Aircraft Mass & Balance

031 AIRCRAFT MASS & BALANCE

© G LONGHURST 1999 All Rights Reserved Worldwide

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EDITION 2.00.00 2001

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TABLE OF CONTENTS


Introduction

The Composition of Aeroplane Weight

The Calculation of Aircraft Weight

Weight and Balance 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



Chapter Page 1 © G LONGHURST 1999 All Rights Reserved Worldwide

Introduction1. As a professional pilot you will deal with aircraft loading situations on every flying day ofyour working life. The course that you are about to embark upon considers the inter-relationshipbetween aircraft loading and other related subjects (principally aircraft performance and flightplanning), and the very important airmanship aspects of proper aircraft loading. In general (non-aircraft type specific) terms, the ways in which the centre of gravity of both unladen and ladenaircraft can be determined and checked as being within safe limits will be discussed. As and whenyou are introduced to new aircraft types, both during your flight training and during yoursubsequent career, you will be taught the loading procedures which are specific to that particularaircraft type.

2. In the Aircraft Performance book the problem of determining the maximum permitted take-off weight for an aircraft in a given situation is addressed. The Flight Planning book addresses thedetermination of the maximum payload, which can be carried on a given flight. In Aircraft Loadingthe 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 theefficient 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. Todischarge this commission the JAA periodically introduces legislation in the form of operating rulesor regulations and minimum performance requirements, which are complementary. All publictransport 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 maximummass 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 insteadof the word ‘weight’. In all British and American publications, weight is still preferred and used toexpress the downward force exerted by mass. The reason the JAA use mass is because weight = massx acceleration i.e. weight = mass x 1. Therefore weight and mass are synonymous. Throughout thisbook 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 JAAand it may be necessary to convert Imperial or American quantities to metric equivalents. If such isthe case use the following method.

Conversion between Weight and Volume6. The weights and volumes obtained for the purpose of centre of gravity calculations arefrequently given as a mixture of metric and imperial measures. For example a British or Americanbuilt aircraft may well have its weights presented in the Aeroplane Flight Manual (AFM) in poundsand 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 orkilograms. Although the conversion between differing units of weight and volume, and indeed theconversion between volume and weight for fluids with a given specific gravity, is covered elsewherein 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 beconsidered. The density is expressed as a specific gravity (SG). 1 litre of pure water weighs 1 kg and1 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 thespecific gravity, or when converting kilograms to litres the weight must be divided by the specificgravity. Similarly, when converting imperial gallons to pounds the volume must be multiplied by (10x the specific gravity), or to convert pounds to imperial gallons the volume must be divided by (10 xthe specific gravity) of the liquid.

9. Aviation fuels and oils are lighter than pure water, therefore their specific gravities will be lessthan 1.0.

10. The diagram at Figure 0-1 may help you with these conversions. When using the diagram atFigure 0-1 and moving in the direction of the arrows, multiply (as shown). Conversely, when movingin the opposite direction, divide.

Volume Conversions11. In some problems the oil is measured in quarts. They may be in Imperial measurements orAmerican. 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 0-1Weight/Volume Conversion

13. When travelling in the direction of the arrows multiply, when travelling in the oppositedirection divide.



031 Aircraft Mass & Balance



Weight Limitations




Chapter 1 Page 1 © G LONGHURST 1999 All Rights Reserved Worldwide

1The Composition of Aeroplane Weight

1. The total weight of an aeroplane is the weight of the aeroplane and everyone and everythingcarried on it or in it. Total weight comprises three elements, the basic weight, the variable load andthe disposable load.

Basic Weight. This is the aeroplane weight plus basic equipment, unusable fuel and undrainableoil. Basic equipment is that which is common to all roles plus unconsumable fluids such as hydraulicfluid.

Variable Load. This includes the role equipment, the crew and the crew baggage. Roleequipment is that which is required to complete a specific tasks such as seats, toilets and galley forthe 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 thetotal weight of passengers, baggage and cargo, including any non-revenue load. The disposable loadis sometimes referred to as the useful load.

2. Although these are the weight definitions used in the load sheet there are other terms whichare commonly used. These are:

Absolute Traffic Load. The maximum traffic load that may be carried in any circumstances. Itis a limitation caused by the stress limitation of the airframe and is equal to the maximum zero fuelweight minus the aircraft prepared for service 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 thestructural requirements for its own safety.

Dry Operating Weight. The total weight of the aeroplane for a specific type of operationexcluding all usable fuel and traffic loads. It includes such items as crew, crew baggage, cateringequipment, removable passenger service equipment, and potable water and lavatory chemicals. Theitems to be included are decided by the Operator. The dry operating weight is sometimes referred toas 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, crewand traffic load but including fixed ballast, engine oil, engine coolants (if applicable) and allhydraulic fluid and all other fluids required for normal operation and aircraft systems, exceptpotable water, lavatory pre-charge water and fluids intended for injection into the engine (de-mineralised water or water-methanol used for thrust augmentation).

Landing Weight. The gross weight of the aeroplane, including all of its contents, at the time oflanding.

Maximum Ramp Weight. The maximum weight at which an aircraft may commence taxiingand its equal to the maximum take-off weight plus taxi fuel and run-up fuel. It must not exceed thesurface load bearing strength.

Maximum Structural Landing Weight. The maximum permissible total aeroplane weight onlanding in normal circumstances. [JAR-OPS 1.607 (c)].





Maximum Structural Take-Off Weight. The maximum permissible total aeroplane weight atthe start of the take-off run. [JAR-OPS 1.607 (d)].

Maximum Total Weight Authorised (MTWA). The maximum total weight of aircraftprepared for service, the crew (unless already included in the APS weight), passengers, baggage andcargo at which the aircraft may take-off anywhere in the world, in the most favourable circumstancesin 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 usablefuel. The weight of fuel contained in particular tanks must be included in the zero fuel mass when itis explicitly mentioned in the Aeroplane Flight Manual limitations. This is a structural limitationimposed 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 anysomeone other than the operation. In other words anything or anyone carried that earns money forthe airline.

Total Loaded Weight. The sum of the aircraft basic weight, the variable load and disposableload.

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 theweight of the aeroplane without the weight of usable fuel.





Equipment

Ballast. Additional fixed weights which can be removed, if necessary, that are carried, to ensurethe 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 forwhich the operator intends to use the aircraft.

Load Spreader. A mechanical device inserted between the cargo and the aircraft floor todistribute 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 orposition of particular tanks.

Unusable Oil. That part of the oil lubrication system that cannot be removed due to theconstruction of the system.





FIGURE 1-1The Composition of Aeroplane Weight





3. The total weight of an aeroplane comprises many different components, all of which, togetherwith the appropriate lever arms, are recorded in the weight and CG Schedule.

4. The standard empty weight of the aeroplane is the weight of the aircraft excluding the usablefuel, the crew and the traffic load but including any fixed ballast, unusable fuel, all engine coolantand all hydraulic fluid.

5. The basic weight of an aeroplane is essentially the empty weight plus the weight of basicequipment, that is equipment which is common to all roles in which the aircraft may be required toperform. The basic weight and the corresponding CG position, together with the declared basicequipment showing the weight and arm of each item, are shown in Part A of the Weight and CGSchedule or in the Loading and Distribution Schedule as appropriate.

6. To equip an aircraft to perform a particular role it may be necessary to fit additionalequipment. This is known as role equipment, an example would be the passenger seats, toilets andgalleys, which may vary in quantity for a large public transport aircraft.

7. The role equipment (variable load) detailed in Part B may be for as many roles as the operatorwishes, but for every role the weights and moments must be stated. The weight and moment of thecrew is included in Part B. Under certain circumstances, standard crew (and passenger) weights areassumed, otherwise the weight of each crew member must be determined by weighing. Theoccasions on which standard weights may be used are discussed in the Chapter entitled ‘JointAirworthiness Requirements’.

8. With the role equipment fitted the aircraft is ready to enter service. The weight of the aircraftin this condition is called the Aircraft Prepared for Service (APS) weight, or the Dry OperatingWeight (DOW). The total weight of the aeroplane comprises the APS weight plus the disposableload, which is made up of usable fuel and the payload.





9. Details of the disposable load must be entered in Part C of the Weight and CG Schedule,which contains the lever arm of each cargo stowage position, hold and each row of passenger seats.Full details of all fuel and oil tanks are also included in this part of the Schedule stating the arm,maximum capacity and weight when full for aircraft exceeding an MTWA of 2730 kg.

10. For an aircraft having a valid Certificate of Airworthiness a valid Weight and CG Schedulemust be completed every time the aircraft is weighed. Each Schedule must be preserved for a periodof six months following the subsequent re-weighing of the aircraft.

11. If the person who is the operator ceases to be the operator, he (or his representative if he dies)must retain the Schedule or pass it on to the new operator for retention for the requisite period.

Weight Limitations12. The factors which may limit the maximum Take-Off Weight (TOW) are:

The Structural Limits. These are weight limits, which are imposed by the manufacturer, andagreed by the Authority, to ensure the aeroplane is not over-stressed. These structural weightsinclude the maximum structural ramp weight, the maximum structural take-off weight, themaximum zero fuel weight and the maximum structural landing weight.

The Field-Length Limited Take-Off Weight. This is the TOW as limited by the available fieldlengths and the prevailing meteorological conditions at the departure aerodrome.

The Weight-Altitude-Temperature (WAT) Limit. This limitation is imposed on TOW byminimum climb gradient requirements, which are specified in Joint Airworthiness Requirements(JARs).





The En-Route Requirements. The weight of the aircraft at any stage of the flight en-route mustbe such that the aircraft can safely clear any objects within a specified distance of the aircraft’sintended track. Depending on the aircraft’s performance category, the loss of power from a specifiednumber of engines will be assumed when determining the maximum weight at which the aircraft cansafely clear en-route obstacles. En-route terrain clearance may impose a limitation on the take-offweight.

The Maximum Landing Weight. This may be dictated by the structural limitation, the Field-Length Limit or the WAT Limit at the destination or alternate aerodromes.

The Maximum Take-off Weight. The lowest restricted weight of the field-length limitation, theWAT limitation and the structural limitation is the maximum TOW.

13. As already discussed, the disposable load consists of the usable fuel and the traffic load. Inorder that the maximum traffic load can be carried it may be necessary to limit the amount of fuelwhich is carried to a safe minimum. Whether or not the fuel carried actually limits the traffic load, itis normally prudent to reduce the fuel load to a safe minimum in order to reduce the all up weight ofthe aircraft. This will result in lower operating costs, higher cruise levels, reduced thrust take-offsand/or easier compliance with noise abatement procedures on take-off. The total fuel required onany particular flight comprise the following:

Route Fuel. This is the fuel used from departure to destination aerodromes and may beminimised by operating at the most economical pressure altitude accounting for the temperature andwind component, but not below the minimum safe altitude.

Diversion Fuel. The fuel required to proceed from the destination to the alternate aerodrome inthe prevailing conditions.





Holding Allowance. The fuel required to enable the aircraft to hold at a specified pressurealtitude and for a specified period of time.

Contingency Allowance. An amount of fuel carried to counter any disadvantage sufferedbecause of unforecast adverse conditions.

Landing Allowance. The fuel required to be used from overhead the landing aerodrome to theend of the landing roll.

14. On occasions it is advantageous to carry more than the minimum fuel for a given sector. Theobvious example is when fuel will not be available at the destination aerodrome. Alternatively, thecost of fuel at the destination aerodrome may be so high that the cost differential (departureaerodrome fuel cost versus destination aerodrome fuel cost) may be so great that it is cheaper tocarry the fuel for the return or subsequent sector outbound from the original departure aerodrome.In either event, when this is done the first sector would be termed a ‘Tankering Sector’.

15. The size of the traffic load may be restricted by reasons other than the disposable load whichis available once the fuel load has been decided. It may be impossible to distribute the traffic loadsuch that the centre of gravity of the laden aircraft remains within the safe specified limits, in whichcase some of the traffic load may have to be off-loaded. Floor loading factors may have to beconsidered. With a payload which is light in weight but bulky it may be physically impossible to fitthe traffic load into the aircraft.





Operating Overweight16. A safely loaded aircraft is one in which the total weight of traffic load is equal to or less thanthe maximum permissible traffic load for a given flight and the distribution of that traffic load is suchthat the centre of gravity of the laden aircraft lies within the fore and aft limits of centre of gravitywhich are permitted for that aircraft operating in the specified role.

17. The effects of operating in an overweight condition include:

(a) Reduced acceleration on the ground run for take-off. The take-off speeds areincreased because of the weight, and this results in an increased take-off run requiredand an increased take-off distance required.

(b) Decreased gradient and rate of climb which decreases obstacle clearance capabilityafter take-off and the ability to comply with the minimum climb gradientrequirements.

(c) Increased take-off speeds impose a higher load on the undercarriage and increased tyreand wheel temperatures. Together these reduce the aeroplane’s ability to stop rapidlyin the event of an abandoned take-off.

(d) Increased stalling speed which reduces the safety margins.

(e) Reduced cruise ceiling which increases the fuel consumption resulting in a decreasedoperational range. It may also cause en-route terrain clearance problems.

(f) Impaired manoeuvrability and controllability.





(g) Increased approach and landing speeds causing a longer landing distance, landingground run, increased tyre and wheel temperatures and reduced braking effectiveness.

(h) Reduced one-engine inoperative performance on multi-engined aircraft.

(i) Reduced structural strength safety martins with the possibility of overstressing theairframe.

18. In addition to ensuring that the maximum permissible all-up weight of an aircraft is notexceeded it is of vital importance to ensure that the distribution of the permissible weight is such thatthe balance of the aircraft is not upset.






Weight and Traffic Load





2The Calculation of Aircraft Weight

From the diagram at Figure 1-1 it can be determined that:

• Aircraft Weight + Basic Equipment = Basic Weight

• Basic Weight + Usable Oil = Standard Empty Weight

• Standard Empty Weight + Optional Equipment = Basic Empty Weight

(Note if no optional equipment is added, Standard Empty Weight = Basic Empty Weight).

• Basic Empty Weight + Variable Load = Aircraft Prepared for Service Weight (APS).

• APS Weight + Removable Ballast = Dry Operating Weight.

(Note if there is no removable ballast, APS Weight = Dry Operating Weight).

• Dry Operating Weight + Traffic Load = Zero Fuel Weight.

• Zero Fuel Weight + Usable Fuel = All Up Weight

Problems related to these fomulae will be met as follows:

(Note optional equipment and removable ballast will not be mentioned unless it is carried).





EXAMPLE 2-1

EXAMPLE 2-2

EXAMPLE

Given:

Take-off mass 80,000 kgs; Traffic load 12,000 kgs; Usable fuel 10,000 kgs; Crew 1000 kgs.

Calculate the dry operating weight.

SOLUTION

80,000 - 12,000 - 10,000 = 58,000 kgs.

EXAMPLE

Given:

Basic weight 50,000 kgs; Basic equipment 5,000 kgs; Usable oil 500 kgs; Variable load 6000 kgs; Traffic load 3000 kgs; Usable fuel 7000 kgs.

Calculate the APS weight.

SOLUTION

50,000 + 500 + 6000 = 56,500 kgs





EXAMPLE 2-3

EXAMPLE 2-4

Weight and Traffic Load1. Problems concerning the traffic load capacity of an aircraft often occur in the Flight Planning,Navigation or Mass and Balance examination papers. The problems are not complicated becausethere is no consideration of whether the centre of gravity of the laden aircraft lies within the trimenvelope.

EXAMPLE

Given the same details as Example 2-2, calculate the disposable load.

SOLUTION

3000 + 7000 = 10,000 kgs.

EXAMPLE

Given:

Take-off mass 77,500 kgs; Disposable load 10,000 kgs; Variable load 4000 kgs.

Calculate the basic empty mass.

SOLUTION

77,500 - 10,000 - 4000 = 63,500 kgs.





2. To avoid getting lost in a mass of figures and definitions, remember that the All Up Weight ofan aircraft at any stage of flight consists of three elements:

(a) The Aircraft Prepared for Service Weight (or Dry Operating Mass).

(b) The weight of the Fuel Onboard.

(c) The traffic load carried.

3. The APS weight and the traffic load remain constant throughout the flight whereas the weightof the fuel will progressively decrease.

4. In the examination you will be required to calculate the weight of the traffic load that can becarried, as limited by one of three limiting maximum weights:

(a) Maximum Take-Off Weight.

(b) Maximum Landing Weight.

(c) Maximum Zero Fuel Weight.

5. For an aircraft to perform a particular role it may be necessary to fit additional equipment.This is known as role equipment, for example the passenger seats and galleys required in a publictransport aircraft, which makes the aircraft ready to enter service. The weight of the aircraft in thiscondition is called the Aircraft Prepared for Service (APS) weight, or the Dry Operating Weight. TheTotal Weight of the aeroplane then comprises of the APS weight plus the Disposable Load, which ismade up of the usable fuel and traffic load.





6. To answer this type of question use the layout shown in the following examples and approachthe problem in a logical manner remembering the total weight at any time comprises the APS weight,the fuel and the traffic load.

EXAMPLE 2-5EXAMPLE

Given:

Determine the traffic load which can be carried from A to B.

Maximum Take-Off Weight at A 145,000 kg.

Maximum Landing Weight at B 97,900 kg.

Maximum Zero Fuel Weight 90,100 kg.

Weight Less Fuel and Payload 67,400 kg.

Reserve Fuel (remains unused) 7,500 kg.

Mean TAS 470 kt.

Sector Distance A to B 3,600 nm.

Mean Fuel Flow 5,500 kg/hr.

Wind Component -20 kt.





SOLUTION

First, calculate the fuel required for the sector.

Maximum traffic load is the lower of the three calculated values i.e. 22,700 kg. This is the onlytraffic load that will not exceed either the MTOW, MLW or the MZFW limitations.

TAS = 470 kt.

Wind Component = -20 kt.

Groundspeed = 450 Kt.

Sector Time =

Sector Fuel Required = Fuel flow x time = 5,500 x 8 = 44,000 kg

Sector DistanceGroundspeed

---------------------------------------- 3 600,450

---------------- 8 hours= =

MTOW Limit MLW Limit MZFW Limit

MTOW +145,000 kg. MLW + 97,900 kg. MZFW + 90,100 kg

APS Wt. – 67,400 kg. APS Wt. –67,400 kg. APS Wt. - 67,400 kg

Fuel: Leg - 44,000 kg

Res - 7,500 Res: - 7,500

Payload +26,100 kg. +23,000 kg. +22,700kg





In the above example, the Fuel Required calculation could have been conducted in one step using the following method:

Sector Fuel Required Sector DistanceGroundspeed

------------------------------------- Fuel Flow×

3 600,450

--------------- 5 500,× 44 000 kg ,

=

= =





EXAMPLE 2-6EXAMPLE

Given:

Calculate:

(a) The maximum Payload that can be carried.

(b) The Maximum Range with the Payload.

(c) What Payload can be carried over the Maximum Range of the aircraft.

Maximum Take-Off Weight 150,000 kg.

Maximum Landing Weight 100,000 kg.


APS Weight 70,000 kg.

Total Fuel On-Board at Take-Off 50,000 kg.

Reserve Fuel 6,000 kg.

Sector Distance 1,250 nm.

TAS 300 kt.

Wind Component -50 kt.

Fuel Flow 6,000 kg./hr.





SOLUTION

Calculate the Sector Fuel:

If the aircraft had a total of 50,000 kg. of fuel at take-off and burnt 30,000 kg. of fuel in transitingthe sector distance then there would be 20,000 kg. of fuel remaining in the tanks on landing.

