Tail-heavy loading affects stability about which axis?

• A. Lateral axis
• B. Longitudinal axis
• C. Vertical axis
• D. None

Answer: (A)

Tail-heavy loading shifts the center of gravity toward the tail, which reduces the effectiveness of the tail in producing a pitching moment to restore level flight. Pitch stability—that is, stability about the lateral axis (the axis running wingtip to wingtip)—depends on a proper balance between the aerodynamic forces ahead of and behind the center of gravity. When the CG moves aft, the restoring moment for pitch disturbances weakens, making the aircraft less stable in pitch. The longitudinal axis governs roll, and the vertical axis governs yaw, which are not primarily affected by tail heaviness in this way. So the stability most affected is about the lateral axis.