te mperature is acc eptable at the inlet of t he engine varies fro m one eng ine t ype to the other. Therefore, engine manufacturers so metime require a t emperature margin to fuel freezing point t o guarantee correct operation. The engine manufacturer‟s margins relative to the fuel freezing point are as follows: • IAE: 4°C
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b) Fuel heat management system limitation This limitation ref lects t he engine capability t o warm-up a given wat er-saturated fuel flow to such a point that no accumulation of ice crystals may c log the fuel filter. Such a limitation does not appear in the documentation for some engine types when outside the environ mental enve lope. When applicable, the resulting limitation is a fixed temperature below which, flight (or takeoff only, if high fuel flows only c annot be warmed- up enough) is not permitt ed. The most restrict ive of t he two limitations above (a and b) should be considered. Note: The fuel anti-icing additives authorized by engine manufacturers decrease the freezing temperature of the water contained in the fuel (decrease the fuel heat management system temperature limitation), but have no effect on the fuel freezing temperatu re itself. The fuel freezing point t o be considered is the actual fuel freezing point . If the actual freezing point of the fuel being used is unknown, the minimum fuel specification values as indic ated below should be used as authorized by the AFM/FCOM. JET A
JP5
JET A1/JP8
RT/TS-1
JET B
TH
JP4
-40°C
-46°C
-47°C
-50°C
-50°C
-53°C
-58°C
Note 1: The freezing point, as defined in the ASTM test methods, is the temper ature at which t he visible solid f uel par ticles (waxing) disappear on warming dry fuel (water free) which has previously been chilled until crystal appear. However, for Russian and some other Eastern European fuels (RT, TS-1, TH) using the GOST test method, the fuel freezing point is equal to the temperature at which solid fuel particles first appear, (waxing) when cooling dry fue l. This means that Russian fuels with a dec lared freezing point of -50°C under GOST specificat ion would have an equivalent f reezing point of -47°C when test ed to ASTM method. Hence JET A1, RT and TS-1 norma lly have the same fuel freezing temperature. Note 2: The freezing point temperature for Russian RT and TS-1 fuels is dependent upon the region. RT and TS-1 fuels have maximum fue l freezing temper atures of -50°C for all areas where t he ground level air temperat ure is not below -30°C during 24 hours before departure. For areas where the ground level air temperat ure is below -30°C during 24 hours bef ore departure then upon customer request the following fuel freezing temperature specification applies RT: -55°C and TS-1: -60°C. As far as the fuel freezing point limitation is concerned and depending on the aircraft type, the following applies:
A fuel temperature sensor is insta lled in each outer and inner cell on the A320. Different means are provided to avoid flying below minimum allowed fuel temperature: •
The Flight Manual mentio ns: «When using JET A: If TAT reac hes 34°C, call ECAM fuel page and monitor that fuel temperature remains higher than -36°C.»
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An ECAM ECAM advisory adv isory is act ivated as soon as fuel t empe emperature rature in any tank reaches - 40°C
•
An ECAM ECAM wa rning rning «FUEL OUTE R / INNER (FUEL (F UEL WING on A3 21) TK LO TEMP» is activated when fuel temperature in any tank reaches - 45°C. 45°C. On ground before takeoff, t his his warning is assoc iated with «DELAY «DELAY T.O» message.
FUEL FREEZING LIMITATIONS Please, Please, bear in mind:
The minimum minimum allowed fuel te mperature may either be limite limited d by: - The fuel freezing point to prevent fuel lines and filters from becoming blocked by waxy waxy fuel (variable with t he fuel being used) or -
The engine engine fuel heat ma nagement nagement system to prevent ice crystals, contained in the fuel, from blocking the fuel filter (fixed temperature). The latter is often outside the flight envelope and, thus, transparent to the pilot.
Different fuel types having variable freezing points may be used as mentioned in the FCOM. When the actual freezing point of the fuel being used is unknown, the limitation is given by the minimum fuel specification values. In addition, a margin for the engine engine is somet somet imes require require d. The resulting resulting li mitat mitat ion may be penalizing penalizing under c ertain tempe tempe rature rature c onditions onditions especially when JET A is used (maximum freezing point -40°C). In such cases, knowledge of the actual freezing point of the fuel being used generally provides a large operational benefit as surveys have shown a significant give- away. Although the fuel freezing limitation should not be deliberately exceeded, it should be known known t hat it ensures ensures a signi signiff icant safety margin.
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6.
LOW TEMPERA T EMPERAT T URE EFFECT ON ALT ALT IMET IMETER ER INDICAT INDICATION ION
6.1.
GENERAL
The pressure (barometric) altimeters installed on the aircraft are calibrated to indicate true altitude under under Inte rnational rnational Standard At mosphe re (ISA) (ISA) conditions. This means that the pressure altimeter indicates the elevation above the pressure reference reference by follow follow ing ing the standard standard at mosphe ric ric prof prof ile. ile. Any deviation from ISA will, therefore, result in an incorrect reading, whereby the indicat indicat ed altitude differs differs from the t rue rue altitude.
Temperature greatly influences the isobaric surface spacing which affects altimeter indications. When the temperature is lower than ISA, the true altitude of the aircraft will be lower than the f igure igure indicat ed by the altimeter. altimeter. Specifically, this occurs in cold weather conditions, where the temperature may be considerably lower than the temperature of the standard atmosphere and may lead to a significant significant altimeter altimeter error. A low temperature may decrease terrain clearance and may create a potential terrain c learanc learanc e hazard. hazard. It may also be the origin orig in of an altit altit ude/posit ion e rror. 6.2.
CORRECTIONS
Various methods are available to correct indicated altitude, when the temperature is lower than ISA. In all cases, the correction has to be applied on the height above the elevation of the altimeter setting source. T he alti altim meter sett ing ing source is genera lly the at mosphere pressure at an airport, and the correction on the height above the airport has to be applied on the indicated altitude. The same correction value is applied when flying at either QFE or at QNH. The choice of a method method depe nds on of the a mount of precision precision needed for the c orrection orrection..
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6.2.1. LOW ALTITUDE TEMPERATURE CORRECTIONS APPROXIMATE CORRECTION Increase obstacle elevation by 4% per 10°C below ISA of the height above the elevation of the altimeter setting source or, decrease aircraft indicated altitude by 4% per 10°C below below ISA of t he height height above the elevation of the altimeter altimeter set ting sourc sourc e. This method is generally used to adjust minimum safe altitudes and may be applied for all altimeters setting source altitudes for t emperatures emperatures above -15°C.
Example: Let‟s assume an airport elevation of 1000 ft. The airport elevation is the same as altimeter sett ing ing source source altitudes elevation elevation = 1000 ft. The ISA te mperature at 1000 ft is 13°C. 13°C. Let‟s now assume that the Actual Outside Air Temperature (OAT) is -2°C. The ISA deviation is then, ΔISA = (13°C) - (-2°C) = -15°C. It is assumed assumed that the minimum required actual altitude to clear the obstacle is 1200 1200 ft. In order to account for the ISA deviation, the terrain/obstacle elevation has to be increased by: 1200 x 0.04 x 15/10 = 72 ft In other words, words, t he altimeter must read 1272 ft in order order t o have an act ual heigh heightt of 1200 ft. TABULATED CORRECTIONS ICAO publishes the following tables in the «PANS-OPS Flight Procedures» manual. They are based on an airport elevation of 2000 ft however, they may be used operationally at any airport.
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Example: Solving the previous example with this method: - Enter the table with 1200 ft. To avoid an inte rpolation, use 1500 ft . - Enter the t able with - 2°C. To avoid an interpolation, use - 10°C. - Read that the correction on the altimeter indication must be 120 ft.
F ORMULA Low altitude correction: ∆Z = [(Q NHalt - Zt) * ∆T] / [288.15 - (QNHalt * L / 2)] ∆ T = difference between the airport temperature and ISA temperature of the airport ( ∆ ISA°C). Zt = airport altitude. QNHalt = aircraft indicated altitude above sea level. L = temperature gradient: 0.0065°C per m or 0.00198°C per ft in function of the unit chosen for Zt and QNHalt. The following table is illustrated in the FCOM, and is based on the above-noted formula. Low altitude correction t able:
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Example: Solving the previous e xample with this table: -
Enter the table with 1200 ft. T o avoid an interpolation, use 150 0 ft.
-
Enter the table with ∆ISA
= -15°C. To avoid an interpolation, use -
20°C. -
Read that t he correction on the altimeter indication must be 105 ft.
TRUE ALTITUDE = QNH ALTITUDE + ∆Z Note: A constant ∆ISA from ground to airplane level has been assumed APPLICATION OF LOW ALTITUDE CORRECTIONS Corrections on an indicated altitude have to be applied on the published minimum altitude except when the criteria used to determine minimum flight altitudes are already published and t ake into account low t emperatu re influences (Mentioned on AIP). On approach, at least the following published altitudes must be increased in low OAT conditions: MSA FAF altitude Step- down altitude(s) and MDA(H) during a no n-precision approach OM altitude dur ing an ILS approach Waypoint crossing altitudes during a GPS approach flown with vertical navigation
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As it is not allowed to modify the altitude constraints of a non-precision approach, a minimum OAT to fly the approach with the «FINAL APPR» FMGC mode must be established. For OAT lower than this minimum, selected vertical navigation must be used. Remark: The determination of the lowest useable flight levels by Air Traffic Control units within controlled airspace does not relieve the pilot-in-command from the responsibility of ensuring that adequate terrain clearance will exist, except when an IFR flight is being vectored by radar.