The Limiting Payload is 10,000 kg

To calculate the maximum range with this payload, consider that the aircraft has landed with20,000 kg of fuel on-board although the reserve fuel requirement was only 5,000 kg. This meansthat there is an additional 15,000 kg of fuel available to increase the sector distance. We now needto calculate this extra distance.

Maximum Range = Original Sector Distance of 1250 + 625 = 1,875 nm.

Sector FuelSector DistanceGround speed

------------------------------------- Fuel Flow× 1250250

------------ 6000× 30000 kg= = =

MTOW Limit MLW Limit MZFW Limit

MTOW +150,000 kg MLW +100,000 kg MZFW +90,000 kg

APS Weight -70,000 kg -70,000 kg -70,000 kg

Fuel -50,000 kg -20,000 kg -

Payload +30,000 kg +10,000 kg +20,000 kg

DistanceFuel Available

Fuel Flow----------------------------------- Groundspeed× 15000

6000--------------- 250× 625 Nm= = =





EXAMPLE 2-7EXAMPLE

An aircraft is to fly from A to B and then on to C without refuelling at B.

Given: APS weight 23,500kgs

Determine the maximum payload that could be loaded at A and B.

Maximum Take-Off Weight at A 41,800 kg.

Maximum Take-Off Weight at B 37,000 kg.

Maximum Landing Weight at B 38,000 kg.

Maximum Landing Weight at C 36,500 kg.

Maximum Taxi Weight at B 37,320 kg.


APS Weight 23,500 kg.

Distance A to B 521 nm.

Distance B to C 703 nm.

Mean Groundspeed A to B 453 kt.

Mean Groundspeed B to C 388 kt.

Mean Fuel Consumption A to B 3,100 kg/hr.

Mean Fuel Consumption B to C 2,950 kg/hr.

Reserve Fuel (Unused) 2,000 kg.





SOLUTION

Note the taxi fuel at B (the difference between the Maximum Taxi Weight and the Maximum Take-Off Weight) is also to be considered in the calculation of the fuel on-board the aircraft from thepoint of take-off at A.

The maximum payload that can be loaded at A is 6,835 kg.

The maximum payload that can be loaded at B is 6,155 kg.

Calculate fuel required A to B521453--------- 3100× 3565 kg= =

Calculate fuel required B to C703388--------- 2950× 5345 kg= =

MTOW A MLW B MZFW MTOW B MLW C

Limitation +41,800 +38,000 +31,300 +37,000 +36,500

APS Weight -23,500 -23,500 -23,500 -23,500 -23,500

Fuel A - B -3,565

Fuel B - C -5,345 -5,345 -5,345

Taxi Fuel at B -320 -320

Reserve Fuel -2,000 -2,000 -2,000 -2,000

Payload +7,070 +6,835 +7,800 +6,155 +11,000






Reference Datum

The Centre of Gravity Envelope

The Newton

Aeroplane Weight Determination





3Weight and Balance Theory

1. In order to understand the concept of weight and balance as it applies to aeroplanes it isessential to have a thorough knowledge of the basic theory of balance and force moments. This isbest described by using a child’s seesaw to illustrate the terms, cause and effect.

2. If the bar of a seesaw having a uniform density and cross section is placed on a fulcrum (orpivot) for support such that the fulcrum is exactly half way along the length of the seesaw, the weightof the seesaw will act vertically downwards through the fulcrum. In this case at any specifieddistance from the fulcrum, the turning moment (that is the downward force imposed at that point)will be equal on both sides of the fulcrum. The seesaw is said to be in equilibrium or to be balanced,and will therefore rest in a horizontal position.

3. The turning moment at any particular point can be determined by multiplying the weight (thedownward force) by the arm (the distance of that point from the fulcrum). Moments can beexpressed foot pounds (ft. lb.) inch pounds (in. lb.) or metre kilograms (m. kg.).

4. The position through which all of the weight acts in a vertically downward direction isreferred to as the Centre of Gravity (CG). In the case considered above and illustrated at Figure 3-1,the CG of the seesaw is immediately above the fulcrum.





FIGURE 3-1Balanced Condition

5. If a weight is placed on one side of the seesaw it will impart an unbalancing force or turningmoment about the fulcrum. The moment of this force is equal to the product of the weight and thedistance at which it is placed from the fulcrum. For example, if a 20 kg weight is placed on theseesaw at a distance of 80 cm from the fulcrum the moment (20 kg x 80 cm) is equal to 1600 cm kgor 16 m kg as shown at Figure 3-2.

FIGURE 3-2Unbalanced Condition





6. In order to restore the balance or equilibrium of the seesaw the unbalancing moment of 16 mkg must be counterbalanced. This may be done by placing a weight on the opposite side of thefulcrum such that the moment produced is equal and opposite to the unbalancing force. Thereforeany product combination of weight and arm which gives a moment of 16 m kg will suffice.Figure 3-3 shows only three of the infinite combinations possible.





FIGURE 3-3Restored Balanced Condition





7. At Figure 3-3 (b) the same effect is achieved by placing a 40 kg weight at a distance of 40 cmfrom the fulcrum (40 kg x 40 cm = 16 m kg).

8. Figure 3-3 (c) the same effect is achieved by placing a 80 kg weight at a distance of 20 cmfrom the fulcrum (80 kg x 20 cm = 16 m kg).

NOTE:

All of the weights used in the above examples are assumed to be of uniformdensity and construction such that the weight acts vertically downwardthrough the centre of the weight.

Reference Datum9. The point from which the arms of force moments are measured is termed the referencedatum. In the preceding examples the reference datum was the centre of gravity of the unladenseesaw, which was coincident with the fulcrum.

10. The CG of an aircraft is the point through which all of its weight is assumed to act in avertically downward direction. The position of the CG measured along the fore and aft axis of theaircraft will change due to changes in aircraft configuration (passenger configuration with seats in,freight configuration with seats out), total weight and distribution of the fuel load at any given pointin the flight, total weight and distribution of the payload, and so on. It is therefore important toappreciate that with an aircraft the reference datum cannot be the position of the CG, but willinstead be a fixed point on the aircraft structure, or indeed a point on the extension of the aircraft’sfore and aft axis which is in fact forward of the aircraft’s nose.





11. On large aircraft the bulkhead separating crew and passenger compartments is frequentlyused as a reference datum, whereas in single engine aircraft the fire wall between cabin and enginebay is often specified as the reference datum, or alternatively the tip of the propeller spinner.

12. In order to determine the position of the CG of a laden aircraft the weight and distance foreor aft of the datum (arm) of each piece of equipment, cargo and person on board the aircraft must beknown. By convention any weight which is positioned forward of the reference datum has a negativearm and therefore produces a negative moment.

13. Conversely, by convention, any weight which is aft of the reference datum has a positive armand therefore produces a positive moment.

The Centre of Gravity Envelope14. In order to ensure that an aeroplane can be safely controlled by the aerodynamic controlsurfaces the CG must remain within safe limits. The distance between the maximum safe forwardposition of the CG and the maximum safe aft position of the CG is termed the CG envelope. Theenvelope dimensions are determined by the manufacturer, approved by the CAA, and subsequentlydescribed in the Approved Flight Manual (AFM), which is part of the Certificate of Airworthiness. Itis a legal requirement that the CG remains within the CG envelope at all times. Some aircraft havemore than one CG envelope.

15. Public transport aeroplanes may have two CG envelopes, one for public transport flights andone for use on ferry or training flights. The CG envelope will be wider in the latter case, however itmay still be necessary to use ballast in order to position the CG of the essentially empty aeroplanewithin limits.





16. Similarly, some light aircraft are certified in two categories, semi-aerobatic category CGenvelope will be significantly narrower than the non-aerobatic CG envelope (or utility, or normal)category, the aft limit is likely to be especially restrictive. The maximum weight at which semi-aerobatic manoeuvres may be conducted may also be limited.

The Newton17. The mass of a body is the amount of matter which it contains. The weight of a body is theforce due to gravity acting on that mass. Weight and mass are often taken to be synonymous.

18. When considering SI units, the unit of mass is the kilogram and the unit of force is theNewton. From Newton’s second law it is known that:

Force = Mass x Acceleration

and therefore

1 Newton=1 kilogram x 1 metre/second/second

19. The acceleration due to gravity at the earth’s surface is 9.81 metres/second2, and therefore theweight force of gravity acting on a 1 kilogram mass is 9.81 Newtons.

20. If one now accepts mass and weight as being synonymous, then 1 kilogram is equal to 9.81Newtons.

21. It is possible, although presently unlikely, that you may encounter aircraft weights expressedin Newtons. In the examination, you may find that gravity is given as 10m/s/s in which case 1kg isequal to 10 Newtons.





The Forces Acting On An Aeroplane In Flight22. The centre of gravity is that point on the longitudinal axis through which all of the weightacts vertically downward. The centre of pressure is that point on the longitudinal axis throughwhich all of the lift is assumed to act upward at 90° to the axis.

23. The four forces which act on an aircraft in straight and level flight are lift, weight, thrust anddrag. Lift acts through the centre of pressure and weight through the centre of gravity. Forsimplicity, thrust and drag forces are considered as acting parallel to the longitudinal axis, and theirdisplacement from this axis depends on the design of the aircraft, high wing or low wing, the positionof the engine(s), and so on.

24. In order to maintain steady flight the forces acting on an aeroplane must be in balance, withno turning moment about any axis. In this condition the aircraft is said to be trimmed. Thecondition is achieved by balancing the lift, weight, thrust and drag forces acting at the aircraft’s C ofG and C of P so that:

(a) Lift equals weight, otherwise the aircraft would climb or descend.

(b) Thrust equals drag, otherwise the aircraft would accelerate or decelerate.

25. Providing that the centre of gravity and the centre of pressure are not coincident a forcecouple will be set up by the lift and the weight forces, and this will result in a pitching moment, asshown at Figure 3-4.





FIGURE 3-4The Forces on an Aeroplane in Level Flight

26. The magnitude of the pitching moment will depend on the magnitude of lift and weightforces, but also on the distance between the centre of gravity and the centre of pressure.

27. The position of the C of G will depend on the way in which the aircraft is loaded, and on themanner in which fuel is transferred/consumed in flight. The position of the centre of pressuredepends on the angle of attack, with the C of P moving slowly forward as the angle increases, andthen rapidly backwards at the stalling angle.

28. It is rarely possible to design an aircraft in which the forces of lift, weight, thrust and drag areexactly in equilibrium in flight. The centre of pressure moves with changing angle of attack, as doesthe drag line. The centre of gravity moves with changes in the distribution of load and fuel. Thepitching couples are set up when the weight line is not coincident with the lift line or the drag line isnot coincident with the thrust line and are offset by the tailplane and/or elevators.





29. Consequently, the forward and aft limits of the centre of gravity are determined by thecapability of the elevators (or stabilator or all moving tailplane) to control the aircraft in pitch at thelowest flight speed. These limits are established by the aircraft manufacturer.

30. The forward centre of gravity limit is established to ensure there is sufficient elevatormovement available at minimum flight airspeed. In other words to avoid a situation where theelevators are fully deflected in order to maintain a level pitch attitude.

31. The aft centre of gravity limit is the most rearward position at which the centre of gravity canbe located for the most critical manoeuvre or operation. As the centre of gravity moves rearwardsaircraft longitudinal stability decreases. This means that the aircraft’s natural ability to return tostable flight after a disturbance, a manoeuvre or a gust, is degraded.

32. It is therefore of paramount importance to safe flight that the aircraft is never operated withthe centre of gravity beyond the limits set down by the manufacturer and agreed by the Authority.

33. The effects of operating with the centre of gravity forward of the permitted forward limitinclude:

(a) Difficulty in rotating to take-off altitude.

(b) Difficulty in flaring, rounding-out, or holding the nose-wheel off the ground aftertouchdown on landing.

(c) Possible damage to nose-wheel, nose oleo and propeller tips.

(d) Restricted elevator trim resulting in an unstable approach.

(e) Increased stalling speed against full up elevator.





(f) Additional tail down force requires more lift from wing resulting in greater induceddrag, higher fuel consumption and reduced range.

(g) Slow rotation on take-off.

(h) Inability to trim out elevator stick forces.

34. The effects of operating with the centre of gravity aft of the permitted aft limit include:

(a) Pitch up at low speeds causing early rotation on take-off or inadvertent stall in theclimb.

(b) Difficulty in trimming especially at high power.

(c) Longitudinal instability, particularly in turbulence, with the possibility of a reverssalof control forces.

(d) Degraded stall qualities to an unknown degree.

(e) More difficult spin recovery, unexplored spin behaviour, delayed or even inability torecover.

Aeroplane Weight Determination35. In order to determine the weight and the arm of the basic aircraft, the first step is to determinethe aircraft empty weight (without fuel and payload) by measuring the weight acting through eachwheel (on a small aircraft) or through each jacking point (on larger aircraft).





36. Since the position of each wheel or jacking point (relative to the datum) is known, it is now asimple step to determine the position of the CG of the empty aircraft, and to express this positionrelative to the datum.

37. The following examples illustrate the method of calculating the weight and arm of emptyaircraft with various datum positions.





EXAMPLE 3-1EXAMPLE

The main wheels of a light aircraft are in line with the datum, and the nose-wheel is 75 inchesforward of the datum. The weights measured through each wheel are:

Determine the weight of the aircraft, and the position of the aircraft CG relative to the datum.

SOLUTION

The situation is as shown at Figure 3-5.

FIGURE 3-5

Left Hand Main Wheel 810 lb.

Right Hand Main Wheel 815 lb.

Nose-Wheel 320 lb.





The simple calculation is completed in the following manner:

The aircraft weight is therefore 1945 pounds, and the CG lies 12.34 inches forward of the datum.

Weight Arm Moment

Nose-Wheel 320 lb. -75 in -24,000 in lb.

Left Main Wheel 810 lb. 0 0

Right Main Wheel 815 lb. 0 0

Total 1945 lb. -24,000 in lb.

CG24000 in lb–1945 lb

------------------------------ 12.34 in–= =





EXAMPLE 3-2EXAMPLE

The datum is in line with the tip of the propeller spinner of a single engined light aircraft. Thenose-wheel is 10 inches aft of the datum and the main wheels are 120 inches aft of the datum.The weights measured through each wheel are:


SOLUTION


FIGURE 3-6



Nose-Wheel 320 lb.





The calculation is now completed as follows:

The aircraft weight is therefore 1945 pounds, and the CG lies 101.9 inches aft of the datum.

Weight Arm Moment

Nose-Wheel 320 lb. +10 in +3,200 in lb.

Left Main Wheel 810 lb. +120 in +97,200 in lb.

Right Main Wheel 815 lb. +120 in +97,800 in lb.

Total 1945 lb. +198,200 in lb.

CG+ 198,200 in lb

1945 lb------------------------------------= +101.9 in=





EXAMPLE 3-3EXAMPLE

The datum is positioned between the nose and the main wheels of a single engined lightaircraft. The nose-wheel is 45 inches forward of the datum and the main wheels are 55 inchesaft of the datum. The weights measured through each wheel are:


SOLUTION


FIGURE 3-7



Nose-Wheel 320 lb.





The calculation is now completed as follows:

The aircraft weight is therefore 1945 pounds and the CG lies 38.55 inches aft of the datum.

Weight Arm Moment

Nose-Wheel 320 lb. -45 in -14,400 in lb.

Left Main Wheel 810 lb. +55 in +44,550 in lb.

Right Main Wheel 815 lb. +55 in +44,825 in lb.

Total 1945 lb. +74,975in lb.

CG+74,975 in lb

1945 lb-------------------------------- +38.55 in= =





Self Assessed Exercise No. 1

QUESTIONS:QUESTION 1.

List the elements of basic weight.

QUESTION 2.

What does all up weight minus disposable load equal?

QUESTION 3.

Given: MTOW 48t; MLW44t; MZFW 36t; Taxi fuel 0.5t; Contingency fuel 1t; Alternate fuel 1t;Final reserve 1.5t; Trip fuel 8t. Calculate the actual TOW if ZFW = MZFW.

QUESTION 4.

Define reference datum.

QUESTION 5.

What is the difference between zero fuel weight and dry operating weight?

QUESTION 6.

What consideration limits maximum ramp weight?

QUESTION 7.

Define maximum zero fuel weight.





QUESTION 8.

Specify the maximum weight to which an aeroplane may be loaded prior to starting the engines.

QUESTION 9.

If the CG is at the forward limit state the stability of the aeroplane.

QUESTION 10.

How will the elevators feel if the CG moves AFT?

QUESTION 11.

The total weight of the aeroplane excluding the usable fuel and traffic load is called?

QUESTION 12.

Define the CG of an aeroplane.

QUESTION 13.

Given: Dry operating weight 30,000kgs; Maximum take-off weight 52,000kgs; Maximum zero fuelweight 43,000 kgs; Maximum landing weight 46,000kgs: Fuel at take-off 10,000kgs; Trip fuel5,000kgs. Calculate the maximum traffic load.

QUESTION 14.

Does traffic load include the crew?





QUESTION 15.

Who determines the structural limitations of an aeroplane?

QUESTION 16.

List the factors that may limit the take-off weight.

QUESTION 17.

What effect does an overweight take-off have on stalling speed?

QUESTION 18.

Define a Newton.

QUESTION 19.

How does stalling speed change if the CG moves to the AFT of the envelope?

QUESTION 20.

What determines the value of the maximum zero fuel weight.





ANSWERS:ANSWER 1.

Page 1-4

ANSWER 2.

Page 1-4. Dry operating weight

ANSWER 3.

Page 2-1. Taxi fuel will be used before take-off. The total fuel required for the flight = Contingency+ Alternative + Final reserve + Trip fuel = 1t + 1t + 1.5t + 8t = 11.5t

ZFW + Fuel = TOW = 36t + 11.5t = 47.5t which does not exceed MTOW. LW = TOW – Trip fuel =47.5t – 8t = 39.5t which does not exceed MLW

ANSWER 4.

Page 3-3

ANSWER 5.

Page 1-4. Zero fuel weight – Dry operating weight = Traffic load

ANSWER 6.

Page 1-2





ANSWER 7.

Page 1-2

ANSWER 8.

Page 1-2. – Maximum ramp weight

ANSWER 9.

Page 3-6 Paragraph 31. – Extremely stable

ANSWER 10.

Page 3-6 Paragraph 31. – Very light

ANSWER 11.

Page 1-4. Dry operating weight

ANSWER 12.

Page 3-1. The CG is the point on the longitudinal axis through which all of the weight acts verticallydownward.





ANSWER 13.

Page 2-3 Example 2-5

Maximum Traffic Load = 11,000 kgs

ANSWER 14.

Page 1-4. No

ANSWER 15.

Page 3-4 Paragraph 14. The Manufacturer

ANSWER 16.

Page 1-6 Paragraph 12

ANSWER 17.

Page 1-8 Paragraph 17 (d). Increases stalling speed

MTOW MLW MZFW

+ 52000 kgs + 46000 kgs + 43000 kgs

DOW - 30,000 kgs - 30,000 kgs - 30,000 kgs

Fuel - 10,000 kgs - 5,000 kgs ––

Traffic Load + 12000 kgs + 11000 kgs +13,000 kgs





ANSWER 18.

Page 3-4 Paragraph 18

ANSWER 19.

Page 3-5 Paragraph 33. By inference stalling speed decreases

ANSWER 20.

Page 1-2. The strength of the wing roots.





4Centre of Gravity Calculations

1. The CG of an aeroplane is determined by calculating the moments of the basic aeroplane andtogether with the moments of all additional items (fuel, passengers, freight and so on) containedwithin the aeroplane and dividing the sum of these moments by the total weight.

