ATPLessentials: Mass and Balance

Mass refers to the quantity of matter in a body as measured by its inertia

Holiday Charter

Mass & Balance 1

• Mass of individual Pax may be determined from a verbal statement

Other

by or on behalf of the pax if < 6 seats available

• Considerable amout of pax or baggage exceeding the standard

Infant (0y ...2y)

masses: Operator should use individual masses or add an adequate mass increment • Weighing machine for pax: Capacity ≧150kg; graduations of 500g • Max weight of cabin crew in 19-seat AC on Holiday Charter = 75kg • Baggage = Personal belongings • Standard mass for baggage (15kg) may be used if >20 seats • If no carry-on baggage is carried: Subtract 6kg from standard masses

35kg; 1seat

Child (2y ...12y)

♂ 83kg

♀ 69kg

Adult

84kg

or avg. of 76kg

Limitations Structural

Performance

Other

Limiting in “Hot & High” conditions

Regulated TOM = Lower of both structural and performance limited TOM

= MRM • Maximum certified Ramp (or Taxi) Mass • Mass an AC may be loaded prior to engine start • Fixed value listed in AC Flight Manual

Definitions

Ramp Mass - RM

Taxi Fuel

Takeoff Mass - TOM

= MTOM • = max. permissible total AC mass @ start of TO run • May not be exceeded on any TO • Normally the limiting factor on TL on long distance flights

Traffic Load (TL) Useful Load (UL)

• Trip Fuel (TF)

Operating Mass - OM

Takeoff (useable) fuel (TOF)

• Usable TOM: Consider MLM + Fuel burn

Takeoff (useable) fuel (TOF)

Landing Mass - LM

• If exceeded, undercarriage could collapse on LDG

• Contingency • Alternate • Final reserve • Passengers • Cargo

Traffic Load (TL)

= MLM

Zero Fuel Mass - ZFM

= MZFM

•

• Structural limit due to max permissible bending moment

AC mass with no USEABLE fuel

If AC < max. structural LM but > max. performance limited LM:

• Tire temperature limits could be exceeded • Runway may be too short • No go-around possible •Structural fatigue increased

•Limited by strength of runway •Amount of fuel to jettison: To a safe level at or below regulated Landing Mass

@ wing root (on AC without central tank)

• Imposes fuel dumping from the inner wing tank first • Regulatory limitation • Calculated for a LF of +2.5g • Fixed value stated in AC Operating Manual •Limiting factor on TL on short legs with minimum fuel

• Operator must establish

TL by actual weighing or in accordance with standard masses specified in JAR-OPS Part J

Dry Operating Mass - DOM Standard Masses:

Crew

• Flight Crew = 85kg • Cabin Crew = 75kg • Incl hand baggage allowance

Responsibility for determination lies with the operator!

Aircraft must be weighed:

•

Includes fixed equipment needed to carry out a specific flight AC mass ready for a specific type or operation

• Crew baggage

Operating • Catering • Removable pax equipment Items • Potable water • Lavatory liquids

Weighing

•

Specific equipment integral to the particular aircraft configuration

• On initial entry into service • If the mass and balance records have not been adjusted for alterations

Basic Empty Mass - BEM • • •

or modifiactions

• Whenever the cumulative changes to the dry operating mass exceed plus or minus 0.5% of the maximum landing mass

• If the cumulative change in CG position exceeds 0.5% of the MAC • If individual masses are used the mass of an aeroplane must be •

determined prior to initial entry into service and thereafter at intervals of 4y if no modifications have taken place. Where an operator uses "fleet masses" and provided that changes have been correctly documented, this interval is 9y for each aeroplane.

• It is not required to drain all engine tank oil or fuel tanks • Must take place in an enclosed, non-air conditioned hangar • With a minimum of three points of support • Aeroplane has to be clean and equipment complete for weighing

Unusable fuel + Full Operating Fluids Furnishings

•

= Weighed Mass Determined by manufacturer Found in the latest version of the weighing schedule as corrected to allow for modifications Is amended to take account of changes due to modifications of the AC

Calculation of Max. Masses for TO & LDG

Standard Empty Mass

Systems Power Plants Aeroplane Structure

Limiting Structural TOM = (minimum of: Payload (=TL) = (

TF TOF MTOM +MLM +MZFM --------------------------------------... ... ... ) - || -

) - DOM - TOF

Mass & Balance 2 The Datum is the point on the aeroplane designated by the manufacturers from which all CG measurements and calcuations are made. Its position is given in the aeroplane Flight or Loading Manual. It is located at a convenient point which may not physically be on the aeroplane. The datum is a fixed vertical plane from which all the arm distances are measured

CG in %MAC is the location of CG in relation to the Mean Aerodynamic Chord of the wing. Loads must be adequately secured in order to avoid 0% unplanned CG movement and aircraft damage.

CG (MAC) =

Center of Gravity (CG) •= the point of a body through which the sum of the forces of all masses is considered to act •= the point where all the aircraft mass is considered to be concentrated

Changing tailplane incident angle does not change CG position!

Total MAC

MAC 50%

25%

75%

100%

CG

LE

CG location is calculated/measured along the longitudinal axis

Distance: Leading Edge (LE) - CG

range is between front and rear CG [ CG safelimits ] and includes both limits

A location in the aeroplane, identified by a number designating its distance from the datum = A Station

Standard CG Calculation Walkthrough 1.Calculate Moment = Arm * Force for all stations 2.Add up all moments => Total Moment (taking out weight = negative Moment!) 3.Add up all forces (weights) => Total Weight 4.Calculate CG position with Arm = Total Moment / Total Weight

Weight •Acts in a direction parallel to the gravity vector •On ground or in level, non accelerated flight vertically through CG

Units •If the actual fuel density is not known, conversion from volume to mass can be done by using std. fuel density according to the OM •1US.gal. = 3.785l = 0.833Imp.gal. = 6lbs AVGAS •1kg = 2.2lb

Moment • All moments turning clockwise arund datum are positive; • If all moments given are positive, the datum must be at the nose or in front of the AC

=

Arm = Moment Arm = Balance Arm = Horizontal distance from Datum to CG

*

Force use N or kg consistently!

Other •Once the mass and balance documentation has been signed prior to flight, acceptable last minute changes to the load must be documented •Index Method: In Mass and balance calculations the index is the moment divided by a constant

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