(1)
The sudden failure of the critical engine.
(2)
Configuration changes, including deployment or retraction of deceleration devices.
In the following chapter all limitations are detailed by flight phase.
rotation A. GENERALITIES
4.2. Take-off Limitations
4.2.1. Structural limitation
Main gear strength : AFT limit (take off)
b) Nose gear Strength:
.
The more the CG is forward, the more the weight over the nose gear
.
The strength of the nose gear limits the forward position of the CG for high TOW.
Nose gear strength : FWD limit (take off)
c) Wing strength:
The structural limits of the wing will have an effect on the CG limits at high weights.
WEIGHT AND
BALANCE
WEIGHT AND
BALANCE
A. GENERALITIES
4.2.2. Taxi and Take-off run
a) Nose Gear adherence:
During taxi and at the beginning of the take-off run, when the speed of the aircraft is not sufficient for the rudder to be effective, the only possible means of controlling the aircraft on the ground is the nose gear steering. In order to be effective, the nose gear wheel must have enough adherence. To have an appropriate adherence, enough weight must be applied on the nose gear.
This adherence is further reduced during the take-off run when full power is applied on the
engines, thus creating a pitch up moment. (This pitch up moment is due to the engines being
located beneath the CG of the aircraft)
The further aft the CG, the lesser the adherence.
Nose gear adherence : AFT limit (take off)
b) Take-off Rotation
A forward CG means that the aircraft has a —heavy“ nose. This leads to a difficult rotation. The CG position can be moved forward until it reaches the point where rotation becomes impossible.
An aft CG means that the aircraft‘s nose is relatively —light“. This facilitates the rotation.
However, an aft CG limit has to be established in order to prevent a tail-strike during the rotation.
Note: A forward CG implies an A/C nose-up trim setting, while an aft CG implies an A/C nose-down trim setting. If the correct trim setting is made prior to take-off, the pilot will always have the same feel during rotation no matter the CG position. However, flight-testing is performed with a forward CG position and an A/C nose-down trim setting (conversely with an aft CG position and an A/C nose-up trim setting) in order to cover the critical condition.
Impossible rotation : FWD limit (take off)
Tail strike : AFT limit (take off)
A. GENERALITIES
4.3. Aircraft stability and maneuverabilityLimitations
During all flight phases the aircraft must remain stable and maneuverable.
The aircraft CG position has an influence on the aircraft static longitudinal stability in steady flight
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：Getting to Grips with Aircraft Weight and Balance(44)