2. In order to determine the individual moments the weight of each specific item is multiplied byits arm (distance from the reference datum). It is vital that you remember that the arm and theresulting moment is, by convention, considered to be negative if the item is forward of the datum andpositive if the item is aft of the datum. Frequently the reference datum is given as a point on anextension of the fore and aft axis forward of the nose of the aircraft. The advantage of such areference datum is that all arms and moments will be positive.

3. In the event that the position of the undercarriage (extended or retracted) will significantlyaffect the position of the basic aircraft CG, the loading information contained in Part C of the Weightand CG Schedule will contain a statement of the total moment change which occurs when theundercarriage is lowered. This is because the position of the basic aircraft CG is given with theundercarriage the aircraft weight is therefore 1945 pounds and the CG lies 38.55 inches aft of thedatum extended.

4. In order to demonstrate how the position of the loaded aircraft CG can be determined a smalltwin piston aircraft is considered in Figure 4-1 and Figure 4-2. A general description of the CG limitsfor this aeroplane is given at Figure 4-1 and is shown diagrammatically at Figure 4-2. Figure 4-3shows the load form, which is appropriate to this aeroplane. The layout of the seats, baggagestowage areas and fuel tanks is shown at Figure 4-4 and Figure 4-5.





FIGURE 4-1Centre of Gravity Limits (Gear Extended)

NOTE:

Straight line variation between the points given. Datum line is located 137 inahead of the wing main spar centreline. Maximum landing weight 7000 lb.

Weight in Pounds Forward Limit Inches Aft of Datum

Aft Limit Inches Aft of Datum

7045 (Max. Ramp Weight) 126 135

7000 (Max. Take-off Weight) 126 135

6200 122 135

5200 or less 120 135





FIGURE 4-2Aeroplane CG Envelope





FIGURE 4-3Blank Load Sheet

Item Weight Lb. Arm Inches Moment Inches Lbs.

Basic Aeroplane

Pilot’s Seat + 95.0

Co-Pilot’s Seat + 95.0

Seat No.3 + 137.0

Seat No.4 + 137.0

Seat No.5 + 195.0

Seat No.6 + 195.0

Seat No.7 + 229.0

Seat No.8 + 242.0

Forward Baggage + 19.0

Rear Baggage + 255.0

Right Nacelle Locker Forward + 145.0

Right Nacelle Locker Aft + 192.0

Left Nacelle Locker Forward + 145.0

Left Nacelle Locker Aft + 192.0

Inboard Fuel + 126.8

Outboard Fuel + 148.0





CG Location for Take-Off

Other

Total Weight Total Moment





FIGURE 4-4Layout of Aeroplane Weight





FIGURE 4-5Profile of Aeroplane

NOTE:

Note that on the form shown at Figure 4-3 that neither the weight nor the armappropriate to the aircraft itself is given. The information is contained withinthe aircraft weight schedule, and is appropriate to one particular airframe.





5. When loading the aeroplane care must be taken not to exceed the maximum weight permittedin specific baggage areas. Floor loading/maximum weight details are not given in the form atFigure 4-3, but are listed separately in the operating manual or, for larger aircraft, in the loadingmanual, and are normally placarded in the aircraft itself.

EXAMPLE 4-1EXAMPLE

Given that the aircraft described at Figure 4-2, Figure 4-3, and Figure 4-4, is loaded in thefollowing manner, determine the take-off weight and the position of the CG at take-off.

Basic aircraft 4,600 lb.

Arm 122.5 inches

Captain 170 lb.

Co-pilot 150 lb.

Seat 3 120 lb.

Seat 4 145 lb.

Seat 5 80 lb.

Seat 6 0 lb.

Seat 7 0 lb.

Seat 8 0 lb.

Forward baggage hold 40 lb.

Rear baggage hold 120 lb.





The left and right forward and the left and right aft nacelle lockers each contain 50 lb. of baggage.

SG of fuel 0.72

SOLUTION

First calculate the weight of fuel in pounds.

Therefore the weight of fuel in the inboard tanks is 635 lb., and in the outboard tanks is 635 lb.Now complete the table to appear as Figure 4-6.

Inboard fuel tanks 200 litres port 200 litres starboard

Outboard fuel tanks 200 litres port 200 litres starboard

200 litres x 0.72 = 144 kg

144 kg x 2.205 = 317.5 lb





FIGURE 4-6


Basic Aeroplane 4 6 0 0 + 122.5

Pilot’s Seat 1 7 0 + 95.0

Co-Pilot’s Seat 1 5 0 + 95.0

Seat No.3 1 2 0 + 137.0

Seat No.4 1 4 5 + 137.0

Seat No.5 8 0 + 195.0

Seat No.6 0 + 195.0

Seat No.7 0 + 229.0

Seat No.8 0 + 242.0

Fwd Baggage 4 0 + 19.0

Rear Baggage 1 2 0 + 255.0

Right Nacelle Locker Forward 5 0 + 145.0

Right Nacelle Locker Aft 5 0 + 192.0

Left Nacelle Locker Forward 5 0 + 145.0

Left Nacelle Locker Aft 5 0 + 192.0





Check that the total weight is within the permitted limits shown at Figure 4-1, which it is. Next calculate the moments by multiplying the weights by their associated arms. Now add all of the moments together to get, in this case, 885,363 inch-pounds. Finally divide the total moment by the total weight to get:

The completed table should now appear as shown at Figure 4-7.

Inboard Fuel 6 3 5 + 126.8

Outboard Fuel 6 3 5 + 148.0

Other

Total Weight 6 8 9 5 Tot Moment

885 363 inch-pounds,6 895 lb,

---------------------------------------------------- +128.4in=





FIGURE 4-7


Basic Aeroplane 4 6 0 0 + 122.5 5 6 3 5 0 0

Pilot’s Seat 1 7 0 + 95.0 1 6 1 5 0

Co-Pilot’s Seat 1 5 0 + 95.0 1 4 2 5 0

Seat No.3 1 2 0 + 137.0 1 6 4 4 0

Seat No.4 1 4 5 + 137.0 1 9 8 6 5

Seat No.5 8 0 + 195.0 1 5 6 0 0

Seat No.6 0 + 195.0 0

Seat No.7 0 + 229.0 0

Seat No.8 0 + 242.0 0

Fwd Baggage 4 0 + 19.0 7 6 0

Rear Baggage 1 2 0 + 255.0 3 0 6 0 0

Right Nacelle Locker Forward 5 0 + 145.0 7 2 5 0

Right Nacelle Locker Aft 5 0 + 192.0 9 6 0 0

Left Nacelle Locker Forward 5 0 + 145.0 7 2 5 0

Left Nacelle Locker Aft 5 0 + 192.0 9 6 0 0





Take the planned take-off weight and the calculated CG and go to Figure 4-2. You can now see that the CG lies within the envelope on take-off. This is shown at Figure 4-8.

You should of course appreciate that, although the C of A maximum take-off weight has not been exceeded, the actual take-off weight may in fact be limited by aircraft performance considerations (such as the runway length available, obstacles in the take-off flight path and so on); by the requirement to clear obstacles en-route to the destination of any nominated alternate aerodrome; or by the landing weight (with aircraft where the maximum landing weight is lower than the maximum take-off weight).

Inboard Fuel 6 3 5 + 126.8 8 0 5 1 8

Outboard Fuel 6 3 5 + 148.0 9 3 9 8 0

Other

Total Weight 6 8 9 5 Tot Moment 8 8 5 3 6 3

885,363 inch-pounds6 895lb,

-------------------------------------------------- +128.4in=





FIGURE 4-8





EXAMPLE 4-2EXAMPLE

The aircraft in Example 4-1 is planned to burn 650 litres of fuel en-route. The outboard tanks willbe used initially until they contain only 20 litres each, the inboard tanks will then be used for theremainder of the flight. Determine the landing weight and position of the CG on touchdown.

SOLUTION

The question doesn't indicate that we've lost any passengers en-route, and therefore the onlychange is going to be the weight of fuel, and the change in the position of the CG which hasresulted from the reduction in fuel load. Fuel remaining 150 litres.

20 litres in each of the outboard tanks weigh 31.75 lb. per tank, total 64 lb. (to the nearest lb.)

55 litres in each of the inboard tanks weigh 87.32 lb. per tank, total 175 lb. (to the nearest lb.)

The amended table should now appear as at Figure 4-9. With this aircraft the maximum landing weight is the same as the maximum take-off weight and so there is no problem (but the landing distance required will need checking). The new CG falls well within the envelope as shown at Figure 4-10.





FIGURE 4-9

Item Weight Lb. Arm Inches Moment Inches Lbs. (+)

Basic Aeroplane 4 6 0 0 + 122.5 5 6 3 5 0 0

Pilot’s Seat 1 7 0 + 95.0 1 6 1 5 0

Co-Pilot’s Seat 1 5 0 + 95.0 1 4 2 5 0

Seat No.3 1 2 0 + 137.0 1 6 4 4 0

Seat No.4 1 4 5 + 137.0 1 9 8 6 5

Seat No.5 8 0 + 195.0 1 5 6 0 0

Seat No.6 0 + 195.0 0

Seat No.7 0 + 229.0 0

Seat No.8 0 + 242.0 0

Fwd Baggage 4 0 + 19.0 7 6 0

Rear Baggage 1 2 0 + 255.0 3 0 6 0 0

Right Nacelle Locker Fwd 5 0 + 145.0 7 2 5 0

Right Nacelle Locker Aft 5 0 + 192.0 9 6 0 0

Left Nacelle Locker Fwd 5 0 + 145.0 7 2 5 0

Left Nacelle Locker Aft 5 0 + 192.0 9 6 0 0





CG Location for Landing

Inboard Fuel 1 7 5 + 126.8 2 2 1 9 0

Outboard Fuel 6 4 + 148.0 9 4 7 2

Other

Total Weight 5 8 6 4 Total Moment 7 4 2 5 2 7

742 527,5864

--------------------- 126.6 in=





FIGURE 4-10





#

Example 4-2 Alternative Solution.

An alternative procedure is shown below for determining the position of the CG on landing.

The fuel used from the outboard tanks (400 - 40) is 360 litres or 571 lb.

The moment change for the outboard tanks (571 x 148) is 84,508 in. lb.

The fuel used from the inboard tanks (650 - 360) is 290 litres or 460 lb.

The moment change for the inboard tanks (460 x 126.8) is 58,328 in. lb.

The total weight change during flight (571 + 460) is 1031 lb.

The landing weight is the take-off weight less the total weight of fuel used in flight.

The landing weight (6895 - 1031) is therefore 5864 lb.

The total moment change during flight (84,508 + 58,328) is 142,836 in. lb.

The landing moment is the take-off moment less the total moment change during flight.

The landing moment (885,363 - 142,836) is therefore 742,527 in. lb.

The position of the CG on landing (742,527 ÷ 5864) is 126.6".





EXAMPLE 4-3EXAMPLE

Determine the position of the CG of an aircraft at take-off, given the following information:

Maximum weight for take-off and landing 8000 lb. CG envelope from 1 inch to 4 inches forward of the datum at all weights.

Aeroplane Details for Example 4-3.

FIGURE 4-11

Item Weight or Volume Arm

Basic Aircraft 6000 lb. 5" forward of datum

Crew 350 lb. 40" forward of datum

Passengers 330 lb. 36" aft of datum

Fuel 150 Imp gallons SG 0.72 11" aft of datum

Engine Oil 8 Imp gallons SG 0.875 6" forward of datum





SOLUTION

Figure 4-12 shows schematically the distribution of the various weights about the datum andillustrates the need in this example to consider both positive and negative moments.

FIGURE 4-12

150 Imperial gallons of fuel (150 x 10 x 0.72) weigh 1080 lb. 8 Imperial gallons of oil (8 x 10 x 0.875) weigh 70 lb.





Solution to Example 4-3

FIGURE 4-13

The CG therefore lies within the approved envelope for take-off.

Item Weight Lb. Arm Inches Moment Inch / lbs

Basic Aircraft 6000 - 5 -30,000

Crew 350 -40 -14,000

Passengers 330 +36 +11,880

Fuel 1080 +11 +11,880

Oil 70 - 6 -420

7830 -44,420 +23,760

-20,660

CG- 20,660 inch pound

7830 lb------------------------------------------------ 2.64 inches–==





EXAMPLE 4-4EXAMPLE

Given that the aircraft described in Example 4-3 flies for 3 hours and that the mean rate of fuelconsumption is 32 Imperial gallons per hour, determine the position of the CG on landing.

SOLUTION

Fuel used in flight (3 x 32 x 10 x 0.72) is 691 lb. (to the nearest lb.). Fuel remaining (1080 -691) is 389 lb.

FIGURE 4-14

Item Weight Lb. Arm Inches Moment Inch/lbs

Basic Aircraft 6000 - 5 -30,000

Crew 350 -40 -14,000

Passengers 330 +36 +11,880

Fuel 389 +11 +4,279

Oil 70 - 6 -420

7139 -44,420 +16,159

-28,261





The CG on touchdown lies close, but within, the forward limit of the envelope.

Alternative Solution:

96 gallons of fuel weighing 691 lb. is burnt off during the flight. The aircraft weight is reducedby this amount to become 7139 lb.

The positive moments are reduced by (691 lb. x 11"), or 7601 inch pounds.

The revised algebraic sum of the moments is [(-20,660) - (+7601)], or -28,261 inch-pounds.

The new position of the CG is therefore (-28,261 ÷ 7139), or -3.96" (forward of the datum).

CG- 28,261 inch pound

7139 lb------------------------------------------------ -3.96 inches= =





EXAMPLE 4-5EXAMPLE

The following details apply to a six-seat twin engined aircraft. Maximum take-off and landingweight 6000 lb.

Maximum baggage weights:

Port and starboard wing lockers 120 lb. each

Nose bay 350 lb.

Aft cabin baggage area 340 lb.

Fuel capacities

Main tanks (x 2) 50 US gallons each

Auxiliary tanks (x 2) 30 US gallons each

80 x 2 = 160 US gallons

Specific gravity of the fuel 0.72

Basic aircraft:





Basic aircraft:

Weight 3900 lb., CG is 143 inches aft of datum.

Relevant arms, given in inches aft of the datum:

Nose bay baggage area 77

Pilot/Co-pilot 137

Row 1 passengers 175

Row 2 passengers 204

Aft cabin baggage area 242

Main fuel tanks 150

Auxiliary fuel tanks 162

Loading:

Two pilots 340 lb

Two pax row 1 320 lb

One pax row 2 80 lb

Nose baggage bay 50 lb

Aft cabin baggage 310 lb

Fuel main tanks 100 US gallons

Fuel auxiliary tanks (If take-off weight permits) 60 US gallons





The centre of gravity limits for the aircraft in this example are shown graphically below.

FIGURE 4-15

Determine whether or not the CG will lie within the envelope at take-off, with the aircraft loaded as described.





SOLUTION

The first thing is to decide whether or not the maximum permitted weight for take-off (6000 lb.)will permit full auxiliary fuel tanks:

The maximum fuel weight is therefore 1000 lb. The weight of aircraft plus crew, passengers and baggage is 5000 lb. The main tanks are full and contain (100 ÷ 1.2 x 10 x 0.72), 600 lbs. of fuel.

If filled, the auxiliary tanks will between them hold (60 ÷ 1.2 x 10 x 0.72), 360 lb. of fuel.

It is therefore possible to fill the auxiliary tanks, and take-off at maximum all-up weight minus 40 lb. Now construct and complete a table in the approved manner.

FIGURE 4-16

Item Weight Lb. Arm Inches Moment Inch Pounds

Basic Aircraft 3900 +143 +557,700

Crew 340 +137 +46,580

Row 1 Passengers 320 +175 +56,000

Row 2 Passengers 80 +204 +16,320

Nose Bay Bags 50 +77 +3850

Aft Cabin Bags 310 +242 +75,020

Main Tanks 600 +150 +90,000

Aux Tanks 360 +162 +58,320

5960 +903,790





Plotting CG against weight gives us a point outside of the envelope, see Figure 4-17. Plotted Answer to Example 4-5

FIGURE 4-17

The aircraft cannot fly whilst loaded in this manner and quantity of baggage will have to be moved from the aft baggage area to the nose bay baggage area in order to move the CG to within safe limits.

Position CG903 790,

5960--------------------- +151.6 inches (aft of datum)= =





EXAMPLE 4-6EXAMPLE

Determine the minimum amount of baggage that must be moved from the aft baggage areato the nose bay baggage area, in order to move the CG calculated in Example 4-5 to the aftsafe limit. The baggage to be moved comprises individual packages each weighing 10 lb.

SOLUTION

The maximum aft safe CG position is 149", see Figure 4-17.

The movement of baggage will not change the total weight of the aircraft but it will alterthe total moments. The required total moments, that is the moments which will result froma CG at 149" and a total (unchanged) weight of 5960 lb., will be 888,040 in. lb.

The change of moment caused by moving 1 lb. of baggage from the aft baggage area (at anarm of +242") to the nose bay baggage area (at an arm of +77") is -165 in. lb.

The change of moment is minus since load is being moved forward.

The total change of moment required is determined by subtracting the total moments for aCG at +149" from the total moments for a CG at +151.6" from Example 4-5.

The total change of moment required (903,790 - 888,040) is therefore 15,750 in/lb.

The amount of baggage which must be moved from the aft baggage area to the nose baybaggage area (15,750 ÷ 165) is therefore 95.45 lb.

The baggage can only be moved in 10 lb. increments and therefore it is necessary to move100 lb. The revised baggage distribution is therefore as shown in the table which follows.





FIGURE 4-18

Plotting CG against weight gives us a point inside of the envelope, see Figure 4-19.

Item Weight Lb. Arm Inches Moment Inch Pounds

Basic Aircraft 3900 +143 +557,700

Crew 340 +137 +46,580

Row 1 Passengers 320 +175 +56,000

Row 2 Passengers 80 +204 +16,320

Nose Bay Bags 150 +77 +11,550

Aft Cabin Bags 210 +242 +50,820

Main Tanks 600 +150 +90,000

Aux Tanks 360 +162 +58,320

5960 +887,290

Position CG887 290,

5960--------------------- +148.9 in (aft of datum)= =





FIGURE 4-19





EXAMPLE 4-7EXAMPLE

The mean fuel consumption for the flight is 180 lb. per hour, and the flight time is 4.5 hours.Given that the aircraft is loaded as described in Example 4-5, and that the fuel which remains ontouchdown is all contained in the main tanks, check that the CG lies within the envelope onlanding.

SOLUTION

Fuel on take-off 960 lb.

Fuel consumed in flight 810 lb.

Fuel on touchdown 150 lb.





FIGURE 4-20Item Weight Lb. Arm Inches Moment Inch/lbs

Basic Aircraft +557,700

Crew +46,580

Row 1 Passengers +56,000

Row 2 Passengers +16,320

Nose Bay Bags +11,550

Aft Cabin Bags +50,820

Main Tanks 150 +150 +22,500

Aux Tanks - - -

5960

-810

5150

+761,470

Position CG 761 470,

5150--------------------- 147.9 in (aft of datum)= =





The CG lies within the envelope, see Figure 4-21.

Plotted Answer to Example 4-7.

FIGURE 4-21

The conventional graph used to present the CG envelope, which we have used so far, employs a vertical ‘total aircraft weight’ axis and a horizontal ‘distance from datum’ axis. An alternative presentation is shown at Figure 4-22.





