The variable incidence tail plane with stabilizer trim as an alternative to a conventional elevator primarily reduces which of the following?

• A. Can produce excessively high
• B. Reduces residual control forces
• C. Control forces if out of trim
• D. Increases drag

Answer: (B)

A trimming approach that uses a variable-incidence tailplane changes the amount of pitching moment produced by the tail, so the airplane can be pitched to the desired attitude without large elevator deflections. By setting the tailplane angle, part of the required trim moment is generated directly by the tail rather than by continuous elevator input. When the aircraft is properly trimmed, the elevator does not have to work as hard to hold the attitude, so the forces the pilot feels on the controls are reduced. That reduction in the effort needed to maintain pitch is what’s meant by lowering the residual control forces. Drag effects from trim changes aren’t the primary benefit, and while re-trimming is needed if conditions shift, the main advantage is lighter control forces in steady flight.