Accelerating through the critical Mach number may lead to which issue as a compressibility effect?

Accelerating through the critical Mach number may lead to which issue as a compressibility effect?

• A. Thrust Loss
• B. Increased Wing Bending
• C. Control Difficulties
• D. Greater Landing Distance

Answer: (C)

As speed approaches the critical Mach number, parts of the flow reach sonic conditions and a shock forms on the wing’s surface. This shock changes the pressure distribution abruptly and can cause boundary-layer separation, especially on control surfaces. The result is a loss or reduction of elevator, aileron, and rudder effectiveness, making the aircraft harder to maneuver and more difficult to control—classic control difficulties from compressibility effects. While wave drag and structural loads can also increase, the primary issue tied to accelerating through the critical Mach number is degraded control authority due to shock-induced flow changes and buffet.

As speed approaches the critical Mach number, parts of the flow reach sonic conditions and a shock forms on the wing’s surface. This shock changes the pressure distribution abruptly and can cause boundary-layer separation, especially on control surfaces. The result is a loss or reduction of elevator, aileron, and rudder effectiveness, making the aircraft harder to maneuver and more difficult to control—classic control difficulties from compressibility effects. While wave drag and structural loads can also increase, the primary issue tied to accelerating through the critical Mach number is degraded control authority due to shock-induced flow changes and buffet.