At Figure 4-22 the vertical axis of the graph remains as ‘total aircraft weight’, in this case usingpounds as the unit of weight. The horizontal axis has changed and now represents the ‘totalaircraft moments’, in this case using units of ‘total inch-pounds divided by 1000’. Dividing thetotal moment by 1000 is simply a device which is used in order to keep the numbers to amanageable magnitude.

FIGURE 4-22





Transverse Loading6. So far all of the calculations concerning the position of the CG of an aircraft have consideredthe position along the fore and aft axis. It is important that an aircraft be loaded such that it isreasonably balanced about the centreline. The most common reason for an aircraft to be unbalancedabout the centreline is that the wing fuel is unevenly loaded. Wing tanks, especially outboard tanksand possibly wingtip tanks, have a considerable arm from the centreline. Aircraft operating and/orloading manuals will frequently contain limits as to the amount of permissible imbalance in respectof lateral fuel distribution.

7. Should it be necessary to determine the position of the CG relative to the centreline,appreciate that, by convention, arms to the left (port) of the centreline are positive and arms to theright (starboard) of the centreline are negative.





EXAMPLE 4-8EXAMPLE

An aircraft is loaded such that the weight is evenly distributed about the centreline, withthe exception of the fuel, which is loaded such that there is 400 lb. of fuel in the left wingand 500 lb. of fuel in the right wing. The lateral arm for the wing fuel tanks is 127". Ifthe loaded weight of the aeroplane is 9000 lbs, determine the lateral position of the CG.

SOLUTION

Total moments = (+ 400 x 127) + ( - 500 x 127)

= 50,800 - 63,500

= - 12,700 in. lb.

Lateral CG =

= -1.41"

= 1.41" right of the centreline

-12,7009000

------------------





C of G Practice Calculations

Question 1Aeroplane Data

(a) Calculate the C of G arm

(b) If the fuel consumption is 40 Imp. gals/hr and the oil consumption is 2 Imp. gals/hr,calculate the arm of the C of G after three hours.

Maximum Authorised Weight 8000 lbs

C of G limits 4" to 0.5" forward of datum

Basic weight 6000 lbs arm 5" forward of datum

Fuel 150 Imp. gals arm 11" aft of datum

Oil 8 Imp. gals arm 6" forward of datum

Crew 340 lbs arm 40" forward of datum

Passengers 340 lbs arm 36" aft of datum

SG of fuel 0.72 SG of oil 0.90





Question 2 Aeroplane Data

(a) Calculate the arm of the C of G at take-off

(b) If the fuel consumption is 204 Imp. gals/hr and the oil consumption is 4 pints/hr, whatis the arm of the C of G after 4 hours?

Maximum Authorised Weight 60,000 lbs

C of G limits 1.5 ft. aft of datum to 2.5 ft. aft of datum

Basic weight 26,000 lbs arm 1 ft. aft of datum

Crew 300 lbs arm 5 ft. forward of datrum

Freight in hold A 10,400 lbs arm 6 ft. aft of datum

Freight in hold B 800 lbs arm 1 ft. forward of datrum

Fuel 2000 Imp. gals on the datum

Oil 25 Imp. gals arm 1 ft. forward of datum






Question 3Aeroplane Data

(a) Calculate the C of G for take-off

(b) Calculate the C of G for landing after three hours.

Maximum Authorised Weight 8500 lbs

C of G limits 18 to 29" aft of datum

Basic weight 5000 lbs arm 30" aft of datum

Crew 340 lbs arm 30" forward of datum

Fuel 200 US gals arm 10" forward of datum

Oil 15 US gals arm 8" aft of datum

Passengers 340 lbs arm 40" aft of datum


Fuel consumption 50 US gals/hr

Oil consumption 2 US gals/hr





C of G Practice Calculation Answers

Answer 1C of G limits -4" to -0.5"

C of G arm

(a) Weight Arm Moment

APS 6000 lbs -5" -30,000 ins/lbs

Fuel 1080 lbs +11" +11,880 ins/lbs

Oil 72 lbs -6" -432 ins/lbs

Crew 340 lbs -40" -13,600 ins/lbs

PAX 340 lbs +36" +12,240 ins/lbs

Totals 7832 lbs -19,912 ins/lbs

19912–7832

------------------ 2.542″–=





C of G arm (out of limits)

(b) Fuel used 40 x 3 = 120 Imp. gals = 864 lbs

Oil used 2 x 3 = 6 Imp. gals = 54 lbs

Weight change - 918 lbs

Moment change (-864 x +11) - (54 x-6) = -9180

Revised weight 7832 - 918 = 6914 lbs

Revised moment -19,912 - 9180 = 29092 ins/lbs

29092–6914

------------------ 4.208– ″=





Answer 2

C of G arm


APS 26,000 lbs +1 ft +26,000 ft/lbs

Crew 300 lbs -5 ft - 1500 ft/lbs

Hold A 10,400 lbs + 6ft + 62,400 ft/lbs

Hold B 800 lbs - 1ft - 800 ft/lbs

Fuel 14,400 lbs 0 0

Oil 225 lbs - 1ft -225 ft/lbs

Totals 52,125 lbs

+85 875,52 125,

--------------------- +1.647 ft=





C of G arm

(b) 4 hrs fuel 816 gals = 5875.2 lbs

4 hrs oil 2 gals = 18 lbs

Change of weight - 5893.2 lbs

Revised AUW 46,231.8 lbs

Moment change fuel = 0

oil = -18 x = 85,893 ft/lbs

Revised moment 85,875 + 18 = 85,893 ft/lbs

85 893,46 231.8,---------------------- 1.8579 ft=





Answer 3

C of G arm


APS 5000 lbs +30" +150,000 ins/lbs

Crew 340 lbs - 30" -10,200 ins/lbs

Fuel 1200 lbs -10" -12,000 ins/lbs

Oil 112.5 lbs +8" +900 ins/lbs

PAX 340 lbs +40" +13,600 ins/lbs

Totals 6992.5 lbs + 142,300 ins/lbs

+142.3006992.5

---------------------- +20.35″=





C of G arm

(b) 3 hrs fuel 150 US gals = 125 Imp. gals = 900 lbs

3 hrs oil 6 US gals = 5 Imp. gals = 45 lbs

Revised AUW 6992.5 - 45 = 6047.5 lbs

Moment change - 900 x -10 = +9000 ins/lbs

- 45 x +8 = -360 ins/lbs

total +8640 ins/lbs

Revised moment +142,300 + 8640 = +150,940 ins/lbs

+150,9406047.5

---------------------- +24.96″=






Adding or Removing Load

Repositioning a Load





5Adding, Removing and Repositioning Loads

1. When a detailed description of the weight and arms of an aeroplane and all of its contents isavailable, the method used to determine the position of the laden aircraft CG is to complete a trimsheet. Having done this, if the CG is outside of the approved envelope it is necessary to redistributethe load in order to move the CG to within limits, if possible. If this is not possible then some of theload will need to be removed from the aircraft altogether in order to put the CG within the envelope.

2. Frequently, once the trim sheet is complete, additional payload is added (last minute changes)and it is essential that the new CG is calculated in order to ensure that it is still within limits.

Adding or Removing Load3. To facilitate the rapid and easy calculation of either the new CG position, when a load isadded or removed, or the amount of load which must be removed in order to achieve a given CGposition there is an algebraic solution. By introducing an algebraic value for the unknown quantityinto the following formula, the value of the unknown quantity can be determined. The formula is:

4. In the formula above the ‘Load moment’ is the product of the weight and arm of the loadwhich is added or removed from the aircraft. The symbol will therefore appear as a + if a load isadded or a – if a load is removed.

New Total Moments = Old Total Moments + or – Load Moment





5. If the formula is to be utilised to account the use of fuel it may be modified (by replacing‘Load Moment’ with ‘Fuel Moment’) and used to recalculate the CG position for landing if a largeror smaller quantity of fuel has been consumed in flight than was originally planned.

EXAMPLE 5-1EXAMPLE

Given an aeroplane all up weight of 120,000 lb. and CG arm 4 ft aft of the reference datum.Determine how much load must be removed from a cargo hold 33 ft aft of the datum in order tomove the CG 1–ft forward from its original position.





SOLUTION

Let W be the unknown, in this case the amount of load to be removed.

New Total Moments = Old Total Moments – Load Moment

New CG arm = +4 ft – 1 ft.

= +3 ft.

New weight = 120,000 – W lb.

New Total Moments = (120,000 – W) x (+3) ft. lb.

= 360,000 – 3W ft. lb.

Old Total Moments = 120,000 x (+4) ft. lb.

= +480,000 ft. lb.

Load moment = W (+33) ft. lb.

= 33W ft. lb.


360,000 –3W = 480,000 – 33W

33W – 3W = 480,000 – 360,000

30W = 120,000

W = 4000 lb.

In order to position the CG 3–ft aft of the datum it is therefore necessary to remove 4000 lb. of load.





EXAMPLE 5-2EXAMPLE

Given an all up weight of 80,000 kg and a CG 16 metres aft of the datum which is the nose ofthe aircraft, determine the change in the position of the CG, if 5,000 kg of freight is nowloaded in a hold 23 metres aft of the datum.

SOLUTION

Let D = The unknown distance of the New CG Arm.

New Total Moments = Old Total Moments + Load moment

(80,000 + 5,000) x D = (80,000 x (+16)) + (5,000 x (+23))

85,000 x D = 1,280,000 + 115,000

D =

D = +16.412 m.

Change to CG Arm = New CG Arm – Old CG Arm

Change = (+16.412 – (+16))

= +0.412 m.

The CG has therefore moved 0.412 metres aft of its original position.

1 395 000, ,85 000,

---------------------------





EXAMPLE 5-3EXAMPLE

Given an all up weight of 65,000 lb. and a CG 18.5–ft aft of the datum, which is the nose of theaircraft. Determine the change in the position of the CG if 3,200 lb. of freight is removed from ahold 14 ft aft of the datum.

SOLUTION


Let D be the new CG arm.

(65,000 – 3200) x D = (65,000 x (+18.5)) – (3200 x (+14))

61,800 x D = 1,202,500 – 44,800

D =

D = +18.733 ft

Change to CG Arm = New CG Arm – Old CG Arm

Change = (+18.733 – (+18.5))

= +0.233 ft

The CG has therefore moved 0.233 metres aft of its original position.

1 157 700, ,61 800,

--------------------------- ft





6. If freight or fuel is added or removed from an aeroplane and the cargo hold or fuel tank ismeasured relative to the present CG position, the change to the CG can be determined by a simpleformula. If the freight or fuel is added, then the weight value is positive and if it is removed it is anegative value. If the distance of the hold or fuel tank is ahead of the present CG the distance is anegative value and if it is aft of the present CG it is a positive value. The formula is:

EXAMPLE 5-4

Freight/fuel distance from present CG×New aircraft weight

------------------------------------------------------------------------------------------------- change to CG=

EXAMPLE

Given: Aircraft weight 150,000 kgs, if 5000 kgs of freight is added to a hold 10 m ahead of thepresent CG, determine the change to the CG

SOLUTION

. New CG is 0.323 m ahead of old CG.5000 10–×155000

--------------------------- 0.323m–=





EXAMPLE 5-5

Repositioning a Load7. As already discussed, the CG position is influenced by the relocation of the load. Whendealing with this type of problem it is convenient to use the following formula:

or

8. The signs to be used in this formula for ‘cc’ and ‘d’ are + for a rearward movement of the loadand – for a forward movement of the load.

EXAMPLE

Given: Aircraft weight 30,000 lbs, if 2000 lbs of fuel is used from a fuel tankpositioned 5 ft forward of the present CG, determine the change to the CG.

SOLUTION

The new CG is 0.357 ft aft of the old CG.2000 5–×–+28000

--------------------------- +0.357 ft=

Wt of load to be movedTotal weight

--------------------------------------------------------Change to CG arm

Distance load moved--------------------------------------------------=

wW-----

ccd-----=





NOTE:

Note this formula can only be used with ‘moving load within an aeroplane’problems. It cannot be used for problems involving removing loads, using fuelor adding loads or increasing the fuel on board. However, the originalformula: New Total Moments = Old Total Moments + Load Moment can beused for ‘moving loads within an aeroplane’ problems. It is used in thismanner: New Total Moments = Old Total Moments – Load Moment + LoadMoment. The – Load Moment is used for removing it from the original holdand the + Load Moment is used for loading it back on the aeroplane in the newhold.





EXAMPLE 5-6EXAMPLE

Given an All Up Weight of 60,000 kg and a CG 22 metres aft of the datum, which is thenose of the aircraft. Determine the change in the position of the CG if 3,000 kg of load ismoved from a hold 14 metres aft of the datum to a hold 29 metres aft of the datum.

SOLUTION

The load (3,000 lb.) is to be moved aft by 15 metres as illustrated below.





=

=

= cc

cc = –0.75 metres (aft movement)

New Total Moments = Old Total Moments – Load Moment + Load Moment

(600,000 x D) = 60,000 x (+22)] – [3,000 x (+14)] + [3,000 x (+29)]

60,000 D = 132,000 – 42,000 + 87,00

60,000 D = 1,365,000

D = 22.75 m.

Change to CG Arm = New C G Arm – Old CG Arm

= 22.75 m. – 22 m.

+0.75 m. = 0.75 m. Aft.

wW-----

ccd-----

300060 000,------------------

cc+15---------

3000x 15+60 000,

---------------------------





EXAMPLE 5-7EXAMPLE

Given an All Up Weight of 25,000 kg and a CG 9 metres aft of the datum. Determine thechange in the position of the CG if 1,000 kg of load is moved from a hold 12 metres aft ofthe datum to another 5 metres aft of the datum.

SOLUTION

The load (1,000 kg) is to be moved forward by 7 metres as illustrated here.





=

=

= cc

cc = –0.28 metres or

–28cm (forward movement)

New Total Moments = Old Total Moments – Load Moment + Load Moment

(25,000 x D) = 25,000 x (+9)] [1,000 x (+12)] + [1,000 x (+5)]

25,000 D = 225,000 – 12,000 + 5,000

25,000 D = 218,000

D = 8.72 m.

Change = 8.72 –9 = –0.28 m. = 0.28 m. forward

wW-----

ccd-----

100025 000,------------------

cc- 7------

1000x 7–25 000,

------------------------





EXAMPLE 5-8EXAMPLE

Given an All Up Weight of 145,000 lb. And a CG 21 ins. forward of the datum. Determinehow much freight must be moved from a hold 96 ins. forward of the datum to a hold 84 ins.aft of the datum in order to move the CG 1.5 ins. aft of its original position.

SOLUTION

=

=

w =

w = 1208 lb

wW-----

ccd-----

w145 000,---------------------

+1.5+180------------

+1.5 x 145,000+180

------------------------------------





EXAMPLE 5-9EXAMPLE

Given an All Up Weight of 120,000 lb and a CG 4 ft aft of the reference datum.Determine how much load must be moved from a hold 35 ft aft of the datum to a hold25 ft forward of the datum in order to move the CG to a point 3 ft aft of the datum.

SOLUTION

=

=

w =

w = 2000 lb

wW-----

ccd-----

w120 000,--------------------- 1–

-60--------

1 x 120,000–60–

-------------------------------





It should be understood that fuel usage in flight can move the position of the CG, particularly inlonger aircraft with heavy fuel loads in numerous tanks. Faithful adherence to the fuel managementprocedures as laid down in the AFM will ensure that the CG remains within the specified limitsduring the flight. With large aircraft the usage of fuel can be arranged such that the CG is kept asclose as possible to the optimum position for significant periods of the flight, again in accordancewith AFM Procedures. This procedure ensures the CG remains just forward of the Aft Limit, and isreferred to as flying the ‘Flat’ aeroplane. It results in a significant increase in range.

Formula Practice Questions

Question 1

Question 2

Given AUW 60,000 lbs. C of G 2 ft. forward of datum.

Calculate: How much freight must be added to hold arm 5 ft. aft of datum to move the C of G to 1 ft. forward of datum?

Given AUW 100,000 kgs. Datum at nose. C of G 15m aft of datum.

Calculate: The change to C of G arm if 4,000 kgs of freight is removed from hold 25m aft of datum.





Question 3

Question 4

Question 5

Given AUW 60,000 kgs. C of G arm 6m aft of datum.

Calculate: The change to C of G arm if 10,000 kgs of fuel is used from tank arm 1m forward of datum.

Given AUW 12,000 lbs. C of G 2 ft aft of datum.

Calculate: How much freight must be removed from hold 4 ft aft of datum to move C of G 6 inches forward?

Given AUW 50,000 kgs datum at nose. C of G 25m. aft of datum.

Calculate: Change to C of G arm if 1,000 kgs of freight is moved from hold 50m aft of datum to hold 30m aft of datum.





Question 6

Question 7

Formula Practice Answers

Answer 1

Calculate: If the freight in Question 5 is removed, what is the arm of the new C of G?

Given AUW 30,000 lbs. C of G arm 3 ft aft of datum.

Calculate: How much freight must be removed from hold 5 ft aft of datum to move C of G 6 inches forward?

New Total Moments = Old Total Moments ± Freight/Fuel Moment

Let w = Unknown freight

(60,000 + w) x (-1) = [60,000 x (-2)] + [(w x (+5)]

- 60,000 - w = 120,000 + 5w

120,000 - 60,000 lbs = 5w + w

60,000 lbs = 6w

10,000 lbs = w





Answer 2

Answer 3

Let d = New C of G arm

(96,000 x d) = [100,000 x (+15)] - [4,000 x (+25)]

96,000 d = 1,500,000 - 100,000

d = 1,400,000 ÷=96,000 = +14.58m

Change to C of G = +14.58 - 15.0 = -0.42m

= 0.42m Forward

Let d = New C of G Arm

(50,000 x d) = [60,000 x (+6)] - [10,000 x (-1)]

50,000 d = 360,000 + 10,000

d = 370,000 ÷ 50,000 = +7.4m

Change to C of G Arm = 7.4 - 6 = +1.4m





Answer 4

Answer 5

Let w = Freight to be removed

(12,000 - w) x 1.5 = [12,000 x (+2)] - [w x (+4)]

18,000 - 1.5w = 24,000 - 4w

4w - 1.5w = 24,000 - 18,000

2.5w = 6,000

w = 2.4000 lbs.


(50,000 d) = [50,000 x (+25)] - [1,000 x (+50)] + [1,000 x (+30)]

50,000 d = 1,250,000 - 50,000 + 30,000

d = 1,230,000 ÷ 50,000 = +24.6m

Change to C of G Arm = +24.6 - 25.0 = -0.4m = 0.4m Forward





Answer 6

or

Answer 7


(1) 49,000 d = [50,000 x (+25)] - [1,000 x (+50)]

49,000 d = 1,250,000 - 50,000 = 1,200,000

d = 1,200,000 ÷ 49,000 = +24.49m

(2) 49,000 d = [50,000 x (+24.6)] - [1,000 x (+30)]

49,000 d = 1,230,000 - 30,000 = 1,200,000

d = 1,200,000 ÷ 49,000 = +24.49m

Let w = Freight to be removed

(30,000 - w) x 2.5 = [30,000 x (+3)] - (w x5)

75,000 - 2.5w = 90,000 - 5w

5w - 2.5w = 90,000 - 75,000

2.5 w = 15,000

w = 6,000 lbs





6The Mean Aerodynamic Chord

1. On large transport aircraft the position of the CG is often expressed in relation to theaircraft’s Mean Aerodynamic Chord (MAC). The MAC is precisely what the name implies. If youtake the plan view of a swept and tapered wing and draw a number of chord lines across the wing,each chord will necessarily be of a different length (longer at the wing root and shorter at the wingtip) and a different distance from the nose of the aircraft (the shorter distance at the wing root andthe furthest distance at the wing tip). If you now take the mathematical mean of all these chord linesyou have the MAC, expressed as a single length starting at a stated distance from the reference datumof the aircraft. For example an aircraft’s MAC might be expressed as 205 inches in length extendingfrom 790 to 995 inches aft of the reference, as shown at Figure 6-1.