6.2.2. HIGH ALTITUDE TEMPERATURE CORRECTIONS (EN-ROUTE) Formula:
IA = TA x T°std / T°
IA =
Indicat ed Altitude
TA =
True Altitude
T°std =
Temperature standard (°K)
T° =
Actual temperatu re (°K)
Example: Let‟ s assume that the actual altitude is 16500 ft and actual temperature is 48°C. T°st d: temperature standard at 16500 ft = -18°C = 255°K T°: actual temperature at 16500ft = -48°C = 225°K (ISA -30°C) IA = 16500 x 255/225 = 18700 ft
The following chart is illustrated in the F COM, and is based on the above- noted formula.
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This formula doesn‟t take into account the elevation of the altimeter setting source. It has to be used en route and must not be used to adjust low altitude. APPLICATION OF HIGH ALTITUDE TEMPERATURE CORRECTIONS. In theory, this correction applies to the air column between ground and aircraft. When flying above mountain areas, the use of this correction gives a conservative margin. Special care should be exercised, in case of depressurization failure or engine failure, to avoid flying c loser to the obst acles.
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INTENTIONALLY LEFT BLANK
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Part II – A 320 TYPE SPECIFFIC. EQUIPEMENT and PROCEDURES 7.
AERODROME
7.1.
RWY CONTAMINATION, BRAKING CONDITIONS AND REPORTS 7.1.1. RWY CONTAMINATION
A runway is contaminated when more than 25% of it‟s surface is covered by contaminant.
DAMP:
A runway is damp when the surface is not dry, but when the water on it does not give it a shiny appearance.
WET:
A runway is considered as wet when the surface has a shiny appearance due to a thin layer of water. When this layer does not exceed 3 mm depth, there is no substantial risk of hydroplaning.
STANDING WATER:
is caused by heavy rai nfall and /or insufficient runway drainage with a depth of more than 3 mm.
SLUSH:
is water saturated with snow which spatters when stepping firmly on it. It is encountered at t emperatures around 5° C and its density is approximately 0.85 kg/liter (7.1 lb/US GAL).
WET SNOW:
is a condition where, if compacted by hand, snow will stick together and tend to form a snowball. Its density is approximately 0.4 kg/lite r (3.35 lb/US GAL).
DRY SNOW:
is a condition where snow can be blown if loose, or if compact ed by hand, will fall apart aga in upon release. Its density is approximately 0. 2 kg/liter (1.7 lb/US GAL).
COMPACTED SNOW:
is a condition where snow has been compressed (a typical friction coefficient is 0.2).
ICY:
is a condition where the friction coefficient is 0.05 or below.
7.1.2. ASSESSME NT OF TYPE AND DEPT OF DEPOSIT WATER ON THE R UNWAY A report of the RWY state including the depth of water representative for the centre half of the width of the RWY is operationally needed. However, such reports are only made if the water is associated with snow, slush or ice. Also, a representative assessment of the depth is very difficult. Hence, only ‟damp‟, ‟wet‟, etc. is usually given.
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SNOW AND ICE ON THE R UNWAY Whenever a RWY is affected by snow and ice and it has not been possible to clear the precipitant fully, the condition of the RWY should be assessed and the braking conditions measured. In daily practice the type of deposit is assessed subjectively. The mean depth can be measured only w ith a limite d acc uracy of approx. 2 CM fo r dry snow, 1 CM for wet snow and 3 MM for slush. The depth of other deposits e.g. rime, rolled snow, ice, etc. is not considered to be of operational significance since it does not affect the acceleration or deceleration of an ACFT (no drag). T herefore, it is not t o be reported.
7.1.3. ASSESSMENT OF BRAKING CONDITIONS GENERAL Operationa l considerations require re liable and uniform reports on braking c onditions whenever RWYs are contaminated and subsequent updating when conditions change significantly. The reported Friction Coefficient (FC) is a relative measure for the achievable friction in the tire to surface interface of a braked wheel and should be the maximum which occurs when a wheel is slipping but still rolling. Measurements should be made at a distance of 3 M or the distance from the CL where most operations take place. The reported Braking Action (BA) may reflect FC converted to BA as well as subjective pilot‟s reports or assessments by empirical methods (see also 2.1.4). Therefore, for operational applications the FC is generally preferable to the BA which often lacks a proper standardized reference basis. If BA is reported it is recommended to request the FC if measured or, if the BA originates from pilot‟s reports, to be informed on the ACFT type involved. The FC and especially the BA should not be taken as absolute due to the many methods of assessment used and the different variables such as ACFT weight, speed, braking pe rformanc e, tyres and undercarriage c haract eristics, etc. PECULARITIES OF MEASURING DE VICES All types of measuring equipment do not permit to measure with satisfactory reliability when standing water, slush and wet snow i.e. aquaplaning condition or more than a thin layer of loose snow are present. In such cases the braking conditions should be reported as ”unreliable”. Also, when considering friction coefficients of wet RWYs (esp. those with smooth surface) it should be not ed that t he friction may drop markedly with increasing speed. Measuring equipment providing continuous measurement of friction along the entire RWY are preferable to those allowing only spot measurements as the latter may give misleading i nformation. Howeve r, various d ifferent types of devices are in use. Equipment permitt ing continuous measurement: GRT - Grip Test er SFH - SAAB/Surface Friction Tester SKH - BV11/Skiddometer ( high p ressure t yre) RUN - Runway Analyser and Recorder VIN - Vertec Inspector
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These provide reliable f rict ion coefficients on rolled snow, ic e etc . and thin layers of loose snow. If the depth of dry loose snow is considerable, the values may be pessimistic. Decelerometers (spot measurement s only): JBD - James Brake Decelerometer TAP - T apley Met er DBV - Diagonal Braked Vehicle BRD - Brakemeter-Dynometer These may provide reliable friction coefficients on rolled snow ice etc. but not on loose snow or slush since the drag influences the measurement. None of the above provide reliable fric tion measurements on st anding wat er, slush and wet snow. Subjective methods permitting assessment of Braking Action only: Truck, car, pilot‟s report. T he reliability of suc h reports is questionable, see 7.1.4. R ELIABILITY OF REPORTED FRICTION COEFFICIENTS ON STANDING WATER , SLUSH AND WET SNOW
When airport temperatures are close to zero and the RWY is contaminated by standing water (>3mm), slush (>3mm) or wet snow (>6mm), refer to company gross weight chart for detailed instructions.
7.1.4. RELATIONSHIP BETWEEN FC AND BA Braking conditions reported as BA may reflect measured FC as well as empirical, subjective assess ments. The relation bet ween FC and empirically assessed BA e.g. by c ar as well as subjective pilot‟s reports is rather loose due to the lack of a proper standardized reference basis referring e.g. to the type of vehicle and it‟s tyres used, the pilot‟s experienc e, the ACFT type and it‟s performance in such conditions.
7.1.5. DISSEMINAT ION OF RWY STATE INFORMATION R EPORTING BY ATC ATIS FOR TKOF AND LDG Information on RWY state and braking conditions as contained in SNOWTAM is available from ATC and is usually broadcasted on ATIS. When giving landing information, the thirds of t he RWY are referred to as f irst, second and third part of t he RWY as seen in the direction of landing. Other information e.g. st ate of TWY, apron etc. are added. On ATIS and VOLMET the term ‟SNOCLO‟ may be used to notify that the AD is closed due to snow. Note: Except in connection with snow and ice no warnings are usually provided on hazardous RWY conditions such as RWY slippery when wet or poor BA if wet in combination with dust. Such information may be provided by remarks on instrument approach and lending chart and by NOTAM. ATC will only inform that RWY is damp wet, etc. Always try to get FC values and time when measured in order to avoid statements like e.g. BA medium, which might be misleading information.
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SNOWTAM The SNOWTAM is a specialized NOTAM notifying the presence or removal of hazardous RWY c onditions due to snow, ice , etc. by means of a spec ific format. It is disseminated over AFTN and is available at the AIS office as soon as the presence of contaminations is considered to be operationally significant. SNOWTAMs are not routinely issued at regular time intervals but new SNOWTAMs are provided according to the criteria for significant weather c hanges. Note: The closure of a RWY for clearance and the subsequent reopening may be notified by a normal NOTAM. MOTNE RUNWAY REPORTS For most EUR ADs of which MET information is disseminated on the Meteorological Operational Teletype Network Europe/ MOTNE runway reports are provided in the abbreviated form of 8-figure groups appended to weather reports (METAR). These reports are derived from the sa me observation/measurements as the SNOWTAM. For obvious reasons e.g. traffic density the halfhourly rythm of METARs is not practicable for RWY c ondition observations. T hus a repetition of the previous RWY report may mean that no significant change has occurred. As soon as contamination conditions have ceased to exist, a clearance report is sent, then the promulgation of RWY reports is terminated u ntil new c ontamination occ urs. If an AD is closed due to snow or removal of snow and ice, the term ‟SNOCLO‟ may replace the 8-figure c ode group. For decoding and det ailed reporting procedures see 7.2 bellow. 7.2.
