031 AIRCRAFT MASS & BALANCE
© G LONGHURST 1999 All Rights Reserved Worldwide
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EDITION 2.00.00 2001
This is the second edition of this manual, and incorporates all amendments to previous editions, in
whatever form they were issued, prior to July 1999.
EDITION 2.00.00
© 1999,2000,2001
G LONGHURST
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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
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TABLE OF CONTENTS
The Weighing of Aeroplanes
Documentation
Definitions
CAP 696 - Loading Manual
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Introduction
1.
As a professional pilot you will deal with aircraft loading situations on every flying day of
your working life. The course that you are about to embark upon considers the inter-relationship
between aircraft loading and other related subjects (principally aircraft performance and flight
planning), and the very important airmanship aspects of proper aircraft loading. In general (nonaircraft type specific) terms, the ways in which the centre of gravity of both unladen and laden
aircraft can be determined and checked as being within safe limits will be discussed. As and when
you are introduced to new aircraft types, both during your flight training and during your
subsequent career, you will be taught the loading procedures which are specific to that particular
aircraft type.
2.
In the Aircraft Performance book the problem of determining the maximum permitted takeoff weight for an aircraft in a given situation is addressed. The Flight Planning book addresses the
determination of the maximum payload, which can be carried on a given flight. In Aircraft Loading
the problems of distributing the load within the aircraft such that the resultant centre of gravity is,
firstly, within the safe limits laid down for the aircraft and, secondly, positioned so as to enhance the
efficient performance of the aircraft, are addressed.
3.
The Joint Aviation Authority has the task of ensuring that all public transport aircraft,
irrespective of size or number of engines, are operated to the highest possible level of safety. To
discharge this commission the JAA periodically introduces legislation in the form of operating rules
or regulations and minimum performance requirements, which are complementary. All public
transport aircraft are divided into Classes in which the types have similar levels or performance.
There is a set of rules and requirements for each Class of aeroplanes, which dictate the maximum
mass at which an aeroplane may be operated during any particular phase of flight.
Chapter Page 1
© G LONGHURST 1999 All Rights Reserved Worldwide
4.
With the introduction of the Joint Aviation Authority syllabus the word ‘mass’ is used instead
of the word ‘weight’. In all British and American publications, weight is still preferred and used to
express the downward force exerted by mass. The reason the JAA use mass is because weight = mass
x acceleration i.e. weight = mass x 1. Therefore weight and mass are synonymous. Throughout this
book the word ‘weight’ has been used and may be exchanged for the word ‘mass’ if preferred.
5.
In addition to this the metric system of measuring weight and volume is preferred by the JAA
and it may be necessary to convert Imperial or American quantities to metric equivalents. If such is
the case use the following method.
Conversion between Weight and Volume
6.
The weights and volumes obtained for the purpose of centre of gravity calculations are
frequently given as a mixture of metric and imperial measures. For example a British or American
built aircraft may well have its weights presented in the Aeroplane Flight Manual (AFM) in pounds
and when loaded on the continent the load may be quoted in kilograms. Fuel is delivered in litres,
imperial gallons or US gallons, but of course must figure in the load sheet calculations in pounds or
kilograms. Although the conversion between differing units of weight and volume, and indeed the
conversion between volume and weight for fluids with a given specific gravity, is covered elsewhere
in the course, the following paragraphs are included in this manual for your guidance.
7.
To convert a volume of liquid to weight and vice versa the density of the liquid must be
considered. The density is expressed as a specific gravity (SG). 1 litre of pure water weighs 1 kg and
1 imperial gallon pure water weights 10 lb. The SG of pure water is taken as the datum SG of 1.0.
Chapter Page 2
© G LONGHURST 1999 All Rights Reserved Worldwide
8.
When converting litres of any liquid to kilograms the volume must be multiplied by the
specific gravity, or when converting kilograms to litres the weight must be divided by the specific
gravity. Similarly, when converting imperial gallons to pounds the volume must be multiplied by (10
x the specific gravity), or to convert pounds to imperial gallons the volume must be divided by (10 x
the specific gravity) of the liquid.
9.
Aviation fuels and oils are lighter than pure water, therefore their specific gravities will be less
than 1.0.
10.
The diagram at Figure 0-1 may help you with these conversions. When using the diagram at
Figure 0-1 and moving in the direction of the arrows, multiply (as shown). Conversely, when moving
in the opposite direction, divide.
Volume Conversions
11.
In some problems the oil is measured in quarts. They may be in Imperial measurements or
American. It does not matter, the conversion is the same as shown below in Paragraph 12.
12.
Chapter Page 3
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2 Pints
= 1 Quart
4 Quarts
= 1 Gallon
8 Pints
= 1 Gallon
FIGURE 0-1
Weight/Volume
Conversion
13.
When travelling in the direction of the arrows multiply, when travelling in the opposite
direction divide.
Chapter Page 4
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031 Aircraft Mass & Balance
The Composition of Aeroplane Weight
Weight Limitations
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The Composition of Aeroplane Weight
The Composition of Aeroplane
Weight
1
1.
The total weight of an aeroplane is the weight of the aeroplane and everyone and everything
carried on it or in it. Total weight comprises three elements, the basic weight, the variable load and
the disposable load.
Basic Weight.
This is the aeroplane weight plus basic equipment, unusable fuel and undrainable
oil. Basic equipment is that which is common to all roles plus unconsumable fluids such as hydraulic
fluid.
Variable Load.
This includes the role equipment, the crew and the crew baggage. Role
equipment is that which is required to complete a specific tasks such as seats, toilets and galley for
the passenger role or roller convey or, lashing points and tie down equipment for the freight role.
Disposable Load.
The traffic load plus usable fuel and consumable fluids. The traffic load is the
total weight of passengers, baggage and cargo, including any non-revenue load. The disposable load
is sometimes referred to as the useful load.
2.
Although these are the weight definitions used in the load sheet there are other terms which
are commonly used. These are:
Absolute Traffic Load.
The maximum traffic load that may be carried in any circumstances. It
is a limitation caused by the stress limitation of the airframe and is equal to the maximum zero fuel
weight minus the aircraft prepared for service weight.
Chapter 1 Page 1
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The Composition of Aeroplane Weight
All Up Weight (AUW).
The total weight of an aircraft and all of its contents at a specific time.
Design Minimum Weight. The lowest weight at which an aeroplane complies with the
structural requirements for its own safety.
Dry Operating Weight. The total weight of the aeroplane for a specific type of operation
excluding all usable fuel and traffic loads. It includes such items as crew, crew baggage, catering
equipment, removable passenger service equipment, and potable water and lavatory chemicals. The
items to be included are decided by the Operator. The dry operating weight is sometimes referred to
as the Aircraft Prepared for Service (APS) weight. The traffic load is the total weight of passengers,
baggage and cargo including non-revenue load. [JAR-OPS 1.607 (a)].
Empty Weight.
(Standard Empty Weight) The weight of the aircraft excluding usable fuel, crew
and traffic load but including fixed ballast, engine oil, engine coolants (if applicable) and all
hydraulic fluid and all other fluids required for normal operation and aircraft systems, except
potable water, lavatory pre-charge water and fluids intended for injection into the engine (demineralised water or water-methanol used for thrust augmentation).
Landing Weight.
The gross weight of the aeroplane, including all of its contents, at the time of
landing.
Maximum Ramp Weight.
The maximum weight at which an aircraft may commence taxiing
and its equal to the maximum take-off weight plus taxi fuel and run-up fuel. It must not exceed the
surface load bearing strength.
Maximum Structural Landing Weight.
The maximum permissible total aeroplane weight on
landing in normal circumstances. [JAR-OPS 1.607 (c)].
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The Composition of Aeroplane Weight
Maximum Structural Take-Off Weight.
The maximum permissible total aeroplane weight at
the start of the take-off run. [JAR-OPS 1.607 (d)].
Maximum Total Weight Authorised (MTWA).
The maximum total weight of aircraft
prepared for service, the crew (unless already included in the APS weight), passengers, baggage and
cargo at which the aircraft may take-off anywhere in the world, in the most favourable circumstances
in accordance with the Certificate of Airworthiness in force in respect of aircraft.
Maximum Zero Fuel Weight.
The maximum permissible weight of an aeroplane with no usable
fuel. The weight of fuel contained in particular tanks must be included in the zero fuel mass when it
is explicitly mentioned in the Aeroplane Flight Manual limitations. This is a structural limitation
imposed to ensure that the airframe is not overstressed. [JAR-OPS 1.607 (b)].
Payload.
Anyone or anything on board the aeroplane the carriage of which is paid for any
someone other than the operation. In other words anything or anyone carried that earns money for
the airline.
Total Loaded Weight.
The sum of the aircraft basic weight, the variable load and disposable
load.
Traffic Load. The total mass of passengers, baggage and cargo, including any non-revenue load.
[JAR-OPS 1.607 (f)].
Zero Fuel Weight.
This is the dry operating weight plus the traffic load. In other words it is the
weight of the aeroplane without the weight of usable fuel.
Chapter 1 Page 3
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The Composition of Aeroplane Weight
Equipment
Ballast.
Additional fixed weights which can be removed, if necessary, that are carried, to ensure
the centre of gravity remains within the safe limits, in certain circumstances.
Basic Equipment. The unconsumable fluids and the equipment which is common to all roles for
which the operator intends to use the aircraft.
Load Spreader.
A mechanical device inserted between the cargo and the aircraft floor to
distribute the weight evenly over a greater floor area.
Unusable Fuel.
That part of the fuel carried which is impossible to use because of the shape or
position of particular tanks.
Unusable Oil. That part of the oil lubrication system that cannot be removed due to the
construction of the system.
Chapter 1 Page 4
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The Composition of Aeroplane Weight
FIGURE 1-1
The Composition
of Aeroplane
Weight
Chapter 1 Page 5
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The Composition of Aeroplane Weight
3.
The total weight of an aeroplane comprises many different components, all of which, together
with 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 usable
fuel, the crew and the traffic load but including any fixed ballast, unusable fuel, all engine coolant
and all hydraulic fluid.
5.
The basic weight of an aeroplane is essentially the empty weight plus the weight of basic
equipment, that is equipment which is common to all roles in which the aircraft may be required to
perform. The basic weight and the corresponding CG position, together with the declared basic
equipment showing the weight and arm of each item, are shown in Part A of the Weight and CG
Schedule 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 additional
equipment. This is known as role equipment, an example would be the passenger seats, toilets and
galleys, 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 operator
wishes, but for every role the weights and moments must be stated. The weight and moment of the
crew is included in Part B. Under certain circumstances, standard crew (and passenger) weights are
assumed, otherwise the weight of each crew member must be determined by weighing. The
occasions on which standard weights may be used are discussed in the Chapter entitled ‘Joint
Airworthiness Requirements’.
8.
With the role equipment fitted the aircraft is ready to enter service. The weight of the aircraft
in this condition is called the Aircraft Prepared for Service (APS) weight, or the Dry Operating
Weight (DOW). The total weight of the aeroplane comprises the APS weight plus the disposable
load, which is made up of usable fuel and the payload.
Chapter 1 Page 6
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The Composition of Aeroplane Weight
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 Schedule
must be completed every time the aircraft is weighed. Each Schedule must be preserved for a period
of 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 Limitations
12.
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, and
agreed by the Authority, to ensure the aeroplane is not over-stressed. These structural weights
include the maximum structural ramp weight, the maximum structural take-off weight, the
maximum 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 field
lengths and the prevailing meteorological conditions at the departure aerodrome.
The Weight-Altitude-Temperature (WAT) Limit.
This limitation is imposed on TOW by
minimum climb gradient requirements, which are specified in Joint Airworthiness Requirements
(JARs).
Chapter 1 Page 7
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The Composition of Aeroplane Weight
The En-Route Requirements.
The weight of the aircraft at any stage of the flight en-route must
be such that the aircraft can safely clear any objects within a specified distance of the aircraft’s
intended track. Depending on the aircraft’s performance category, the loss of power from a specified
number of engines will be assumed when determining the maximum weight at which the aircraft can
safely clear en-route obstacles. En-route terrain clearance may impose a limitation on the take-off
weight.
The Maximum Landing Weight.
This may be dictated by the structural limitation, the FieldLength 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, the
WAT 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. In
order that the maximum traffic load can be carried it may be necessary to limit the amount of fuel
which is carried to a safe minimum. Whether or not the fuel carried actually limits the traffic load, it
is normally prudent to reduce the fuel load to a safe minimum in order to reduce the all up weight of
the aircraft. This will result in lower operating costs, higher cruise levels, reduced thrust take-offs
and/or easier compliance with noise abatement procedures on take-off. The total fuel required on
any particular flight comprise the following:
Route Fuel. This is the fuel used from departure to destination aerodromes and may be
minimised by operating at the most economical pressure altitude accounting for the temperature and
wind component, but not below the minimum safe altitude.
Diversion Fuel.
The fuel required to proceed from the destination to the alternate aerodrome in
the prevailing conditions.
Chapter 1 Page 8
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The Composition of Aeroplane Weight
Holding Allowance. The fuel required to enable the aircraft to hold at a specified pressure
altitude and for a specified period of time.
Contingency Allowance.
An amount of fuel carried to counter any disadvantage suffered
because of unforecast adverse conditions.
Landing Allowance.
The fuel required to be used from overhead the landing aerodrome to the
end of the landing roll.
14.
On occasions it is advantageous to carry more than the minimum fuel for a given sector. The
obvious example is when fuel will not be available at the destination aerodrome. Alternatively, the
cost of fuel at the destination aerodrome may be so high that the cost differential (departure
aerodrome fuel cost versus destination aerodrome fuel cost) may be so great that it is cheaper to
carry 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 which
is available once the fuel load has been decided. It may be impossible to distribute the traffic load
such that the centre of gravity of the laden aircraft remains within the safe specified limits, in which
case some of the traffic load may have to be off-loaded. Floor loading factors may have to be
considered. With a payload which is light in weight but bulky it may be physically impossible to fit
the traffic load into the aircraft.
Chapter 1 Page 9
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The Composition of Aeroplane Weight
Operating Overweight
16.
A safely loaded aircraft is one in which the total weight of traffic load is equal to or less than
the maximum permissible traffic load for a given flight and the distribution of that traffic load is such
that the centre of gravity of the laden aircraft lies within the fore and aft limits of centre of gravity
which are permitted for that aircraft operating in the specified role.
17.
Chapter 1 Page 10
The effects of operating in an overweight condition include:
(a)
Reduced acceleration on the ground run for take-off. The take-off speeds are
increased because of the weight, and this results in an increased take-off run required
and an increased take-off distance required.
(b)
Decreased gradient and rate of climb which decreases obstacle clearance capability
after take-off and the ability to comply with the minimum climb gradient
requirements.
