Increasing tail-arm distance (CG to tail) affects elevator effectiveness how?

Increasing tail-arm distance (CG to tail) affects elevator effectiveness how?

• A. Increases the pitching moment produced by a given tail lift
• B. Decreases the pitching moment
• C. Has no effect
• D. Reverses moment direction

Answer: (A)

The key idea is that any force acting at the tail creates a moment about the airplane’s center of gravity equal to the force times the distance from the CG to the tail. If you deflect the elevator and the tail lift changes by the same amount, increasing the distance between the CG and the tail multiplies that force into a larger pitching moment. So, for a given tail lift, a longer tail arm produces a stronger moment about the CG, meaning greater elevator effectiveness. The direction of the moment depends on whether the tail force is upward or downward, but the magnitude of the effect grows with carry distance.

The key idea is that any force acting at the tail creates a moment about the airplane’s center of gravity equal to the force times the distance from the CG to the tail. If you deflect the elevator and the tail lift changes by the same amount, increasing the distance between the CG and the tail multiplies that force into a larger pitching moment. So, for a given tail lift, a longer tail arm produces a stronger moment about the CG, meaning greater elevator effectiveness. The direction of the moment depends on whether the tail force is upward or downward, but the magnitude of the effect grows with carry distance.