FAA Flight Instructor Airplane (FIA)Performance, Weight and BalanceMedium
An airplane weighs 2,100 lb with its CG located 82.0 inches aft of datum. A flight instructor loads 100 lb of baggage at a compartment with an arm of 95.0 inches. What is the new CG location?
- A82.6 inches
- B91.8 inches
- C95.0 inches
- D83.5 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 82.6 inches
Total moment = (2,100 × 82.0) + (100 × 95.0) = 172,200 + 9,500 = 181,700 lb-in. New total weight = 2,200 lb. New CG = 181,700 ÷ 2,200 = 82.59, or about 82.6 inches.
Why the other options are wrong
- B. Confuses the baggage arm with the resulting CG.
- C. This is the baggage arm, not the new overall CG.
- D. Overestimates the CG shift caused by the added baggage.
CG Calculation After Loading
New CG = Total Moment ÷ Total Weight, where total moment is the sum of each item's weight times its arm.
- Moment = Weight × Arm
- Sum all moments and divide by total weight to find new CG
- Always verify the result falls within the CG envelope limits
Memory trick: Moment in, moment out, divide by the total weight throughout