(c)
Increased take-off speeds impose a higher load on the undercarriage and increased tyre
and wheel temperatures. Together these reduce the aeroplane’s ability to stop rapidly
in 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 decreased
operational range. It may also cause en-route terrain clearance problems.
(f)
Impaired manoeuvrability and controllability.
© G LONGHURST 1999 All Rights Reserved Worldwide
The Composition of Aeroplane Weight
(g)
Increased approach and landing speeds causing a longer landing distance, landing
ground 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 the
airframe.
18.
In addition to ensuring that the maximum permissible all-up weight of an aircraft is not
exceeded it is of vital importance to ensure that the distribution of the permissible weight is such that
the balance of the aircraft is not upset.
Chapter 1 Page 11
© G LONGHURST 1999 All Rights Reserved Worldwide
031 Aircraft Mass & Balance
The Calculation of Aircraft Weight
Weight and Traffic Load
© G LONGHURST 1999 All Rights Reserved Worldwide
The Calculation of Aircraft Weight
2
The 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).
Chapter 2 Page 1
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The Calculation of Aircraft Weight
EXAMPLE 2-1
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 2-2
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
Chapter 2 Page 2
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The Calculation of Aircraft Weight
EXAMPLE 2-3
EXAMPLE
Given the same details as Example 2-2, calculate the disposable load.
SOLUTION
3000 + 7000 = 10,000 kgs.
EXAMPLE 2-4
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.
Weight and Traffic Load
1.
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 because
there is no consideration of whether the centre of gravity of the laden aircraft lies within the trim
envelope.
Chapter 2 Page 3
© G LONGHURST 1999 All Rights Reserved Worldwide
The Calculation of Aircraft Weight
2.
To avoid getting lost in a mass of figures and definitions, remember that the All Up Weight of
an 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 weight
of the fuel will progressively decrease.
4.
In the examination you will be required to calculate the weight of the traffic load that can be
carried, 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 public
transport aircraft, which makes the aircraft ready to enter service. The weight of the aircraft in this
condition is called the Aircraft Prepared for Service (APS) weight, or the Dry Operating Weight. The
Total Weight of the aeroplane then comprises of the APS weight plus the Disposable Load, which is
made up of the usable fuel and traffic load.
Chapter 2 Page 4
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The Calculation of Aircraft Weight
6.
To answer this type of question use the layout shown in the following examples and approach
the problem in a logical manner remembering the total weight at any time comprises the APS weight,
the fuel and the traffic load.
EXAMPLE 2-5
EXAMPLE
Given:
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.
Determine the traffic load which can be carried from A to B.
Chapter 2 Page 5
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The Calculation of Aircraft Weight
SOLUTION
First, calculate the fuel required for the sector.
TAS
=
470 kt.
Wind Component
=
-20 kt.
Groundspeed
=
450 Kt.
Sector Time
=
Sector
Distance- = --------------3, 600- = 8 hours
--------------------------------------Groundspeed
450
Sector Fuel Required
=
Fuel flow x time = 5,500 x 8 = 44,000 kg
MTOW Limit
MLW Limit
MZFW Limit
MTOW
+145,000 kg.
MLW
+ 97,900 kg. MZFW
APS Wt.
– 67,400 kg.
APS Wt.
–67,400 kg.
Res:
- 7,500
+ 90,100 kg
APS Wt. - 67,400 kg
Fuel: Leg - 44,000 kg
Res
Payload
- 7,500
+26,100 kg.
+23,000 kg.
+22,700kg
Maximum traffic load is the lower of the three calculated values i.e. 22,700 kg. This is the only
traffic load that will not exceed either the MTOW, MLW or the MZFW limitations.
Chapter 2 Page 6
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The Calculation of Aircraft Weight
In the above example, the Fuel Required calculation could have been conducted in one step using
the following method:
Sector Distance
Sector Fuel Required = ------------------------------------- × Fuel Flow
Groundspeed
3, 600
= --------------- × 5, 500 = 44, 000 kg
450
Chapter 2 Page 7
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The Calculation of Aircraft Weight
EXAMPLE 2-6
EXAMPLE
Given:
Maximum Take-Off Weight
150,000 kg.
Maximum Landing Weight
100,000 kg.
Maximum Zero Fuel Weight
90,000 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.
Calculate:
Chapter 2 Page 8
(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.
© G LONGHURST 1999 All Rights Reserved Worldwide
The Calculation of Aircraft Weight
SOLUTION
Calculate the Sector Fuel:
Sector Distance
1250
Sector Fuel = ------------------------------------- × Fuel Flow = ------------ × 6000 = 30000 kg
Ground speed
250
If the aircraft had a total of 50,000 kg. of fuel at take-off and burnt 30,000 kg. of fuel in transiting
the sector distance then there would be 20,000 kg. of fuel remaining in the tanks on landing.
MTOW Limit
MTOW
+150,000 kg
MLW Limit
MLW +100,000 kg
MZFW Limit
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
The Limiting Payload is 10,000 kg
To calculate the maximum range with this payload, consider that the aircraft has landed with
20,000 kg of fuel on-board although the reserve fuel requirement was only 5,000 kg. This means
that there is an additional 15,000 kg of fuel available to increase the sector distance. We now need
to calculate this extra distance.
Fuel Available
15000
Distance = ----------------------------------- × Groundspeed = --------------- × 250 = 625 Nm
Fuel Flow
6000
Maximum Range = Original Sector Distance of 1250 + 625 = 1,875 nm.
Chapter 2 Page 9
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The Calculation of Aircraft Weight
EXAMPLE 2-7
EXAMPLE
An aircraft is to fly from A to B and then on to C without refuelling at B.
Given: APS weight 23,500kgs
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.
Maximum Zero Fuel Weight
31,300 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.
Determine the maximum payload that could be loaded at A and B.
Chapter 2 Page 10
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The Calculation of Aircraft Weight
SOLUTION
521
Calculate fuel required A to B = --------- × 3100 = 3565 kg
453
703
Calculate fuel required B to C = --------- × 2950 = 5345 kg
388
Note the taxi fuel at B (the difference between the Maximum Taxi Weight and the Maximum TakeOff Weight) is also to be considered in the calculation of the fuel on-board the aircraft from the
point of take-off at A.
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
-320
-320
Reserve Fuel
-2,000
-2,000
Payload
+7,070
+6,835
Taxi Fuel at B
-5,345
+7,800
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.
Chapter 2 Page 11
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-2,000
-2,000
+6,155
+11,000
031 Aircraft Mass & Balance
Weight and Balance Theory
Reference Datum
The Centre of Gravity Envelope
The Newton
Aeroplane Weight Determination
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Weight and Balance Theory
3
Weight and Balance Theory
1.
In order to understand the concept of weight and balance as it applies to aeroplanes it is
essential to have a thorough knowledge of the basic theory of balance and force moments. This is
best 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 (or
pivot) for support such that the fulcrum is exactly half way along the length of the seesaw, the weight
of the seesaw will act vertically downwards through the fulcrum. In this case at any specified
distance 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 (the
downward force) by the arm (the distance of that point from the fulcrum). Moments can be
expressed 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 is
referred 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.
Chapter 3 Page 1
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Weight and Balance Theory
FIGURE 3-1
Balanced
Condition
5.
If a weight is placed on one side of the seesaw it will impart an unbalancing force or turning
moment about the fulcrum. The moment of this force is equal to the product of the weight and the
distance at which it is placed from the fulcrum. For example, if a 20 kg weight is placed on the
seesaw at a distance of 80 cm from the fulcrum the moment (20 kg x 80 cm) is equal to 1600 cm kg
or 16 m kg as shown at Figure 3-2.
FIGURE 3-2
Unbalanced
Condition
Chapter 3 Page 2
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Weight and Balance Theory
6.
In order to restore the balance or equilibrium of the seesaw the unbalancing moment of 16 m
kg must be counterbalanced. This may be done by placing a weight on the opposite side of the
fulcrum such that the moment produced is equal and opposite to the unbalancing force. Therefore
any 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.
Chapter 3 Page 3
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Weight and Balance Theory
FIGURE 3-3
Restored Balanced
Condition
Chapter 3 Page 4
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Weight and Balance Theory
7.
At Figure 3-3 (b) the same effect is achieved by placing a 40 kg weight at a distance of 40 cm
from 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 cm
from 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 uniform
density and construction such that the weight acts vertically downward
through the centre of the weight.
Reference Datum
9.
The point from which the arms of force moments are measured is termed the reference
datum. In the preceding examples the reference datum was the centre of gravity of the unladen
seesaw, 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 a
vertically downward direction. The position of the CG measured along the fore and aft axis of the
aircraft 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 point
in the flight, total weight and distribution of the payload, and so on. It is therefore important to
appreciate that with an aircraft the reference datum cannot be the position of the CG, but will
instead be a fixed point on the aircraft structure, or indeed a point on the extension of the aircraft’s
fore and aft axis which is in fact forward of the aircraft’s nose.
Chapter 3 Page 5
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Weight and Balance Theory
11.
On large aircraft the bulkhead separating crew and passenger compartments is frequently
used as a reference datum, whereas in single engine aircraft the fire wall between cabin and engine
bay 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 fore
or aft of the datum (arm) of each piece of equipment, cargo and person on board the aircraft must be
known. By convention any weight which is positioned forward of the reference datum has a negative
arm and therefore produces a negative moment.
13.
Conversely, by convention, any weight which is aft of the reference datum has a positive arm
and therefore produces a positive moment.
The Centre of Gravity Envelope
14.
In order to ensure that an aeroplane can be safely controlled by the aerodynamic control
surfaces the CG must remain within safe limits. The distance between the maximum safe forward
position of the CG and the maximum safe aft position of the CG is termed the CG envelope. The
envelope dimensions are determined by the manufacturer, approved by the CAA, and subsequently
described in the Approved Flight Manual (AFM), which is part of the Certificate of Airworthiness. It
is a legal requirement that the CG remains within the CG envelope at all times. Some aircraft have
more than one CG envelope.
15.
Public transport aeroplanes may have two CG envelopes, one for public transport flights and
one for use on ferry or training flights. The CG envelope will be wider in the latter case, however it
may still be necessary to use ballast in order to position the CG of the essentially empty aeroplane
within limits.
Chapter 3 Page 6
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Weight and Balance Theory
16.
Similarly, some light aircraft are certified in two categories, semi-aerobatic category CG
envelope 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 semiaerobatic manoeuvres may be conducted may also be limited.
The Newton
17.
The mass of a body is the amount of matter which it contains. The weight of a body is the
force 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 the
Newton. 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 the
weight 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 9.81
Newtons.
21.
It is possible, although presently unlikely, that you may encounter aircraft weights expressed
in Newtons. In the examination, you may find that gravity is given as 10m/s/s in which case 1kg is
equal to 10 Newtons.
Chapter 3 Page 7
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Weight and Balance Theory
The Forces Acting On An Aeroplane In Flight
22.
The centre of gravity is that point on the longitudinal axis through which all of the weight
acts vertically downward. The centre of pressure is that point on the longitudinal axis through
which 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 and
drag. Lift acts through the centre of pressure and weight through the centre of gravity. For
simplicity, thrust and drag forces are considered as acting parallel to the longitudinal axis, and their
displacement from this axis depends on the design of the aircraft, high wing or low wing, the position
of the engine(s), and so on.
24.
In order to maintain steady flight the forces acting on an aeroplane must be in balance, with
no turning moment about any axis. In this condition the aircraft is said to be trimmed. The
condition is achieved by balancing the lift, weight, thrust and drag forces acting at the aircraft’s C of
G 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 force
couple will be set up by the lift and the weight forces, and this will result in a pitching moment, as
shown at Figure 3-4.
Chapter 3 Page 8
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Weight and Balance Theory
FIGURE 3-4
The Forces on an
Aeroplane in Level
Flight
26.
The magnitude of the pitching moment will depend on the magnitude of lift and weight
forces, 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 the
manner in which fuel is transferred/consumed in flight. The position of the centre of pressure
depends on the angle of attack, with the C of P moving slowly forward as the angle increases, and
then 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 are
exactly in equilibrium in flight. The centre of pressure moves with changing angle of attack, as does
the drag line. The centre of gravity moves with changes in the distribution of load and fuel. The
pitching couples are set up when the weight line is not coincident with the lift line or the drag line is
not coincident with the thrust line and are offset by the tailplane and/or elevators.
Chapter 3 Page 9
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Weight and Balance Theory
29.
Consequently, the forward and aft limits of the centre of gravity are determined by the
capability of the elevators (or stabilator or all moving tailplane) to control the aircraft in pitch at the
lowest flight speed. These limits are established by the aircraft manufacturer.
30.
The forward centre of gravity limit is established to ensure there is sufficient elevator
movement available at minimum flight airspeed. In other words to avoid a situation where the
elevators 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 can
be located for the most critical manoeuvre or operation. As the centre of gravity moves rearwards
aircraft longitudinal stability decreases. This means that the aircraft’s natural ability to return to
stable 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 with
the 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 limit
include:
Chapter 3 Page 10
(a)
Difficulty in rotating to take-off altitude.
(b)
Difficulty in flaring, rounding-out, or holding the nose-wheel off the ground after
touchdown 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.
© G LONGHURST 1999 All Rights Reserved Worldwide
Weight and Balance Theory
34.
(f)
Additional tail down force requires more lift from wing resulting in greater induced
drag, higher fuel consumption and reduced range.
(g)
Slow rotation on take-off.
(h)
Inability to trim out elevator stick forces.
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 the
climb.
(b)
Difficulty in trimming especially at high power.
(c)
Longitudinal instability, particularly in turbulence, with the possibility of a reverssal
of control forces.
(d)
Degraded stall qualities to an unknown degree.
(e)
More difficult spin recovery, unexplored spin behaviour, delayed or even inability to
recover.
Aeroplane Weight Determination
35.
In order to determine the weight and the arm of the basic aircraft, the first step is to determine
the aircraft empty weight (without fuel and payload) by measuring the weight acting through each
wheel (on a small aircraft) or through each jacking point (on larger aircraft).
Chapter 3 Page 11
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Weight and Balance Theory
36.
Since the position of each wheel or jacking point (relative to the datum) is known, it is now a
simple step to determine the position of the CG of the empty aircraft, and to express this position
relative to the datum.
37.
The following examples illustrate the method of calculating the weight and arm of empty
aircraft with various datum positions.
Chapter 3 Page 12
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Weight and Balance Theory
EXAMPLE 3-1
EXAMPLE
The main wheels of a light aircraft are in line with the datum, and the nose-wheel is 75 inches
forward of the datum. The weights measured through each wheel are:
Left Hand Main Wheel
810 lb.
Right Hand Main Wheel
815 lb.
Nose-Wheel
320 lb.