FIGURE 6-1Example Mean Aerodynamic Chord

2. The following examples illustrate how to convert the position of a CG which is given as apercentage of the MAC into a position which is relative to the reference datum, and the reverse.





EXAMPLE 6-1EXAMPLE

The MAC limits of an aircraft are 802.7 inches to 1020.5 inches aft of datum. The CG is 31% ofthe MAC. Determine the position of the CG relative to the datum.

SOLUTION

See Figure 6-2.

MAC (1020.5 – 802.7) = 217.8 inches.

CG Position = 802.7 + 67.5 = 870.2 inches aft of datum.

31% MAC217.8100

------------- 31× 67.5 inches= =





FIGURE 6-2





EXAMPLE 6-2EXAMPLE

The CG of a loaded aircraft is given as 503.6 inches aft of the datum. The MAC for this aircraftextends from 482.2 inches to 536.7 inches aft of the datum. Express the position of the CG as apercentage of the MAC.

SOLUTION

See Figure 6-3.

MAC (536.7 – 482.2) = 54.5 inches

CG Position= 503.6 – 482.2 = 21.4 inches aft

(Relative to forward MAC Limit)

CG as % MAC21.454.5---------- 100× 39.3 %= =





FIGURE 6-3






Securing Aircraft Loads

Weight Limits





7Structural Limitations

1. In addition to the weight and C of G limitations already described it is necessary to imposefurther restrictions to ensure that the aeroplane floor is not overloaded or that the aeroplanestructure is not over-stressed. These limitations are divided into overall limitations and floor loadinglimitations.

Overall Limitations. An aeroplane is constructed about its main spar because it is this that mustsupport it in flight. Most large aeroplanes have a double main spar. The forward spar supportingthe weight in front of it whilst the rear spar supports the weight aft of it. Hence it may be consideredto be two cantilever beams, as shown in Figure 7-1. If the weight of the aeroplane is unevenlydistributed about the double spar the fuselage will bend about the spar bending greatest toward theheavier weight. Although the bending caused by unevenly distributed loading will not beimmediately apparent the forces do exist and if the unequal division of the load is overmuch are aserious potential source of damage to the aeroplane.





FIGURE 7-1The Effect of Uneven Load Distribution

2. The fact that the C of G is within limits does not necessarily mean that the loaded aeroplaneis within the bending limitations. Nor does the fact that the load is within the individualcompartment load limitations ensure that it is loaded within the bending limits.

3. There are Tables and Graphs provided by the manufacturer to check the compliance of theloaded aeroplane with the requirements.

Floor Loading Limitations. The strength of the aeroplane floor varies throughout its length andwidth according to the construction and location of the individual panels and their supportingbeams. There are two limitations imposed on floor panels to protect them and the aircraft fromdamage. They are the linear and area load maxima.

Linear Limitations. This is the maximum weight per unit length of the floor. The width of theload does not affect this limitation. The limitation may be expressed in lbs/linear ft or kgs/linearmetre. This restriction therefore requires that due consideration be given to the way in which theitems loaded are orientated. The linear load limitation is often referred to as the ‘Running Load’.





FIGURE 7-2Linear Loading

Box A loaded laterally equals 300 kg/linear m.

Box B Same weight and length as A but loaded longitudinally, equals 60 kg/linear m.





Area Limitations. To provide protection for individual floor panels an area limitation is imposedand is expressed in kg/sq.m. or lbs./sq. ft. Items which have a large surface area impose a low areafloor load. However, those having a small area of contact with the floor have a high area floor loade.g. the wheels of a vehicle. Often ‘Load Spreaders’ are used with this type load, this is some type ofmaterial, usually wood, which has a larger contact area with the floor and is placed by the item’scontact points and the floor. Thus the weight of the item is distributed over a larger area reducingthe area floor load. Again orientation of the load is all important. In the following exampleFigure 7-3 is loaded in five different ways producing three different floor loads.





FIGURE 7-3Area Loading





4. All five boxes are the same size and weight 600 kgs. But each has a different effect on thefloor. In the example the area floor loading limitation is 100 kgs/sq.m. and linear load limitation is200 kgs/linear m.

5. To find the area load divide the weight by the floor area.

6. To calculate the linear load divide the weight by the longitudinal length.

Box 1 - 300 kgs/sq.m. and 600 kgs/linear m. (exceeds both limitations).

Box 2 - 200 kgs/sq.m. and 600 kgs/linear m. (exceeds both limitation).

Box 3 - 100 kgs/sq.m. and 300 kgs/linear m. (exceeds linear limitation).

Box 4 - 200 kgs.sq.m. and 200 kgs/linear m. (exceeds area limitation).

Box 5 - 100 kgs.sq.m. and 200 kgs/linear m. (complies with both limitations).

7. To keep the area and linear loads to a minimum, the longest side must be along thelongitudinal axis and the second longest side should be along the athwartships axis.

Securing Aircraft Loads8. The safety of an aeroplane is of paramount importance and depends on many different peoplecompetently completing their individual tasks. Incorrect loading of the aircraft could haveimmediate and devastating consequences.

Weight Limits9. The weight of any particular load may be restricted by one of three limitations:





(a) The total weight of the aeroplane including its load must not exceed the maximumpermitted take-off weight.

(b) The load must not exceed the maximum permissible floor loading, measured in kg/m2

or lb/ft2, for each individual cargo or baggage compartment.

(c) The load must not exceed the capacity of the load restraint.

Floor Loading10. It is important to minimise the floor loading. If the load has a flat base, which is all in contactwith the aircraft floor, then the weight of the load is distributed over the whole base area. However,if by virtue of its shape, the weight of the load is imposed on the floor through a small area in contactwith the floor then it may exceed the maximum floor load. To distribute the load over a greater floorarea and thus reduce the floor load a mechanical device known as a load spreader may be insertedbetween the load and the aircraft floor. See Chapter 2.

Load Factor11. The load factor is the ratio of an externally applied force to a load with a given weight:

Load Factor Applied ForceWeight

------------------------------------=





12. The load factor is described using multiples of the gravitational force (g) acting on the load.The load factor is therefore +1g under normal gravity conditions. The plus sign indicates that theload is acting vertically downwards. In a 60° bank turn the aircraft, and its contents, are subject to aload factor of +2g. In a bunt manoeuvre the aircraft and its contents are subject to negative g (anegative load factor), which will tend to lift unsecured items off the floor. Similarly, rapidaccelerations will tend to move loads backwards and rapid decelerations will tend to move the loadsforwards, under the effects of inertia.

Load Restraint13. In order to ensure that the load does not move during any phase of flight it must beadequately secured in all directions using the most suitable equipment in a planned tie-down scheme.Failure to prevent movement of the load could hazard the safety of the aeroplane by virtue of themomentum or inertia of the load.

14. The restraint factor for fixed wing aircraft is expressed in multiples of the force of gravity.This determines the strength of the lashing and tie-down equipment required to secure the load. Thecurrent restraint load factors are:

Forwards 3g

Rearwards 1.5g

Lateral 1.5g

Vertical 2g





15. On flights where passengers and cargo are required to share the same compartment, therestraint load factors are increased to coincide with the load factors for passenger seats. These loadfactors are listed shortly.

Restraint Equipment16. On a cargo aeroplane there are many different types of equipment that may be usedindividually or together to secure a load. Most require attachment to aircraft floor points, which,although they are strong points, have a maximum strength, which must not be exceeded. Theyinclude:

Lashing Chains. These should be applied symmetrically between 30° and 45° both with theaircraft floor and the longitudinal axis.

Tensioners. These are mechanical devices used to take any slack out of the tie-down scheme andtighten the lashing equipment.

Cargo Nets. These are strong webs of nylon or similar material which may be used to secure anumber of small items together as one load by covering them all and securing the net at specificpoints to the aircraft floor.

Side Guidance. This is a means of protecting the aircraft structure from damage when loadingand unloading the cargo bay.

Grab Hooks. These are a means of securing a cargo net to a lashing point.





Passenger Seats17. Aircraft seats are specifically designed to fit into secure floor points. Aircraft seats areequipped with seat belts. The floor securing system together with the seat belt are intended to enablethe occupant to escape serious injury in the event that the seat and occupant are exposed to thefollowing load factors:

18. In the event of an emergency landing, the deformation of seats and other items of cabinequipment should not be such that they would impede rapid evacuation from the aircraft cabin. Anyitems of significant size or weight within the passenger compartment, galleys or flight deck must berestrained to prevent their movement during an emergency landing. [JAR-25 561 (b) (3)].

Load Shift19. If the load is not correctly secured using an approved tie-down scheme, it may move andcause a hazard to the aeroplane. Load shift is likely to occur:

During Take-Off. At VR the aircraft attitude will cause any loose load to move aft causing theaircraft to pitch up even further, making the aircraft unstable and possibly causing it to stall.

Upward 3.0g

Forwards 9.0g

Sideways 4.0g

Downward 6.0g

Rearward 1.5g





Nose-Down Pitching. On pitching nose down any loose cargo will move forward, causing theaircraft to pitch further nose down. With a severe load shift it may be impossible to return theaircraft to level flight. A forward load shift which occurs during the landing may make it difficult orimpossible to round out.

Deceleration. A rapid deceleration (notably during the landing roll) of the aircraft will cause anunsecured load to move forward due to inertia.

Load Spreaders. A load spreader is material, usually thick wood, placed between the aircraft floorand heavy load items which exceed the floor load intensity limitation and/or have hard or sharpcontact areas. Its purpose is to extend the load intensity over a larger floor area than the base of theitem and at the same time protect the aircraft floor from damage. The effectiveness of a loadspreader is established by its thickness, not its overall size. To utilise its full potential its area must belarge enough to contain a 45° angle from the base of the load item to the aircraft floor.





FIGURE 7-4

Dunnage. Material, usually thick wood, utilised to protect the aircraft floor, including ramps, andprovide a continuous pathway over which wheeled vehicles may transit when being positioned in thefuselage prior to lashing down without exceeding the maximum area limit at any point.






Manual Load and Trim Sheets

Load and Trim Sheet Completion Procedure

Computer Load and Trim Forms

Last Minute Changes

Aircraft Load and Trim Slide Rule





8Manual and Computer Load/Trim Sheets

1. A load and trim sheet may be produced either manually or by computer. It is most importantthat it is thoroughly checked by the aircraft commander and signed by him (or her) as accepting theload and its distribution within the aircraft. A trim slide rule, discussed later in this chapter, may beused for this purpose.

2. A load and trim sheet is a record of the weight of an aircraft and the distribution of itscontents. It must be drawn up by a person qualified in the loading and security of load for flight.The load sheet must be signed in duplicate before flight by the person supervising the loading andpassed to the aircraft commander. If the aircraft commander is satisfied that the load carried is ofsuch weight and is so distributed and secured that the flight can be safely conducted then he is to signthe load sheet as accepting the load. [JAR-OPS 1.625 (a)].

3. If the payload weight and distribution is unchanged from the previous flight and the aircraftis refuelled with the same weight and distribution of fuel as on the previous flight the load sheet forthe previous flight may be used. The aircraft commander must endorse the load sheet of the previousflight with signature, date and place of departure of the next intended flight and intendeddestination.

4. If it is necessary for an aircraft to stop en-route in order to refuel it is likely that the payloadweight and distribution will be unchanged, however the fuel load may differ from the previous sector.In this case an abbreviated load and trim sheet, known as a Nil Change of Payload Form may becompleted.





5. One copy of the load sheet is to be carried in the aircraft during the flight to which it relates.One copy is to be kept on the ground by the operator and retained for 3 months. [Appendix 1 toJAR-OPS 1.1065]. If this is not practical then the second copy must be kept in a special containerin the aircraft provided for the purpose and deposited with the operator at the first opportunity.[JAR-OPS 1.140 (a) (1) (iii)].

6. These load sheet requirements do not apply to an aircraft with an MTWA of 1150 kg or less.Nor do they apply to aircraft with an MTWA of 2730 kg if the flight time is 60 minutes or less and itis a crew training flight or a flight intended to begin and end at the same aerodrome. Helicopterswith an MTWA of 3000 kg or less and a seating capacity of five persons or less are also exempt fromthe load sheet requirements.

Manual Load and Trim Sheets7. The manual load and trim sheet may be completed by the agent or alternatively, by theCaptain or First Officer.

8. The manual load and trim sheet shown at Figure 8-1 looks complex but is in factstraightforward. Let's go through it step by step, which unfortunately isn't from top left to bottomright. Standard weights are assumed for this exercise.





FIGURE 8-1Example Load and Trim Sheet





Load and Trim Sheet Completion Procedure(a) Fill in boxes 1 (aircraft registration), 2 (flight number), 3 (seating configuration, in

this case 167 passenger seats, all in tourist class configuration), 4 (crew configuration,in this case 2 flight deck and 5 cabin crew), 5 (departure aerodrome, in this caseLanzerote), 6 (destination aerodrome, in this case London Gatwick), 7 (date) and 8(Captain's name).

(b) Look up the APS weight and index in the loading manual, which is carried on boardthe aircraft, and insert the figures in Boxes 9, 10, 11, 12 and 13 as appropriate. Theindex is the position of the CG relative to the datum of the aircraft in the APS state(the empty aircraft plus the weight of crew, crew baggage, safety equipment andcatering etc). We have assumed that there are no adjustments to the APS weight orindex, as would result, for example, from the carriage of additional catering or theremoval of seats in order to accommodate a stretcher bound passenger and associatedmedical equipment.

(c) Insert the take-off fuel (total fuel less taxi fuel) in box 14 and determine the wetoperating weight (Box 15).

(d) Enter the maximum zero fuel weight in box 16, add to it the take-off fuel (Box 17)and determine the ZFW limiting take-off weight (Box 18). Next determine themaximum performance limited take-off weight and enter it at box 19. Similarly enterthe performance or C of A limited maximum landing weight at Box 20, add to it thetrip fuel (Box 21) to achieve the landing weight limited take-off weight (Box 22).





(e) Determine which of the three take-off weights (ZFW, take-off or landing, Boxes 18, 19and 22) is the most limiting, in this case it is the take-off itself which is limiting.Subtract from this weight the wet operating weight (Box 23) to determine the allowedtraffic load (Box 24).

(f) Transfer the allowed traffic load to Box 25.

(g) Establish from the agent the passenger breakdown (in this case 69 adult males at165 lb., 73 adult females at 143 lb., 25 children at 86 lb., and complete Boxes 26 and27. In this example the total passenger weight is 23,974 lb., so insert this weight inBox 28. Insert at Box 29 the baggage weight (167 x 7lb) giving 1169 lb.

(h) Establish from the agent the number of pieces of hold baggage (167) and determinethe weight (167 x 29 lb.) 4843 lb. Complete Boxes 30 and 31. Add the weights inBoxes 28, 29 and 31 to determine the total traffic load, which is inserted in Boxes 32and 33.

(i) Subtract the total traffic load (Box 33) from the allowed traffic load (Box 25) to getthe underload before last minute changes (LMCs). The underload is entered in Box34.

(j) Enter the dry operating weight in Box 35 and add the total traffic load to the dryoperating weight to obtain the zero fuel weight (Box 36). Add the take-off fuel(Box 37) to the zero fuel weight to obtain the take-off weight (Box 38).

(k) Add the take-off weight (Box 38) to the underload before LMC (Box 34) and confirmthat the sum of the two is equal to the maximum allowed take-off weight (in this caseBox 19). If it isn't you must find your error before proceeding.





(l) Subtract from the take-off weight (Box 38) the trip fuel (Box 39) to achieve thelanding weight (Box 40). We have now completed the load form and can start on thetrim form.

(m) Establish from the loaders or the agent (and confirm by visual inspection) thedistribution of the hold baggage. In this example we have 100 bags in hold 4 (aft) and67 bags in hold 3 (mid aft). Armed with this information complete Boxes 41 and 42ensuring that the maximum hold weights are not exceeded.

(n) With less than a full complement of passengers we would need to establish where thepassengers are sitting, however in this example we have a full load so complete Boxes43 to 46.

(o) We know how the fuel load is distributed (there is no trim fuel in this example) and sowe can complete Boxes 47 and 48. With this aeroplane the limiting trim is thatassociated with the ZFW rather than the fuel laden aircraft and consequently it is theposition of the ZFW CG within the trim envelope which is important. The trimenvelope (A) looks complex but it isn't. It is the white portion of the envelope withinthe two shaded (ferry) portions, which is the area within which the ZFW CG mustfall. Ignore the "MZFW - Limited Wing Fuel" hatched line, it is relevant to analternative fuel loading regime, which is used for ferry, and training flights.





(p) Start at B with the APS index and drop the line going left or right in the direction ofthe arrows for distances dictated by the diagonal lines and the actual passenger/baggage distribution. Having made the correction for the 24 passengers in bay D takethe drop line vertically downwards ignoring for the moment the fuel load. Mark thepoint on this vertical line which coincides with the actual zero fuel weight and checkthat this point lies within the envelope. Fortunately it does, it is towards the forwardend of the envelope, at 5.25% of the MAC.

(q) Return to the drop line and correct for the 18,500 lb. of fuel in the wings and the16,500 lb. of fuel in the centre tank at take-off. Mark the point on the resultant dropline which coincides with the actual take-off weight and read the TOW CG position asa % MAC, in this case 8.9%. The TOW % MAC goes in box 49. It is this valuewhich is used to set the trim on the variable incidence tail plane for take-off.Assuming that you've done your sums right and that the load is distributed as shown,this should mean that the stick force required to rotate the aircraft at VR will be lightbut positive.

Computer Load and Trim Forms9. The computer generated equivalent of the manual load and trim sheet previously consideredis shown at Figure 8-2. As you can see, there are no graphics on the computer form and it appearsthat you are taking a lot on trust. Experience will tell you whether or not the computer generatedtrim position is appropriate to the type of flight (scheduled, holiday charter, ski flight etc) and thenumber of passengers carried.





Last Minute Changes10. Both the manual and the computer load and trim sheets make provision for last minutechanges (LMCs). This is basically the out of breath family that has made it from check-in to the gatein record time and arrived just as you are about to push back. It is obviously necessary that theweight of the LMCs be considered, however providing that the total weight of LMCs does notexceed a given figure, the effect of this additional weight on the trim of the aircraft can be ignored.The figure in question is agreed between the operator and the CAA, for your guidance it is normallyin the order of 500 kg or 1000 lb. for medium passenger transport aircraft.

Aircraft Load and Trim Slide Rule11. The trim slide rule is a mechanical means of solving the mathematical problem of locating theCG of an aeroplane. Although mainly of historical interest they are still used on rare occasions.

FIGURE 8-2 LOADSHEET CHECKED APPROVED

All Weights in lb

From / To Flight A/C REG Version Crew Date/Time

ACE LGW 454 GRJER 167Y 2/5 2 Feb 95 1847





12. The slide rule consists of a main block body in which several sliders are contained. Each sliderepresents a loading cargo bay or compartment, which is etched with incremental weight.