SNOWTAM AND MOTNE DE-CODING 7.2.1. SNOWTAM
Below is a c ompleted SNOWTAM format and its assoc iated teletype messages SNOWTAM example: GG EHAMZQZX EDDFZQZX EKCHZQZX 070645 LSZHYNYX SWLS01499 LSZH 11070620 SNOWTAM 049 A) LSZH B) 11070620 C) 10 D) 2200 E) 40L F) 4/5/4 G) 20/10/20 H 30/35/30 MUM J) 30/5 L K) YES L L) TOT AL M) 0900 P) YES 12 S) 110709 20 T) FIRST 300M RWY 10 COVERED BY 50 MM SNOW, RWY CONTAMINATION 100%
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SNOWTAM AERODROME LOCATION INDICATOR DATE/TIME OF OBSERVATION (Time of completion of measuremen t in UTC) RUNWAY DESIGNATORS CLEARED RUNWAY LENGT H, IF LESS THAN PU BLISHE D LENGT H (m) CLEARED RUNWAY WIDTH, IF LESS THAN PUBLISHED WIDT H (m; if offset left or right of centre line add "L" or "R") DEPOSITS OVER TOTAL RUNWAY LENGT H (Observed on each third of the runway, starting from threshold having the lower runway designation number) NIL - CLEAR AND DRY 1 - DAMP 5 - WET SNOW 2 - WET or water patches 6 - SLUSH 3 - RIME O R F ROST COVERE D 7 - ICE (Depth normally less than 1 mm) 8 - COMPACTED OR ROLLED SNOW 4 - DRY SNOW 9 - FROZEN RUTS OR RIDGES) MEAN DEPTH (mm) FOR EACH THIRD OF TOTAL RUNWAY LENGTH FRICTION MEASUREMENTS ON EACH THIRD OF RUNWAY AND FRICTION MEASURING DEVICE MEASURED or CALCULATED COEFFICIENT
or ESTIMATED SURFACE FRICTION
0.40 and above 0.39 to 0.36 0.35 to 0.30 0.29 to 0.26 0.25 and below 9 - unreliable
GOOD MEDIUM/GOOD MEDIUM MEDIUM/POOR POOR UNRELIABLE
Serial number 49 A) LSZH B) 11070620 C) 10 D) 2200 E) 40 L
F) 4/5/4
G) 20/10/20 H) 30/35/30
TYPE OF MEASURING EQUIPMENT USED
- 5 - 4 - 3 - 2 - 1 - 9
BRD = BrakemeterSFL = Surface Dynometer Frict ion Tester GRT = Grip Tester SKH = Skiddometer MUM = Mu- meter (high p ressure t ire) RFT = RWY Friction SKL = Skiddometer Tester (low pressure tire) SFH = Surface TAP = Tapley Meter Frict ion Tester (high p ressure t ire) (When quoting a measured c oefficient use the observed two figures, followed by t he abbreviation of the friction measuring devic e used.When quoting an estimate use single digit) CRITICAL S NOWBANKS (If present, insert height (c m)/distance from the edge of runway (m) followed by "L", "R" or "LR" if applicable) RUNWAY LIGHTS (If obsc ured, insert "YES" followed by "L ", "R" or both "LR" if applicable) FURTHER CLEARANCE (If planned, insert length (m)/width (m) to be cleared or if to full dimensions, insert "TOTAL") FURTHER CLEARANCE EXPECTED TO BE COMP LETED BY . . . (UTC) TAXIWAY (If no appropriate taxiway is available, insert "NO") TAXIWAY SNOWBANKS (If more than 60 cm, insert "YES" followed by distance apart, m) APRON (If unusable insert "NO") NEXT PLANNED OBSERVATION/MEASU REMENT IS FOR (month/day/hour in UTC) PLAIN LANGUAGE REMARKS (Inc luding conta minant coverage and other operationa lly significant information, e.g. sanding, de icing)
J) 30/5 L K) YES L L) TOTAL M) 0900 N) ----P) YES 12 R) ----S) 11070920 T) First 300M RWY 10 covered by 50 mm)
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7.2.2. MOTNE RUNWAY REPORTS EUROPE The group: RDRDR[n]/ERCReReRBRBR RDRDR [n] = Runway number with indicator R, L or C if needed: Code A (Some countries do not use the letter “R” in front of runway number) ER = Type of deposit: Code B CR = Extent of coverage: Code C eReR = Dept of deposit: Code D BRBR = Braking conditions: Code E SPECIAL CASES Easily recognised c oding exist for followi ng cases: //99// RU NWAY CLEARANCE: Appea rs when a RWY is being c leared, e.g. R14//99// for RWY 14. ////// REPORT NOT UP-DATE D: Ap pears if RWYs are c ontaminated but reports are not up-dated, e.g. due to night c urfew, e.g. 88////// for all RWY at an AD. CLRD// CLEARA NCE REPORT: Appears if cont amination conditions have c eased, e.g. R14CLRD// for RWY 14, or 88CLRD// for all RWYs at a AD. SNOCLO// AD closed due to snow, etc. This may replace the RWY report (also on VOLMET). CODE A RUNWAY DESIGNATOR PARALLEL RWYs: The right RWY is identified by adding 50 to the Designator, e.g 77 = R27R, whi le the left RWY only the RWY figure appears e.g. 27 = R27L. The figure 88 instead of a RWY designator indicates t hat conditions reported apply to all RWY at the AD. The figure 99 instead of a RWY designator indicates that a previous RWY report is repeated. CODE B TYPE OF DEPOSIT 0 = CLEAR and DRY 1 = DAMP 2 = WET or Water Patches 3 = RIME or FROST (<1mm) 4 = DRY SNOW 5 = WET SNOW 6 = SLUSH 7 = ICE 8 = COMPACTED or ROLLED SNOW 9 = FROZEN RUTS or RIDGES / = TY PE OF DEPOSIT not reported, e.g. due t o RWY clearance/de -icing in progress. CODE C EXTENT OF CONTAMINATION 1 = 10% or less of RWY covered 2 = 11% to 25% of RWY covered 5 = 26% to 50% or RWY covered
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9 = 51% to 100% of RWY covered / = NOT REPO RTE D, e.g. due t o RWY c learance or de -icing in progress. CODE D DEPT H OF DEPOSIT 00 = less than 1mm 01 to 90: depth in mm, e.g. 23 = 23mm 92 = 10c m 93 = 15c m 94 = 20c m 95 = 25c m 96 = 30c m 97 = 35c m 98 = 40c m 99 = RWY not operational due to snow, slush, ice, large drifts or RWY clearance; Depth not reported // = Depth operational ly not significant e.g. with ice or rolled snow, or n ot measurable e.g. RWY wet. CODE E BRAKING CONDITIONS Either the measured Friction Coefficient or an estimated Braking Action is reported as follows: FRICTION COEFFICIENT: Reported figures from 01 to 90 represent FC, e.g. 05=FC 0.05, 28 =F C 0.28 BRAKING ACTION: Reported by following code figures: 91 = POOR 92 = MEDIUM/POOR 93 = MEDIUM 94 = MEDIUM/GOOD 95 = GOOD 99 = UNRELIABLE, BA and FC not possible to assess, misleading, e.g. in case of aquaplaning. // = RWY not operational, BA and FC not reported.
7.2.3. ICAO PROVISIONS AND PROCEDURES CONCERNING SNOWTAM‟S AND MOTNE RUNWAY REPORTS GENERAL SNOWTAM‟s and MOT NE RWY reports are only provided for winter conditions (snow, ice, etc) but not for other hazardous RWY conditions e.g. RWY slippery when wet or, wet combined with dust. Observations and measurements are made at routine intervals but only when RWY‟s are contaminated and/or when there are s ignificant changes.
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VALIDITY OF R UNWAY STATE INFORMATION The maximum validity of SNOWTAM‟s is 24 HR. If the validity expires, a new observation/measurement should be made even if conditions have not changed and a new SNOWTAM should be issued. EUR: A new SNOWTAM should normally be issued every 6 HR. For aerodromes closed at night or which do not have night operations, a new SNOWTAM should be promulgated 2 HR befo re the aerodrome is reopened for operations. Note: MOTNE RWY reports are based on the same observations/measurements as the SNOWTAM and are repeated with every subsequent weather report until a new report is made. SIGNIF ICANT CHANGES New observations/measurements should be made immediately in view of rapidly changing conditions and new reports should be issued if there is any of the following significant changes in the: friction coef ficient of about .05, depth of deposit greater than 20mm for dry snow, 10mm for wet snow and 3mm for slush, available RWY length of 10% or more type of deposit or extent of coverage which requires a reclassification according to t he codes, height or distance from the RWY centreline of critical snowbanks on one or both sides, conspicuity of RWY lights, operationally significant conditions according to local experience or circumstances. DEFINITIONS AND TERMINOLOGY Water on the RWY Whenever water is present on RWY‟s, a desc ription of the conditions on the c entre half of the RWY should be made using the following terms: DAMP - the surface shows a change of colour due to moisture. WET - the surface is soaked but there is no standing water WATER PATCHES - significant patches of standing water are visible STANDING WATER - standing water of significant depth and area which affects significantly t he braking ac tion (aquaplaning) FLOODED - e xtensive standing water is visible. Snow and s lush
DRY SNOW - snow which can be blown if loose or, if compacted by hand, will fall apart again upon release. WET SNOW - snow which, if compact ed by hand w ill stick together and tend t o form a snowball. SLUSH - water saturated snow which with a heel-and-toe slap-down motion against t he ground will be displaced with a splatt er COMPACTED SNOW - snow which has been compressed into a solid mass that resists further compression and will hold together or break up into chunks if picked up.
