031 AIRCRAFT MASS & BALANCE
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CLICK2PPSC LTD EDITION 2.00.00 2001 This is the second edition of this manual, and incorporates all amendments to previous editions, in whatever form they were issued, prior to July 1999.
EDITION 2.00.00
© 1999,2000,2001
G LONGHURST
The information contained in this publication is for instructional use only. only. Every effort has been made to ensure the validity and accuracy of the material contained herein, however no responsibility is accepted for errors or discrepancies. The texts are subject to frequent changes which are are beyond our control.
COPYRIGHT All rights rights reserved. No part of this publication publication may be reproduced, stored in a retrieval retrieval system, or transmitted, in any form or by any a ny means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the author. This publication shall not, by way of trade or o r otherwise, be lent, resold, hired out or otherwise circulated without the author's prior consent. Produced and Published by the
CLICK2PPSC LTD EDITION 2.00.00 2001 This is the second edition of this manual, and incorporates all amendments to previous editions, in whatever form they were issued, prior to July 1999.
EDITION 2.00.00
© 1999,2000,2001
G LONGHURST
The information contained in this publication is for instructional use only. only. Every effort has been made to ensure the validity and accuracy of the material contained herein, however no responsibility is accepted for errors or discrepancies. The texts are subject to frequent changes which are are beyond our control.
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TABLE OF CONTENTS Introduction The Composition of Aeroplane Weight The Calculation of Aircraft Weight Weight and Balance Theory Theory Centre of Gravity Calculations Adding, Removing and Repositioning Loads The Mean Aerodynamic Chord Structural Limitations Manual and Computer Load/Trim Sheets Joint Aviation Regulations
TABLE OF CONTENTS The Weighing of Aeroplanes Documentation Definitions CAP 696 - Loading Manual
Introduction 1. As a professional pilot you will deal with aircraft loading situations on every flying day of your working life. The course that you are about to embark upon considers the inter-relationship between aircraft loading and other related subjects (principally aircraft performance and flight planning), and the very important airmanship aspects of proper aircraft loading. In general (nonaircraft type specific) terms, the ways in which the centre of gravity of both unladen and laden aircraft can be determined and checked as being within safe limits will be discussed. As and when you are introduced to new aircraft types, both during your flight training and during your subsequent career, you will be taught the loading procedures which are specific to that particular aircraft type. 2. In the Aircraft Performance book the problem of determining the maximum permitted takeoff weight for an aircraft in a given situation is addressed. The Flight Planning book addresses the determination of the maximum payload, which can be carried on a given flight. In Aircraft Loading the problems of distributing the load within the aircraft such that the resultant centre of gravity is, firstly, within the safe limits laid down for the aircraft and, secondly, positioned so as to enhance the efficient performance of the aircraft, are addressed. 3. The Joint Aviation Authority has the task of ensuring that all public transport aircraft, irrespective of size or number of engines, are operated to the highest possible level of safety. To discharge this commission the JAA periodically introduces legislation in the form of operating rules or regulations and minimum performance requirements, which are complementary. All public transport aircraft are divided into Classes in which the types have similar levels or performance. There is a set of rules and requirements for each Class of aeroplanes, which dictate the maximum mass at which an aeroplane may be operated during any particular phase of flight.
4. With the introduction of the Joint Aviation Authority syllabus the word ‘mass’ is used instead of the word ‘weight’. In all British and American publications, weight is still preferred and used to express the downward force exerted by mass. The reason the JAA use mass is because weight = mass x acceleration i.e. weight = mass x 1. Therefore weight and mass are synonymous. Throughout this book the word ‘weight’ has been used and may be exchanged for the word ‘mass’ if preferred. 5. In addition to this the metric system of measuring weight and volume is preferred by the JAA and it may be necessary to convert Imperial or American quantities to metric equivalents. If such is the case use the following method.
Conversion between Weight and Volume 6. The weights and volumes obtained for the purpose of centre of gravity calculations are frequently given as a mixture of metric and imperial measures. For example a British or American built aircraft may well have its weights presented in the Aeroplane Flight Manual (AFM) in pounds and when loaded on the continent the load may be quoted in kilograms. Fuel is delivered in litres, imperial gallons or US gallons, but of course must figure in the load sheet calculations in pounds or kilograms. Although the conversion between differing units of weight and volume, and indeed the conversion between volume and weight for fluids with a given specific gravity, is covered elsewhere in the course, the following paragraphs are included in this manual for your guidance. 7. To convert a volume of liquid to weight and vice versa the density of the liquid must be considered. The density is expressed as a specific gravity (SG). 1 litre of pure water weighs 1 kg and 1 imperial gallon pure water weights 10 lb. The SG of pure water is taken as the datum SG of 1.0.
8. When converting litres of any liquid to kilograms the volume must be multiplied by the specific gravity, or when converting kilograms to litres the weight must be divided by the specific gravity. Similarly, when converting imperial gallons to pounds the volume must be multiplied by (10 x the specific gravity), or to convert pounds to imperial gallons the volume must be divided by (10 x the specific gravity) of the liquid. 9. Aviation fuels and oils are lighter than pure water, therefore their specific gravities will be less than 1.0. 10. The diagram at Figure 0-1 may help you with these conversions. When using the diagram at Figure 0-1 and moving in the direction of the arrows, multiply (as shown). Conversely, when moving in the opposite direction, divide.
