Mach tuck in airliners occurs as speed approaches the sound barrier because:

Mach tuck in airliners occurs as speed approaches the sound barrier because:

• A. The center of pressure moves aft, generating a greater pitch-down moment.
• B. The wing stalls due to an excessive angle of attack at high speed.
• C. The tailplane loses effectiveness due to flutter.
• D. The fuselage experiences structural flex causing a nose-up moment.

Answer: (A)

Mach tuck happens because, as speed enters the transonic range, compressibility effects and shock waves on the wing change the lift distribution. The pressure pattern shifts toward the rear of the wing, so the center of pressure moves aft relative to the airplane’s center of gravity. With the center of pressure behind the CG, the aerodynamics produce a nose-down pitching moment. As Mach number increases, this aft shift strengthens the nose-down tendency, which is why the aircraft tends to tuck its nose downward if not countered by trim and elevator authority. This isn’t about stalling from too high an angle of attack, nor is it primarily caused by tailplane flutter or fuselage flex. Those are separate issues; the defining feature of Mach tuck is the aft movement of the center of pressure with increasing speed.

Mach tuck happens because, as speed enters the transonic range, compressibility effects and shock waves on the wing change the lift distribution. The pressure pattern shifts toward the rear of the wing, so the center of pressure moves aft relative to the airplane’s center of gravity. With the center of pressure behind the CG, the aerodynamics produce a nose-down pitching moment. As Mach number increases, this aft shift strengthens the nose-down tendency, which is why the aircraft tends to tuck its nose downward if not countered by trim and elevator authority.

This isn’t about stalling from too high an angle of attack, nor is it primarily caused by tailplane flutter or fuselage flex. Those are separate issues; the defining feature of Mach tuck is the aft movement of the center of pressure with increasing speed.