Optimum Cg

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    Optimum CG positionWhat is the best CG position for an aircraft ?

    Catherine BONNETFlight Operations,

    Weight and Balance Engineer

    Presented by:

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    ment.

    Introduction

    The influence of some parameters on

    fuel consumption

    By Monique Fueri and Yves LemelleSlide 10

    May200916th Performance and Operations conference Page 10AIRBUSS.A.S.

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    Impact of Centre of Gravity

    Centre of gravityCentre of gravity

    Optimize CG:For best takeoff performance

    Usually aft CG minimizes fuel consumption

    To be able to reach optimum CG in flight (aircraftwith trim tank)

    COCKPIT

    PREPARATION

    TAXI IN

    DISPATCH

    TRANSIT

    DEPARTURE

    TAXI OUT

    TAKEOFF

    CLIMB

    CRUISE

    APPROACH

    LANDING

    HOLDING

    DESCENT

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    ment.

    Introduction

    AFT

    as AFT as

    possible

    AFT of what ?

    What is the best CG position

    for an aircraft ?

    25%MAC so

    that the aircraftis balanced

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    Introduction What is the best CG positionfor an aircraft ?

    Well, any CG inside the limits isOK.

    But there is a range of

    recommended CG positions andthis range differs from one

    aircraft to the other."

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    Content

    How to place aircraft CG position at the optimum ?

    Is it a flexible process ?

    Why would I select an optimum CG position ?

    What is the best Center of Gravity position for an

    aircraft?

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    Content

    How to place aircraft CG position at the optimum ?

    Is it a flexible process ?

    Why would I select an optimum CG position ?

    What is the best Center of Gravity position for an

    aircraft?

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    VCC

    C C

    How to place aircraft CG at the optimum ?

    Aircraft Basic configuration

    Low flexibility

    Operators items and DOW

    Low flexibility

    Fuel

    NO flexibility

    VCC

    C C

    VCC

    C C

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    How to place aircraft CG at the optimum ?

    Passengers

    VCC

    C C NO flexibilityPartial flexibility

    High flexibility

    Cargo

    Several constraints:

    Priority

    Temperature and ventilation Incompatibilities

    Pyramidal loading

    Aircraft stability on ground

    .

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    How to place aircraft CG at the optimum ?

    Conclusion:Main actor is the Load Planner

    He can control ZFCG and TOCG positions

    He has many constraints to consider

    It is not so easy to place the CG at the optimum

    Any CG inside the operational limits

    is OK

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    How to place aircraft CG at the optimum ?

    Conclusion:

    Give Load Planners an

    Optimum ZFCG range or an

    Optimum TOCG range

    instead of an optimum CG position

    Load and trim Sheet

    ZFCG

    TOCG

    What is the best CGposit ion for an aircraft ?

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    Content

    How to place aircraft CG position at the optimum ?

    Is it a flexible process ?

    Why would I select an optimum CG position ?

    What is the best Center of Gravity position for an

    aircraft?

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    reserved.

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    How to place aircraft CG position at the optimum ?

    Is it a flexible process ?

    Why would I select an optimum

    What is the best Center of Gravity position for an

    aircraft?

    Content

    range of CG positions ?

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    ument.

    Content

    How to place aircraft CG position at the optimum ?

    Is it a flexible process ?

    Why would I select an optimum range of CG positions ?

    To reduce my fuel consumption

    To benefit from better Takeoff and Landing performance

    What is the best Center of Gravity position for an

    aircraft?

    To reduce my fuel consumption

    To benefit from better Takeoff and Landing performance

    Wh ld I l t ti f CG

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    ument.

    Why would I select an optimum range of CGpositions ?

    To reduce my fuel consumption

    Lift

    Natural pitchdown effect

    AircraftStabilisation

    Tail downforce

    To maintain the aircraft stable, tail down force is mandatory.

    Weight

    Wh ld I l t ti f CG

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    ument.

    Tail downforce

    Why would I select an optimum range of CGpositions ?

    To reduce my fuel consumption

    Lift

    Natural pitchdown effect

    AircraftStabilisation

    Tail downforce

    The more forward the CG, the higher the tail down force.

    The higher the tail down force,

    the higher the lift necessary to maintain the flight

    the higher the dragthe higher the fuel consumption.

    Weight

    Natural pitchdown effect

    AircraftStabilisation

    Lift

    To maintain the aircraft stable, tail down force is mandatory.

    Wh ld I l t ti f CG

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    ument.

    Difference in fuel consumption between two CGpositions inside the CG limits is low

    Optimum CG position highly depends on aircraftFlight Level (FL)

    Optimum CG is not the most aft but somewhereinside the CG limits

    Complex aerodynamic interaction Wing-Tail

    The more forward the CG, the higher the fuel consumption, IN GENERAL, IN GENERAL

    But for Single Aisle aircraft

    Why would I select an optimum range of CGpositions ?

    To reduce my fuel consumption

    The more forward the CG, the higher the fuel consumption, IN GENERAL

    For Single Aisle aircraft, NO effect of CG position on fuel consumption.

    FL1

    FL2

    FL3

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    ument.

    Content

    How to place aircraft CG position at the optimum ?

    Is it a flexible process ?

    Why would I select an optimum range of CG

    positions ?

    To reduce my fuel consumption

    To benefit from better Takeoff and Landing

    performance

    What is the best Center of Gravity position for anaircraft?

    Wh ld I l t ti f CG

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    ument.

    Why would I select an optimum range of CGpositions ?

    To benefit from better Takeoff and Landing performance

    Lift

    Weight

    Natural pitchdown effect

    AircraftStabilisation

    Tail downforce

    The higher the tail down force,

    the higher the lift necessary to maintain the flight

    the higher the minimum speed (Vs1g) necessary to maintain the flight.

    To fly the aircraft, Lift must be higher than (Weight + Tail down force).

    The more forward the CG, the higher the tail down force.

    Tail downforce

    Lift

    Wh ld I l t ti f CG

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