FAA Aviation Mechanic General (AMG)Aircraft Drawings, Weight and BalanceHard
After loading an aircraft, a technician computes a total weight of 3,400 lb and a total moment of 306,000 in-lb. The aircraft's CG envelope specifies a forward limit of 82.0 in and an aft limit of 92.0 in at this weight. Is this loading within limits?
- ANo, because the CG is 90.0 in, which exceeds the aft limit
- BNo, because the CG is 82.0 in, which is at the forward limit exactly
- CYes, because the total moment of 306,000 in-lb is less than the maximum allowed moment
- DYes, because the CG is 90.0 in, which falls within the 82.0–92.0 in range
Show answer & explanationAnswer & explanation
Correct answer: D. Yes, because the CG is 90.0 in, which falls within the 82.0–92.0 in range
CG is found by dividing total moment by total weight: 306,000 in-lb ÷ 3,400 lb = 90.0 in. Since 90.0 in falls between the forward limit of 82.0 in and the aft limit of 92.0 in, the loading is within the CG envelope and is acceptable.
Why the other options are wrong
- A. 90.0 in is less than the aft limit of 92.0 in, so it does not exceed the limit.
- B. The calculated CG is 90.0 in, not 82.0 in, so this option misstates the result.
- C. While true that moment alone isn't the limiting factor, the correct reasoning must be based on computed CG location, not raw moment value.
CG Envelope (Loading Check)
A chart or table defining the forward and aft CG limits for a given aircraft weight; the loaded CG must fall within these limits for safe flight.
- CG = Total Moment ÷ Total Weight
- Must fall between forward and aft limits for that weight
- Limits can vary with total weight (envelope shape)
Memory trick: CG envelope = the safe 'lane' the CG must stay inside.