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
Chapter 3 Page 13
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Weight and Balance Theory
The simple calculation is completed in the following manner:
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
Total
1945 lb.
0
-24,000 in lb.
– 24000 in lb
CG = ------------------------------ = – 12.34 in
1945 lb
The aircraft weight is therefore 1945 pounds, and the CG lies 12.34 inches forward of the datum.
Chapter 3 Page 14
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Weight and Balance Theory
EXAMPLE 3-2
EXAMPLE
The datum is in line with the tip of the propeller spinner of a single engined light aircraft. The
nose-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:
Left Hand Main Wheel
810 lb.
Right Hand Main Wheel
815 lb.
Nose-Wheel
320 lb.
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 3-6.
FIGURE 3-6
Chapter 3 Page 15
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Weight and Balance Theory
The calculation is now completed as follows:
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.
+ 198,200 in lb
CG = ------------------------------------ = +101.9 in
1945 lb
The aircraft weight is therefore 1945 pounds, and the CG lies 101.9 inches aft of the datum.
Chapter 3 Page 16
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Weight and Balance Theory
EXAMPLE 3-3
EXAMPLE
The datum is positioned between the nose and the main wheels of a single engined light
aircraft. The nose-wheel is 45 inches forward of the datum and the main wheels are 55 inches
aft of the datum. The weights measured through each wheel are:
Left Hand Main Wheel
810 lb.
Right Hand Main Wheel
815 lb.
Nose-Wheel
320 lb.
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 3-7.
FIGURE 3-7
Chapter 3 Page 17
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Weight and Balance Theory
The calculation is now completed as follows:
Nose-Wheel
Weight
Arm
Moment
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.
+74,975 in lb
CG = -------------------------------- = +38.55 in
1945 lb
The aircraft weight is therefore 1945 pounds and the CG lies 38.55 inches aft of the datum.
Chapter 3 Page 18
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Weight and Balance Theory
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.
Chapter 3 Page 19
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Weight and Balance Theory
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 fuel
weight 43,000 kgs; Maximum landing weight 46,000kgs: Fuel at take-off 10,000kgs; Trip fuel
5,000kgs. Calculate the maximum traffic load.
QUESTION 14.
Does traffic load include the crew?
Chapter 3 Page 20
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Weight and Balance Theory
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.
Chapter 3 Page 21
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Weight and Balance Theory
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
Chapter 3 Page 22
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Weight and Balance Theory
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 vertically
downward.
Chapter 3 Page 23
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Weight and Balance Theory
ANSWER 13.
Page 2-3 Example 2-5
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
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
Chapter 3 Page 24
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Weight and Balance Theory
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.
Chapter 3 Page 25
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031 Aircraft Mass & Balance
Centre of Gravity Calculations
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Centre of Gravity Calculations
4
Centre of Gravity Calculations
1.
The CG of an aeroplane is determined by calculating the moments of the basic aeroplane and
together with the moments of all additional items (fuel, passengers, freight and so on) contained
within 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 by
its arm (distance from the reference datum). It is vital that you remember that the arm and the
resulting moment is, by convention, considered to be negative if the item is forward of the datum and
positive if the item is aft of the datum. Frequently the reference datum is given as a point on an
extension of the fore and aft axis forward of the nose of the aircraft. The advantage of such a
reference datum is that all arms and moments will be positive.
3.
In the event that the position of the undercarriage (extended or retracted) will significantly
affect the position of the basic aircraft CG, the loading information contained in Part C of the Weight
and CG Schedule will contain a statement of the total moment change which occurs when the
undercarriage is lowered. This is because the position of the basic aircraft CG is given with the
undercarriage the aircraft weight is therefore 1945 pounds and the CG lies 38.55 inches aft of the
datum extended.
4.
In order to demonstrate how the position of the loaded aircraft CG can be determined a small
twin piston aircraft is considered in Figure 4-1 and Figure 4-2. A general description of the CG limits
for this aeroplane is given at Figure 4-1 and is shown diagrammatically at Figure 4-2. Figure 4-3
shows the load form, which is appropriate to this aeroplane. The layout of the seats, baggage
stowage areas and fuel tanks is shown at Figure 4-4 and Figure 4-5.
Chapter 4 Page 1
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Centre of Gravity Calculations
FIGURE 4-1
Centre of Gravity
Limits (Gear
Extended)
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
NOTE:
Straight line variation between the points given. Datum line is located 137 in
ahead of the wing main spar centreline. Maximum landing weight 7000 lb.
Chapter 4 Page 2
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Centre of Gravity Calculations
FIGURE 4-2
Aeroplane CG
Envelope
Chapter 4 Page 3
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Centre of Gravity Calculations
FIGURE 4-3
Blank Load Sheet
Item
Weight Lb.
Arm Inches
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
Chapter 4 Page 4
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Moment Inches Lbs.
Centre of Gravity Calculations
Other
Total Weight
Total Moment
CG Location for Take-Off
Chapter 4 Page 5
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Centre of Gravity Calculations
FIGURE 4-4
Layout of
Aeroplane Weight
Chapter 4 Page 6
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Centre of Gravity Calculations
FIGURE 4-5
Profile of
Aeroplane
NOTE:
Note that on the form shown at Figure 4-3 that neither the weight nor the arm
appropriate to the aircraft itself is given. The information is contained within
the aircraft weight schedule, and is appropriate to one particular airframe.
Chapter 4 Page 7
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Centre of Gravity Calculations
5.
When loading the aeroplane care must be taken not to exceed the maximum weight permitted
in specific baggage areas. Floor loading/maximum weight details are not given in the form at
Figure 4-3, but are listed separately in the operating manual or, for larger aircraft, in the loading
manual, and are normally placarded in the aircraft itself.
EXAMPLE 4-1
EXAMPLE
Given that the aircraft described at Figure 4-2, Figure 4-3, and Figure 4-4, is loaded in the
following manner, determine the take-off weight and the position of the CG at take-off.
Basic aircraft
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
Chapter 4 Page 8
4,600 lb.
0 lb.
Forward baggage hold
40 lb.
Rear baggage hold
120 lb.
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
The left and right forward and the left and right aft nacelle lockers each contain 50 lb. of baggage.
Inboard fuel tanks
200 litres port
200 litres starboard
Outboard fuel tanks
200 litres port
200 litres starboard
SG of fuel 0.72
SOLUTION
First calculate the weight of fuel in pounds.
200 litres x 0.72
=
144 kg
144 kg x 2.205
=
317.5 lb
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.
Chapter 4 Page 9
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Centre of Gravity Calculations
FIGURE 4-6
Item
Weight Lb.
Basic Aeroplane
4
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
8
0
+ 195.0
Seat No.6
0
+ 195.0
Seat No.7
0
+ 229.0
Seat No.8
0
+ 242.0
4
0
+ 19.0
2
0
+ 255.0
Seat No.5
Fwd Baggage
Rear Baggage
Chapter 4 Page 10
Arm Inches
6
1
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
© G LONGHURST 1999 All Rights Reserved Worldwide
Moment Inches Lbs.
Centre of Gravity Calculations
Inboard Fuel
6
3
5
+ 126.8
Outboard Fuel
6
3
5
+ 148.0
8
9
5
Tot Moment
Other
Total Weight
6
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:
885, 363 inch-pounds
---------------------------------------------------- = +128.4in
6, 895 lb
The completed table should now appear as shown at Figure 4-7.
Chapter 4 Page 11
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Centre of Gravity Calculations
FIGURE 4-7
Item
Weight Lb.
Basic Aeroplane
4
Moment Inches Lbs.
6
0
0
+ 122.5
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
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.5
Seat No.8
0
+ 242.0
4
0
+ 19.0
2
0
+ 255.0
Right Nacelle Locker Forward
5
0
Right Nacelle Locker Aft
5
Left Nacelle Locker Forward
5
Left Nacelle Locker Aft
5
Fwd Baggage
Rear Baggage
Chapter 4 Page 12
Arm Inches
© G LONGHURST 1999 All Rights Reserved Worldwide
1
5
0
7
6
0
0
6
0
0
+ 145.0
7
2
5
0
0
+ 192.0
9
6
0
0
0
+ 145.0
7
2
5
0
0
+ 192.0
9
6
0
0
3
Centre of Gravity Calculations
Inboard Fuel
6
3
5
+ 126.8
8
0
5
1
8
Outboard Fuel
6
3
5
+ 148.0
9
3
9
8
0
8
9
5
Tot Moment
8
5
3
6
3
Other
Total Weight
6
8
885,363 inch-pounds
-------------------------------------------------- = +128.4in
6, 895lb
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).
Chapter 4 Page 13
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Centre of Gravity Calculations
FIGURE 4-8
Chapter 4 Page 14
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Centre of Gravity Calculations
EXAMPLE 4-2
EXAMPLE
The aircraft in Example 4-1 is planned to burn 650 litres of fuel en-route. The outboard tanks will
be used initially until they contain only 20 litres each, the inboard tanks will then be used for the
remainder 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 only
change is going to be the weight of fuel, and the change in the position of the CG which has
resulted 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.
Chapter 4 Page 15
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Centre of Gravity Calculations
FIGURE 4-9
Item
Weight Lb.
Basic Aeroplane
4
6
0
+ 122.5
Moment Inches Lbs. (+)
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
1
5
6
0
Seat No.5
0
+ 195.0
Seat No.6
8
0
+ 195.0
0
Seat No.7
0
+ 229.0
0
Seat No.8
0
+ 242.0
0
Fwd Baggage
4
0
+ 19.0
2
0
+ 255.0
Right Nacelle Locker Fwd
5
0
Right Nacelle Locker Aft
5
Left Nacelle Locker Fwd
Left Nacelle Locker Aft
Rear Baggage
Chapter 4 Page 16
0
Arm Inches
© G LONGHURST 1999 All Rights Reserved Worldwide
1
0
7
6
0
0
6
0
0
+ 145.0
7
2
5
0
0
+ 192.0
9
6
0
0
5
0
+ 145.0
7
2
5
0
5
0
+ 192.0
9
6
0
0
3
Centre of Gravity Calculations
Inboard Fuel
1
Outboard Fuel
7
5
+ 126.8
6
4
+ 148.0
6
4
Total Moment
2
2
1
9
0
9
4
7
2
2
5
2
7
Other
Total Weight
5
8
CG Location for Landing
742, 527
--------------------- = 126.6 in
5864
Chapter 4 Page 17
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7
4
Centre of Gravity Calculations
FIGURE 4-10
Chapter 4 Page 18
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Centre of Gravity Calculations
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".
#
Chapter 4 Page 19
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Centre of Gravity Calculations
EXAMPLE 4-3
EXAMPLE
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
Chapter 4 Page 20
Item
Weight or Volume
Arm
Basic Aircraft
6000 lb.
5" forward of datum
Crew
350 lb.
40" forward of datum
Passengers
330 lb.
Fuel
150 Imp gallons SG 0.72
Engine Oil
8 Imp gallons SG 0.875
© G LONGHURST 1999 All Rights Reserved Worldwide
36" aft of datum
11" aft of datum
6" forward of datum
Centre of Gravity Calculations
SOLUTION
Figure 4-12 shows schematically the distribution of the various weights about the datum and
illustrates 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.
Chapter 4 Page 21
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Centre of Gravity Calculations
Solution to Example 4-3
FIGURE 4-13
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
7830
-420
-44,420
-20,660
- 20,660 inch pound
CG = ------------------------------------------------ = – 2.64 inches
7830 lb
The CG therefore lies within the approved envelope for take-off.
Chapter 4 Page 22
© G LONGHURST 1999 All Rights Reserved Worldwide
+23,760
Centre of Gravity Calculations
EXAMPLE 4-4
EXAMPLE
Given that the aircraft described in Example 4-3 flies for 3 hours and that the mean rate of fuel
consumption 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
7139
-420
-44,420
-28,261
Chapter 4 Page 23
© G LONGHURST 1999 All Rights Reserved Worldwide
+16,159
Centre of Gravity Calculations
- 28,261 inch pound
CG = ------------------------------------------------ = -3.96 inches
7139 lb
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 reduced
by 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).
Chapter 4 Page 24
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Centre of Gravity Calculations
EXAMPLE 4-5
EXAMPLE
The following details apply to a six-seat twin engined aircraft. Maximum take-off and landing
weight 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
Basic aircraft:
Chapter 4 Page 25
© G LONGHURST 1999 All Rights Reserved Worldwide
0.72
Centre of Gravity Calculations
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:
Chapter 4 Page 26
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
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
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.
Chapter 4 Page 27
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Centre of Gravity Calculations
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
Chapter 4 Page 28
© G LONGHURST 1999 All Rights Reserved Worldwide
+903,790
Centre of Gravity Calculations
903, 790
Position CG = --------------------- = +151.6 inches (aft of datum)
5960
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.
Chapter 4 Page 29
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Centre of Gravity Calculations
EXAMPLE 4-6
EXAMPLE
Determine the minimum amount of baggage that must be moved from the aft baggage area
to the nose bay baggage area, in order to move the CG calculated in Example 4-5 to the aft
safe 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 alter
the total moments. The required total moments, that is the moments which will result from
a 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 an
arm 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 a
CG 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 bay
baggage 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 move
100 lb. The revised baggage distribution is therefore as shown in the table which follows.
Chapter 4 Page 30
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
FIGURE 4-18
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
887, 290
Position CG = --------------------- = +148.9 in (aft of datum)
5960
Plotting CG against weight gives us a point inside of the envelope, see Figure 4-19.
Chapter 4 Page 31
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Centre of Gravity Calculations
FIGURE 4-19
Chapter 4 Page 32
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
EXAMPLE 4-7
EXAMPLE
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 on
touchdown is all contained in the main tanks, check that the CG lies within the envelope on
landing.
SOLUTION
Chapter 4 Page 33
Fuel on take-off
960 lb.
Fuel consumed in flight
810 lb.
Fuel on touchdown
150 lb.
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
FIGURE 4-20
Item
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
+761,470
-810
5150
761, 470
Position CG = --------------------- = 147.9 in (aft of datum)
5150
Chapter 4 Page 34
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
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.
Chapter 4 Page 35
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
At Figure 4-22 the vertical axis of the graph remains as ‘total aircraft weight’, in this case using
pounds as the unit of weight. The horizontal axis has changed and now represents the ‘total
aircraft moments’, in this case using units of ‘total inch-pounds divided by 1000’. Dividing the
total moment by 1000 is simply a device which is used in order to keep the numbers to a
manageable magnitude.
FIGURE 4-22
Chapter 4 Page 36
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
Transverse Loading
6.
So far all of the calculations concerning the position of the CG of an aircraft have considered
the position along the fore and aft axis. It is important that an aircraft be loaded such that it is
reasonably balanced about the centreline. The most common reason for an aircraft to be unbalanced
about the centreline is that the wing fuel is unevenly loaded. Wing tanks, especially outboard tanks
and possibly wingtip tanks, have a considerable arm from the centreline. Aircraft operating and/or
loading manuals will frequently contain limits as to the amount of permissible imbalance in respect
of 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 the
right (starboard) of the centreline are negative.
