FAA Airline Transport Pilot (ATM)Aircraft Performance and Weight and BalanceHard
Using the takeoff trim setting chart, a dispatcher calculates the CG for Flight 220 at 18% MAC (near the forward limit) and for Flight 221 at 30% MAC. Both flights use the same flap setting and takeoff weight range on the chart. How should the required horizontal stabilizer trim setting for Flight 220 compare to that of Flight 221?
- ABoth flights require an identical trim setting because flap setting, not CG, determines trim
- BFlight 220 requires a greater nose-down trim setting than Flight 221
- CFlight 220 requires a greater nose-up (more airplane-nose-up) trim setting than Flight 221
- DTrim setting is unrelated to CG position and depends only on weight
Show answer & explanationAnswer & explanation
Correct answer: C. Flight 220 requires a greater nose-up (more airplane-nose-up) trim setting than Flight 221
A more forward CG creates a longer moment arm requiring more nose-up elevator/stabilizer trim authority to rotate and maintain the desired pitch attitude for takeoff. Takeoff trim charts are keyed to %MAC precisely because a forward CG (18% MAC) requires more airplane-nose-up (ANU) stabilizer trim than a more aft CG (30% MAC).
Why the other options are wrong
- A. Trim setting charts are indexed to CG (%MAC), not flap setting alone.
- B. This reverses the relationship; forward CG needs more nose-up, not nose-down, trim.
- D. CG position is the primary variable on takeoff trim setting charts, along with weight.
Takeoff Stabilizer Trim Setting vs. CG
The required horizontal stabilizer trim setting for takeoff is determined from CG position (%MAC): a more forward CG requires a greater nose-up trim setting.
- Forward CG requires more airplane-nose-up (ANU) trim
- Aft CG requires less nose-up (or more nose-down) trim
- Trim setting charts use %MAC and takeoff weight as inputs
- Improper trim setting can cause tail strikes or reduced rotation performance
Memory trick: Forward CG is nose-heavy — crank in more nose-up trim to help it rotate