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Combinations of ice, snow and/or standing water Such combinations, especially when rain, sleet or snow is falling, may have a rather transparent appearance due to their high water/ice content. (They shall be considered the same way as slush. Note also that wet ice may be e xtremely slippery). ACCURACY OF DEPTH OF DEPOSIT When dry or wet snow or slush is present on a RWY, an assessment of the mean depth should be made to an accuracy of approximately 20 mm for dry snow, 10 mm for wet snow and 3 mm for slush. If mean deposit is not measurable or operationally not significant, “xx” will be shown. Norway: The depth is given in millimetres, in intervals of 8 mm for dry snow, 6 mm for wet snow and 3 mm for slush and rounded upwards, i.e. wet snow between 6 and 12 mm is reported as 12 mm. The depth of deposit of compacted/solid contaminants such as ice, compacted snow or frozen ruts or ridges which do not cause a drag (retarding rolling) is not considered to be operationally significant and needs not t o be assessed and reported. The depth of standing water is very difficult to assess. Hence it is often reported as ‟not measurable‟. ASSESSMENT OF EXTENT OF R UNWAY C OVERAGE The extent of the coverage of the RWY reported in percent is the best possible estimate but shall not be understood t o be an acc urate measurement. R ELATIONSHIP BETWEEN FC AND BA The table below which has been developed by ICAO is based on measurements on ice and compacted snow. It should not be taken to be absolute and applicable in all conditions and shou ld not be used for conversion for operational purposes. Friction Coefficient 0.40 and above 0.39 - 0.36 0.35 - 0.30 0.29 - 0.26 0.25 and below 9 = Unreliable
Braking action GOOD MEDIUM to GOO D MEDIUM MEDIUM to POOR POOR
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A 320 AIRCRAFT
NOTE: This chapter represents general view of A 320 aircraft systems only. For detailed and up-t o-date information see FCOM. 8.1.
ICE AND RAIN PROTECTION 8.1.1. GENERAL
The ice and rain protection system allows unrestricted operation of the aircraft in icing conditions and heavy rain. Icing conditions may be e xpect ed when the OAT (on ground and for takeoff), or when the TAT (in flight) is at or below 10 °C, and there is visible moisture in the air (such as clouds, fog with low visibility of one mile or less, rain, snow, sleet, ice crystals) or standing water, slush, ice or snow is present on the taxiways or runways. ANTI-ICING Either hot air or electrical heating protects critical areas of the aircraft as follows. HOT AIR
three outboard leading-edge slats of each wing engine air intakes
ELECTRICAL HEATING flight compart ment windows sensors, pitot probes and static ports waste-water drain mast RAIN REMOVAL Wipers and when necessary, fluid rain repellent, remove rain from the front windshield panels.
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8.1.2. WING ANTI-ICE DESCRIPTION In flight, hot air from the pneumatic system heats the three outboard slats (3-4-5) of each wing. Air is supplied through one valve in each wing. The “WING” pushbutton on t he ANTI-ICE panel c ontrols the valves. When the aircraft is on ground, the flight crew can initiate a 30-second test sequence by turning the syst em ON. If the system detects a leak during normal operation, the affected sides wing anti-ice valve auto matically c loses. When wing anti- ice is selected, the EPR limit is automatically reduced, and the idle EPR is automatically i ncreased. If the electrical power supply fails, t he valves c lose.
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C ONTROLS AND INDICATIONS WING ANTI ICE pb sw This switch controls the wing anti ice system on the left and right sides simultaneously. ON It light s up blue. WING A. ICE appears on the ECAM MEMO page. Wing anti ice control valves open if a pneumatic supply is available. On the ground the wing anti-icing control valves open for 30 seconds only (test sequence). OFF
ON light goes off. Wing anti-icing cont rol valves close.
FAULT
The position of the anti- icing control valve is not the required position, or low pressure is detected. Note : The amber FAULT light c omes on briefly as the valves transit.
WARNINGS AND CAUTIONS
E / WD : FAILURE TITLE conditions WING A. ICE OPEN ON GND On ground, valves remain open more than 35 seconds after wing anti-ice is selected ON.
AURAL WARNING
MASTER LIGHT
SINGLE CHIME
MASTER CAUT
SYS FAULT Valve not open when wing anti-ice selected ON.
SD PAGE CALLED BLEED
LOCAL WARNING NIL
3, 4, 5, 6, 7, 8
ANTI ICE WING FAULT lt
3, 4, 5, 7, 8
L (R) VALVE OPEN Valve not closed when wing anti-ice selected off HI PR High pressure detect ed when the wing anti-ice is selected ON.
FLT PHASE INHIB
4, 5, 7, 8 NIL
NIL
NIL
3, 4, 5, 7, 8
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MEMO DISPLAY The "WING A. ICE" message is displayed in green, if the WING ANTI ICE pushbutton is ON.
8.1.3. ENGINE ANTI-ICE DESCRIPTION An independent air bleed from the high pressure compressor protects each engine nacelle from ice. Air is supplied through a two-position (open and closed) valve that the flight crew controls with t wo pushbuttons, one for each engine. The valve automatically closes, if air is unavai lable (engine not running). When an engine anti-ice valve is open, the EPR limit is automatically reduced and, if necessary, the idle EPR is automatically increased for both engines in order to provide the required pressure. If elect rical power fails, the valves open.
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C ONTROLS AND INDICATIONS ENG 1 (2) pb sw ON
Iight comes on blue. ECAM MEMO displays "ENG A. ICE". Engine anti-ic e valve opens if bleed a ir is available from the eng ine. Continuous ignition is selected when the valve is opened and the ANTI ICE ENG pushbutton switch is selected ON. This makes the IGNITION memo appear on the ECAM.
OFF
ON light goes out. Engine anti- ice valve c loses.
FAULT
Amber light comes on, and caution messa ge appears on ECAM, if the position of the anti-icing valve disagrees with the ENG 1 (2) pushbutton selection. Note : T he amber FAULT light c omes on briefly as valve transits.
WARNINGS AND CAUTIONS
E / WD : FAILURE TITLE conditions ENG 1(2) VALVE OPEN Valve disagree in the open position. ENG 1(2) VALVE CLSD Valve disagree in the closed position.
SD AURAL MASTER PAGE LOCAL WARNING LIGHT CALLED WARNING
FLT PHASE INHIB
SINGLE CHIME
3, 4, 5, 7, 8
MASTER NIL CAUT
ENG 1 (2) ANTI ICE FAULT lt
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MEMO DISPLAY This display shows "ENG A. ICE" in green, if one or both ENG A. ICE pushbutt ons are ON.
8.1.4. WINDOW HEAT DESCRIPTION The aircraft uses electrical heating for anti-icing each windshield and demisting the cockpit side windows. Two independent Window Heat Computers (WHCs), one on each side, automatically regulate the system, p rotect it against overheating, and indicat e faults. Window heating comes on: automatically when at least one engine is running, or when the aircraft is in flight. manually, before engine start, when the flight crew switches ON the PROBE/WINDOW HEAT pushbutton switc h. Windshield heating operates at low power on the ground and at normal power in flight. The changeover is auto matic. Only one heating level exists for the windows.
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C ONTROLS AND INDICATIONS PROBE/WINDOW HEAT pb AUTO
Probes/Windows are heated automatically: - in flight, or - on the ground (except TAT probes) provided one engine is running.
ON
Probes and windows are heated permanently. Blue light comes on.
WARNINGS AND CAUTIONS
E / WD : FAILURE TITLE conditions
SD AURAL MASTER PAGE LOCAL WARNING LIGHT CALLED WARNINGS NIL
L(R) WINDSHIELD Failure of L or R windshield heating
SINGLE CHIME
MASTER CAUT
NIL
NIL
FLT PHASE INHIB
NIL 3, 4, 5, 7, 8
L+R WINDSHIELD Failure of both windshield heating L(R) WINDOW Failure of L or R window heating
8.1.5. PROBES HEAT DESCRIPTION Elect rical heat ing protects: pitot heads static ports Angle-Of- Attack probes (AOAs) Tot al Air Temperatu re (TAT) probes Three independent Probe Heat Co mputers (PHCs) auto matically cont rol and monitor: Captain probes F/O probes
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STBY probes
They protect against overheating a nd indicat e faults. The probes are heated: automatically when at least one engine is running, or when the aircraft is in flight manually, when the flight crew switches ON the PROBE/WINDOW HEAT pushbutton switch On the ground, the TAT probes are not heated and pitot heating operates at a low level (the changeover to normal power in flight is automatic).
C ONTROLS AND INDICATIONS PROBE/WINDOW HEAT pb AUTO
Probes/Windows are heated automatically: - in flight, or - on the ground (except TAT probes) provided one engine is running.
ON
Probes and windows are heated permanently. Blue light comes on.
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WARNINGS AND CAUTIONS
E / WD : FAILURE TITLE conditions CAPT (F/O) PITOT CAPT (F/O) L(R) STAT CAPT (F/O) AOA CAPT (F/O) T AT Failure of corresponding probe heating
SD AURAL MASTER PAGE LOCAL WARNING LIGHT CALLED WARNING SINGLE CHIME
MASTER NIL CAUT
NIL
FLT PHASE INHIB 3, 4, 5, 7,8
STBY PITOT STBY L(R) STAT STBY AOA Failure of corresponding probe heating CAPT (F/O) (STBY) PROBES Failure of one probe heat channel/computer CAPT + F/O PITOT CAPT + STBY PITOT F/O + STBY PITOT Failure of the corresponding probes heating
4, 5, 8
ALL PITOT Failure of CAPT, F/O and STBY probes heating
8.1.6. RAIN REMOVAL DESCRIPTION WIPERS Each front windshield has a t wo-speed electric wiper. A rotary select or controls eac h. RAIN REPELLENT In moderate to heavy rain, the flight crew can spray a rain repellent liquid on the windshield to improve visibility.
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After about 30 sec onds, the windows is c overed by spray. Separate pushbuttons control the rain repellent application on each side of the windshield.
C ONTROLS AND INDICATIONS OVERHEAD PANEL See above scheme. WIPER rotary selector Each rotary selector controls its wiper at low or high speed. When turned off, the wiper stops out of view. RAIN RPLNT pushbutt ons Each of these buttons controls the application of rain repellent fluid to the corresponding side of the front windshield.When the flight crew pushes the button, the timer applies a measured quantity of rain repellent t o the windshield. To repeat t he cycle, the flight c rew must push the button again.This function is inhibited when the aircraft is on the ground and the engines are stopped.
