FAA Flight Instructor Airplane (FIA)Aerodynamics and Principles of FlightMedium
A CFI is reviewing the three axes of rotation with a client. Which pairing of axis, primary control surface, resulting movement, and type of stability is correct?
- ALateral axis, elevator, pitch, longitudinal stability
- BLongitudinal axis, elevator, pitch, longitudinal stability
- CLongitudinal axis, rudder, roll, lateral stability
- DVertical axis, aileron, yaw, directional stability
Show answer & explanationAnswer & explanation
Correct answer: A. Lateral axis, elevator, pitch, longitudinal stability
The elevator moves the airplane in pitch about the lateral axis (wingtip to wingtip), which is governed by longitudinal stability. The ailerons control roll about the longitudinal axis (lateral stability), and the rudder controls yaw about the vertical axis (directional stability).
Why the other options are wrong
- B. Elevator produces pitch about the lateral axis, not the longitudinal axis.
- C. Rudder controls yaw about the vertical axis, not roll about the longitudinal axis.
- D. Ailerons control roll, not yaw; yaw is controlled by the rudder.
Three Axes of Rotation
An airplane rotates about three axes intersecting at the CG: longitudinal (roll), lateral (pitch), and vertical (yaw), each controlled by a specific flight control.
- Longitudinal axis/ailerons/roll/lateral stability
- Lateral axis/elevator/pitch/longitudinal stability
- Vertical axis/rudder/yaw/directional stability
Memory trick: 'ELP-Y': Elevator-Lateral-Pitch, Yaw-Vertical-rudder, Longitudinal-aileron-roll.