Weight

Load in compartments 4843 1/- 2/- 3/1943 4/2900

Passenger / Cabin Load 25143 69/73/25/- TTL 167

Total Traffic Load 29886

Dry Operating Weight 86606

Zero Fuel Weight 116592 MAX 122000

Take-Off Fuel 35000

Take-Off Weight Actual 151592 MAX 154760

Trip Fuel 26000

Landing Weight Actual 125592 MAX 139500

Balance Last Minute Changes

MAXZFW 5.25

MAXTOW 8.9 3168

STD PAX WTS LMC TOTAL + -





13. On each slide is a datum arrow, which is positioned against the appropriate value on the slideabove. When using the trim slide rule a moment is referred to as an index. The index for the basicweight of the aircraft is a known value.

14. To use the slide rule the moment of the basic weight, known as the basic index is located onthe body of the rule and the datum arrow of the first slider positioned against it. The slides aremoved left for negative moments and right for positive moments.

15. The final position is drawn down from the lowest slide on a chart on which the forward andaft limits of the CG envelope are depicted together with the maximum take-off weight, the maximumlanding weight and the maximum zero fuel weight. If the intersection of the weight and the final linefall within the envelope it is safe. If it is outside the envelope then it is unsafe.

16. The main advantage of this method of determining the CG is that of speed, with a secondaryadvantage of the ability of making adjustments for ‘last minute changes’. The major disadvantage isthat no record is kept and unless each slide can be locked in position, errors are difficult to trace;furthermore large transport aircraft would require a considerable number of slides making theinstrument unwieldy to manage.

17. Recently this type of slide rule has been superseded by a circular slide rule, which has rotatingscales.





EXAMPLE 8-1EXAMPLE

Given:

Determine whether or not it is safe to take-off and land with the aircraft loaded in this way.

Maximum take-off weight 36,000 lb.

Maximum landing weight 33,000 lb.

Maximum zero fuel weight 30,000 lb

Basic aircraft weight 22,000 lb Index 5.0

Crew weight 300 lb.

15 pax @ 170 lb. aft cabin 2,550 lb.

12 pax @ 170 lb. fwd cabin 2,040 lb.

Aft cargo 445 lb.

Forward cargo 50 lb.

Zero fuel weight 27,385 lb.

Fuel 700 Imperial gallons 5,040 lb. SG 0.72

Take-off weight 32,425 lb

Sector fuel to touch down

300 Imperial gallons -2,160 lb. SG 0.72

Landing weight 30,265 lb.





SOLUTION

It should be noted that the slide rule illustrated at Figure 8-3 assumes a fixed passenger weight of170 lb., consequently the passenger slides are indexed in passenger numbers, as shown. The fuelslide is indexed in Imperial gallons. As can be seen from Figure 8-3, the CG is within limits forboth take-off and landing.





FIGURE 8-3

Figure 8-3. The Trim Slide Rule Solution to Example 8-1





The MRJT Trim SheetThe specimen aeroplane that will be used in any questions in the JAA examination is the MRJT. It istherefore advantageous to be familiar with the load and trim sheet used for this aeroplane. As youcan see from the following diagram the method of use is precisely the same as the previous example.It is simply the layout that is different.

At the top right is a table of passenger seats in each compartment, which corresponds to those listedto the left of the trim diagram. The method of determining the C of G position is as before. Start atthe top of the diagram at the dry operating index and work downward moving in the directionindicated by each arrow the appropriate number of divisions. In the final C of G envelope plot theTOW and landing weight. Both positions must fall within the envelope. If they don’t adjustmentsmust be made to the load distribution to bring the C of G back into the envelope.





FIGURE 8-4





EXAMPLE 8-2EXAMPLE

Given:

Dry Operating Mass 35,000 kgs; Index 48;

Take-off Fuel 10,000 kgs;

Cargo Hold 1 2,000 kgs;

Cargo Hold 4 4,000 kgs;

Passengers 10a, 15b, 20c, 20d, 20e, 15f and 10g. All at standard mass 84 kgs;

Fuel Index –10;

Trip Fuel 8,000 kgs;

Taxi Fuel 200 kgs.

Determine the underload and the MAC for Zero Fuel Mass, Take-Off Mass and Landing Mass.





SOLUTION

1. Extract from Loading Manual.

Maximum Take-Off Mass 62,800 kgs. Insert at (1), (8) and (16).Maximum Landing Mass 54,900 kgs. Insert at (2) and (9).Maximum Zero Fuel Mass 51,300 kgs. Insert at (3) and (10).Dry Operating Mass 35,000 kgs. Insert at (4) and (11).

2. Calculate fuel at take-off = 10,200 –200 = 10,000 kgs. Insert at (5), (6) and (7).

3. Add DOM to take-off fuel, insert at (12) and (13) = 45,000 kgs.

4. Insert Trip Fuel at (14) and (24) = 8,000 kgs.

5. Add Trip Fuel to Maximum Landing Mass to derive landing limited maximum TOM, insert at (15).

6. Add Take-off Fuel to Maximum Zero Fuel Mass to obtain structurally limited TOM, insert at (17).

7. The lowest of (15), (16) and (17) is the maximum TOM permitted.

8. Subtract the Operating Mass from the maximum permitted TOM to obtain the allowed Traffic Load, insert at (18).

9. Calculate the total Passenger Mass = 84 x 110 = 9,240 kgs.

10. Add passenger to total Fuel Mass to obtain total traffic load = 9,240 +6000 = 15,240 kgs. Insert at (19) and (20).

11. Subtract total Traffic Load from allowed Traffic Load to obtain underload = 1060 kgs. Insert at (21).





12. Add total Traffic Load to Dry Operating Mass to obtain the Zero Fuel Mass = 50,240 kgs. Insert at (22).

13. Add Take-Off Fuel to Zero Fuel Mass to obtain Take-Off Mass = 60,240 kgs. Insert at (23).

14. Subtract Trip Fuel from Take-Off Mass to obtain Landing Mass = 52,040 kgs. Insert at (25).

15. Insert cargo at Hold 1 at (26) and Hold 4 at (27).

16. Insert Dry Operating Index at (28) and mark on the index scale (29).

17. Insert the number of passengers in each of the stations (a) to (g).

18. Commence the plot at the Dry Operating Index and continue as in Example 8-1.





FIGURE 8-5






Mass and Balance





9Joint Aviation Regulations

Mass and Balance

Mass values for Crew JAR-OPS 1.615:1. An operator shall use the following mass values to determine the dry operating mass:

(i) Actual masses including any crew baggage; or

(ii) Standard masses, including hand baggage, of 85 kg for flight crew membersand 75 kg for cabin crew members; or

(iii) Other standard masses acceptable to the Authority.

2. An operator must correct the dry operating mass to account for any additional baggage. Theposition of this additional baggage must be accounted for when establishing the centre of gravity ofthe aeroplane.





Mass Values for Passengers and Baggage JAR-OPS 1.620:3. An operator shall compute the mass of passengers and checked baggage using either theactual weighed mass of each person and the actual weighed mass of baggage or the standard massvalues specified in Tables 9-1 to 9-3 below except where the number of passenger seats available isless than 10, when the passenger mass may be established by a verbal statement by or on behalf ofeach passenger or by estimation. The procedure specifying when to select actual or standard massesmust be included in the Operations Manual.

4. If determining the actual mass by weighing an operator must ensure that passenger’s personalbelongings and hand baggage are included. Such weighing must be conducted immediately prior toboarding and at an adjacent location.

5. If determining the mass of passengers using standard mass values, the standard mass values inTables 9-1 and 9-2 below must be used. The standard masses include hand baggage and the mass ofany infant below 2 years of age carried by an adult on one passenger seat. Infants occupyingseparate passenger seats must be considered as children for the purpose of this sub-paragraph.

Mass values for Passengers – 20 seats or more(a) Where the total number of passenger seats available on an aeroplane is 20 or more,

the standard masses of male and female in Figure 9-1 are applicable. As analternative, in cases where the total number of passenger seats available is 30 or more,the ‘All Adult’ mass values in Figure 9-1 are applicable.

(b) For the purpose of Figure 9-1, holiday charter means a charter flight solely intended asan element of a holiday travel package.





JAR-OPS 1.620(d) Table 1

FIGURE 9-1Aircraft with 20 or more Passenger Seats

Passenger Seats 20 or More

Male Female

30 or More

All Adult

All flights except Holiday Charters 88kg 70kg 84kg

Holiday Charters 83kg 69kg 76kg

Children 35kg 35kg 35kg





JAR-OPS 1.620(e) Table 2

FIGURE 9-2Mass Values for Aircraft with 19 or less Passenger Seats

6. Where the total number of passenger seats available on an aeroplane is 19 or less, thestandard masses in Figure 9-2 are applicable.

7. On flights where no hand baggage is carried in the cabin or where hand baggage is accountedfor separately, 6 kg may be deducted from the above male and female masses. Articles such as anovercoat, an umbrella, a small handbag or purse, reading material or a small camera are notconsidered as hand baggage for the purpose of this sub-paragraph.

8. Mass Values for Baggage

Passenger Seats 1 - 5 6 - 9 10 - 19

Male 104kg 96kg 92kg

Female 86kg 78kg 74kg

Children 35kg 35kg 35kg





(c) Where the total number of passenger seats available on the aeroplane is 20 or morethe standard mass value given in Figure 9-3 are applicable for each piece of checkedbaggage. For aeroplanes with 19 passenger seats or less, the actual mass of checkedbaggage, determined by weighing, must be used.

For the purpose of Figure 9-3:

(i) Domestic flight means a flight with origin and destination within the bordersof one State.

(ii) Flights within the European region means flights, other than Domestic flights,whose origin and destination are within the area specified in Appendix 1 toJAR-OPS 1.620 (f); and

(iii) Intercontinental flight, other than flights within the European region, means aflight with origin and destination in different continents.

FIGURE 9-3Aircraft with 20 or more Seats

JAR-OPS 1.620(f) Table 3

Type of Flight Baggage Standard Mass

Domestic 11 kg

Within the European Region 13 kg

Intercontinental 15 kg

All Other 13 kg





(iv) If an operator wishes to use standard mass values other than those containedin Figure 9-1 to Figure 9-3 above, he must advise the Authority of his reasonsand gain its approval in advance. He must also submit for approval a detailedweighing survey plan and apply the statistical analysis method given inAppendix 1 to JAR-OPS 1.620 (g). After verification and approval by theAuthority of the results of the weighing survey, the revised standard massvalues are only applicable to that operator. The revised standard mass valuescan only be used in circumstances consistent with those under which the surveywas conducted. Where revised standard masses exceed those in Figure 9-1 toFigure 9-3, then such higher values must be used. [See IEM-OPS 1.620 (g)].

(v) On any flight identified as carrying a significant number of passengers whosemasses, including hand baggage, are expected to exceed the standard passengermass, an operator must determine the actual mass of such passengers byweighing or by adding an adequate mass increment. [See IEM-OPS 1.620 (h)and (i)].

(vi) If standard mass values for checked baggage are used and a significant numberof passengers check in baggage that is expected to exceed the standard baggagemass, an operator must determine the actual mass of such baggage by weighingor by adding an adequate mass increment. [See IEM-OPS 1.620 (h) and (i)].

(vii) An operator shall ensure that a commander is advised when a non-standardmethod has been used for determining the mass of the load and that thismethod is stated in the mass and balance documentation.





Appendix 1 to JAR-OPS 1.620 (f)

Definition of the Area for Flights within the European Region9. For the purpose of JAR-OPS 1.620 (f), flights within the European region, other thandomestic flights, are flights conducted within the area bounded by rhumb lines between the followingpoints:

As depicted in Figure 9-4 below.

N7200 E04500

N4000 E04500

N3500 E03700

N3000 E03700

N3000 W00600

N2700 W00900

N2700 W03000

N6700 W03000

N7200 W01000

N7200 E04500





FIGURE 9-4





Appendix to JAR-OPS 1.620 (g)

Procedure for Establishing Revised Standard Mass Values for Passengers and Baggage. [See IEM to Appendix 1 to JAR-OPS 1.620 (g)]

Passengers10. Weight Sampling Method. The average mass of passengers and their hand baggage must bedetermined by weighing, taking random samples. The selection of random samples must by natureand extent be representative of the passenger volume, considering the type of operation, thefrequency of flights on various routes, in/outbound flights, applicable season and seat capacity of theaeroplane.

11. Sample Size. The survey plan must cover the weighing of at least the greatest of:

(a) A number of passengers calculated from a pilot sample, using normal statisticalprocedures and based on a relative confidence range (accuracy) of 1% for all adultand 2% for separate male and female average masses. The statistical procedure,complemented with a worked example for determining the minimum required samplesize and the average mass, is included in IEM-OPS 1.620 (g), and;

(b) For Aeroplanes:

(i) With a passenger seating capacity of 40 or more, a total of 2000 passengers,or;





(ii) With a passenger seating capacity of less than 40, a total number of 50 x (thepassenger seating capacity).

Passenger Masses12. Adults and Children. Adults are defined as persons of an age of 12 years and above. Theyare further classified as male or female. No differentiation according to sex shall be made forchildren, who are defined as persons of an age of two years but who have not yet reached theirtwelfth birthday. Passenger masses must include the mass of the passengers’ belongings, which arecarried when entering the aeroplane.

13. Infants. Infants are defined as persons who have not yet reached their second birthday.When taking random samples of passenger masses, infants shall be weighed together with theaccompanying adult.

14. Weighing Location. The location for the weighing of passengers shall be selected as close aspossible to the aeroplane, at a point where a change in the passenger mass by disposing of or byacquiring more personal belongings is unlikely to occur before the passenger’s board the aeroplane.

15. Weighing Machine. The weighing machine to be used for passenger weighing shall have acapacity of at least 150 kg. The mass shall be displayed at minimum graduations of 500 g. Theweighing machine must be accurate to within 0.5% or 200 g whichever is the greater.

16. Recording of Mass Values. For each flight the mass of the passengers, the correspondingpassenger category (i.e. male/female/children) and the flight number must be recorded.





Checked Baggage17. The statistical procedure for determining revised standard baggage mass values based onaverage baggage mass values based on average baggage masses of the minimum required sample sizeis basically the same as for passengers and as specified in sub-paragraph (a) (1) [See also IEM-OPS1.620 (g)]. For baggage, the relative confidence range (accuracy) amounts to 1%. A minimum of2000 pieces of checked baggage must be weighed.

Determination of Revised Standard Mass Values for Passengers and Checked Baggage

(a) To ensure that, in preference to the use of actual masses determined by weighing, theuse of revised standard mass values for passengers and checked baggage does notadversely affect operational safety; a statistical analysis (see IEM-OPS 1.620 (g)) mustbe carried out. Such an analysis will generate average mass values for passengers andbaggage as well as other data.

(b) On aeroplanes with 20 or more passenger seats these averages apply as revisedstandard male and female mass values.

(c) On smaller aeroplanes, the following increments must be added to the averagepassenger mass to obtain the revised standard mass value:





FIGURE 9-5Revised Standard Mass Increments for Aircraft with 19 or less Passenger Seats

18. Alternatively, all adult revised standard (average) mass values may be applied on aeroplaneswith 30 or more passenger seats. Revised standard (average) checked baggage mass values areapplicable to aeroplanes with 20 or more passenger seats.

(d) Operators have the option to submit a detailed survey plan to the Authority forapproval and subsequently a deviation form the revised standard mass value providingthis deviating value is determined by use of the procedure explained in the Appendix.Such deviations must be reviewed at intervals not exceeding five years. [See AMC toAppendix 1 to JAR-OPS 1.620 (g), sub-paragraph (c) (4)].

(e) All adult revised standard mass values must be based on a male/female ratio of 80/20in respect of all flights except holiday charters which are 50/50. If an operator wishesto obtain approval for use of a different ratio on specific routes or flights then datamust be submitted to the Authority showing that the alternative male/female ratio isconservative and covers at least 84% of the actual male/female ratios on a sample ofat least 100 representative flights.

(f) The average mass values found are rounded to the nearest whole number in kg.Checked baggage mass values are rounded to the nearest 0.5 kg figure, as appropriate.

Number of Passenger Seats Required Mass Increment

1 – 5 Inclusive 16 kg








Joint Airworthiness Requirement

Determination of the Dry Operating Mass of an Aeroplane

Special Standard Masses for the Traffic Load





10The Weighing of Aeroplanes

Joint Airworthiness Requirement1. The weight and C of G of an aeroplane must be established by the operator by actuallyweighing it prior to initial entry into service and every four years thereafter if individual aeroplaneweights are used or every nine years if fleet weights are used. The cumulative effect of modificationsand/or repairs have on the weight and balance must be accounted and documented. Aeroplanes thathave been modified but the effects on the weight and balance are unknown must be re-weighed.[JAR-OPS 1.605 (1) (b)].Appendix 1 to JAR-OPS 1.605 and Mass and Balance – General (See JAR-OPS 1.605)

Determination of the Dry Operating Mass of an Aeroplane

Weighing of an Aeroplane(a) New aeroplanes are normally weighed at the factory and are eligible to be placed into

operation without re-weighing if the mass and balance records have been adjusted foralterations or modifications to the aeroplane. Aeroplanes transferred from one JAAoperator with an approved mass control programme to another JAA operator with anapproved programme need not be weighed prior to use by the receiving operatorunless more than four years have elapsed since the last weighing.





(b) The individual mass and centre of gravity (CG) position of each aeroplane shall be re-established periodically. The maximum interval between two weighings must bedefined by the operator and must meet the requirements of JAR-OPS 1.605 (b). Inaddition, the mass and the CG of each aeroplane shall be re-established either by:

(i) Weighing, or;

(ii) Calculation, if the operator is able to provide the necessary justification toprove the validity of the method of calculation chosen.

whenever the cumulative changes to the dry operating mass exceed + 0.5% of the maximum landingmass or the cumulative change in CG position exceeds 0.5% of the mean aerodynamic chord.[Appendix to JAR-OPS 1.605 (a) (1)].

Fleet Mass and CG Position(a) For a fleet or group of aeroplanes of the same model and configuration, an average

dry operating mass and CG position may be used as the fleet mass and CG position,provided that the dry operating masses and CG positions of the individual aeroplanesmeet the tolerances specified below. Furthermore, the criteria specified in ‘Use ofFleet-Values’ and ‘Number of Aeroplanes to be Weighed’ below are applicable.





Tolerances(i) If the dry operating mass of any aeroplane weighed, or the calculated dry

operating mass of any aeroplane of a fleet, varies by more than + 0.5% of themaximum structural landing mass from the established dry operating fleetmass or the CG position varies by more than + 0.5% of the mean aerodynamicchord from the fleet CG, that aeroplane shall be omitted from that fleet.Separate fleets may be established, each with differing fleet mean masses.

(ii) In cases where the aeroplane mass is within the dry operating fleet masstolerance but its CG position falls outside the permitted fleet tolerance, theaeroplane may still be operated under the applicable dry operating fleet massbut with an individual CG position.

(iii) If an individual aeroplane has, when compared with other aeroplanes of thefleet, a physical, accurately accountable difference (e.g. galley or seatconfiguration), that causes exceedance of the fleet tolerances, this aeroplanemay be maintained in the fleet provided that appropriate corrections areapplied to the mass and/or CG position for that aeroplane.

(iv) Aeroplanes for which no mean aerodynamic chord has been published must beoperated with their individual mass and CG position values or must besubjected to a special study and approval.





Use of Fleet Values(i) After the weighing of an aeroplane, or if any change occurs in the aeroplane

equipment or configuration, the operator must verify that this aeroplane fallswithin the tolerances specified in ‘Tolerances’ above.

(ii) Aeroplanes which have not been weighed since the last fleet mass evaluationcan still be kept in a fleet operated with fleet values, provided that theindividual values are revised by computation and stay within the tolerancesdefined in ‘Tolerances’ above. If these individual values no longer fall withinthe permitted tolerances, the operator must either determine new fleet valuesfulfilling the conditions of ‘Fleet-Mass and CG Position’ and ‘Tolerances’above, or operate the aeroplanes not falling within the limits with theirindividual values.

