Aircraft CG cannot be located forward of CG2.
Maximum elevator deflection (max load factor) : FWD limit (all phases)
WEIGHT AND
BALANCE
WEIGHT AND
BALANCE
A. GENERALITIES
4.4. Final Approach Limitations
4.4.1. THS stall
a) Standard approach
During approach, the flaps and slats are extended. This configuration gives the aircraft a pitch-
down attitude. This pitch-down moment is countered by an aircraft nose-up THS setting.
A forward CG position increases the pitch-down moment and is also countered by an aircraft
nose-up THS setting.
The combination of the two effects can lead to an important aircraft nose-up THS setting which
can eventually lead to a THS stall.
b) Approach + push-over
When during approach the pilot excessively reduces the speed, in order not to stall and regain a
proper approach speed, he will push the stick (—push-over“).
In case of a forward CG position countered by an aircraft nose-up THS setting, this procedure
may lead to the THS stall because of the aircraft attitude change.
THS stall limit : FWD limit (flight and landing)
(and take off for final approach in case of emergency landing)
4.4.2. Go Around
Setting the engines at full throttle creates a significant pitch-up moment which must be
compensated by the elevator.
The more aft the CG, the higher the pitch- up moment.
The CG position can be moved aft until it reaches the point where the pitch-up moment cannot
be compensated anymore by the elevator deflection.
Go around : AFT limit (flight and landing)
(and take off for final approach in case of emergency landing)
4.4.3. Alpha Floor Protection
Alpha floor protection configuration: high angle of attack, low speed and TOGA power. Low speed implies low elevator efficiency. TOGA implies high pitch-up moment.
The more the CG is aft, the higher the pitch-up moment.
The CG position can be moved aft until it reaches the point where the pitch-up moment cannot
be compensated anymore by the elevator deflection.
That will limit the aft position of the CG more than the go around limitation.
Alpha floor protection : AFT limit (flight and landing)
(and take off for final approach in case of emergency landing)
A. GENERALITIES
4.5. Landing Limitations
4.5.1. Structural limitations
Landing structural limitations are similar to take off ones, they are usually less limiting as the aircraft is less heavy then at take off.
Main gear strength : AFT limit (landing)
Nose gear strength : FWD limit (landing)
4.5.2. Maneuverability and elevator efficiency
This limitation concerns all flight phases (ref. B.1.2.3.2) but it is important just before landing, at low speed, when the elevator must enable the pilot to flare out.
Thus, elevator maximum deflection and aircraft maneuverability limit the CG position forward.
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本文链接地址：Getting to Grips with Aircraft Weight and Balance(47)
