FAA Aircraft Dispatcher (ADX)Flight Planning and PerformanceMedium
An aircraft's leading edge of the mean aerodynamic chord (LEMAC) is located at fuselage station 400, and the mean aerodynamic chord (MAC) length is 100 inches. If the calculated center of gravity is at fuselage station 435, what is the CG expressed as %MAC?
- A45% MAC
- B40% MAC
- C35% MAC
- D30% MAC
Show answer & explanationAnswer & explanation
Correct answer: C. 35% MAC
%MAC = [(CG station - LEMAC)/MAC length] x 100 = [(435-400)/100] x 100 = 35%. This tells the dispatcher/loadmaster where the CG falls within the certificated CG envelope.
Why the other options are wrong
- A. Would require CG at station 445.
- B. Would require CG at station 440.
- D. Would result from an incorrect CG station of 430.
%MAC (Percent Mean Aerodynamic Chord)
A standardized way of expressing CG location as a percentage of the chord length, independent of aircraft type, used to verify CG is within certified limits.
- %MAC = (CG station - LEMAC)/MAC length x 100
- LEMAC = Leading Edge of Mean Aerodynamic Chord station
- Loading manifests/W&B forms plot CG as %MAC vs weight
- Must fall within forward/aft CG envelope limits
Memory trick: LEMAC is the starting line; %MAC is how far down the track the CG sits