Chapter 4 Page 37
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
EXAMPLE 4-8
EXAMPLE
An aircraft is loaded such that the weight is evenly distributed about the centreline, with
the exception of the fuel, which is loaded such that there is 400 lb. of fuel in the left wing
and 500 lb. of fuel in the right wing. The lateral arm for the wing fuel tanks is 127". If
the loaded weight of the aeroplane is 9000 lbs, determine the lateral position of the CG.
SOLUTION
Total moments
Lateral CG
Chapter 4 Page 38
© G LONGHURST 1999 All Rights Reserved Worldwide
=
(+ 400 x 127) + ( - 500 x 127)
=
50,800 - 63,500
=
- 12,700 in. lb.
=
-12,700
-----------------9000
=
-1.41"
=
1.41" right of the centreline
Centre of Gravity Calculations
C of G Practice Calculations
Question 1
Aeroplane Data
Chapter 4 Page 39
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
(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.
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
Question 2
Aeroplane Data
Maximum Authorised Weight
60,000 lbs
C of G limits 1.5 ft. aft of datum to 2.5 ft. aft of datum
Chapter 4 Page 40
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
SG of fuel 0.72
SG of oil 0.90
(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, what
is the arm of the C of G after 4 hours?
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
Question 3
Aeroplane Data
Chapter 4 Page 41
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
SG of fuel 0.72
SG of oil 0.90
Fuel consumption
50 US gals/hr
Oil consumption
2 US gals/hr
(a)
Calculate the C of G for take-off
(b)
Calculate the C of G for landing after three hours.
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
C of G Practice Calculation Answers
Answer 1
C of G limits -4" to -0.5"
(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
– 19912
C of G arm ------------------ = – 2.542″
7832
Chapter 4 Page 42
© G LONGHURST 1999 All Rights Reserved Worldwide
-19,912 ins/lbs
Centre of Gravity Calculations
(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
C of G arm ------------------ = – 4.208 ″ (out of limits)
6914
Chapter 4 Page 43
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
Answer 2
(a)
APS
Arm
Moment
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
C of G arm --------------------- = +1.647 ft
52, 125
Chapter 4 Page 44
Weight
© G LONGHURST 1999 All Rights Reserved Worldwide
Centre of Gravity Calculations
(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, 893
C of G arm ---------------------- = 1.8579 ft
46, 231.8
Chapter 4 Page 45
© G LONGHURST 1999 All Rights Reserved Worldwide
85,875 + 18 = 85,893 ft/lbs
Centre of Gravity Calculations
Answer 3
(a)
APS
Arm
Moment
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
C of G arm ---------------------- = +20.35″
6992.5
Chapter 4 Page 46
Weight
© G LONGHURST 1999 All Rights Reserved Worldwide
+ 142,300 ins/lbs
Centre of Gravity Calculations
(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
total
Revised moment
+150,940
C of G arm ---------------------- = +24.96″
6047.5
Chapter 4 Page 47
© G LONGHURST 1999 All Rights Reserved Worldwide
= -360
ins/lbs
+8640 ins/lbs
+142,300 + 8640 = +150,940 ins/lbs
031 Aircraft Mass & Balance
Adding, Removing and Repositioning
Loads
Adding or Removing Load
Repositioning a Load
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Adding, Removing and Repositioning Loads
Adding, Removing and Repositioning
Loads
5
1.
When a detailed description of the weight and arms of an aeroplane and all of its contents is
available, the method used to determine the position of the laden aircraft CG is to complete a trim
sheet. Having done this, if the CG is outside of the approved envelope it is necessary to redistribute
the load in order to move the CG to within limits, if possible. If this is not possible then some of the
load 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 Load
3.
To facilitate the rapid and easy calculation of either the new CG position, when a load is
added or removed, or the amount of load which must be removed in order to achieve a given CG
position there is an algebraic solution. By introducing an algebraic value for the unknown quantity
into the following formula, the value of the unknown quantity can be determined. The formula is:
New Total Moments
=
Old Total Moments + or – Load Moment
4.
In the formula above the ‘Load moment’ is the product of the weight and arm of the load
which is added or removed from the aircraft. The symbol will therefore appear as a + if a load is
added or a – if a load is removed.
Chapter 5 Page 1
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Adding, Removing and Repositioning Loads
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 larger
or smaller quantity of fuel has been consumed in flight than was originally planned.
EXAMPLE 5-1
EXAMPLE
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 to
move the CG 1–ft forward from its original position.
Chapter 5 Page 2
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Adding, Removing and Repositioning Loads
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.
=
Old Total Moments – Load Moment
New Total Moments
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.
Chapter 5 Page 3
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Adding, Removing and Repositioning Loads
EXAMPLE 5-2
EXAMPLE
Given an all up weight of 80,000 kg and a CG 16 metres aft of the datum which is the nose of
the aircraft, determine the change in the position of the CG, if 5,000 kg of freight is now
loaded 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.
1, 395, 000
--------------------------85, 000
The CG has therefore moved 0.412 metres aft of its original position.
Chapter 5 Page 4
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Adding, Removing and Repositioning Loads
EXAMPLE 5-3
EXAMPLE
Given an all up weight of 65,000 lb. and a CG 18.5–ft aft of the datum, which is the nose of the
aircraft. Determine the change in the position of the CG if 3,200 lb. of freight is removed from a
hold 14 ft aft of the datum.
SOLUTION
New Total Moments
=
Old Total Moments – Load Moment
(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
Let D be the new CG arm.
1, 157, 700
--------------------------- ft
61, 800
The CG has therefore moved 0.233 metres aft of its original position.
Chapter 5 Page 5
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Adding, Removing and Repositioning Loads
6.
If freight or fuel is added or removed from an aeroplane and the cargo hold or fuel tank is
measured relative to the present CG position, the change to the CG can be determined by a simple
formula. If the freight or fuel is added, then the weight value is positive and if it is removed it is a
negative value. If the distance of the hold or fuel tank is ahead of the present CG the distance is a
negative value and if it is aft of the present CG it is a positive value. The formula is:
Freight/fuel × distance from present CG
------------------------------------------------------------------------------------------------- = change to CG
New aircraft weight
EXAMPLE 5-4
EXAMPLE
Given: Aircraft weight 150,000 kgs, if 5000 kgs of freight is added to a hold 10 m ahead of the
present CG, determine the change to the CG
SOLUTION
5000 × – 10
--------------------------- = – 0.323m . New CG is 0.323 m ahead of old CG.
155000
Chapter 5 Page 6
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Adding, Removing and Repositioning Loads
EXAMPLE 5-5
EXAMPLE
Given: Aircraft weight 30,000 lbs, if 2000 lbs of fuel is used from a fuel tank
positioned 5 ft forward of the present CG, determine the change to the CG.
SOLUTION
– 2000 × – 5
--------------------------- = +0.357 ft The new CG is 0.357 ft aft of the old CG.
+28000
Repositioning a Load
7.
As already discussed, the CG position is influenced by the relocation of the load. When
dealing with this type of problem it is convenient to use the following formula:
Wt of load to be moved
Change to CG arm
-------------------------------------------------------- = -------------------------------------------------Total weight
Distance load moved
or
w
cc
----- = ----W
d
8.
The signs to be used in this formula for ‘cc’ and ‘d’ are + for a rearward movement of the load
and – for a forward movement of the load.
Chapter 5 Page 7
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Adding, Removing and Repositioning Loads
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 fuel
or adding loads or increasing the fuel on board. However, the original
formula: New Total Moments = Old Total Moments + Load Moment can be
used for ‘moving loads within an aeroplane’ problems. It is used in this
manner: New Total Moments = Old Total Moments – Load Moment + Load
Moment. The – Load Moment is used for removing it from the original hold
and the + Load Moment is used for loading it back on the aeroplane in the new
hold.
Chapter 5 Page 8
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Adding, Removing and Repositioning Loads
EXAMPLE 5-6
EXAMPLE
Given an All Up Weight of 60,000 kg and a CG 22 metres aft of the datum, which is the
nose of the aircraft. Determine the change in the position of the CG if 3,000 kg of load is
moved 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.
Chapter 5 Page 9
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Adding, Removing and Repositioning Loads
w
----W
=
cc
----d
3000
-----------------60, 000
=
cc
--------+15
3000x + 15
--------------------------60, 000
= 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.
Chapter 5 Page 10
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Adding, Removing and Repositioning Loads
EXAMPLE 5-7
EXAMPLE
Given an All Up Weight of 25,000 kg and a CG 9 metres aft of the datum. Determine the
change in the position of the CG if 1,000 kg of load is moved from a hold 12 metres aft of
the 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.
Chapter 5 Page 11
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Adding, Removing and Repositioning Loads
w
----W
=
cc
----d
1000
-----------------25, 000
=
cc
------7
1000x – 7
-----------------------25, 000
cc
= cc
= –0.28 metres or
–28cm (forward movement)
Chapter 5 Page 12
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
© G LONGHURST 1999 All Rights Reserved Worldwide
Adding, Removing and Repositioning Loads
EXAMPLE 5-8
EXAMPLE
Given an All Up Weight of 145,000 lb. And a CG 21 ins. forward of the datum. Determine
how 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
Chapter 5 Page 13
w
----W
=
cc
----d
w
--------------------145, 000
=
+1.5
-----------+180
w
=
+1.5 x 145,000
-----------------------------------+180
w
= 1208 lb
© G LONGHURST 1999 All Rights Reserved Worldwide
Adding, Removing and Repositioning Loads
EXAMPLE 5-9
EXAMPLE
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 hold
25 ft forward of the datum in order to move the CG to a point 3 ft aft of the datum.
SOLUTION
Chapter 5 Page 14
w
----W
=
w
--------------------120, 000
=
w
=
w
= 2000 lb
© G LONGHURST 1999 All Rights Reserved Worldwide
cc
----d
–1
--------60
– 1 x 120,000
------------------------------– 60
Adding, Removing and Repositioning Loads
It should be understood that fuel usage in flight can move the position of the CG, particularly in
longer aircraft with heavy fuel loads in numerous tanks. Faithful adherence to the fuel management
procedures as laid down in the AFM will ensure that the CG remains within the specified limits
during the flight. With large aircraft the usage of fuel can be arranged such that the CG is kept as
close as possible to the optimum position for significant periods of the flight, again in accordance
with AFM Procedures. This procedure ensures the CG remains just forward of the Aft Limit, and is
referred to as flying the ‘Flat’ aeroplane. It results in a significant increase in range.
Formula Practice Questions
Question 1
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?
Question 2
Chapter 5 Page 15
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.
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Adding, Removing and Repositioning Loads
Question 3
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.
Question 4
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?
Question 5
Chapter 5 Page 16
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.
© G LONGHURST 1999 All Rights Reserved Worldwide
Adding, Removing and Repositioning Loads
Question 6
Calculate:
If the freight in Question 5 is removed, what is the arm of the new C of G?
Question 7
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?
Formula Practice Answers
Answer 1
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
Chapter 5 Page 17
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Adding, Removing and Repositioning Loads
Answer 2
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
Answer 3
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
Chapter 5 Page 18
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Adding, Removing and Repositioning Loads
Answer 4
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.
Answer 5
Let d = New C of G Arm
(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
Chapter 5 Page 19
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Adding, Removing and Repositioning Loads
Answer 6
Let d = New C of G Arm
(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
or
(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
Answer 7
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
Chapter 5 Page 20
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Adding, Removing and Repositioning Loads
Chapter 5 Page 21
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031 Aircraft Mass & Balance
The Mean Aerodynamic Chord
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The Mean Aerodynamic Chord
6
The Mean Aerodynamic Chord
1.
On large transport aircraft the position of the CG is often expressed in relation to the
aircraft’s Mean Aerodynamic Chord (MAC). The MAC is precisely what the name implies. If you
take 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 wing
tip) and a different distance from the nose of the aircraft (the shorter distance at the wing root and
the furthest distance at the wing tip). If you now take the mathematical mean of all these chord lines
you have the MAC, expressed as a single length starting at a stated distance from the reference datum
of the aircraft. For example an aircraft’s MAC might be expressed as 205 inches in length extending
from 790 to 995 inches aft of the reference, as shown at Figure 6-1.
Chapter 6 Page 1
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The Mean Aerodynamic Chord
FIGURE 6-1
Example Mean
Aerodynamic
Chord
2.
The following examples illustrate how to convert the position of a CG which is given as a
percentage of the MAC into a position which is relative to the reference datum, and the reverse.
Chapter 6 Page 2
© G LONGHURST 1999 All Rights Reserved Worldwide
The Mean Aerodynamic Chord
EXAMPLE 6-1
EXAMPLE
The MAC limits of an aircraft are 802.7 inches to 1020.5 inches aft of datum. The CG is 31% of
the MAC. Determine the position of the CG relative to the datum.
SOLUTION
See Figure 6-2.
MAC (1020.5 – 802.7) = 217.8 inches.
217.8
31% MAC = ------------- × 31 = 67.5 inches
100
CG Position = 802.7 + 67.5 = 870.2 inches aft of datum.
Chapter 6 Page 3
© G LONGHURST 1999 All Rights Reserved Worldwide
The Mean Aerodynamic Chord
FIGURE 6-2
Chapter 6 Page 4
© G LONGHURST 1999 All Rights Reserved Worldwide
The Mean Aerodynamic Chord
EXAMPLE 6-2
EXAMPLE
The CG of a loaded aircraft is given as 503.6 inches aft of the datum. The MAC for this aircraft
extends from 482.2 inches to 536.7 inches aft of the datum. Express the position of the CG as a
percentage 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)
21.4
CG as % MAC = ---------- × 100 = 39.3 %
54.5
Chapter 6 Page 5
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The Mean Aerodynamic Chord
FIGURE 6-3
Chapter 6 Page 6
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031 Aircraft Mass & Balance
Structural Limitations
Securing Aircraft Loads
Weight Limits
© G LONGHURST 1999 All Rights Reserved Worldwide
Structural Limitations
7
Structural Limitations
1.
In addition to the weight and C of G limitations already described it is necessary to impose
further restrictions to ensure that the aeroplane floor is not overloaded or that the aeroplane
structure is not over-stressed. These limitations are divided into overall limitations and floor loading
limitations.
Overall Limitations.
An aeroplane is constructed about its main spar because it is this that must
support it in flight. Most large aeroplanes have a double main spar. The forward spar supporting
the weight in front of it whilst the rear spar supports the weight aft of it. Hence it may be considered
to be two cantilever beams, as shown in Figure 7-1. If the weight of the aeroplane is unevenly
distributed about the double spar the fuselage will bend about the spar bending greatest toward the
heavier weight. Although the bending caused by unevenly distributed loading will not be
immediately apparent the forces do exist and if the unequal division of the load is overmuch are a
serious potential source of damage to the aeroplane.