(iii) To add an aeroplane to a fleet operated with fleet values, the operator withfleet values, the operator must verify by weighing or computation that itsactual values fall within the tolerance specified in ’Tolerances’ above.

(iv) To comply with ‘Fleet Mass and CG Position’ above, the fleet values must beupdated at least at the end of each fleet mass evaluation. [Appendix to JAR-OPS 1.605 (a) (2)].





Number of Aeroplanes To Be weighed to Obtain Fleet Values

(a) If ‘n’ is the number of aeroplanes in the fleet using fleet values, the operator must atleast weigh, in the period between two fleet mass evaluations, a certain number ofaeroplanes defined in Figure 10-1:

FIGURE 10-1

(b) In choosing the aeroplanes to be weighed, aeroplanes in the fleet which have not beenweighed for the longest time should be selected.

(c) The interval between 2 fleet mass evaluations must not exceed 48 months.

Weighing Procedure(a) The weighing must be accomplished either by the manufacturer or by an approved

maintenance organisation.

Number of Aeroplanes in the Fleet Minimum Number of Weighings

2 or 3 n

4 to 9

10 or More

n 3+2

------------

n 51+10

---------------





(b) Normal precautions must be taken consistent with good practices such as:

(i) Checking for completeness of the aeroplane and equipment.

(ii) Determining that fluids are properly accounted for.

(iii) Ensuring that the aeroplane is clean, and;

(iv) Ensuring that weighing is accomplished in an enclosed building.

2. Any equipment used for weighing must be properly calibrated, zeroed, and used inaccordance with the manufacture’s instructions. Each scale must be calibrated either by themanufacturer, by a civil department of weights and measures or by an appropriately authorisedorganisation within two years or within a time period defined by the manufacturer of the weighingequipment, whichever is less. The equipment must enable the mass of the aeroplane to be establishedaccurately. [Appendix to JAR-OPS 1.605 (a) (4)].

Special Standard Masses for the Traffic Load3. In addition to standard masses for passengers and checked baggage, an operator can submitfor approval to the Authority standard masses for other load items.

Aeroplane Loading(a) An operator must ensure that the loading of its aeroplanes is performed under the

supervision of qualified personnel.





(b) An operator must ensure that the loading of the freight is consistent with the data usedfor the calculation of the aeroplane mass and balance.

(c) An operator must comply with additional structural limits such as the floor strengthlimitations, the maximum load per running metre, the maximum mass per cargocompartment and/or the maximum seating limits. [Appendix to JAR-OPS 1.605 (a)(4)].

Centre of Gravity Limits

Operational CG Envelope. Unless seat allocation is applied and the effects of the number ofpassengers per seat row, of cargo in individual cargo compartments and of fuel in individual tanks isaccounted for accurately in the balance calculation, operational margins must be applied to thecertificated centre of gravity envelope. In determining the CG margins, possible deviations from theassumed load distribution must be considered. If free seating is applied, the operator must introduceprocedures to ensure corrective action by flight or cabin crew if extreme longitudinal seat selectionoccurs. The CG margins and associated operational procedures, including assumptions with regardto passenger seating, must be acceptable to the Authority. [See IEM to Appendix 1 to JAR-OPS1.605 (d)].

In-Flight Centre of Gravity. Further to sub-paragraph above, the operator must show that theprocedures fully account for the extreme variation in CG travel during flight caused by passenger/crew movement and fuel consumption/transfer.





British Civil Airworthiness Requirement4. The above are the requirements of the Joint Aviation Authority (JAA), however, these will notbe legally enforceable until a statute has been passed by Parliament to make JAR-OPS a legallybinding document. Until such time the legal requirements of British Civil Airworthinessrequirements remain in force and have different requirements with respect to the weighing ofaeroplanes and are as follows:

(a) An aircraft is weighed when all manufacturing processes are complete. It must be re-weighed within two years of the date of manufacture and subsequently at intervals notexceeding five years and at such times as the CAA may require if the maximum totalweight authorised exceeds 5700 kg. If the MTWA does not exceed 5700 kg theaeroplane must be re-weighed at such times as the CAA may require.

(b) The aircraft should be re-weighed after a major servicing has been carried out or whena modification or engine change has been done which may have a significant effect onthe aircraft weight and balanced. It would be prudent to re-weigh the aircraft if it isnot attaining is scheduled performance level.

(c) With the approval of the Authority, when an operator has three or more aircraft of thesame type, the fleet mean weight and CG may be used for the whole fleet, except forthose that differ significantly from the remainder of the fleet.

(d) For an aircraft having a valid Certificate of Airworthiness a valid Weight and CGSchedule must be completed every time the aircraft is weighed. Each Schedule must bepreserved for a period of six months following the subsequent re-weighing of theaircraft.





(e) If the person who is the operator ceases to be the operator, he (or his representative ifhe dies) must retain the Schedule or pass it on to the new operator for retention for therequisite period. [BCAR Section A, Chapter A5-47].





Self Assessed Exercise No. 2

QUESTIONS:QUESTION 1.

List four items not considered to be hand baggage when using the standard mass value of JAR-OPS1.620(e) table 2.

QUESTION 2.

According to JAR-OPS1, when should an aeroplane be weighed?

QUESTION 3.

What precautions should be taken when weighing an aircraft?

QUESTION 4.

What are the floor area maximum load intensity and the running load maximum between balancearm 343 and 500 for the cargo compartments of the MRJT?

QUESTION 5.

What is the purpose of Dunnage?

QUESTION 6.

Specify the current restraint load factor forward for lashing and tie-down equipment for fixed wingaircraft.





QUESTION 7.

State the load factor formula.

QUESTION 8.

Given the mean aerodynamic chord is from 750ins to 1000ins aft of the Datum. Express the GG850ins AFT of the Datum as a % of MAC.

QUESTION 9.

What determines the maximum zero fuel weight?

QUESTION 10.

How is the stalling speed affected by the position of the CG?

QUESTION 11.

Given: AUW 30,000lbs. CG 1ft AFT of Datum. How much freight must be added to a hold 10ftforward of Datum to move the CG 1ft forward.

QUESTION 12.

If 300lbs of cargo is moved from a hold 10ft aft of the Datum to hold 5ft forward of the Datum whatchange will occur to the CG for an aeroplane weighing 5000lbs.

QUESTION 13.

If 2,000kgs of freight added to a hold 5m ahead of the present CG of an aeroplane weighing10,000kgs. The change to the CG is?





QUESTION 14.

If the main wheels retract athwarships and the nose wheel retracts forward. How will the CG moveon lowering the undercarriage to land?

QUESTION 15.

What is the critical angle between the edge of freight and the edge of load spreader for it to be fullyeffective:

QUESTION 16.

If the centre tank of the MRJT contains 500kgs of fuel how much fuel must be in the wing tanks?

QUESTION 17.

Given: Cargo 1500kgs in hold 10m forward of Datum and cargo 1000kgs in a hold 15m AFT ofDatum. What are the total freight moments?

QUESTION 18.

Given: Fuel at take-off 6000lbs in tank 10ft forward of Datum. The fuel in the same tank onLanding 2000lbs calculate the change of moments.

QUESTION 19.

At what age is a child assumed to be an adult for the purposes of mass and balance?





QUESTION 20.

What increment must be added to the average mass for a passenger of an aeroplane having 6 to 9passenger seats?

ANSWERS:ANSWER 1.

Page 9-2 paragraph 7

ANSWER 2.

Page 10-1 paragraph 1

ANSWER 3.

Page 10-4 paragraph 1 (b)

ANSWER 4.

CAP 696 Page 24

ANSWER 5.

Page 7-7

ANSWER 6.

Page 7-5





ANSWER 7.

Page 7-4

ANSWER 8.

ANSWER 9.

The strength of the wing roots.

Page 1-2

ANSWER 10.

Page 3-6 and 3-7

ANSWER 11.

(30000 + w) x 0 = (30000 x +1) + (w x –10)

0 = 30,000 – 10w

10w = 30,000

w= 3000 lbs

850 750–( )1000 750–( )

-------------------------------% 100250---------% 40% of MAC==





ANSWER 12.

CC =

ANSWER 13.

= -0.83m = 0.83 ahead of old CG

ANSWER 14.

CG moves with the nose wheel. CG moves AFT.

ANSWER 15.

45°

Page 7-7

ANSWER 16.

The wing tanks must be full.

CAP 696 Page 22

ANSWER 17.

(1500 x –10) + (1000 x +15) = 0

wW-----

CCd

--------=300

5000------------

CC15–

---------=4500–

5000--------------- 0.9ft–=

2000 5–×12 000,

------------------------





ANSWER 18.

Moments at take-off = 6000 x –10 = -60,000 ft. lbs.

Moments at landing = 2000 x –10 = -20,000 ft. lbs.

Change in moments = -20,000 – (-60,000) = + 40,000 ft. lbs.

ANSWER 19.

12 years old

Page 9-6

ANSWER 20.

8 kgs

Page 9-8





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UK National Requirements



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11Documentation

Mass and Balance Documentation JAR-OPS 1.625 [See Appendix 1 to JAR-OPS 1.625]1. An operator shall establish mass and balance documentation prior to each flight specifyingthe load AND its distribution. The mass and balance documentation must enable the commander todetermine by inspection that the load and its distribution is such that the mass and balance limits ofthe aeroplane are not exceeded. The person preparing the mass and balance documentation must benamed on the document. The person supervising the loading of the aeroplane must confirm bysignature that the load and its distribution are in accordance with the mass and balancedocumentation. This document must be acceptable to the commander, his acceptance beingindicated by countersignature or equivalent. [See also IEM-OPS 1.1055 (a) (12)].

2. An operator must specify procedures for Last Minute Changes to the load.

3. Subject to the approval of the Authority, an operator may use an alternative to the proceduresrequired by paragraphs (a) and (b) above.

Signature or Equivalent IEM-OPS 1.1055 (a) (12) [See JAR-OPS 1.1055 (a) (12)]4. JAR-OPS 1.1055 requires a signature or its equivalent. This IEM gives and example of howthis can be arranged where normal signature by hand is impracticable and it is desirable to arrangethe equivalent verification by electronic means.



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5. The following conditions should be applied in order to make an electronic signature theequivalent of a conventional hand-written signature:

(a) Electronic ‘signing’ should be achieved by entering a Personal Identification Number(PIN) code with appropriate security etc.

(b) Entering the PIN code should generate a print-out of the individual’s name andprofessional capacity on the relevant document(s) in such a way that it is evident toanyone having a need for that information, who has signed the document.

(c) The computer system should log information to indicate when and where each PINcodes has been entered.

(d) The use of PIN code is, from a legal and responsibility point of view, considered to befully equivalent to signature by hand.

(e) The requirements for record keeping remain unchanged, and

(f) All personnel concerned should be made aware of the conditions associated withelectronic signature and should confirm this in writing.



Documentation


Appendix 1 to JAR-OPS 1.625 Mass and Balance Documentation [See IEM to Appendix 1 to JAR-OPS 1.625]

Mass and Balance Documentation

Contents(a) The mass and balance documentation must contain the following information:

(i) The aeroplane registration and type.

(ii) The flight identification number and date.

(iii) The identity of the Commander.

(iv) The identity of the person who prepared the document.

(v) The dry operating mass and the corresponding CG of the aeroplane.

(vi) The mass of the fuel at take-off and the mass of trip fuel.

(vii) The mass of consumables other than fuel.

(viii) The components of the load including passengers, baggage, freight and ballast.

(ix) The Take-Off Mass, Landing Mass and Zero Fuel Mass.

(x) The load distribution.



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(xi) The applicable aeroplane CG positions; and

(xii) The Limiting Mass and CG Values.

6. Subject to the approval of the Authority, an operator may omit some of this Data from themass and balance documentation.

7. Last Minute Change. If any last minute change occurs after the completion of the mass andbalance documentation, this must be brought to the attention of the Commander and the last minutechange must be entered on the mass and balance documentation. The maximum allowed change inthe number of passengers or hold load acceptable as a last minute change must be specified in theOperations Manual. If this number is exceeded, new mass and balance documentation must beprepared.

Computerised Systems8. Where mass and balance documentation is generated by a computerised mass and balancesystem, the operator must verify the integrity of the output data. He must establish a system to checkthat amendments of his input data are incorporated properly in the system and that the system isoperating correctly on a continuous basis by verifying the output data at intervals not exceeding sixmonths.

Onboard Mass and Balance Systems9. An operator must obtain the approval of the Authority if he wishes to use an onboard massand balance computer system as a primary source for despatch.



Documentation


Datalink10. When mass and balance documentation is sent to aeroplane via datalink, a copy of the finalmass and balance documentation as accepted by the Commander must be available on the ground.

Mass and Balance Documentation [See IEM to Appendix 1 to JAR-OPS 1.625]11. For Performance Class B aeroplanes, the CG position need not be mentioned on the mass andbalance documentation if for example the load distribution is in accordance with a pre-calculatedbalance table or if it can be shown that for the planned operations a correct balance can be ensured,whatever the real load is.

UK National Requirements

The Weight and Balance Report12. The following are the requirements of the CAA as specified in BCAR, Section A.

(a) Weight and Balance Report – Aircraft Exceeding 5700 kg.

(b) A Weight and Balance Report shall be produced for each Prototype, Variant and Seriesaircraft the Maximum Weight Authorised of which exceeds 5700 kg.



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(c) The Weight and Balance Report shall record such loading data as is essential to enablethe particular aircraft to be correctly loaded, and shall include sufficient informationfor an operator to produce written loading instructions in compliance with therequirements of the Air Navigation Order.

(d) The Weight and Balance Report shall apply to the aircraft in the condition in which itis to be delivered to the user.

(e) One copy of the Weight and Balance Report shall be sent to the CAA SafetyRegulation Group.

(f) The Weight and Balance Report shall include the following items:

(g) Reference Number and date.

(h) Designation, nationality, and registration marks of the aircraft, or if these are notknown the constructor’s serial number.

(i) A copy of the Weighing Record.

(j) A copy of the Weight and Centre-of-Gravity Schedule including the list of BasicEquipment, if this is separate from Part A of the Schedule.

(k) A diagram and a description of the datum points which are used for weighing andloading and an explanation of the relationship of these points to the fuselage framenumbering system of other identifiable points, and where applicable, to the StandardMean Chord (SMC).



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(l) Information on the level arms appropriate to items of Disposable Load. (This shouldinclude the lever arms of fuel, oil and other consumable fluids or substances in thevarious tanks (including agricultural material in hoppers) which, if necessary, shouldbe shown diagrammatically or graphically; lever arms of passengers in seatsappropriate to the various seating layouts; mean lever arms of the various baggageholds or compartments.)

(m) Details of any significant effect on the aircraft CG of any change in configuration,such as retraction of the landing gear.

Weight and Centre-of-Gravity Schedule – Aircraft Exceeding 2730 kg13. A Weight and Centre-of-Gravity Schedule shall be provided for each aircraft the MaximumTotal Weight Authorised of which exceeds 2730 kg, except that for an aircraft the Maximum TotalWeight Authorised or which exceeds 5700 kg the information contained in Parts B and C of theSchedule may, for a new aircraft, be given as part of the Weight and Balance Report.

NOTE:

1) The Weight and Centre-of-Gravity Schedule may be in the form set down inAppendix 1, but variations are permitted within the Requirements.



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NOTE:

2) Here reference is made in Appendix 1 to the Flight Manual, but such adocument has not been issued, it will be necessary to refer to the Certificate ofAirworthiness.

14. Each Schedule shall be identified by the aircraft designation, nationality and registrationmarks, or if these are not known, by the constructor’s serial number. The date of issue of theSchedule shall be given and the Schedule shall be signed by a representative of an approvedOrganisation or a person acceptable to the CAA. A statement shall be included indicating that theSchedule supersedes all previous issues.

15. The date and reference number of the Weight and Balance Report, or, as appropriate to theweight, other acceptable information upon which the Schedule is based, shall be given.

NOTE:

For aircraft for which a Weight and Balance Report is not mandatory, theWeighing Record would normally used.

16. A copy of each issue of the Schedule shall be retained by the operator, and where the Scheduleis re-issued the previous issue shall be retained with the aircraft records. A copy of the currentSchedule and any related list of Basic Equipment (see Part A Basic Weight), shall be sent to the CAASafety Regulation Group.



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17. For aircraft the Maximum Total Weight Authorised of which does not exceed 5700 kg, acopy of the Schedule shall be included in the Flight Manual, if a Flight Manual is applicable, or if thisis not the case, displayed or retained in the aircraft in a suitably identified stowage.

18. Operators shall issue a revised Weight and Centre-of-Gravity Schedule when the weight ande.g. is known to have changed to an extent greater than that which has been agreed by the CAA asapplicable to a particular aircraft type.

19. If the aircraft has not been re-weighed, the revised Weight and Centre-of-Gravity Scheduleshall contain a statement that calculations have been based on the last Weight and Balance Report, orother information, and the known weight and CG changes.

20. The datum to which CG limits relate is defined in Part A (see Part A Basic Weight) and thismay be different from the datum defined in the Certificate of Airworthiness or Flight Manual. Whena different datum is used it shall be adequately defined, its precise relationship to the datum in theCertificate of Airworthiness or Flight Manual shall be given, and any lever arms and moments whichappear in any part of the Schedule shall be consistent with the datum so declared.

NOTE:

In the case of helicopters, it may be necessary to present lever arms andmoments about more than one axis, depending on the CG limits specified inthe Flight Manual.

21. Part A Basic Weight. The Basic Weight and the associated position of the CG of the aircraftas derived from the most recent Weight and Balance Report or other information together with anysubsequent weight and CG changes shall be stated. The position (retracted or extended) of thelanding gear associated with this information shall be stated.



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22. Where the Maximum Total Weight Authorised does not exceed 5700 kg, Part A shall alsoinclude the list of Basic Equipment showing the weight and lever arm of each item, or thisinformation may form separate pages attached to the Weight and Centre-of-Gravity Schedule, with asuitable reference in Part A of the Schedule to this procedure.

23. Where the Maximum Total Weight Authorised exceeds 5700 kg, Part A shall include the listof basic equipment showing the weight, lever arm moment of each item, or shall make reference tothe document in which such a list is included.

24. Part B Variable Load. The Variable Load may be detailed for as many roles as the operatorwishes, but for every role the weights and moments shall be given. Weights of crew members may beassumed to be not less than the weights shown in the Air Navigation (General) Regulations, providedthat the Maximum Total Weight Authorised exceeds 5700 kg, or the aircraft has a total seatingcapacity for 12 or more persons. Otherwise the weight of each person must be determined byweighing.

25. Part C Loading Information. This shall include all relevant information so that, knowing theDisposable Load which is intended to be carried, the weight and the position of the Centre-of-Gravity of the aircraft can be calculated. At least the following shall be given:

(i) The lever arm of the CG of a passenger in each seat.

(ii) The mean lever arm of each compartment or area in the aircraft whereDisposable Load, such as luggage or freight, may be placed.

(iii) Any significant change in the CG of the aircraft (change in moment) which willresult from a change in configuration, such as the retraction and extension ofthe landing gear.



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(iv) The lever arm of the CG of fuel, oil and other consumable fluids or substancesin each tank, including any significant variation of the lever arm with thequantity loaded.

(v) The maximum total usable capacities of the tanks for fuel, oil and otherconsumable fluids or substances and the weight of fluids or substances whenthe tanks are filled to their capacities assuming typical densities.