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REAR COCKPIT
RAIN RPLNT pressure indicator This gauge shows t he nitrogen pressure in the rain repellent bott le. When the needle is in the yellow sector the bottle should be replaced. RAIN RPLNT quantity indicator When the REFILL float is in view the bottle should be replaced.
8.1.7. ICE DETECTION SYST EM DESCRIPTION VISUAL ICE INDICATO R An external visual ice indicator is installed between t he two windshields. The indicator has also a light.
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8.1.8. ELECTRICAL SUPLY BUS EQUIPMENT LIST NORM
AC WING ANTI ICE
L and R SHUT OFF VALVES
ENG ANTI ICE CLOSURE
VALVE
WINDOW HEAT
WHC
PROBE HEAT
2
DC2
1
DC1
2
DC2
R
AC2
PHC
CAPT
TAT
WIPER
RAIN REPELLENT ICE DETECT SYSTEM
DC1
AC1
AOA
RAIN REMOVAL
1
L
PITOT
AC ESS
DC ESS SHED
HEATING POWER
STATICS
DC
EMER ELEC
X
F/O
DC2
STBY
DC1
CAPT and STBY
DC1
F/O
DC2
CAPT
X (1)
F/O
AC2
STBY
AC1
CAPT
SHED
F/O
AC2
STBY
AC1
CAPT
AC1
F/O
AC2
CAPT
DC1
F/O
DC2
CAPT
X
F/O
DC2
DETECTOR 1
AC1
DETECTOR 2
AC2
HOT
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PERFORMANCE 8.2.1. CONTAMINATED RUNWAY
For performance calculations, RWY contamination has been divided into two categories which are determined by the depth of the contaminant. For each of these categories an equivalent depth of contaminant has been defined for which the performance deterioration is the sa me. Note: 1. On a damp runway no pe rformanc e degradation should be considered. 2. It is not recommended to t ake off from a runway c overed with more than 4 inches of dry snow or 1 inch of wet snow. WET RUNWAY and EQUIVALENT Equivalent of a wet runway is a runway covered with or less than: 2 mm (0.08 inch) slush 3 mm (0.12 inch) water 4 mm (0.16 inch) wet snow 15 mm (0.59 inch) dry snow CONTAMINATED RUNWAY An equivalence bet ween depth of slush and snow has been defined: 12.7 mm (1/2 inch) wet snow is equivalent t o 6.3 mm (1/4 inch) slush 25.4 mm (1 inch) wet snow is equivalent to 12.7 mm (1/2 inch) slush 50.8 mm (2 inches) dry snow is equivalent t o 6.3 mm (1/4 inch) slush 101.6 mm (4 inches) dry snow is equivalent to 12.7 mm (1/2 inch) slush Contaminated runway parameters c an include t he following data: Runway fric tion coefficient; Braking action; Conta mination c haract eristics and measurements. For Take-off and landing performance calculations use contamination characteristics and measurements only. No conversion is to be done from runway friction coefficients and/or braking action measurements to determine the contamination status of the runway for take-off and landing performances c alculations.
8.2.2. TAKE-OFF PERF ORMANCE CALCULATIONS Use cont amination c haract eristics and measurements t o enter the EFRAS software. When the level of contamination permits, use “WET runway and EQUIVALENT” or “CONTAMI NATED runway EQ UIVALENT” tables in FCOM. Note: “WET runway and EQUIVALENT ” or “CONTAMINATED runway EQUIVALENT” tables are available on the reverse side of the normal C/L. Performanc e penalties for takeoff are c omputed with the following assumptions: The contaminant is in a layer of uniform dept h and density over the entire length of the runway.
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Antiskid and spoilers are operative. The frict ion coefficient is based on studies and c hecked by actual tests. The screen height at the end of takeoff segment is 15 feet, not 35 feet.
In addition, fo r contaminated runways only: There is drag due to rolling resistance of the wheels. There is drag due to spray on the airframe and gears. Reve rse thrust is used for the dec eleration phase. Maximum thrust is used for takeoff. Note: The net flight path c lears obstac les by 15 feet instead of 35 feet.
8.2.3. LANDING DISTANCE CALCULATIONS Use the landing distance tables given in QRH together with “WET runway and EQUIVALENT” or “CONTAMINATED runway EQ UIVALENT” tables in FCOM. Note: “WET runway and EQUIVALENT” or “CONTAMINATED runway EQUIVALENT ” tables are available on reverse side of the normal C/L. For flight planning purpose, factorized landing distances have to be used as per table below: RUNWAY CONDITION
DRY WET CONTAMINATED
To determine LANDING DISTANCE REQUIRED multiply: ACTUAL LANDING DISTANCE DRY ACTUAL LANDING DISTANCE DRY ACTUAL LANDING DISTANCE CO NTAMINATE D
By
X 1.67 X 1.92* X 1.15**
*1.92 = 1.67 X 1.15 **Required landing distance on CONTAMINATED runway cannot be shorter than required landing distanc e on WET runway
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FLIGHT CREW PROCEDURES
9.1.
LIMITATIONS
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Take off f rom an icy runway is not reco mmended. It is not recommended to take off from a runway covered with more than 4 inches of dry snow or 1 inch of wet snow. Operation on runway covered with ICE and no reported breaking action is not permitted. Operation on narrow runway contaminated by compacted snow or ice is not permitted. Take-off is prohibited in the following weat her conditions: ‐ Heavy snow ( +SN) ‐ Heavy snow pellets ( +GS) ‐ Heavy snow grains (+SG) ‐ Heavy ice pellets (+PL) ‐ Moderate/heavy freezing rain (FZRA, +FZ RA) ‐ Moderate/heavy hail (GR, +GR) Reduced trust take- off (FLEX TO) on c ontaminated runway is not permitt ed. The Captain is PF for operations on contaminated runways. The following cross-wind limitat ions apply on c ontaminated runway:
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(*) Normative friction coefficient is used in Russia and some countries of the former Soviet Union. In case it will not be possible to determine which system or which unit is used, assume t hat normative frict ion coefficient is used. Note: Auto roll-out guidance is demonstrated on dry and wet runways only.
9.2.
OPERATION IN ICING CONDITIONS
9.2.1. ICING CONDITIONS Icing conditions may be expected when the OAT (on ground and for takeoff), or when the TAT (in flight) is at or below 10°C, and there is visible moisture in the air (such as clouds, fog with low visibility of 1000 meters or less, rain, snow, sleet, ice crystals) or standing water, slush, ice or snow is present on the taxiways or runways.
9.2.2. FLIGHT IN ICING CONDITIONS Wizz Air aircraft are certified for known-icing conditions. Whether or not an airplane type has been certified for flight in icing conditions, it is not certified for take- off or flight when carrying ice deposits resulting from ground operations or storage. The Commander shall therefore ensure that de- and anti-icing operations appropriate to the conditions are carried out on the ground before departure and that pre-flight inspection indicates that all significant deposits of hoar, frost, ice and snow have been removed before any attempt is made to take off. Any effect of ground de-icing on airplane performance must be taken into account. All equipment for anti- or de-icing shall be used according to the prevailing conditions and as reco mmended in the AFM.
9.2.3. PROCEDURE See 9.4.7.
9.3.
ON GROUND DE-ICING/ANTI ICING
9.3.1. TERMI NOLOGY IC ING CO NDITIONS Means an at mospheric environment that may c ause ice t o form on t he aircraft or in the engines. Icing conditions may be expected when the OAT (on ground and for takeoff), or when the TAT (in flight) is at or below 10°C, and there is visible moisture in the air (such as clouds, fog with low visibility of 1 000 meters or less, rain, snow, sleet, ic e c rystals) or standing water, slush, ice or snow is present on the taxiways or runways. CLEAR ICE Clear ice, also referred to as "glaze ice", is a crystal clear and solid layer of ice on the top of airplane critic al surfaces, which can almost not be detec ted visually and could only be
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checked by "hands-on " check (tactile). Clear ice is formed by a relatively s low freezing of large super cooled droplets from freezing fog, drizzle or rain. Clear ice as a result of rain or high humidity on cold soaked wings may even occur at ambient temperatures of 15oC. An indication that this condition may exist is, when ice/frost has formed on the lower wing skin surface at the fuel tank area. (Upper wing skin temperature can be lower than OAT due to the radiation when the aircraft was parked outside overnight or when after flight cold fuel still contact s the wing upper skin.). Clear Ice may be hidden unde r a layer of snow or slush on t he wings etc . BLADE ICE Blade Ice can form on the bac k side of fan blades when the engine rotates overnight, in a humid at mosphere, at t emperatures c lose to or below 0 degrees C. It c an be det ected reliably only by a tactile check of the rear of the blade. It must be removed, using hot air, befo re dispatc h. RIME ICE Rime ice is a whitish rough deposit of ice formed by instantaneous freezing of small super-cooled water droplets (e.g.: caused by freezing fog, drizzle or rain) on any part of the airplane, in particular on t he windward side. FROST Frost forms by the process of sublimation when the temperature of a collecting surface and the dew point are both below freezing. The water vapour changes directly to ice in the form of frost. This is a white, crystalline coating. Frost can form on aircraft surfaces in clear air when the airplane is parked in sub-zero temperatures. DE- IC ING De-icing is a method by which ice, slush or snow is physically removed from the airplane by means of spraying the airplane w ith de- icing fluid. ANTI-ICING Anti-icing is a precautionary method to provide protection against the formation of ice, slush and snow for a limited period by applying a layer of anti-icing fluid on the airplane critical surfaces, which is assumed to flow off during take- off. ONE-STEP DE- IC ING/A NTI- IC ING With this method de-icing and anti-icing are applied in one single step. One-step deicing/anti-icing includes anti-icing. In this process, the residual fluid film - regardless of the type of fluid used - will provide only a very limited duration of anti- ice protect ion. TWO STEP DE- IC ING/A NTI- IC ING With this method de-icing is carried out in the first step with just hot water or a hot mixture of anti-icing fluid and water. Anti-icing is carried out in the second step with a hot or cold anti-icing fluid, undiluted or diluted with water, to give protection against freezing or refreezing. This second step (anti-icing) must be performed within three minutes after the st art of the first st ep and, if needed, area by area. Concentration of t he anti-icing fluid mixture for the second step is based upon OAT and weather conditions to provide t he desired holdover t ime. PREVE NTIVE ANTI- IC ING Preventive anti-icing can be carried out as a precautionary measure well in advance of a flight (e.g. during overnight stop) to prevent frost, ice, snow or slush to form and/or accumulate on the p rotected surfaces of an aircraft. This treatment will be applied before the flight crew arrives at the aircraft.