Chapter 7 Page 1
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Structural Limitations
FIGURE 7-1
The Effect of
Uneven Load
Distribution
2.
The fact that the C of G is within limits does not necessarily mean that the loaded aeroplane
is within the bending limitations. Nor does the fact that the load is within the individual
compartment 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 the
loaded aeroplane with the requirements.
Floor Loading Limitations.
The strength of the aeroplane floor varies throughout its length and
width according to the construction and location of the individual panels and their supporting
beams. There are two limitations imposed on floor panels to protect them and the aircraft from
damage. They are the linear and area load maxima.
Linear Limitations. This is the maximum weight per unit length of the floor. The width of the
load does not affect this limitation. The limitation may be expressed in lbs/linear ft or kgs/linear
metre. This restriction therefore requires that due consideration be given to the way in which the
items loaded are orientated. The linear load limitation is often referred to as the ‘Running Load’.
Chapter 7 Page 2
© G LONGHURST 1999 All Rights Reserved Worldwide
Structural Limitations
FIGURE 7-2
Linear Loading
Chapter 7 Page 3
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.
© G LONGHURST 1999 All Rights Reserved Worldwide
Structural Limitations
Area Limitations. To provide protection for individual floor panels an area limitation is imposed
and is expressed in kg/sq.m. or lbs./sq. ft. Items which have a large surface area impose a low area
floor load. However, those having a small area of contact with the floor have a high area floor load
e.g. the wheels of a vehicle. Often ‘Load Spreaders’ are used with this type load, this is some type of
material, usually wood, which has a larger contact area with the floor and is placed by the item’s
contact points and the floor. Thus the weight of the item is distributed over a larger area reducing
the area floor load. Again orientation of the load is all important. In the following example
Figure 7-3 is loaded in five different ways producing three different floor loads.
Chapter 7 Page 4
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Structural Limitations
FIGURE 7-3
Area Loading
Chapter 7 Page 5
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Structural Limitations
4.
All five boxes are the same size and weight 600 kgs. But each has a different effect on the
floor. In the example the area floor loading limitation is 100 kgs/sq.m. and linear load limitation is
200 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 the
longitudinal axis and the second longest side should be along the athwartships axis.
Securing Aircraft Loads
8.
The safety of an aeroplane is of paramount importance and depends on many different people
competently completing their individual tasks. Incorrect loading of the aircraft could have
immediate and devastating consequences.
Weight Limits
9.
Chapter 7 Page 6
The weight of any particular load may be restricted by one of three limitations:
© G LONGHURST 1999 All Rights Reserved Worldwide
Structural Limitations
(a)
The total weight of the aeroplane including its load must not exceed the maximum
permitted 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 Loading
10.
It is important to minimise the floor loading. If the load has a flat base, which is all in contact
with 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 contact
with the floor then it may exceed the maximum floor load. To distribute the load over a greater floor
area and thus reduce the floor load a mechanical device known as a load spreader may be inserted
between the load and the aircraft floor. See Chapter 2.
Load Factor
11.
The load factor is the ratio of an externally applied force to a load with a given weight:
ForceLoad Factor = Applied
----------------------------------Weight
Chapter 7 Page 7
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Structural Limitations
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 the
load is acting vertically downwards. In a 60° bank turn the aircraft, and its contents, are subject to a
load factor of +2g. In a bunt manoeuvre the aircraft and its contents are subject to negative g (a
negative load factor), which will tend to lift unsecured items off the floor. Similarly, rapid
accelerations will tend to move loads backwards and rapid decelerations will tend to move the loads
forwards, under the effects of inertia.
Load Restraint
13.
In order to ensure that the load does not move during any phase of flight it must be
adequately 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 the
momentum 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. The
current restraint load factors are:
Chapter 7 Page 8
Forwards
3g
Rearwards
1.5g
Lateral
1.5g
Vertical
2g
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Structural Limitations
15.
On flights where passengers and cargo are required to share the same compartment, the
restraint load factors are increased to coincide with the load factors for passenger seats. These load
factors are listed shortly.
Restraint Equipment
16.
On a cargo aeroplane there are many different types of equipment that may be used
individually 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. They
include:
Lashing Chains. These should be applied symmetrically between 30° and 45° both with the
aircraft floor and the longitudinal axis.
Tensioners.
These are mechanical devices used to take any slack out of the tie-down scheme and
tighten the lashing equipment.
Cargo Nets.
These are strong webs of nylon or similar material which may be used to secure a
number of small items together as one load by covering them all and securing the net at specific
points to the aircraft floor.
Side Guidance.
This is a means of protecting the aircraft structure from damage when loading
and unloading the cargo bay.
Grab Hooks.
Chapter 7 Page 9
These are a means of securing a cargo net to a lashing point.
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Structural Limitations
Passenger Seats
17.
Aircraft seats are specifically designed to fit into secure floor points. Aircraft seats are
equipped with seat belts. The floor securing system together with the seat belt are intended to enable
the occupant to escape serious injury in the event that the seat and occupant are exposed to the
following load factors:
Upward
3.0g
Forwards
9.0g
Sideways
4.0g
Downward
6.0g
Rearward
1.5g
18.
In the event of an emergency landing, the deformation of seats and other items of cabin
equipment should not be such that they would impede rapid evacuation from the aircraft cabin. Any
items of significant size or weight within the passenger compartment, galleys or flight deck must be
restrained to prevent their movement during an emergency landing. [JAR-25 561 (b) (3)].
Load Shift
19.
If the load is not correctly secured using an approved tie-down scheme, it may move and
cause 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 the
aircraft to pitch up even further, making the aircraft unstable and possibly causing it to stall.
Chapter 7 Page 10
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Structural Limitations
Nose-Down Pitching. On pitching nose down any loose cargo will move forward, causing the
aircraft to pitch further nose down. With a severe load shift it may be impossible to return the
aircraft to level flight. A forward load shift which occurs during the landing may make it difficult or
impossible to round out.
Deceleration. A rapid deceleration (notably during the landing roll) of the aircraft will cause an
unsecured load to move forward due to inertia.
Load Spreaders. A load spreader is material, usually thick wood, placed between the aircraft floor
and heavy load items which exceed the floor load intensity limitation and/or have hard or sharp
contact areas. Its purpose is to extend the load intensity over a larger floor area than the base of the
item and at the same time protect the aircraft floor from damage. The effectiveness of a load
spreader is established by its thickness, not its overall size. To utilise its full potential its area must be
large enough to contain a 45° angle from the base of the load item to the aircraft floor.
Chapter 7 Page 11
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Structural Limitations
FIGURE 7-4
Dunnage. Material, usually thick wood, utilised to protect the aircraft floor, including ramps, and
provide a continuous pathway over which wheeled vehicles may transit when being positioned in the
fuselage prior to lashing down without exceeding the maximum area limit at any point.
Chapter 7 Page 12
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031 Aircraft Mass & Balance
Manual and Computer Load/Trim Sheets
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
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Manual and Computer Load/Trim Sheets
Manual and Computer Load/Trim
Sheets
8
1.
A load and trim sheet may be produced either manually or by computer. It is most important
that it is thoroughly checked by the aircraft commander and signed by him (or her) as accepting the
load and its distribution within the aircraft. A trim slide rule, discussed later in this chapter, may be
used for this purpose.
2.
A load and trim sheet is a record of the weight of an aircraft and the distribution of its
contents. 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 and
passed to the aircraft commander. If the aircraft commander is satisfied that the load carried is of
such weight and is so distributed and secured that the flight can be safely conducted then he is to sign
the 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 aircraft
is refuelled with the same weight and distribution of fuel as on the previous flight the load sheet for
the previous flight may be used. The aircraft commander must endorse the load sheet of the previous
flight with signature, date and place of departure of the next intended flight and intended
destination.
4.
If it is necessary for an aircraft to stop en-route in order to refuel it is likely that the payload
weight 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 be
completed.
Chapter 8 Page 1
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Manual and Computer Load/Trim Sheets
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 to
JAR-OPS 1.1065]. If this is not practical then the second copy must be kept in a special container
in 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 it
is a crew training flight or a flight intended to begin and end at the same aerodrome. Helicopters
with an MTWA of 3000 kg or less and a seating capacity of five persons or less are also exempt from
the load sheet requirements.
Manual Load and Trim Sheets
7.
The manual load and trim sheet may be completed by the agent or alternatively, by the
Captain or First Officer.
8.
The manual load and trim sheet shown at Figure 8-1 looks complex but is in fact
straightforward. Let's go through it step by step, which unfortunately isn't from top left to bottom
right. Standard weights are assumed for this exercise.
Chapter 8 Page 2
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Manual and Computer Load/Trim Sheets
FIGURE 8-1
Example Load and
Trim Sheet
Chapter 8 Page 3
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Manual and Computer Load/Trim Sheets
Load and Trim Sheet Completion Procedure
Chapter 8 Page 4
(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 case
Lanzerote), 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 board
the aircraft, and insert the figures in Boxes 9, 10, 11, 12 and 13 as appropriate. The
index 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 and
catering etc). We have assumed that there are no adjustments to the APS weight or
index, as would result, for example, from the carriage of additional catering or the
removal of seats in order to accommodate a stretcher bound passenger and associated
medical equipment.
(c)
Insert the take-off fuel (total fuel less taxi fuel) in box 14 and determine the wet
operating 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 the
maximum performance limited take-off weight and enter it at box 19. Similarly enter
the performance or C of A limited maximum landing weight at Box 20, add to it the
trip fuel (Box 21) to achieve the landing weight limited take-off weight (Box 22).
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Manual and Computer Load/Trim Sheets
Chapter 8 Page 5
(e)
Determine which of the three take-off weights (ZFW, take-off or landing, Boxes 18, 19
and 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 allowed
traffic 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 at
165 lb., 73 adult females at 143 lb., 25 children at 86 lb., and complete Boxes 26 and
27. In this example the total passenger weight is 23,974 lb., so insert this weight in
Box 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 determine
the weight (167 x 29 lb.) 4843 lb. Complete Boxes 30 and 31. Add the weights in
Boxes 28, 29 and 31 to determine the total traffic load, which is inserted in Boxes 32
and 33.
(i)
Subtract the total traffic load (Box 33) from the allowed traffic load (Box 25) to get
the underload before last minute changes (LMCs). The underload is entered in Box
34.
(j)
Enter the dry operating weight in Box 35 and add the total traffic load to the dry
operating 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 confirm
that the sum of the two is equal to the maximum allowed take-off weight (in this case
Box 19). If it isn't you must find your error before proceeding.
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Manual and Computer Load/Trim Sheets
Chapter 8 Page 6
(l)
Subtract from the take-off weight (Box 38) the trip fuel (Box 39) to achieve the
landing weight (Box 40). We have now completed the load form and can start on the
trim form.
(m)
Establish from the loaders or the agent (and confirm by visual inspection) the
distribution of the hold baggage. In this example we have 100 bags in hold 4 (aft) and
67 bags in hold 3 (mid aft). Armed with this information complete Boxes 41 and 42
ensuring that the maximum hold weights are not exceeded.
(n)
With less than a full complement of passengers we would need to establish where the
passengers are sitting, however in this example we have a full load so complete Boxes
43 to 46.
(o)
We know how the fuel load is distributed (there is no trim fuel in this example) and so
we can complete Boxes 47 and 48. With this aeroplane the limiting trim is that
associated with the ZFW rather than the fuel laden aircraft and consequently it is the
position of the ZFW CG within the trim envelope which is important. The trim
envelope (A) looks complex but it isn't. It is the white portion of the envelope within
the two shaded (ferry) portions, which is the area within which the ZFW CG must
fall. Ignore the "MZFW - Limited Wing Fuel" hatched line, it is relevant to an
alternative fuel loading regime, which is used for ferry, and training flights.
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Manual and Computer Load/Trim Sheets
(p)
Start at B with the APS index and drop the line going left or right in the direction of
the 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 take
the drop line vertically downwards ignoring for the moment the fuel load. Mark the
point on this vertical line which coincides with the actual zero fuel weight and check
that this point lies within the envelope. Fortunately it does, it is towards the forward
end 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 the
16,500 lb. of fuel in the centre tank at take-off. Mark the point on the resultant drop
line which coincides with the actual take-off weight and read the TOW CG position as
a % MAC, in this case 8.9%. The TOW % MAC goes in box 49. It is this value
which 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 light
but positive.
Computer Load and Trim Forms
9.
The computer generated equivalent of the manual load and trim sheet previously considered
is shown at Figure 8-2. As you can see, there are no graphics on the computer form and it appears
that you are taking a lot on trust. Experience will tell you whether or not the computer generated
trim position is appropriate to the type of flight (scheduled, holiday charter, ski flight etc) and the
number of passengers carried.
Chapter 8 Page 7
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Manual and Computer Load/Trim Sheets
Last Minute Changes
10.
Both the manual and the computer load and trim sheets make provision for last minute
changes (LMCs). This is basically the out of breath family that has made it from check-in to the gate
in record time and arrived just as you are about to push back. It is obviously necessary that the
weight of the LMCs be considered, however providing that the total weight of LMCs does not
exceed 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 normally
in the order of 500 kg or 1000 lb. for medium passenger transport aircraft.
Aircraft Load and Trim Slide Rule
11.
The trim slide rule is a mechanical means of solving the mathematical problem of locating the
CG 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
Chapter 8 Page 8
From / To
Flight
A/C REG
Version
Crew
Date/Time
ACE LGW
454
GRJER
167Y
2/5
2 Feb 95 1847
© G LONGHURST 1999 All Rights Reserved Worldwide
Manual and Computer Load/Trim Sheets
Weight
Load in compartments
4843
1/-
Passenger / Cabin Load
25143
69/73/25/-
Total Traffic Load
29886
Dry Operating Weight
86606
Zero Fuel Weight
116592
Take-Off Fuel
35000
Take-Off Weight Actual
151592
Trip Fuel
26000
Landing Weight Actual
125592
Balance
2/-
3/1943
4/2900
TTL 167
MAX 122000
MAX 154760
MAX 139500
Last Minute Changes
MAXZFW
5.25
MAXTOW
8.9
STD PAX WTS
3168
LMC TOTAL + -
12.
The slide rule consists of a main block body in which several sliders are contained. Each slide
represents a loading cargo bay or compartment, which is etched with incremental weight.
Chapter 8 Page 9
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Manual and Computer Load/Trim Sheets
13.
