Which has the more critical center of gravity range?

• A. Aircraft
• B. Helicopter
• C. Glider
• D. Unmanned aerial vehicle

Answer: (B)

The center of gravity range is the allowable fore-and-aft location of the weight that keeps the aircraft stable and controllable throughout the flight regime. In rotorcraft, this range is especially critical because the main rotor is the sole lift source and is positioned high above or relative to the fuselage. Small shifts in CG can dramatically affect how the helicopter pitches, how much tail-rotor thrust is needed to balance torque, and how easily the aircraft responds to cyclic inputs, particularly in hover and slow-speed flight. If the CG is too far forward or aft, control authority can be reduced, and the tail rotor may be overloaded or unable to maintain stable yaw, making precise control much harder.

Fixed-wing airplanes and gliders, while still requiring a properly located CG, generally operate with more forgiving stability characteristics at their typical speeds and flight attitudes, so their acceptable CG envelope isn’t as tightly constrained as that of a rotorcraft. Unmanned aerial vehicles can vary widely in design, but many fixed-wing and multi-rotor UAVs do not face the same combination of hover-based control challenges and torque management that helicopter systems demand. That's why the helicopter has the most critical center of gravity range.