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9.3.2. CRITICAL SURF ACES Critical surfaces are: Leading edges and upper surfac es of wings Vertical and horizontal st abilize rs All control surfaces Slats and flaps
9.3.3. EFFECT ON FROZEN DEPOSIT Effects of frozen deposits are: Loss of lift More drag More weight Increase of stall speed Stall before warning Stall at lower angle of attack Less efficient flight c ontrols Loss of engine thrust Fan/engine vibration Incorrect readings on instruments Frozen wheels/brakes/landing gear
9.3.4. RESPONSIBILITIES COMMANDER Although no pe rson may release or take off with an aircraft with f rozen deposits adhering to the aircraft surfaces, the Commander has the final responsibility for ensuring that the all ai rcraft surfaces are free of f rost, ice, snow or slush prior to departure and at take -off. This is called the "Clean Aircraft Concept". Dry Snow is not to be left on the surfaces to blow off during the take-off run. Thin hoarfrost is ac ceptable on the upper surface of the fuselage. On the underside of t he wing tank area, a maximum layer of 3 mm (1/8 inch) of frost will not penalize takeoff performance. Note: 1. Thin hoarfrost is typically a white crystalline deposit, which usually develops uniformly on exposed surfaces on cold and cloudless nights; it is so thin that a person can distinguish surface features (lines or markings) beneath it. 2. The co mmander may request ground agents to move the st airs next to the wing to satisfy himself that upper wing is free of clear ice. Should this not be possible, the commande r may c onsider preventive de -icing. GROUND ENGINEER AND/OR DE-ICING/ANTI-ICING AGENT At stations where a ground engineer is available, the ground engineer is responsible for release of the aircraft free of frost, snow or slush. He is also responsible for the correct and complete de-ic ing/anti-icing treatment of t he aircraft . At stations where no ground engineer is available, the de-icing/anti-icing handling agent is responsible for the correc t and complete de -ic ing/anti-ic ing treat ment of t he aircraft. Before commencement of de-icing/anti-icing treat ment, he shall report it t o the
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Commander. He shall also report the applicable anti-icing code (type and mixture) and the actual starting time of t he treatment. Afte r co mpletion of the de -icing/anti-icing treatment, the aircraft shall be thoroughly checked. The de-icing/anti-icing handling agent shall carry out these chec ks. To release the aircraft for f lying, the Commander has to be assured that this check has been carried out properly. If only a preventive antiicing treatment was carried out, it shall also be reported t o the Commander.
9.3.5. DE-ICING AND ANTI-IC ING FLUIDS ISO STANDARDS Procedures used in cold weather operation with respect to de-icing and anti-icing are based upon standards from the International Standards Organization (ISO). The ISO anti-icing code has been developed to represent the quality of the treatment the aircraft has received. The Commander can use this code, in correlation with the holdover time tables, to evaluate the amount of protection he has got against re- freezing. FLUID TYPES Only the following three fluid t ypes are approved for Wizz Air operation (ISO and SAE specifications are c onsidered similar): ISO TYPE I ISO Type I de-icing/anti-icing fluids provide a very limited protection against re-freezing during precipitation conditions. The concentration of this fluid is not related to the holdover time. Due to their properties ISO Type I fluids form a thin liquid wetting film that provides limited holdover time especially in conditions of freezing precipitation. With this type of fluid increasing the concentration of the fluid in the fluid/water mix would not provide additional holdover t ime. ISO TYPE II AND TY PE IV ISO Type II and Ty pe IV de-icing/anti-icing fluids provide a n extensive protect ion against re-freezing during precipitation conditions. ISO Type II/IV fluids contain a pseudo-plastic thickening agent that enables the fluid to form a thicker liquid wetting film on external aircraft surfaces. This film provides a longer holdover time especially in conditions of freezing precipitation. With this type of fluid additional holdover time will be provided by increasing the concentration of the fluid in the fluid/water mix, with maximum holdover time available from undiluted fluid. For these fluids the concentration has a relation with the holdover time, so the following codes will be used: Code ISO Type ISO Type ISO Type ISO Type ISO Type ISO Type
II/100 II/75 II/50 IV/100 IV/75 IV/50
Ratio of type II or type IV 100% Type II 75% Type II 50% Type II 100% Type IV 75% Type IV 50% Type IV
Ratio of water 0% 25% 50% 0% 25% 50%
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9.3.6. HOLDOVER TIME The holdover time is the estimated time an anti-icing fluid will prevent frost, ice, snow or slush to form or accumulate on the protected surfaces of an aircraft under average weather conditions mentioned in the holdover time tables. The time of protection will be shortened in heavy weather conditions, heavy precipitation rates or high moisture content. High w ind velocities or jet blast may reduce holdover ti me below the lowest time stated in the range. Holdover times may also be reduced when airplane„s skin temperatu re is lower than OAT. The only acce ptable decision criterion is the shortest time within the applicable holdover time table cell. When weather conditions change after the Commander has determined the applicable holdover time, he shall determine a new applicable holdover t ime based o n the c hanged weather conditions. Anti-icing fluids remaining on the aircraft surfaces ensure ice protection. With a one-step de-icing/anti-icing operation the holdover time begins at the start of the operation and with a t wo-step operation at the start of the final (anti- icing) step. Holdover time will effectively run out when frozen deposits start to form/accumulate on treated aircraft surfaces. Just before take-off, the Commander shall make sure that the holdover time has not run out. If so, the aircraft has to be de-iced/anti-iced again. Under no circumstances can an airplane, that has been anti-iced, receive another coat of Type II/IV fluid on top of the existing film. If the holdover time is exceeded, surfaces must first be de-iced with a mixture of hot water and de-icing fluid, before another application of Type II/IV fluid is made. When the Commander is in doubt about the protection against refreezing within the holdover time, a visual check for the upper wing surfaces shall be made. If this check leaves doubt, t he aircraft has to be de-iced/anti-iced again.
9.3.7. PRECAUTIONS FOR DE- ICING/ANTI ICING FLIGHT C REW In order to have maximum benefit from the anti-icing protection, the de-icing/anti-icing treat ment should be carried out at t he lat est possible time after all passengers have boarded, all doors are closed, boarding ramps are removed and the aircraft is ready to depart, as the holdover time starts at the beginning of t he anti- icing treatment. Engines and/or APU may be running (idle) du ring de- icing/anti-icing treat ment, but air conditioning, anti-icing or bleed air shall be switc hed off as per AFM instruc tions. For this reason the ground engineer or de-icing/anti-icing handling agent has to report when the de-icing/anti-icing treatment will start. GROUND ENGINEER AND/OR DE-ICING/ANTI-ICING AGENT Ground engineers and/or de-icing/anti-icing agents are instructed to inform the Commander when the actual spraying commences. Reasonable precautions shall be made to minimize fluid entry into engines and other intakes. De-icing/anti- icing fluids must not be direct ed into the orifices of pitot heads, static vents or angle of at tack sensors. Before starting engines c heck that compressors and t urbines are free t o rotate.
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Wings, both horizontal stabilizers and both sides of the vertical fin must be treated the same way, not one side of t he aircraft different from the ot her. Any traces of de-icing/anti-icing fluids on cockpit windshield/windows must be removed prior to departure. Particular attention should be paid to windows fitted with wipers. In addition, any forward areas from which fluid may flow back onto windscreens during taxi and take-off must be clean prior to departu re.
9.3.8. HOLDOVER TIME TABLES Considering the weather conditions the Commander can determine the applicable holdover time from the tables for ISO Type I, ISO Type II or ISO Type IV. After de- icing/anti-icing treat ment a take-off is permitted, provided the ti me bet ween start of the final anti-icing treatment and take-off does not exceed the times mentioned in the Holdover T ime T ables for the prevailing weather conditions. Holdover Time Tables are Information" pages 6.2-6.5.
published
in
EAG
documentation
under
"Operations
Take-off is never allowed when the time from start of final anti-icing treatment up to take-off exceeds the applicable holdover t ime o r frozen deposits st art to accu mulate. In case of doubt, select the time that is more restrictive (e.g. use time for moderate instead of light). Use of light freezing rain holdover t imes fo r freezing drizzle is not acce ptable.
9.3.9. PROCEDURE See 9.4.4.
9.3.10.
RECORDING
An ATL entry shal l be made concerning the de- icing/anti- icing treat ment with the c ode of the applied fluid and the st arting ti me of the treatment (e.g.: ISO Type II/75; 15:28).
9.4.