On each slide is a datum arrow, which is positioned against the appropriate value on the slide
above. When using the trim slide rule a moment is referred to as an index. The index for the basic
weight 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 on
the body of the rule and the datum arrow of the first slider positioned against it. The slides are
moved 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 and
aft limits of the CG envelope are depicted together with the maximum take-off weight, the maximum
landing weight and the maximum zero fuel weight. If the intersection of the weight and the final line
fall 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 secondary
advantage of the ability of making adjustments for ‘last minute changes’. The major disadvantage is
that 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 the
instrument unwieldy to manage.
17.
Recently this type of slide rule has been superseded by a circular slide rule, which has rotating
scales.
Chapter 8 Page 10
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Manual and Computer Load/Trim Sheets
EXAMPLE 8-1
EXAMPLE
Given:
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
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.
Take-off weight
32,425 lb
Index 5.0
SG 0.72
Sector fuel to touch down
300 Imperial gallons
-2,160 lb.
Landing weight
30,265 lb.
SG 0.72
Determine whether or not it is safe to take-off and land with the aircraft loaded in this way.
Chapter 8 Page 11
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Manual and Computer Load/Trim Sheets
SOLUTION
It should be noted that the slide rule illustrated at Figure 8-3 assumes a fixed passenger weight of
170 lb., consequently the passenger slides are indexed in passenger numbers, as shown. The fuel
slide is indexed in Imperial gallons. As can be seen from Figure 8-3, the CG is within limits for
both take-off and landing.
Chapter 8 Page 12
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Manual and Computer Load/Trim Sheets
FIGURE 8-3
Figure 8-3. The Trim Slide Rule Solution to Example 8-1
Chapter 8 Page 13
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Manual and Computer Load/Trim Sheets
The MRJT Trim Sheet
The specimen aeroplane that will be used in any questions in the JAA examination is the MRJT. It is
therefore advantageous to be familiar with the load and trim sheet used for this aeroplane. As you
can 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 listed
to the left of the trim diagram. The method of determining the C of G position is as before. Start at
the top of the diagram at the dry operating index and work downward moving in the direction
indicated by each arrow the appropriate number of divisions. In the final C of G envelope plot the
TOW and landing weight. Both positions must fall within the envelope. If they don’t adjustments
must be made to the load distribution to bring the C of G back into the envelope.
Chapter 8 Page 14
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Manual and Computer Load/Trim Sheets
FIGURE 8-4
Chapter 8 Page 15
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Manual and Computer Load/Trim Sheets
EXAMPLE 8-2
EXAMPLE
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.
Chapter 8 Page 16
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Manual and Computer Load/Trim Sheets
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).
Chapter 8 Page 17
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Manual and Computer Load/Trim Sheets
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.
Chapter 8 Page 18
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Manual and Computer Load/Trim Sheets
FIGURE 8-5
Chapter 8 Page 19
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031 Aircraft Mass & Balance
Joint Aviation Regulations
Mass and Balance
© G LONGHURST 1999 All Rights Reserved Worldwide
Joint Aviation Regulations
9
Joint 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 members
and 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. The
position of this additional baggage must be accounted for when establishing the centre of gravity of
the aeroplane.
Chapter 9 Page 1
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Joint Aviation Regulations
Mass Values for Passengers and Baggage JAR-OPS 1.620:
3.
An operator shall compute the mass of passengers and checked baggage using either the
actual weighed mass of each person and the actual weighed mass of baggage or the standard mass
values specified in Tables 9-1 to 9-3 below except where the number of passenger seats available is
less than 10, when the passenger mass may be established by a verbal statement by or on behalf of
each passenger or by estimation. The procedure specifying when to select actual or standard masses
must be included in the Operations Manual.
4.
If determining the actual mass by weighing an operator must ensure that passenger’s personal
belongings and hand baggage are included. Such weighing must be conducted immediately prior to
boarding and at an adjacent location.
5.
If determining the mass of passengers using standard mass values, the standard mass values in
Tables 9-1 and 9-2 below must be used. The standard masses include hand baggage and the mass of
any infant below 2 years of age carried by an adult on one passenger seat. Infants occupying
separate passenger seats must be considered as children for the purpose of this sub-paragraph.
Mass values for Passengers – 20 seats or more
Chapter 9 Page 2
(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 an
alternative, 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 as
an element of a holiday travel package.
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Joint Aviation Regulations
JAR-OPS 1.620(d) Table 1
FIGURE 9-1
Aircraft with 20 or
more Passenger
Seats
Chapter 9 Page 3
Passenger Seats
20 or More
30 or More
Male
Female
All flights except Holiday Charters
88kg
70kg
84kg
Holiday Charters
83kg
69kg
76kg
Children
35kg
35kg
35kg
© G LONGHURST 1999 All Rights Reserved Worldwide
All Adult
Joint Aviation Regulations
JAR-OPS 1.620(e) Table 2
FIGURE 9-2
Mass Values for
Aircraft with 19 or
less Passenger
Seats
Passenger Seats
1-5
6-9
10 - 19
Male
104kg
96kg
92kg
Female
86kg
78kg
74kg
Children
35kg
35kg
35kg
6.
Where the total number of passenger seats available on an aeroplane is 19 or less, the
standard masses in Figure 9-2 are applicable.
7.
On flights where no hand baggage is carried in the cabin or where hand baggage is accounted
for separately, 6 kg may be deducted from the above male and female masses. Articles such as an
overcoat, an umbrella, a small handbag or purse, reading material or a small camera are not
considered as hand baggage for the purpose of this sub-paragraph.
8.
Chapter 9 Page 4
Mass Values for Baggage
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Joint Aviation Regulations
(c)
Where the total number of passenger seats available on the aeroplane is 20 or more
the standard mass value given in Figure 9-3 are applicable for each piece of checked
baggage. For aeroplanes with 19 passenger seats or less, the actual mass of checked
baggage, 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 borders
of 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 to
JAR-OPS 1.620 (f); and
(iii)
Intercontinental flight, other than flights within the European region, means a
flight with origin and destination in different continents.
FIGURE 9-3
Aircraft with 20 or
more Seats
JAR-OPS 1.620(f) Table 3
Type of Flight
Chapter 9 Page 5
Baggage Standard Mass
Domestic
11 kg
Within the European Region
13 kg
Intercontinental
15 kg
All Other
13 kg
© G LONGHURST 1999 All Rights Reserved Worldwide
Joint Aviation Regulations
Chapter 9 Page 6
(iv)
If an operator wishes to use standard mass values other than those contained
in Figure 9-1 to Figure 9-3 above, he must advise the Authority of his reasons
and gain its approval in advance. He must also submit for approval a detailed
weighing survey plan and apply the statistical analysis method given in
Appendix 1 to JAR-OPS 1.620 (g). After verification and approval by the
Authority of the results of the weighing survey, the revised standard mass
values are only applicable to that operator. The revised standard mass values
can only be used in circumstances consistent with those under which the survey
was conducted. Where revised standard masses exceed those in Figure 9-1 to
Figure 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 whose
masses, including hand baggage, are expected to exceed the standard passenger
mass, an operator must determine the actual mass of such passengers by
weighing 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 number
of passengers check in baggage that is expected to exceed the standard baggage
mass, an operator must determine the actual mass of such baggage by weighing
or 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-standard
method has been used for determining the mass of the load and that this
method is stated in the mass and balance documentation.
© G LONGHURST 1999 All Rights Reserved Worldwide
Joint Aviation Regulations
Appendix 1 to JAR-OPS 1.620 (f)
Definition of the Area for Flights within the European Region
9.
For the purpose of JAR-OPS 1.620 (f), flights within the European region, other than
domestic flights, are flights conducted within the area bounded by rhumb lines between the following
points:
N7200
E04500
N4000
E04500
N3500
E03700
N3000
E03700
N3000
W00600
N2700
W00900
N2700
W03000
N6700
W03000
N7200
W01000
N7200
E04500
As depicted in Figure 9-4 below.
Chapter 9 Page 7
© G LONGHURST 1999 All Rights Reserved Worldwide
Joint Aviation Regulations
FIGURE 9-4
Chapter 9 Page 8
© G LONGHURST 1999 All Rights Reserved Worldwide
Joint Aviation Regulations
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)]
Passengers
10.
Weight Sampling Method. The average mass of passengers and their hand baggage must be
determined by weighing, taking random samples. The selection of random samples must by nature
and extent be representative of the passenger volume, considering the type of operation, the
frequency of flights on various routes, in/outbound flights, applicable season and seat capacity of the
aeroplane.
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 statistical
procedures and based on a relative confidence range (accuracy) of 1% for all adult
and 2% for separate male and female average masses. The statistical procedure,
complemented with a worked example for determining the minimum required sample
size and the average mass, is included in IEM-OPS 1.620 (g), and;
(b)
For Aeroplanes:
(i)
Chapter 9 Page 9
With a passenger seating capacity of 40 or more, a total of 2000 passengers,
or;
© G LONGHURST 1999 All Rights Reserved Worldwide
Joint Aviation Regulations
(ii)
With a passenger seating capacity of less than 40, a total number of 50 x (the
passenger seating capacity).
Passenger Masses
12.
Adults and Children. Adults are defined as persons of an age of 12 years and above. They
are further classified as male or female. No differentiation according to sex shall be made for
children, who are defined as persons of an age of two years but who have not yet reached their
twelfth birthday. Passenger masses must include the mass of the passengers’ belongings, which are
carried 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 the
accompanying adult.
14.
Weighing Location. The location for the weighing of passengers shall be selected as close as
possible to the aeroplane, at a point where a change in the passenger mass by disposing of or by
acquiring 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 a
capacity of at least 150 kg. The mass shall be displayed at minimum graduations of 500 g. The
weighing 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 corresponding
passenger category (i.e. male/female/children) and the flight number must be recorded.
Chapter 9 Page 10
© G LONGHURST 1999 All Rights Reserved Worldwide
Joint Aviation Regulations
Checked Baggage
17.
The statistical procedure for determining revised standard baggage mass values based on
average baggage mass values based on average baggage masses of the minimum required sample size
is basically the same as for passengers and as specified in sub-paragraph (a) (1) [See also IEM-OPS
1.620 (g)]. For baggage, the relative confidence range (accuracy) amounts to 1%. A minimum of
2000 pieces of checked baggage must be weighed.
Determination of Revised Standard Mass Values for Passengers and
Checked Baggage
Chapter 9 Page 11
(a)
To ensure that, in preference to the use of actual masses determined by weighing, the
use of revised standard mass values for passengers and checked baggage does not
adversely affect operational safety; a statistical analysis (see IEM-OPS 1.620 (g)) must
be carried out. Such an analysis will generate average mass values for passengers and
baggage as well as other data.
(b)
On aeroplanes with 20 or more passenger seats these averages apply as revised
standard male and female mass values.
(c)
On smaller aeroplanes, the following increments must be added to the average
passenger mass to obtain the revised standard mass value:
© G LONGHURST 1999 All Rights Reserved Worldwide
Joint Aviation Regulations
FIGURE 9-5
Revised Standard
Mass Increments
for Aircraft with
19 or less
Passenger Seats
Number of Passenger Seats
Required Mass Increment
1 – 5 Inclusive
16 kg
6 – 9 Inclusive
8 kg
10 – 19 Inclusive
4 kg
18.
Alternatively, all adult revised standard (average) mass values may be applied on aeroplanes
with 30 or more passenger seats. Revised standard (average) checked baggage mass values are
applicable to aeroplanes with 20 or more passenger seats.
Chapter 9 Page 12
(d)
Operators have the option to submit a detailed survey plan to the Authority for
approval and subsequently a deviation form the revised standard mass value providing
this 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 to
Appendix 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 80/20
in respect of all flights except holiday charters which are 50/50. If an operator wishes
to obtain approval for use of a different ratio on specific routes or flights then data
must be submitted to the Authority showing that the alternative male/female ratio is
conservative and covers at least 84% of the actual male/female ratios on a sample of
at 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.
© G LONGHURST 1999 All Rights Reserved Worldwide
031 Aircraft Mass & Balance
The Weighing of Aeroplanes
Joint Airworthiness Requirement
Determination of the Dry Operating Mass of an Aeroplane
Special Standard Masses for the Traffic Load
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
10
The Weighing of Aeroplanes
Joint Airworthiness Requirement
1.
The weight and C of G of an aeroplane must be established by the operator by actually
weighing it prior to initial entry into service and every four years thereafter if individual aeroplane
weights are used or every nine years if fleet weights are used. The cumulative effect of modifications
and/or repairs have on the weight and balance must be accounted and documented. Aeroplanes that
have 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 JAROPS 1.605)
Determination of the Dry Operating Mass of an
Aeroplane
Weighing of an Aeroplane
(a)
Chapter 10 Page 1
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 for
alterations or modifications to the aeroplane. Aeroplanes transferred from one JAA
operator with an approved mass control programme to another JAA operator with an
approved programme need not be weighed prior to use by the receiving operator
unless more than four years have elapsed since the last weighing.
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
(b)
The individual mass and centre of gravity (CG) position of each aeroplane shall be reestablished periodically. The maximum interval between two weighings must be
defined by the operator and must meet the requirements of JAR-OPS 1.605 (b). In
addition, 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 to
prove the validity of the method of calculation chosen.
whenever the cumulative changes to the dry operating mass exceed + 0.5% of the maximum landing
mass 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)
Chapter 10 Page 2
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 aeroplanes
meet the tolerances specified below. Furthermore, the criteria specified in ‘Use of
Fleet-Values’ and ‘Number of Aeroplanes to be Weighed’ below are applicable.
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
Tolerances
Chapter 10 Page 3
(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 the
maximum structural landing mass from the established dry operating fleet
mass or the CG position varies by more than + 0.5% of the mean aerodynamic
chord 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 mass
tolerance but its CG position falls outside the permitted fleet tolerance, the
aeroplane may still be operated under the applicable dry operating fleet mass
but with an individual CG position.
(iii)
If an individual aeroplane has, when compared with other aeroplanes of the
fleet, a physical, accurately accountable difference (e.g. galley or seat
configuration), that causes exceedance of the fleet tolerances, this aeroplane
may be maintained in the fleet provided that appropriate corrections are
applied to the mass and/or CG position for that aeroplane.
(iv)
Aeroplanes for which no mean aerodynamic chord has been published must be
operated with their individual mass and CG position values or must be
subjected to a special study and approval.
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
Use of Fleet Values
Chapter 10 Page 4
(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 falls
within the tolerances specified in ‘Tolerances’ above.
(ii)
Aeroplanes which have not been weighed since the last fleet mass evaluation
can still be kept in a fleet operated with fleet values, provided that the
individual values are revised by computation and stay within the tolerances
defined in ‘Tolerances’ above. If these individual values no longer fall within
the permitted tolerances, the operator must either determine new fleet values
fulfilling the conditions of ‘Fleet-Mass and CG Position’ and ‘Tolerances’
above, or operate the aeroplanes not falling within the limits with their
individual values.
