Which of the following can be a compressibility-related problem when accelerating past the critical Mach number?

• A. Better Buffet Margin
• B. Lower Transonic Pressure Fluctuations
• C. Control Difficulties
• D. Excessive Engine Wear

Answer: (C)

Past the critical Mach number, flow around the airframe becomes compressible and shock waves form. These shocks create abrupt pressure changes and can cause flow separation, buffet, and a loss of control effectiveness on surfaces like the ailerons and elevators. That combination makes it harder to pilot the aircraft reliably, so control difficulties are the compressibility-related problem you’d expect in this regime. The other options don’t fit: buffet margin isn’t improved by compressibility—buffet is the problem; transonic pressure fluctuations actually increase due to shocks; engine wear isn’t a direct result of reaching or passing the critical Mach number.