FLIGHT –PHASES RELATED PROCEDURES
9.4.1. PRE-FLIGHT BRIEFING
During flight preparation/briefing check all weather reports, NOTAMs and SNOWTAM/MOTNE codes. For de-coding see EAG eRM, METEOROLOGY, SNOWTAM CODES and CODES, p. 1. 4. For flight planning purpose, use fact orized landing distances as per table below to determine usability of destination and alternate airports (Ref OM-B):
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To determine LANDING DISTANCE REQUIRED multiply: ACTUAL LANDING DISTANCE DRY ACTUAL LANDING DISTANCE DRY ACTUAL LANDING DISTANCE CONTAMINATED
By X 1.67 X 1.92* X 1.15**
*1.92 = 1.67 X 1.15 **Required landing distance on CONTAMINATED runway cannot be shorter than required landing distance on WET runway
In case of RWY contamination, crosscheck crosswind limitations (RWY contaminated) as per table below with reported/forecast wind to determine usability of departure, destination and alternate airports (Ref OM- B):
Consider applicability of any of the limitat ions as per 9.1 above. Consider increased fuel consumption for: de-icing at remote stand (running engines), increased taxi time, use of ice and rain protection systems for flight in icing conditions, holdings ( RWY c learing), etc . to determine requi red fuel for the planned flight.
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NOTE: The FC and especially the BA should not be taken as absolute due to the many methods of assessment used and the different variables such as ACFT weight, speed, braking pe rformanc e, tyres and undercarriage c haract eristics, etc.
9.4.2. COCKPIT PREPARATION The preparation and ground ope ration of the a ircraft, after it has been sitting idle in very low te mperatures, may p resent particular p roblems. In such c ases, the flight c rew should use the following procedures, which c omplement t he normal ope rating procedures. Ice accumulates on the aircraft when the air temperature approaches, or falls below, freezing (0°C) and t here is precipitat ion or c ondensation. Ice may also bui ld up when the aircraft is exposed to any form of moisture, after the surfac es have been cold-soaked during previous cruise flight at high altitudes, after the aircraft has been refueled with cold fuel, or after it has been exposed to low overnight air te mperatures. EXTERIOR INSPECTION - P REL IMINARY COCKPIT PREPA RATION ( normal p rocedures)
…………… COMPLETED
APU is started and air conditioning is on. - P ROBE/WINDOW HEAT
……………
ON
- SURFACES
…………… CHECKED FREE OF FROS T, ICE AND SNOW
All surfaces of the aircraft (critical surfaces: leading edges and upper surfaces of wings, vertical and horizontal stabilizers, all control surfaces, slats and flaps) must be clear of snow, frost and ice for takeoff. . Thin
hoarfrost
is
acceptable
on
the
upper
surface
of
the
fuselage.
Note : Thin hoarfrost is typic ally a white c rystalline depos it which usually deve lops uniformly on exposed surfaces on cold and cloudless nights ; it is so thin that a person can distinguish surface features (lines or markings) beneath it. On the underside of the wing tank area, a maximum layer of 3 mm (1/8 inch) of frost will not penalize takeoff performance. - FOLLOWING E QUIPMENT:
…………… CHECKED FREE OF FROST, ICE AND SNOW Landing gear assemblies (lever locks) and tires, landing gear doors. Engine inlets, inlet lips, fans (check for rotation), spinners, fan exhaust ducts. reverser assemblies.
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Drains, b leeds, probes (pitots, static ports, T AT sensors, angle of attack sensors). Fuel tank ventilation. Radome. Verify that the commercial water supplies are not frozen and have been refilled (t hese should have been e mptied prior to t he cold soak). After first engine st art - P ROBE/WINDOW HEAT
…………… AUTO
Heating wi ll continue t o operate but under aut omatic c ontrol. Apply c lear surfaces c oncept. In case on ground de-icing/anti-icing is required: Define applicable de-icing fluid, number of steps and estimated hold over time for the prevailing conditions (te mperatu re/contamination) using hold over ti me tables in EAG docu mentat ion, u nder "Operations Information " pages 6.2 -6.5. Inform handling agent for the required de-icing/anti-icing procedure, type of fluid and st eps. Info rm ATC of on- ground de- icing treat ment requirement in due ti me to avo id delays in cue (on first contact when requesting clearance, or at start up, the latest). Inform SCA.
9.4.3. TAKE-OFF PERF ORMANCE CALCULATIONS Use cont amination c haract eristics and measurements t o enter the EFRAS software. When the level of contamination permits, use “WET runway and EQUIVALENT” or “CONTAMI NATED runway EQ UIVALENT” tables in FCOM. Note: “WET runway and EQUIVALENT” or “CONTAMINATED runway EQUIVALENT” tables are available on reverse side of the normal C/L.
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Performanc e penalties for takeoff are c omputed with t he following assumptions: The contaminant is in a layer of uniform depth and density over the entire length of the runway. Antiskid and spoilers are operative. The frict ion coefficient is based on studies and chec ked by actual tests. The screen height at the end of takeoff segment is 15 feet, not 35 feet. In addition, fo r contaminated runways only: There is drag due to rolling resistance of the wheels. There is drag due to spray on the airframe and gears. Reve rse thrust is used for the dec eleration phase. Maximum thrust is used for takeoff. Note: The net flight path c lears obstac les by 15 feet instead of 35 feet.
9.4.4. ON GROUND DE-ICING/ANTI-ICING In all situations, it is the Captain’s responsibility to decide if the ground crew must deice/anti-ice the aircraft, and/or if additional deicing/anti-icing treatment is required. Note: De-ic e Engine fan blades by hot air only (use ground air heater). The flaps extension, trim settings and flight control check should take place after deicing.
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CAUTION: Make sure that t he low or high-pressure g round connect ors do not supply any external air to t he aircraft. If it is necessary for the ground grew to repeatedly anti- ice the aircraft , they must de-ice the surfaces with a hot fluid mixtu re before ap plying a new layer of anti-icing fluid. Make sure that the ground crew uses the correct de-icing/anti-icing fluids, in accordance with the applicable requirements and Aircraft Maintenance Manual (AMM) instructions. The aircraft can be deiced or anti-iced when the APU and engines are either stopped or running. Howeve r, do not start the engines when the ground crew is spraying fluid on the aircraft. CAUTION: The ground crew should take care when spraying deici ng fluid, and make sure t hat t he engine and APU do not ingest any fluid. Do not move flaps, slats, ailerons, spoilers, or elevators, if they are not free of ice. Always ensure t hat both the left and right sides of the aircraft receive the same, c omplete, and sy mmetric al deicing/anti-ic ing treatment. Note: the De-icing on ground C/L is available on the back of the normal C/L. DE-ICING AFTE R PUSHBACK AND BEFORE ENGINE STA RT
The pushback is done after “start C/L” completed (beacon ON); Perform the “on ground de -icing C/L” (on the back of normal C/L); After de-icing resume normal start procedure and operations.
DE-ICING AFTE R ENGINE START The pushback and start procedures are done normally.
When the second engine is started and peak EGT has bee n reached both pi lot s are to start their chrono for the 5 minute s engine warm- up request; PF is to: Dismiss g round crew, when appropriate; Select Eng Mode Select or to “NORM” ; Select APU Bleed OFF. PNF is to: Select APU OFF; Select STS if required (Pack 1 under INOP SYS is normal at this stage because it has not recycled after start. It may be ignored because a Master Caution will be activated if it does not recover). When clear signal received from ground crew, PF will announce “After Start Check-List postponed, request t axi clearance”. When reaching t he de-ic ing area: Contact de-icing ground crew; Apply the on ground de-icing C/L (on the back of normal C/L);
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DE-ICING PROCEDURE BEFORE SPRAYING FLUID: -
CAB PRESS MODE SEL ENG BLEE D 1 + 2 APU BLEED DITCHING pushbutton
………………………………………………… ………………………………………………… ………………………………………………… …………………………………………………
CHECK AUTO OFF OFF ON
Outflow valve, pack valves, and avionic ventilation inlet and extract valves close. This prevents de-icing fluid from entering the aircraft. Avionic ventilation is in a closed circuit with both fans running. In view of the low OAT, t here is no time l imit fo r this configuration. Note: If the "VENT AVNCS SYS FAULT " warning appears, reset the AEVC circuit breaker at the end of the aircraft de-icing procedure.AIR COND/AVNCS VENT/CTL D06 on 49VU.AIR COND/AVNCS/VENT/MON G Y17 on 122 VU. - THRUST LEVERS - "AIRCRAF T PREPARED FOR SPRAYING"
……………………………………….. ………………………………………..
CHECK IDLE INFORM GROUND C REW
UPON COMPLETION OF THE SPRAYING OPERATION: - DITCHING pushbutton ………………………………………………… - OUTFLOW VALVE ………………………………………………… On the ECAM PRESS page, confirm that the outflow valve indication reaches the open green position to avoid any unexpect ed aircraft pressurization. - ENG BLEED 1 + 2 …………………………………………………
OFF CHECK OPEN
ON
At least 60 seconds after APU start, or on completion of spraying operation: - APU BLEED ON ………………………………………………… - PITOTS and S TATICS ………………………………………………… CHECK (ground crew) - GROUND EQUIPMENT ………………………………………………… REMOVE - DE- IC ING/ANTI- IC ING ………………………………………………… RECEIVED REPORT The information from ground personnel, who performed the de -icing and post-application check, must include (ANTI-ICI NG CODE): Type of fluid used The mix ratio of fluid to water (for example 75/25) When the holdover time began. After de- icing completed, ground c rew must confirm via interpho ne the number of steps, mix and quantity of de-ic ing fluid used for each step, starting time of t he second step. Commande r will fill t he de-icing box in the ATL immediately. Quantity of de-icing fluid used will be sent via ACARS (this may be done in cruise). - NORMAL PROCEDURE RESUME ………………………………………………… Apply a ppropriate no rmal procedu res. Pay special att ention to t he flight c ontrol check.