(iii)
To add an aeroplane to a fleet operated with fleet values, the operator with
fleet values, the operator must verify by weighing or computation that its
actual values fall within the tolerance specified in ’Tolerances’ above.
(iv)
To comply with ‘Fleet Mass and CG Position’ above, the fleet values must be
updated at least at the end of each fleet mass evaluation. [Appendix to JAROPS 1.605 (a) (2)].
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
Number of Aeroplanes To Be weighed to Obtain Fleet
Values
(a)
FIGURE 10-1
If ‘n’ is the number of aeroplanes in the fleet using fleet values, the operator must at
least weigh, in the period between two fleet mass evaluations, a certain number of
aeroplanes defined in Figure 10-1:
Number of Aeroplanes in the Fleet
Minimum Number of Weighings
2 or 3
n
4 to 9
n+3
-----------2
10 or More
n + 51
--------------10
(b)
In choosing the aeroplanes to be weighed, aeroplanes in the fleet which have not been
weighed for the longest time should be selected.
(c)
The interval between 2 fleet mass evaluations must not exceed 48 months.
Weighing Procedure
(a)
Chapter 10 Page 5
The weighing must be accomplished either by the manufacturer or by an approved
maintenance organisation.
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
(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 in
accordance with the manufacture’s instructions. Each scale must be calibrated either by the
manufacturer, by a civil department of weights and measures or by an appropriately authorised
organisation within two years or within a time period defined by the manufacturer of the weighing
equipment, whichever is less. The equipment must enable the mass of the aeroplane to be established
accurately. [Appendix to JAR-OPS 1.605 (a) (4)].
Special Standard Masses for the Traffic Load
3.
In addition to standard masses for passengers and checked baggage, an operator can submit
for approval to the Authority standard masses for other load items.
Aeroplane Loading
(a)
Chapter 10 Page 6
An operator must ensure that the loading of its aeroplanes is performed under the
supervision of qualified personnel.
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
(b)
An operator must ensure that the loading of the freight is consistent with the data used
for the calculation of the aeroplane mass and balance.
(c)
An operator must comply with additional structural limits such as the floor strength
limitations, the maximum load per running metre, the maximum mass per cargo
compartment 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 of
passengers per seat row, of cargo in individual cargo compartments and of fuel in individual tanks is
accounted for accurately in the balance calculation, operational margins must be applied to the
certificated centre of gravity envelope. In determining the CG margins, possible deviations from the
assumed load distribution must be considered. If free seating is applied, the operator must introduce
procedures to ensure corrective action by flight or cabin crew if extreme longitudinal seat selection
occurs. The CG margins and associated operational procedures, including assumptions with regard
to passenger seating, must be acceptable to the Authority. [See IEM to Appendix 1 to JAR-OPS
1.605 (d)].
In-Flight Centre of Gravity. Further to sub-paragraph above, the operator must show that the
procedures fully account for the extreme variation in CG travel during flight caused by passenger/
crew movement and fuel consumption/transfer.
Chapter 10 Page 7
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
British Civil Airworthiness Requirement
4.
The above are the requirements of the Joint Aviation Authority (JAA), however, these will not
be legally enforceable until a statute has been passed by Parliament to make JAR-OPS a legally
binding document. Until such time the legal requirements of British Civil Airworthiness
requirements remain in force and have different requirements with respect to the weighing of
aeroplanes and are as follows:
Chapter 10 Page 8
(a)
An aircraft is weighed when all manufacturing processes are complete. It must be reweighed within two years of the date of manufacture and subsequently at intervals not
exceeding five years and at such times as the CAA may require if the maximum total
weight authorised exceeds 5700 kg. If the MTWA does not exceed 5700 kg the
aeroplane 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 when
a modification or engine change has been done which may have a significant effect on
the aircraft weight and balanced. It would be prudent to re-weigh the aircraft if it is
not attaining is scheduled performance level.
(c)
With the approval of the Authority, when an operator has three or more aircraft of the
same type, the fleet mean weight and CG may be used for the whole fleet, except for
those that differ significantly from the remainder of the fleet.
(d)
For an aircraft having a valid Certificate of Airworthiness a valid Weight and CG
Schedule must be completed every time the aircraft is weighed. Each Schedule must be
preserved for a period of six months following the subsequent re-weighing of the
aircraft.
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
(e)
Chapter 10 Page 9
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. [BCAR Section A, Chapter A5-47].
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
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 balance
arm 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 wing
aircraft.
Chapter 10 Page 10
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
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 GG
850ins 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 10ft
forward 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 what
change 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 weighing
10,000kgs. The change to the CG is?
Chapter 10 Page 11
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
QUESTION 14.
If the main wheels retract athwarships and the nose wheel retracts forward. How will the CG move
on 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 fully
effective:
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 of
Datum. 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 on
Landing 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?
Chapter 10 Page 12
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
QUESTION 20.
What increment must be added to the average mass for a passenger of an aeroplane having 6 to 9
passenger 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
Chapter 10 Page 13
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
ANSWER 7.
Page 7-4
ANSWER 8.
( 850 – 750 )
100
-------------------------------% = --------- % = 40% of MAC
( 1000 – 750 )
250
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
Chapter 10 Page 14
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
ANSWER 12.
w
CC
----- = -------W
d
300
CC
------------ = --------5000
– 15
– 4500
CC = --------------- = – 0.9ft
5000
ANSWER 13.
2000 × – 5
------------------------ = -0.83m = 0.83 ahead of old CG
12, 000
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
Chapter 10 Page 15
© G LONGHURST 1999 All Rights Reserved Worldwide
The Weighing of Aeroplanes
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
Chapter 10 Page 16
© G LONGHURST 1999 All Rights Reserved Worldwide
031 Aircraft Mass & Balance
Documentation
UK National Requirements
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
11
Documentation
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 specifying
the load AND its distribution. The mass and balance documentation must enable the commander to
determine by inspection that the load and its distribution is such that the mass and balance limits of
the aeroplane are not exceeded. The person preparing the mass and balance documentation must be
named on the document. The person supervising the loading of the aeroplane must confirm by
signature that the load and its distribution are in accordance with the mass and balance
documentation. This document must be acceptable to the commander, his acceptance being
indicated 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 procedures
required 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 how
this can be arranged where normal signature by hand is impracticable and it is desirable to arrange
the equivalent verification by electronic means.
Chapter 11 Page 1
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
5.
The following conditions should be applied in order to make an electronic signature the
equivalent of a conventional hand-written signature:
Chapter 11 Page 2
(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 and
professional capacity on the relevant document(s) in such a way that it is evident to
anyone having a need for that information, who has signed the document.
(c)
The computer system should log information to indicate when and where each PIN
codes has been entered.
(d)
The use of PIN code is, from a legal and responsibility point of view, considered to be
fully 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 with
electronic signature and should confirm this in writing.
© G LONGHURST 1999 All Rights Reserved Worldwide
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)
Chapter 11 Page 3
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.
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
(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 the
mass and balance documentation.
7.
Last Minute Change. If any last minute change occurs after the completion of the mass and
balance documentation, this must be brought to the attention of the Commander and the last minute
change must be entered on the mass and balance documentation. The maximum allowed change in
the number of passengers or hold load acceptable as a last minute change must be specified in the
Operations Manual. If this number is exceeded, new mass and balance documentation must be
prepared.
Computerised Systems
8.
Where mass and balance documentation is generated by a computerised mass and balance
system, the operator must verify the integrity of the output data. He must establish a system to check
that amendments of his input data are incorporated properly in the system and that the system is
operating correctly on a continuous basis by verifying the output data at intervals not exceeding six
months.
Onboard Mass and Balance Systems
9.
An operator must obtain the approval of the Authority if he wishes to use an onboard mass
and balance computer system as a primary source for despatch.
Chapter 11 Page 4
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
Datalink
10.
When mass and balance documentation is sent to aeroplane via datalink, a copy of the final
mass and balance documentation as accepted by the Commander must be available on the ground.
Mass and Balance Documentation [See IEM to Appendix 1 to JAROPS 1.625]
11.
For Performance Class B aeroplanes, the CG position need not be mentioned on the mass and
balance documentation if for example the load distribution is in accordance with a pre-calculated
balance 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 Report
12.
Chapter 11 Page 5
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 Series
aircraft the Maximum Weight Authorised of which exceeds 5700 kg.
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
Chapter 11 Page 6
(c)
The Weight and Balance Report shall record such loading data as is essential to enable
the particular aircraft to be correctly loaded, and shall include sufficient information
for an operator to produce written loading instructions in compliance with the
requirements of the Air Navigation Order.
(d)
The Weight and Balance Report shall apply to the aircraft in the condition in which it
is to be delivered to the user.
(e)
One copy of the Weight and Balance Report shall be sent to the CAA Safety
Regulation 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 not
known 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 Basic
Equipment, 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 and
loading and an explanation of the relationship of these points to the fuselage frame
numbering system of other identifiable points, and where applicable, to the Standard
Mean Chord (SMC).
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
(l)
Information on the level arms appropriate to items of Disposable Load. (This should
include the lever arms of fuel, oil and other consumable fluids or substances in the
various tanks (including agricultural material in hoppers) which, if necessary, should
be shown diagrammatically or graphically; lever arms of passengers in seats
appropriate to the various seating layouts; mean lever arms of the various baggage
holds 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 kg
13.
A Weight and Centre-of-Gravity Schedule shall be provided for each aircraft the Maximum
Total Weight Authorised of which exceeds 2730 kg, except that for an aircraft the Maximum Total
Weight Authorised or which exceeds 5700 kg the information contained in Parts B and C of the
Schedule 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 in
Appendix 1, but variations are permitted within the Requirements.
Chapter 11 Page 7
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
NOTE:
2) Here reference is made in Appendix 1 to the Flight Manual, but such a
document has not been issued, it will be necessary to refer to the Certificate of
Airworthiness.
14.
Each Schedule shall be identified by the aircraft designation, nationality and registration
marks, or if these are not known, by the constructor’s serial number. The date of issue of the
Schedule shall be given and the Schedule shall be signed by a representative of an approved
Organisation or a person acceptable to the CAA. A statement shall be included indicating that the
Schedule supersedes all previous issues.
15.
The date and reference number of the Weight and Balance Report, or, as appropriate to the
weight, 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, the
Weighing Record would normally used.
16.
A copy of each issue of the Schedule shall be retained by the operator, and where the Schedule
is re-issued the previous issue shall be retained with the aircraft records. A copy of the current
Schedule and any related list of Basic Equipment (see Part A Basic Weight), shall be sent to the CAA
Safety Regulation Group.
Chapter 11 Page 8
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
17.
For aircraft the Maximum Total Weight Authorised of which does not exceed 5700 kg, a
copy of the Schedule shall be included in the Flight Manual, if a Flight Manual is applicable, or if this
is 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 and
e.g. is known to have changed to an extent greater than that which has been agreed by the CAA as
applicable to a particular aircraft type.
19.
If the aircraft has not been re-weighed, the revised Weight and Centre-of-Gravity Schedule
shall contain a statement that calculations have been based on the last Weight and Balance Report, or
other 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 this
may be different from the datum defined in the Certificate of Airworthiness or Flight Manual. When
a different datum is used it shall be adequately defined, its precise relationship to the datum in the
Certificate of Airworthiness or Flight Manual shall be given, and any lever arms and moments which
appear 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 and
moments about more than one axis, depending on the CG limits specified in
the Flight Manual.
21.
Part A Basic Weight. The Basic Weight and the associated position of the CG of the aircraft
as derived from the most recent Weight and Balance Report or other information together with any
subsequent weight and CG changes shall be stated. The position (retracted or extended) of the
landing gear associated with this information shall be stated.
Chapter 11 Page 9
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
22.
Where the Maximum Total Weight Authorised does not exceed 5700 kg, Part A shall also
include the list of Basic Equipment showing the weight and lever arm of each item, or this
information may form separate pages attached to the Weight and Centre-of-Gravity Schedule, with a
suitable 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 list
of basic equipment showing the weight, lever arm moment of each item, or shall make reference to
the 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 operator
wishes, but for every role the weights and moments shall be given. Weights of crew members may be
assumed to be not less than the weights shown in the Air Navigation (General) Regulations, provided
that the Maximum Total Weight Authorised exceeds 5700 kg, or the aircraft has a total seating
capacity for 12 or more persons. Otherwise the weight of each person must be determined by
weighing.
25.
Part C Loading Information. This shall include all relevant information so that, knowing the
Disposable Load which is intended to be carried, the weight and the position of the Centre-ofGravity of the aircraft can be calculated. At least the following shall be given:
Chapter 11 Page 10
(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 where
Disposable Load, such as luggage or freight, may be placed.
(iii)
Any significant change in the CG of the aircraft (change in moment) which will
result from a change in configuration, such as the retraction and extension of
the landing gear.
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
(iv)
The lever arm of the CG of fuel, oil and other consumable fluids or substances
in each tank, including any significant variation of the lever arm with the
quantity loaded.
(v)
The maximum total usable capacities of the tanks for fuel, oil and other
consumable fluids or substances and the weight of fluids or substances when
the 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 Air
Navigation Order that the Commander satisfies himself before take-off that the load is of such
weight, 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 these
are used consistently and do not conflict with the markings and placards on the aircraft.
Chapter 11 Page 11
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
Weight and Centre-of-Gravity Schedule-Aircraft Not Exceeding 2730
kg
28.
For aircraft the Maximum Total Weight Authorised of which does not exceed 2730 kg, either
a Weight and Centre-of-Gravity Schedule, which complies with 2 and 3.2, or a Loading and
Distribution 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’) shall
contain at least the information in Figure 11-6.
31.
Each Schedule shall be identified by the aircraft designation, nationality and registration
marks, 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 Schedule
is re-issued the previous issue shall be retained with the aircraft records. A copy of the current
Schedule and any related list of Basic Equipment shall be sent to the CAA Safety Regulation Group.
(i)
33.
Operators shall issue a revised Schedule when:
(i)
Chapter 11 Page 12
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 aircraft
in a suitably identified stowage.
The Basic Weight of the aircraft is known to have undergone changes in excess
of 0.5% of the Maximum Total Weight Authorised, or
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
(ii)
The total moment applicable to the Basic Weight is known to have changed to
an extent greater than that, which has been agreed by the CAA as applicable to
a particular aircraft type.
34.
If the aircraft has not been re-weighed the revised Schedule shall contain a statement that
calculations have been based on the last Weighing Record and the known weight and moment
changes.
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 Air
Navigation Order that the Commander satisfies himself before the aircraft takes off that the load is
of 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 these
are used consistently and do not conflict with the markings and placards on the aircraft.
38.
Chapter 11 Page 13
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 any
subsequent changes.
