FAA Private Pilot Helicopter (PRH)Performance and LimitationsMedium
A pilot is computing weight and balance for a flight. Empty weight is 1,500 lb with a moment of 150,000 lb-in. The pilot weighs 170 lb and sits at station 80. Fuel weighs 300 lb and is loaded at station 90. What is the helicopter's center of gravity (CG) location?
- A96.8 inches
- B100.5 inches
- C98.2 inches
- D94.7 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 96.8 inches
Total moment = 150,000 + (170×80=13,600) + (300×90=27,000) = 190,600 lb-in. Total weight = 1,500+170+300 = 1,970 lb. CG = 190,600 ÷ 1,970 = 96.8 inches.
Why the other options are wrong
- B. Far too high; not supported by the given moments and weights.
- C. Too high; likely from an arithmetic error in moment or weight addition.
- D. Too low; does not match the computed total moment divided by total weight.
CG Calculation (Moment Method)
The center of gravity is found by dividing the total moment (weight × arm) by the total weight of the aircraft.
- Moment = weight × arm
- CG = total moment ÷ total weight
- Must fall within the manufacturer's approved CG range
Memory trick: Moment ÷ Weight = Where it sits.