Weight, Balance, and Performance
Weight, balance, and performance questions combine arithmetic with gyroplane-specific limits. The exam expects you to compute loading, check CG against the envelope, and explain how weight, density altitude, and wind change takeoff, climb, and landing performance.
The arithmetic
- Moment = weight × arm. Total weight and total moment give the CG: CG = total moment ÷ total weight.
- Useful load = maximum gross weight − empty weight, and it must cover pilot, passenger, baggage, and fuel.
- Aviation gasoline weighs 6 lb per gallon; oil about 7.5 lb per gallon.
Balance in a gyroplane
Gyroplanes are sensitive to CG position relative to the propeller thrust line. A high thrust line produces a pitch-up couple when power is added, a bunt tendency that has caused fatal accidents; centerline-thrust designs reduce it. Loading aft of the limit reduces static margin and makes the machine pitch-sensitive; forward of the limit, flare authority and takeoff performance suffer.
Performance factors
- Density altitude lengthens takeoff distance and reduces climb rate because rotor and engine both see thinner air.
- Gross weight reduces excess power, raises minimum speed, and lengthens the takeoff run.
- Headwind shortens takeoff and landing distance; a tailwind lengthens both sharply; soft or tall grass adds drag.
- Vx is best angle, Vy best rate, and best glide speed gives the flattest power-off glide.
Worked example
Empty weight 700 lb at arm 60 in; pilot 180 lb at arm 55 in; 10 gallons of fuel at arm 70 in. Moments: 42,000 + 9,900 + 4,200 = 56,100 lb-in. Weight: 700 + 180 + 60 = 940 lb. CG = 56,100 ÷ 940 = 59.7 in. If the envelope runs 58–64 in, the loading is legal but near the forward limit, so expect a longer takeoff and reduced flare authority.
Traps
Forgetting fuel in the moment table; mixing gallons with pounds; assuming under gross means in balance; and ignoring density altitude because the temperature on the ground feels mild.