26. A statement shall be made in the Schedule to the effect that it is a requirement of the AirNavigation Order that the Commander satisfies himself before take-off that the load is of suchweight, and is so distributed and secured, that it may safely be carried on the intended flight.

27. The weights, distances, moments and quantities may be given in any units provided that theseare used consistently and do not conflict with the markings and placards on the aircraft.



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Weight and Centre-of-Gravity Schedule-Aircraft Not Exceeding 2730 kg28. For aircraft the Maximum Total Weight Authorised of which does not exceed 2730 kg, eithera Weight and Centre-of-Gravity Schedule, which complies with 2 and 3.2, or a Loading andDistribution Schedule which complies with 3.1 shall be provided.

29. Loading and Distribution Schedule (Figure 11-6)

30. The Loading and Distribution Schedule (hereinafter referred to as ‘the Schedule’) shallcontain at least the information in Figure 11-6.

31. Each Schedule shall be identified by the aircraft designation, nationality and registrationmarks, or if these are not known, by the constructor’s serial number.

32. A copy of each issue of the Schedule shall be retained by the operator, and when the Scheduleis re-issued the previous issue shall be retained with the aircraft records. A copy of the currentSchedule and any related list of Basic Equipment shall be sent to the CAA Safety Regulation Group.

(i) A copy of the Schedule shall be included in the Flight Manual is applicable, or,if this is not the case, the Schedule shall be displayed or retained in the aircraftin a suitably identified stowage.

33. Operators shall issue a revised Schedule when:

(i) The Basic Weight of the aircraft is known to have undergone changes in excessof 0.5% of the Maximum Total Weight Authorised, or



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(ii) The total moment applicable to the Basic Weight is known to have changed toan extent greater than that, which has been agreed by the CAA as applicable toa particular aircraft type.

34. If the aircraft has not been re-weighed the revised Schedule shall contain a statement thatcalculations have been based on the last Weighing Record and the known weight and momentchanges.

35. Instructions for the use of the Schedule, together with the Loading Graphs, shall be included.

36. A statement shall be given in the Schedule to the effect that it is a requirement of the AirNavigation Order that the Commander satisfies himself before the aircraft takes off that the load isof such a weight, and is so distributed and secured that it may safely be carried on the intended flight.

37. The weight, distances, moments and quantities may be given in any units provided that theseare used consistently and do not conflict with the markings and placards on the aircraft.

38. Part A Basic Data. Part A shall contain the following:

(i) The Basic Weight and the associated moment, and CG position of the aircraft,as derived from the most recent Weighing Record, together with anysubsequent changes.

(ii) The Maximum Total Weight Authorised appropriate to each permitted use (eg.aerobatics).

(iii) The definition of the CG datum.



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(iv) The date and reference number of the Weighing Record and list of BasicEquipment upon which the Schedule is based.

(v) The date and reference of the Loading Graphs of the Loading and DistributionSchedule shall be given.

(vi) A statement of the date of preparation and validity of the Schedule, signed by arepresentative of an approved Organisation, or a person acceptable to theCAA. A statement shall also be included indicating that the Schedulesupersedes all previous issues.

39. Part B Loading. Columns shall be provided which list all standard items of Variable Loadand make provision for the associated weight and CG moments to be recorded and totalled for aparticular flight. Columns shall also be provided for recording an example of a typical aircraftloading calculation. This example shall employ the same weight and CG moment figures as recordedin the Loading Graphs (see Part C).

40. Part C Loading Graphs. Graphs, sufficient to ascertain moments, and to enable the operatorto determine that the aircraft loaded weight and CG moment are within the prescribed limits shall beprovided. The graphs shall be identified by aircraft designation, date of compilation and source.Suitable sources are the aircraft constructor or other competent person. An example applicationshall be included using the same figures as employed in the Loading and Distribution Scheduleexample.

41. Weight and Centre-of-Gravity Schedule (Appendix 2, (3)). In addition the Weight andCentre-of-Gravity Schedule for aircraft the Maximum Total Weight Authorised of which does notexceed 2730 kg, shall contain instructions for the determination of the loaded weight, the total loadmoments and resultant CG positions.



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Appendix No. 1 – Weight and Centre-Of-Gravity Schedules For Aircraft Exceeding 2730 kg42. INTRODUCTION. This Appendix presents a specimen Weight and CG Schedule whichconstitutes an acceptable means of compliance with the appropriate requirements.

NOTE:

Imperial Units are shown on the specimen. Where it is necessary to use S.IUnits these should be used throughout

FIGURE 11-1Specimen Schedule Reference NAL/286

Produced by Loose Aviation Ltd

Aircraft Designation Flynow 2E

Nationality & Registration marks G-BZZZ

Constructor F.L.Y. Co. Ltd

Constructor’s Serial Number 44

Maximum Total Weight Authorised 7300 lb

Centre of Gravity Limits Refer to Flight Manual

Reference Number 90/946



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Part A Basic WeightThe Basic Weight of the aircraft as calculated from Weight and Balance Report/Weighing Record*

NOTE:

The datum is at fuselage station 0 situated 114 inches forward of the wingleading edge. This is the datum defined in the Flight Manual. All lever armsare distances in inches aft of datum

NAL/W/95 dated 31 August 1988 is 5516 lb

The CG of the aircraft in the same Condition at this weight and with the landing gear extended is

127 in aft of datum

The total moment about the datum In this condition in lb.in/100 is 7015



Documentation


FIGURE 11-2

Part B Variable LoadThe weight, lever arms and moments of items of Variable Load are shown below. The Variable Loaddepends upon the equipment carried for the particular role.

FIGURE 11-3

Weight

(lb)

Lever Arm

(in)

Two Marzell propeller type BL-H3Z30 127 each 76

Two engine driven 100 ampere alternators Type GE-362 27 each 117

One 13 Ah Ni Cd battery CB-7 31 153

Weight

(lb)

Lever Arm

(in)

Moment

(100 lb.inc)

Pilot (one) 108

De-icing fluid 1.5 gal 12 140 17

Lift-jackets (7) 14 135 19

Row 1 passenger seats (two) 60 173 104





Documentation


FIGURE 11-4Part C Loading Information (Disposable Loads)

Table 8 256 20

One stretcher and attachments (in place of seat rows 2 and 3)

45 223 100

Medical stores 15 250 37

Weight

(lb)

Lever Arm

(in)

Moment

(100 lb.inc)

Weight

(lb)

Lever Arm

(in)

Capacity

(imp gal)

Fuel in tanks 1 and 2 1368 145 190

Engine Oil 50 70 5.5

Forward baggage 21

Rear baggage 261

Passengers in Row 1 seats 171



Patient in stretcher 223



Documentation


NOTE:

To obtain the total loaded weight of aircraft, add to the Basic Weight theweights of the items of Variable and Disposable Load to be carried for theparticular role.

This Schedule was prepared (date) ……… and supersedes all previous issues.

Signed …………………….Inspector/Engineer

On behalf of …………………………………..

Approval Reference …………………………..

NOTE:

Not part of the specimen Schedule). In Part B, Variable Load, of this Schedulethe actual weight of the pilot is required in accordance with the Air Navigation(General) Regulations for aircraft the Maximum Total Weight Authorised ofwhich does not exceed 4700 kg or with less than 12 persons seating capacity.Hence the pilot’s weight and calculated moment are omitted in the example.

*Densities – Petrol 7.2 lb Imp.gal; Kerosone 8.1 lb. Imp.gal; Oil 9.0 lb

Imp.gal.



Documentation


Appendix No. 2 – Weight and Centre-of-Gravity and Loading Distribution Schedules Aircraft Not Exceeding 2730kg.43. INTRODUCTION. This Appendix contains acceptable means of compliance in respect ofWeight and Centre-of-Gravity and Loading and Distribution Schedules provided in accordance withthe requirements.

44. LOADING AND DISTRIBUTION SCHEDULE. The Schedule (including the graphs) andthe List of Basic Equipment should, as far as is practical, take the form of Figure 11-5, Figure 11-6and Figure 11-7.



Documentation


FIGURE 11-5Front of Schedule



Documentation


FIGURE 11-6Reverse of Schedule



Documentation


FIGURE 11-7List of Basic Equipment



Documentation


45. WEIGHT AND CENTRE OF GRAVITY SCHEDULE. An acceptable means of compliancewith the requirements would be to include in the Schedule instructions on the following lines:

Specimen Instructions(a) By reference to Weight and Centre-of-Gravity Schedule, ascertain the lever arm of

each item (Basic Weight, Variable Load, Disposable Load).

(b) To obtain moment of an item, multiply the weight of the item by the correspondinglever arm, and record the moment for each item of load, giving the moment a positivesign if the item is aft of the datum, and a negative sign if it is forward of the datum.Enter the weight of the item in the weight column.

(c) Total the weight column.

(d) Total the moment columns. If (+) and (-) moments are recorded total each columnand obtain the total resultant moment, by subtracting the lesser from the greater.

(e) Divide the total (or total resultant) moment by the total weight to obtain c.g. position,positive or negative, relative to the datum, and check that this is within the prescribedc.g. limits.

(f) To check that the fuel consumed during a flight does not cause the c.g. position to beoutside the prescribed limits, re-total the weights in 3 and the moments in 4, butomitting the total fuel weight and the corresponding moment(s), respectively. Add theweight and moment of the fuel expected to remain in the tanks at the end of the flight.Divide the final total resultant moment by the final total weight to obtain the c.g.position, and check that it is still within the prescribed c.g. limits.



Documentation


NOTE:

Note: Where there are any other significant quantities of consumable fluids orsubstances (e.g. crop spraying), similar account should be taken of them.





Definitions

Weight

Load

Equipment

Passengers



Definitions


12Definitions

WeightBasic Weight. This is the aeroplane weight plus basic equipment, unusable fuel and undrainableoil. Basic equipment is that which is common to all roles plus unconsumable fluids such as hydraulicfluid.

Dry Operating Weight. This is defined in JAR-OPS 1.607 as the total weight of the aeroplanefor a specific type of operation excluding all usable fuel and traffic load. It includes such items ascrew, crew baggage, catering equipment, removable passenger service equipment, potable water andlavatory chemicals. The dry operating weight is sometimes referred to as the Aircraft Prepared forService (APS) weight.

Empty Weight. This is the basic weight plus role equipment.

Maximum Zero Fuel Weight. The maximum permissible weight of an aeroplane with no usablefuel. The weight of fuel contained in particular tanks must be included in the zero fuel mass when itis explicitly mentioned in the aeroplane Flight Manual limitations. This is a structural limitationimposed to ensure that the airframe is not over-stressed.

Maximum Structural Landing Weight. The maximum permissible total aeroplane weight onlanding in normal circumstances.



Definitions


Maximum Structural Take-Off Weight. The maximum permissible total aeroplane weight atthe start of the take-off run.

Zero Fuel Weight. This is the dry operating weight plus the traffic load. In other words it is theweight of the aeroplane without the weight of fuel.

Aircraft Prepared for Service (APS) Weight. The weight of the aircraft shown in the weightschedule (the basic weight) plus such additional items in or on the aircraft as the operator thinks fitto include.

All Up Weight (AUW). The total weight of an aircraft and all of its contents at a specific time.

Total Loaded Weight. The sum of the aircraft basic weight, the variable load and disposableload.

Design Minimum Weight. The lowest weight at which an aeroplane complies with thestructural requirements for its own safety.

Maximum Ramp Weight. The maximum weight at which an aircraft may commence taxiingand is equal to the maximum take-off weight plus taxi fuel and run-up fuel. It must not exceed thesurface load bearing strength.

Maximum Total Weight Authorised (MTWA). The maximum total weight of the aircraftprepared for service, the crew (unless already included in the APS weight), passengers, baggage,cargo and fuel at which the aircraft may take-off anywhere in the world, in the most favourablecircumstances in accordance with the Certificate of Airworthiness in force in respect of aircraft.



Definitions


Maximum Take-Off Weight. The maximum weight at which take-off is permitted, byconditions other than available performance.

Landing Weight. The gross weight of the aeroplane, including all of its contents, at the time oflanding.

Maximum Landing Weight. The maximum weight at which a landing (except in an emergency)is permitted by considerations other than available performance.

Maximum Taxi Weight. The same as maximum ramp weight.

LoadAbsolute Traffic Load. The traffic load plus usable fuel and consumable fluids. The traffic loadis the total weight of passengers, baggage and cargo, including any non-revenue load.

Floor Load. This is the area load at a specific station.

Index. This is the moment divided by a constant usually 1000.

Maximum Floor Load. The highest area load permitted on any part of the floor of theaeroplane is the maximum floor load.

Running Load. The weight of any object divided by the length of that object measured parallel tothe longitudinal axis is the running or linear load.

Payload. Anyone or anything on board the aeroplane the carriage of which is paid for by someoneother than the operator. In other words anything or anyone carried that earns money for the airline.



Definitions


Traffic Load. The total weight of passengers, baggage and cargo including non-revenue load.

Useful Load. The traffic load plus usable fuel is also referred to as the disposable load.

Variable Load. This includes the role equipment, the crew and the crew baggage. Roleequipment is that which is required to complete a specific task such as seats, toilets, galley for thepassenger role or roller conveyor, lashing points and tie down equipment for the freight roles.

EquipmentBallast. Additional fixed weights which can be removed, if necessary, that are carried, to ensurethe centre of gravity remains within safe limits, in certain circumstances.

Basic Equipment. The inconsumable fluids and the equipment which is common to all roles forwhich the operator intends to use the aircraft.

Load Spreader. A mechanical device inserted between the cargo and the aircraft floor todistribute 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 orposition of particular tanks.

PassengersAdults are defined as persons of an age of 12 years and above. They are further classified as maleor female. [Appendix 1 to JAR-OPS 1.620 (g)].



Definitions


Children are persons of an age of 2 years but who have not yet reached their 12th birthday. Theyare not differentiated by sex.

Infants are persons who have not yet reached their second birthday. Infants shall be weighedtogether with their accompanying adult. When taking random samples.

Standard Weight –is the weight of any item or person as tabulated in JAR-OPS 1.620 or otheritem weight as approved by the JAA.





13CAP 696 - Loading Manual

1. The CAP 696 is published by the CAA for examination purposes. The candidate isresponsible for taking a copy of this CAP in pristine condition to the examination. The details ofthree generic aircraft are contained in the manual which are representative of those used forperformance and flight planning. Pages 2, 3 and 4 of the manual contain definitions which can beused to advantage to answer some of the theoretical questions.

2. The SEP 1. The green pages of the manual contain all of the details of the single enginepiston/propeller aeroplane. The maximum limitations are on page 5 but the floor loading limitationsat the bottom of the page apply to Figure 2-2 on Page 6. Figure 2-3 provides the moments for anygiven quantity of fuel. Page 7 details the procedure to be adopted to determine and plot the CGposition on pages 8 and 9. The following two examples demonstrate the use of the SEP 1 pages.





EXAMPLE 13-1

EXAMPLE 13-2

EXAMPLE

The aeroplane is to carry a pilot and co-pilot each weighing 80 kgs and two passengers eachweighing 70 kgs and have 5 kgs of baggage each, which is in Zone B. The fuel on board at start-up is 60 US gallons of which 30 US gallons will be used for the flight.

Determine the CG for zero fuel weight, take-off and landing. Fill in the pro forma and plot theresults.

EXAMPLE

The aeroplane is to carry a pilot and co-pilot each weighing 85 kgs and two passengers weighing185.6 kgs together in third and fourth seats. Each passenger has 10 kgs of baggage which isloaded in Zone C. The fuel on board is 70 US gallons of which 50 US gallons will be used for theflight.

Fill in the pro forma and plot the results to determine the CG for the zero fuel weight, take-off and landing weights.





FIGURE 13-1Loading Manifest Example 13-1





FIGURE 13-2Centre of Gravity Envelope

Example 13-1





FIGURE 13-3Loading Manifest Example 13-1 Solution






Example 13-1 Solution






Example 13-2






Example 13-2 Solution





3. The MEP 1. The limitations for the multi-engined piston/propeller aircraft are listed on Page12. Notice the reference datum is at the bulkhead of the nose cargo compartment. Page 13 detailsthe calculation procedure and a worked example is shown on pages 14 and 15. Now complete thepro forma and plot the results for the following examples.

EXAMPLE 13-3EXAMPLE

The aeroplane is to carry:

(a) Pilot and front passenger total weight 360 lbs.

(b) Two centre seat passengers total weight 340 lbs.

(c) One rear seat passenger weight 90 lbs.

(d) Baggage in Zone 1 weight 50 lbs.

(e) Fuel in tanks 120.5 US gallons.

(f) 23 lbs of fuel is used for start, taxi and run-up.

(g) 500 lbs is used for the flight.





EXAMPLE 13-4EXAMPLE

The aeroplane is to carry:

(a) Pilot and front passengers total weight 170 kgs.

(b) Two centre seat passengers total weight 150 kgs.

(c) Two rear seat passengers total weight 100 kgs.

(d) Baggage in Zone 1 weight 40 kgs.

(e) Baggage in Zone 4 weight 40 kgs.

(f) Fuel in tanks 75 US gallons.

(g) 5 US gallons used for start, taxi and run-up.

(h) 50 US gallons used for the flight.





FIGURE 13-10 Example 13-3





FIGURE 13-12 Example 13-3 Solution





FIGURE 13-14 Example 13-4





#

FIGURE 13-16 Example 13-4 Solution





4. The MRJT. All the data regarding the medium range jet transport aeroplane are contained inthe white pages of the CAP 696. Page 20 details all the stations and their balance arms. BS is anabbreviation for body station and FS for front spar.

5. On Page 21, Figure 4-3 details the change to the moments caused by flap retraction to 0°,therefore if flap is extended on approach and landing it will have the opposite effect to that which istabulated. Figure 4-4 enables the stabiliser time unit setting to be calculated fro take-off, using either5° or 15° of flap, for any CG position between 5% and 30% of the mean aerodynamic chord. Thedimensions of the MAC are given in paragraph 2.5 and the structural limitations in paragraph 3.1.All details of the fuel are on Page 22, passenger distribution on Page 23 together with standard massvalues for the crew and passengers. Precise details regarding the loading of the cargo compartmentsare on Page 24.

6. The procedure for calculating and plotting the CG is specified on Page 25 using the pro formaon Page 26 and the trim envelope diagram on Page 27. The example load and trim sheet informationon Page 28 and 29 illustrates the completion of this form. At the present it is not envisaged that thecandidate will have to utilise one to answer any question because each airline has their own versionof this form.

Important Points(a) The wing tanks must remain full until the contents of the centre tank are 450 kgs or

less.

(b) The standard mass used for the crew is 90 kgs each instead of the JAR-OPS 1 standardmasses of 85 kgs for flight crew and 75 kgs for cabin crew.





(c) The standard passenger mass is 84 kgs which according to the JAR-OPS 1 is thestandard mass for all flights except holiday charters.

(d) The allowance made for hand baggage is 6 kgs.

(e) The standard mass for baggage is 13 kgs per passenger which according to JAR-OPS 1is that which should be used for European flights only.

THE MESSAGE IS THAT WHEN USING MRJT 1 LOADING MANIFEST THE VALUES USEDFOR STANDARD MASSES ARE NON-STANDARD.





EXAMPLE 13-5EXAMPLE

The details of this example are as shown on Page 28 of CAP 696 and depicted on Page 29. Use thetrim sheet blank at Figure 13-7 below and follow the instructions on Page 28.





FIGURE 13-17Load and Trim Sheet (Blank)



Aircraft Mass & Balance

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