FAA Private Pilot Airplane (PAR)Performance, Weight and BalanceMedium
An aircraft is loaded such that its center of gravity (CG) is located at the aft limit. Which of the following flight characteristics would be most pronounced?
- AIncreased stall speed and reduced cruise performance.
- BDecreased stability and increased elevator effectiveness.
- CIncreased stability and reduced elevator effectiveness.
- DDecreased stall speed and increased control forces.
Show answer & explanationAnswer & explanation
Correct answer: B. Decreased stability and increased elevator effectiveness.
When the CG is at or near the aft limit, the aircraft becomes less stable because the tail's ability to create a restoring moment is reduced. This also means less force is required from the elevator to change pitch, leading to increased elevator effectiveness and potentially over-controlling.
Why the other options are wrong
- A. Aft CG generally decreases stall speed slightly and can improve cruise performance due to reduced induced drag, but these are not the most pronounced effects related to control.
- C. Aft CG decreases stability and increases elevator effectiveness.
- D. Aft CG decreases stall speed and reduces control forces, making the aircraft feel 'lighter' on the controls.
Aft CG Effects
An aft center of gravity reduces longitudinal stability, increases elevator effectiveness, and can lead to dangerous pitch oscillations and difficulty recovering from stalls.
- Reduced longitudinal stability.
- Increased elevator effectiveness (lighter controls).
- Tendency to pitch up.
- More difficult stall recovery.
- Slightly lower stall speed.
- Improved cruise performance (less induced drag).
Memory trick: Aft is Agile, Forward is Stable.