Stability around the lateral axis is called which stability?

• A. Lateral stability
• B. Longitudinal stability
• C. Directional stability
• D. Vertical stability

Answer: (B)

Stability around the lateral axis is pitch stability, which is referred to as longitudinal stability. The lateral axis runs wingtip to wingtip, and rotations about it are pitching motions (nose up or down). Longitudinal stability describes the aircraft’s tendency to return to or hold a steady pitch attitude after a disturbance, involving how the wing design, tail surface, and the position of the center of gravity create a restoring moment in the pitch plane. The tail plane’s lift or downforce and the CG location work together to oppose nose-up or nose-down tendencies, helping the aircraft settle back to its trimmed pitch.

Directional stability relates to yaw about the vertical axis, and lateral stability would pertain to roll about the longitudinal axis, so those do not describe stability in the pitch (lateral) sense.