PNF is to complete the after start scan;
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When clear signal received from ground crew, PF ask for “AFTER START CHECKLIST” (PF verifies Pitch Trim MAC from FUEL PRED); Resume normal ope rations.
In freezing precipitation, perform the appropriate checks to evaluate aircraft icing. Base the dec ision on whether to t akeoff, or t o re- protect t he aircraft, on t he amount of ice that has built up on the critical surfaces since the last de-icing, as revealed by a personal inspection from the inside and outside of the aircraft. Make this inspection before the holdover time expires, or just before takeoff. Note : If the fuselage has been sprayed, there is a risk of de-icing fluid ingestion by the APU air intake, resulting in specific odors, or SMOKE warnings. Thus, consider APU BLEED OFF during takeoff.
9.4.5. TAXI OUT/IN After engines st art: ENG A NTI ICE ....................................................................... AS RQRD During ground operation, when in icing conditions and the OAT is plus 3 deg C or less, or if significant engine vibration occurs, the following procedure should be applied for ice shedding: CAUTION: If, during thrust increase, t he aircraft starts to move, im mediately retard the thrust levers t o IDLE. If ground surface conditions and the environment permit, the flight crew should accelerate the engines to minimum 50% of N1 at intervals not greater than 15 minutes. There is no requ irement t o maintain the high trust settings. In addition, this engine acceleration should also be performed just before take-off, with particular at tention to engine parameters to ensure normal engine operation. ATC should be informed of the intention to carry out this run up for traffic sequencing c onsiderations. Note: When performing the static run-up, the 61-74 % N1 range should be avoided. If ENG ANTI ICE is selected ON and the valve(s) do not open (FAULT light(s) remain on), increase the N2 of the associated engine by about 5 %. When the valves are open, retard the t hrust lever(s) to idle. If ENG ANTI ICE is switc hed on, the IGNITION memo appears on the ECAM because continuous ignition is auto matically select ed. WING ANTI ICE.......................................................................AS RQRD When wing ANTI ICE is switc hed-on on t he ground, the ant i ice valves open for about 30 seconds (test sequence) then close as long as t he aircraft is on ground.
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- FOLLOWING TAXIING PROCEDURES Avoid high t hrust sett ings. When taxiing on slippery surfaces, stay well behind preceding aircraft. Taxi at low speed. Note t hat antiskid does not operate at low taxi speeds. On slippery taxiways during turns with large nose wheel steering angles, noise and vibration may result from the wheels slipping sideways. Keep speed as low as possible to make a smooth turn with minimum radius. Differential power may be needed. If taxiing in icing conditions with precipitation on runways and taxiways c ontaminated with slush or snow: Before takeoff keep flaps/slats retracted until reaching the holding point on the takeoff runway t o avoid contaminating the mechanism. At holding point extend FLAPS and perform “Change of RWY/Intersection” C/L before line -up. When taxiing in aft er landing, do not retract the flaps/slats t o avoid damage of t he struct ure. ………………………………
CONSIDER
After engine shutdown make a visual inspection to determine that t he flap/slat mechanism is free of c ontamination. When the mechanism is clean, use the following procedure to retract the flaps/slats before the aircraft electric network is de-energized: Set the YELLOW ELEC PUMP to ON Check that the BLUE ELEC PUMP is in the AUTO position Set the BLUE PUMP OVRD to ON Retract the FLAPS and monitor retraction on ECAM page. Select off the YELLOW ELEC PUMP and BLUE PUMP OVRD and resume w ith normal proc edure. Note: 1. On contaminated runways and taxiways, the radio altitude indications may fluctuate and auto call outs or GPWS warnings may be act ivated. Disregard them. 2. During taxi on snowy runways, the radio altimeters may not compute any data and the ECAM warnings 'DUAL ENG FAILURE', 'ANTI ICE CAPT TAT FAULT', 'ANTI ICE F/O TAT FAULT', 'L/G SHOCK ABSORBER FAULT' may be triggered. Disregard these warnings.
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9.4.6. TAKE-OFF - FOLLOWING TAKEOFF PROCEDURES For contaminated runways, select MAX T O. Do not abort takeoff for minor deficiencies even at low speeds. If you have to abort takeoff, maintain directional control with the rudder and small inputs t o the nose wheel. If nec essary, use differential braking to regain the center line when stopping distanc e permits. Do not lift the nose wheel before VR in an attempt to avoid splashing slush on t he aircraft, because this produces additional ae rodynamic drag. Rotate, lift off and retract gear and high lift devices in the normal manner.
……………………………….
CONSIDER
9.4.7. CLIMB/CRUISE/DESCENT Consider Operation in icing conditions (see 9.2.) ENGINE ANTI-ICE
ENGINE ANTI ICE must be ON during all ground and flight operations, when icing conditions exist, or are anticipated, except during climb and cruise when the SAT is below - 40° C. ENGINE ANTI ICE must be ON before and during a descent in icing conditions, even if the SAT is below - 40° C.
WING ANTI-ICE
WING ANTI ICE may either be used to prevent ice formation, or to remove ice accumulation from the wing leading edges. WING ANTI ICE should be selected ON, whenever there is an indication that airframe icing exists. This can be evidenced by ice accumulation on the visual ice indicator (located between the two cockpit windshields), or on the windshield w ipers.
CAUTION: Extende d flight, in icing conditions with the slats extended, should be avoided. If there is evidence of significant ice accretion and to take into account ice formation on non heated st ructure, the mini mum speed should be: In configuration full, VLS + 5 knots, and the landing distance must be multiplied by 1.1. In configuration lower than FULL, VLS + 10 knots, and the landing distance in CONF 3 must be multiplied by 1.15. If there is evidence of ice accretion on de-iced parts (WING ANTI ICE inoperative) of the airf rame, the minimu m speeds should be: In clean configuration, VLS + 15 knots. In CONF 1, 2, 3, FULL, VLS + 10 knots, refer to QRH part 2 or FCOM 3.02.80 for landing distance determination.
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9.4.8. APPROACH AND LENDING Consider the limitations defined in 4.1, including cross wind limitations for contaminated RWY, and landing distance before commence ment of the approach. LANDING DISTANCE CALCULATIONS Use the landing distance tables given in QRH 4.02/4.03 together with “WET runway and EQUIVALENT” or “CO NTAMINATE D runway EQ UIVA LENT” tables in FCOM. CORRECTIONS FOR LOW TEMPE RATURE OPERATIO NS When the approach is flown in low temperature conditions (equal o r below ST D-20) and the DA/MDA refers to baro-altimeter, the MDA value inserted in the MCDU should be corrected. The following table gives the correction to be added to DA/MDA according the ISA condition (left column). The upper line is t he DH/MDH rea d on the approach c hart (height and not altitude): MDH ISA-20 ISA-30 ISA-40 ISA-50
100 0 10 10 20
200 10 20 30 40
300 20 30 40 60
400 30 40 60 80
500 30 50 80 100
600 40 70 90 120
700 50 80 110 140
800 60 90 129 160
900 60 100 140 190
1000 70 110 160 210
When the approach is flown in low temperature conditions (equal o r below ST D-20) and no altitude clearly given by ATC (just cleared for approach ‟ ), the intermediate altitude should also be corrected. The following table gives the correction to be added to the intermediate altitude according the ISA condition (left column). The upper line is the intermediate height read on the approach c hart (height and not altitude): INTERMEDIATE HEIGHT ISA-20 ISA-30 ISA-40 ISA-50
1500
2000
2500
3000
3500
4000
4500
110 170 240 310
150 230 320 420
190 290 400 520
220 340 480 630
260 400 560 730
300 460 640 840
330 520 720 940
5000 370 580 800 1050
5500 410 640 880 1150
Caution: ATC takes already into account the temperature factor, any cleared altitude ordered by ATC has to be followed.
6000 450 690 960 1260
Page 118
TRAINING DEPARTMENT
COLD WEATHER OPERATIONS
REV 0 [5/2012]
LANDING - FOLLOWING LANDING PROCEDURES ………………………………… Avoid landing on contaminated runways if the antiskid is not functioning. The use of autobrake LOW or MED is recommended provided that t he contamination is evenly d istributed. Approach at the normal speed. Make a positive t ouchdown after a brief flare. As soon as the aircraft has touched down, lower the nose wheel onto the runway and select maximum reverse thrust. Do not hold the nose wheel off the ground. If necessary, the maximu m reverse thrust c an be used until the aircraft is fully st opped. If the runway length is limiting, apply the brakes before lowering the nose gear onto the runway, but be prepared to apply back stick to counter the nose down pitch produced by the brakes application. (The strength of this pitching moment will depend on the brake torque att ainable on the slippery runway). Maintain directional control with the rudder as long as possible, use nose wheel steering with c are. When the aircraft is at taxi speed, follow the rec ommendations fo r taxiing. Note :
CONSIDER
If there is snow, visibility may be reduced by snow blowing forward at low speeds if reversers are not cancelled.
9.4.9. SECURING THE AIRCRAFT SECURING THE AIRCRAFT FOR COLD SOAK After switching off all bleeds, and before switc hing off AC power: - DITCHING pushbutton
………………………………………………………
ON
This closes the outf low valve, t he pack valves, and t he avionic ventilation inlet and extract valves. - PARKING BRAKE
………………………………………………………
OFF
Check choc ks in place, and release t he parking brake to preve nt brakes from freez ing. After switching off the batte ries: - DITCHING pushbutton - P ROTECTIVE COVERS
……………………………………………………… ………………………………………………………
Install protec tive covers and plugs to protect the aircraft and engines from snow and ice.
OFF INSTALL
