What does tailplane trim authority refer to?

• A. The ability of the tailplane to produce a pitching moment to hold a desired attitude.
• B. It only affects drag.
• C. It controls yaw stability.
• D. It is not present on most aircraft.

Answer: (A)

Tailplane trim authority is the tailplane’s ability to generate a pitching moment that can hold the aircraft at a chosen pitch attitude with minimal control input. By adjusting the stabilizer (via trim tabs or trimming actuators), the tailplane creates lift on the horizontal surface that acts behind the aircraft’s center of gravity, producing a nose-up or nose-down moment to balance aerodynamic forces. When trim authority is adequate, the airplane can stay at the desired pitch across different speeds, weights, and configurations without constant elevator input, reducing pilot workload.

This is not about drag alone, and trim influence isn’t about yaw stability—that’s mainly handled by the vertical stabilizer and rudder. Trim is also a standard feature on most aircraft, used to set steady pitch under a wide range of flight conditions.