(ii)
The Maximum Total Weight Authorised appropriate to each permitted use (eg.
aerobatics).
(iii)
The definition of the CG datum.
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
(iv)
The date and reference number of the Weighing Record and list of Basic
Equipment upon which the Schedule is based.
(v)
The date and reference of the Loading Graphs of the Loading and Distribution
Schedule shall be given.
(vi)
A statement of the date of preparation and validity of the Schedule, signed by a
representative of an approved Organisation, or a person acceptable to the
CAA. A statement shall also be included indicating that the Schedule
supersedes all previous issues.
39.
Part B Loading. Columns shall be provided which list all standard items of Variable Load
and make provision for the associated weight and CG moments to be recorded and totalled for a
particular flight. Columns shall also be provided for recording an example of a typical aircraft
loading calculation. This example shall employ the same weight and CG moment figures as recorded
in the Loading Graphs (see Part C).
40.
Part C Loading Graphs. Graphs, sufficient to ascertain moments, and to enable the operator
to determine that the aircraft loaded weight and CG moment are within the prescribed limits shall be
provided. 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 application
shall be included using the same figures as employed in the Loading and Distribution Schedule
example.
41.
Weight and Centre-of-Gravity Schedule (Appendix 2, (3)). In addition the Weight and
Centre-of-Gravity Schedule for aircraft the Maximum Total Weight Authorised of which does not
exceed 2730 kg, shall contain instructions for the determination of the loaded weight, the total load
moments and resultant CG positions.
Chapter 11 Page 14
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
Appendix No. 1 – Weight and Centre-Of-Gravity Schedules For
Aircraft Exceeding 2730 kg
42.
INTRODUCTION. This Appendix presents a specimen Weight and CG Schedule which
constitutes an acceptable means of compliance with the appropriate requirements.
NOTE:
Imperial Units are shown on the specimen. Where it is necessary to use S.I
Units these should be used throughout
FIGURE 11-1
Specimen
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
Chapter 11 Page 15
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
Part A Basic Weight
The Basic Weight of the aircraft as calculated from Weight and Balance Report/Weighing Record*
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
NOTE:
The datum is at fuselage station 0 situated 114 inches forward of the wing
leading edge. This is the datum defined in the Flight Manual. All lever arms
are distances in inches aft of datum
Chapter 11 Page 16
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
FIGURE 11-2
Weight
Lever Arm
(lb)
(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
Part B Variable Load
The weight, lever arms and moments of items of Variable Load are shown below. The Variable Load
depends upon the equipment carried for the particular role.
FIGURE 11-3
Weight
Lever Arm
Moment
(lb)
(in)
(100 lb.inc)
Pilot (one)
Chapter 11 Page 17
108
De-icing fluid 1.5 gal
12
140
17
Lift-jackets (7)
14
135
19
Row 1 passenger seats (two)
60
173
104
Row 2 passenger seats (two)
60
215
129
Row 3 passenger seats (two)
60
248
149
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Documentation
Weight
Lever Arm
Moment
(lb)
(in)
(100 lb.inc)
Table
8
256
20
One stretcher and attachments (in
place of seat rows 2 and 3)
45
223
100
Medical stores
15
250
37
FIGURE 11-4
Part C Loading
Information
(Disposable
Loads)
Chapter 11 Page 18
Weight
Lever Arm
Capacity
(lb)
(in)
(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
Passengers in Row 2 seats
213
Passengers in Row 3 seats
246
Patient in stretcher
223
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
NOTE:
To obtain the total loaded weight of aircraft, add to the Basic Weight the
weights of the items of Variable and Disposable Load to be carried for the
particular 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 Schedule
the actual weight of the pilot is required in accordance with the Air Navigation
(General) Regulations for aircraft the Maximum Total Weight Authorised of
which 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.
Chapter 11 Page 19
© G LONGHURST 1999 All Rights Reserved Worldwide
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 of
Weight and Centre-of-Gravity and Loading and Distribution Schedules provided in accordance with
the requirements.
44.
LOADING AND DISTRIBUTION SCHEDULE. The Schedule (including the graphs) and
the List of Basic Equipment should, as far as is practical, take the form of Figure 11-5, Figure 11-6
and Figure 11-7.
Chapter 11 Page 20
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
FIGURE 11-5
Front of Schedule
Chapter 11 Page 21
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
FIGURE 11-6
Reverse of
Schedule
Chapter 11 Page 22
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
FIGURE 11-7
List of Basic
Equipment
Chapter 11 Page 23
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
45.
WEIGHT AND CENTRE OF GRAVITY SCHEDULE. An acceptable means of compliance
with the requirements would be to include in the Schedule instructions on the following lines:
Specimen Instructions
Chapter 11 Page 24
(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 corresponding
lever arm, and record the moment for each item of load, giving the moment a positive
sign 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 column
and 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 prescribed
c.g. limits.
(f)
To check that the fuel consumed during a flight does not cause the c.g. position to be
outside the prescribed limits, re-total the weights in 3 and the moments in 4, but
omitting the total fuel weight and the corresponding moment(s), respectively. Add the
weight 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.
© G LONGHURST 1999 All Rights Reserved Worldwide
Documentation
NOTE:
Note: Where there are any other significant quantities of consumable fluids or
substances (e.g. crop spraying), similar account should be taken of them.
Chapter 11 Page 25
© G LONGHURST 1999 All Rights Reserved Worldwide
031 Aircraft Mass & Balance
Definitions
Weight
Load
Equipment
Passengers
© G LONGHURST 1999 All Rights Reserved Worldwide
Definitions
12
Definitions
Weight
Basic Weight.
This is the aeroplane weight plus basic equipment, unusable fuel and undrainable
oil. Basic equipment is that which is common to all roles plus unconsumable fluids such as hydraulic
fluid.
Dry Operating Weight. This is defined in JAR-OPS 1.607 as the total weight of the aeroplane
for a specific type of operation excluding all usable fuel and traffic load. It includes such items as
crew, crew baggage, catering equipment, removable passenger service equipment, potable water and
lavatory chemicals. The dry operating weight is sometimes referred to as the Aircraft Prepared for
Service (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 usable
fuel. The weight of fuel contained in particular tanks must be included in the zero fuel mass when it
is explicitly mentioned in the aeroplane Flight Manual limitations. This is a structural limitation
imposed to ensure that the airframe is not over-stressed.
Maximum Structural Landing Weight.
landing in normal circumstances.
Chapter 12 Page 1
© G LONGHURST 1999 All Rights Reserved Worldwide
The maximum permissible total aeroplane weight on
Definitions
Maximum Structural Take-Off Weight.
The maximum permissible total aeroplane weight at
the start of the take-off run.
Zero Fuel Weight.
This is the dry operating weight plus the traffic load. In other words it is the
weight of the aeroplane without the weight of fuel.
Aircraft Prepared for Service (APS) Weight. The weight of the aircraft shown in the weight
schedule (the basic weight) plus such additional items in or on the aircraft as the operator thinks fit
to 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 disposable
load.
Design Minimum Weight. The lowest weight at which an aeroplane complies with the
structural requirements for its own safety.
Maximum Ramp Weight.
The maximum weight at which an aircraft may commence taxiing
and is equal to the maximum take-off weight plus taxi fuel and run-up fuel. It must not exceed the
surface load bearing strength.
Maximum Total Weight Authorised (MTWA).
The maximum total weight of the aircraft
prepared 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 favourable
circumstances in accordance with the Certificate of Airworthiness in force in respect of aircraft.
Chapter 12 Page 2
© G LONGHURST 1999 All Rights Reserved Worldwide
Definitions
Maximum Take-Off Weight.
The maximum weight at which take-off is permitted, by
conditions other than available performance.
Landing Weight.
The gross weight of the aeroplane, including all of its contents, at the time of
landing.
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.
Load
Absolute Traffic Load.
The traffic load plus usable fuel and consumable fluids. The traffic load
is the total weight of passengers, baggage and cargo, including any non-revenue load.
Floor Load.
Index.
This is the area load at a specific station.
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 the
aeroplane is the maximum floor load.
Running Load. The weight of any object divided by the length of that object measured parallel to
the longitudinal axis is the running or linear load.
Payload.
Anyone or anything on board the aeroplane the carriage of which is paid for by someone
other than the operator. In other words anything or anyone carried that earns money for the airline.
Chapter 12 Page 3
© G LONGHURST 1999 All Rights Reserved Worldwide
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. Role
equipment is that which is required to complete a specific task such as seats, toilets, galley for the
passenger role or roller conveyor, lashing points and tie down equipment for the freight roles.
Equipment
Ballast.
Additional fixed weights which can be removed, if necessary, that are carried, to ensure
the centre of gravity remains within safe limits, in certain circumstances.
Basic Equipment. The inconsumable fluids and the equipment which is common to all roles for
which the operator intends to use the aircraft.
Load Spreader.
A mechanical device inserted between the cargo and the aircraft floor to
distribute the weight evenly over a greater floor area.
Unusable Fuel.
That part of the fuel carried which is impossible to use because of the shape or
position of particular tanks.
Passengers
Adults are defined as persons of an age of 12 years and above. They are further classified as male
or female. [Appendix 1 to JAR-OPS 1.620 (g)].
Chapter 12 Page 4
© G LONGHURST 1999 All Rights Reserved Worldwide
Definitions
are persons of an age of 2 years but who have not yet reached their 12th birthday. They
are not differentiated by sex.
Children
Infants
are persons who have not yet reached their second birthday. Infants shall be weighed
together 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 other
item weight as approved by the JAA.
Chapter 12 Page 5
© G LONGHURST 1999 All Rights Reserved Worldwide
031 Aircraft Mass & Balance
CAP 696 - Loading Manual
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
13
CAP 696 - Loading Manual
1.
The CAP 696 is published by the CAA for examination purposes. The candidate is
responsible for taking a copy of this CAP in pristine condition to the examination. The details of
three generic aircraft are contained in the manual which are representative of those used for
performance and flight planning. Pages 2, 3 and 4 of the manual contain definitions which can be
used 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 engine
piston/propeller aeroplane. The maximum limitations are on page 5 but the floor loading limitations
at the bottom of the page apply to Figure 2-2 on Page 6. Figure 2-3 provides the moments for any
given quantity of fuel. Page 7 details the procedure to be adopted to determine and plot the CG
position on pages 8 and 9. The following two examples demonstrate the use of the SEP 1 pages.
Chapter 13 Page 1
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
EXAMPLE 13-1
EXAMPLE
The aeroplane is to carry a pilot and co-pilot each weighing 80 kgs and two passengers each
weighing 70 kgs and have 5 kgs of baggage each, which is in Zone B. The fuel on board at startup 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 the
results.
EXAMPLE 13-2
EXAMPLE
The aeroplane is to carry a pilot and co-pilot each weighing 85 kgs and two passengers weighing
185.6 kgs together in third and fourth seats. Each passenger has 10 kgs of baggage which is
loaded in Zone C. The fuel on board is 70 US gallons of which 50 US gallons will be used for the
flight.
Fill in the pro forma and plot the results to determine the CG for the zero fuel weight, take-off and
landing weights.
Chapter 13 Page 2
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-1
Loading Manifest
Chapter 13 Page 3
Example 13-1
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-2
Centre of Gravity
Envelope
Chapter 13 Page 4
Example 13-1
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-3
Loading Manifest
Chapter 13 Page 5
Example 13-1 Solution
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-4
Centre of Gravity
Envelope
Chapter 13 Page 6
Example 13-1 Solution
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-5
Loading Manifest
Chapter 13 Page 7
Example 13-2
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-6
Centre of Gravity
Envelope
Chapter 13 Page 8
Example 13-2
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CAP 696 - Loading Manual
FIGURE 13-7
Loading Manifest
Chapter 13 Page 9
Example 13-2 Solution
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-8
Centre of Gravity
Envelope
Chapter 13 Page 10
Example 13-2 Solution
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
3.
The MEP 1. The limitations for the multi-engined piston/propeller aircraft are listed on Page
12. Notice the reference datum is at the bulkhead of the nose cargo compartment. Page 13 details
the calculation procedure and a worked example is shown on pages 14 and 15. Now complete the
pro forma and plot the results for the following examples.
EXAMPLE 13-3
EXAMPLE
The aeroplane is to carry:
Chapter 13 Page 11
(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.
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
EXAMPLE 13-4
EXAMPLE
The aeroplane is to carry:
Chapter 13 Page 12
(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.
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-9
Loading Manifest
Chapter 13 Page 13
Example 13-3
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
Example 13-3
FIGURE 13-10
Chapter 13 Page 14
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-11
Loading Manifest
Chapter 13 Page 15
Example 13-3 Solution
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
Example 13-3 Solution
FIGURE 13-12
Chapter 13 Page 16
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-13
Loading Manifest
Chapter 13 Page 17
Example 13-4
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
Example 13-4
FIGURE 13-14
Chapter 13 Page 18
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-15
Loading Manifest
Chapter 13 Page 19
Example 13-4 Solution
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
#
Example 13-4 Solution
FIGURE 13-16
Chapter 13 Page 20
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
4.
The MRJT. All the data regarding the medium range jet transport aeroplane are contained in
the white pages of the CAP 696. Page 20 details all the stations and their balance arms. BS is an
abbreviation 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 is
tabulated. Figure 4-4 enables the stabiliser time unit setting to be calculated fro take-off, using either
5° or 15° of flap, for any CG position between 5% and 30% of the mean aerodynamic chord. The
dimensions 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 mass
values for the crew and passengers. Precise details regarding the loading of the cargo compartments
are on Page 24.
6.
The procedure for calculating and plotting the CG is specified on Page 25 using the pro forma
on Page 26 and the trim envelope diagram on Page 27. The example load and trim sheet information
on Page 28 and 29 illustrates the completion of this form. At the present it is not envisaged that the
candidate will have to utilise one to answer any question because each airline has their own version
of this form.
Important Points
Chapter 13 Page 21
(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 standard
masses of 85 kgs for flight crew and 75 kgs for cabin crew.
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
(c)
The standard passenger mass is 84 kgs which according to the JAR-OPS 1 is the
standard 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 1
is that which should be used for European flights only.
THE MESSAGE IS THAT WHEN USING MRJT 1 LOADING MANIFEST THE VALUES USED
FOR STANDARD MASSES ARE NON-STANDARD.
Chapter 13 Page 22
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
EXAMPLE 13-5
EXAMPLE
The details of this example are as shown on Page 28 of CAP 696 and depicted on Page 29. Use the
trim sheet blank at Figure 13-7 below and follow the instructions on Page 28.
Chapter 13 Page 23
© G LONGHURST 1999 All Rights Reserved Worldwide
CAP 696 - Loading Manual
FIGURE 13-17
Load and Trim
Sheet (Blank)
Chapter 13 Page 24
© G LONGHURST 1999 All Rights Reserved Worldwide