Volume Conversions 11. In some problems the oil is measured in quarts. They may be in Imperial measurements or American. It does not matter, the conversion is the same as shown below in Paragraph 12. 12. 2 Pints
= 1 Quart
4 Quarts
= 1 Gallon
8 Pints
= 1 Gallon
FIGURE 0-1 Weight/Volume Conversion
13. When travelling in the direction of the arrows multiply, when travelling in the opposite direction divide.
031 Aircraft Mass & Balance
The Composition of Aeroplane Weight Weight Limitations
The Composition of Aeroplane Weight
The Composition of Aeroplane Weight 1
1. The total weight of an aeroplane is the weight of the aeroplane and everyone and everything carried on it or in it. Total weight comprises three elements, the basic weight, the variable load and the disposable load.
Basic Weight.
This is the aeroplane weight plus basic equipment, unusable fuel and undrainable oil. Basic equipment is that which is common to all roles plus unconsumable fluids such as hydraulic fluid.
Variable Load.
This includes the role equipment, the crew and the crew baggage. Role equipment is that which is required to complete a specific tasks such as seats, toilets and galley for the passenger role or roller convey or, lashing points and tie down equipment for the freight role.
Disposable Load.
The traffic load plus usable fuel and consumable fluids. The traffic load is the total weight of passengers, baggage and cargo, including any non-revenue load. The disposable load is sometimes referred to as the useful load. 2. Although these are the weight definitions used in the load sheet there are other terms which are commonly used. These are:
Absolute Traffic Load.
The maximum traffic load that may be carried in any circumstances. It is a limitation caused by the stress limitation of the airframe and is equal to the maximum zero fuel weight minus the aircraft prepared for service weight.
The Composition of Aeroplane Weight All Up Weight (AUW).
The total weight of an aircraft and all of its contents at a specific time.
Design Minimum Weight.
The lowest weight at which an aeroplane complies with the structural requirements for its own safety.
Dry Operating Weight.
The total weight of the aeroplane for a specific type of operation excluding all usable fuel and traffic loads. It includes such items as crew, crew baggage, catering equipment, removable passenger service equipment, and potable water and lavatory chemicals. The items to be included are decided by the Operator. The dry operating weight is sometimes referred to as the Aircraft Prepared for Service (APS) weight. The traffic load is the total weight of passengers, baggage and cargo including non-revenue load. [ JAR-OPS 1.607 (a)].
Empty Weight.
(Standard Empty Weight) The weight of the aircraft excluding usable fuel, crew and traffic load but including fixed ballast, engine oil, engine coolants (if applicable) and all hydraulic fluid and all other fluids required for normal operation and aircraft systems, except potable water, lavatory pre-charge water and fluids intended for injection into the engine (demineralised water or water-methanol used for thrust augmentation).
Landing Weight.
The gross weight of the aeroplane, including all of its contents, at the time of
landing.
Maximum Ramp Weight.
The maximum weight at which an aircraft may commence taxiing and its equal to the maximum take-off weight plus taxi fuel and run-up fuel. It must not exceed the surface load bearing strength.
Maximum Structural Landing Weight.
The maximum permissible total aeroplane weight on landing in normal circumstances. [ JAR-OPS 1.607 (c)].
The Composition of Aeroplane Weight Maximum Structural Take-Off Weight.
The maximum permissible total aeroplane weight at the start of the take-off run. [ JAR-OPS 1.607 (d)].
Maximum Total Weight Authorised (MTWA).
The maximum total weight of aircraft prepared for service, the crew (unless already included in the APS weight), passengers, baggage and cargo at which the aircraft may take-off anywhere in the world, in the most favourable c ircumstances in accordance with the Certificate of Airworthiness in force in respect of aircraft.
Maximum Zero Fuel Weight.
The maximum permissible weight of an aeroplane with no usable fuel. The weight of fuel contained in particular tanks must be included in the zero fuel mass when it is explicitly mentioned in the Aeroplane Flight Manual limitations. This is a structural limitation imposed to ensure that the airframe is not overstressed. [ JAR-OPS 1.607 (b)].
Payload.
Anyone or anything on board the aeroplane the carriage of which is paid for any someone other than the operation. In other words anything or anyone carried that earns money for the airline.
Total Loaded Weight.
The sum of the aircraft basic weight, the variable load and disposable
load.
Traffic Load.
The total mass of passengers, baggage and cargo, including any non-revenue load. [ JAR-OPS 1.607 (f)].
Zero Fuel Weight.
This is the dry operating weight plus the traffic load. In other words it is the weight of the aeroplane without the weight of usable fuel.
The Composition of Aeroplane Weight
Equipment Ballast.
Additional fixed weights which can be removed, if necessary, that are carried, to ensure the centre of gravity remains within the safe limits, in certain circumstances.
Basic Equipment.
The unconsumable fluids and the equipment which is common to all roles for which the operator intends to use the aircraft.
Load Spreader.
A mechanical device inserted between the cargo and the aircraft floor to distribute the weight evenly over a greater floor area.
Unusable Fuel.
That part of the fuel carried which is impossible to use because of the shape or position of particular tanks.
Unusable Oil.
That part of the oil lubrication system that cannot be removed due to the construction of the system.
The Composition of Aeroplane Weight FIGURE 1-1 The Composition of Aeroplane Weight
