As Mach approaches and exceeds the critical Mach, which compressibility effect may occur?

As Mach approaches and exceeds the critical Mach, which compressibility effect may occur?

• A. Increased Fuel Flow
• B. Cabin Pressure Variation
• C. No Change in Handling Characteristics
• D. Drag Increases

Answer: (D)

As Mach approaches and passes the critical Mach, compressibility effects become significant as shock waves form on the aircraft surfaces. These shocks disrupt the smooth pressure distribution, causing a large increase in drag known as wave drag. This drag rise occurs even if the lift doesn’t grow correspondingly, so the overall drag increases as speed crosses into transonic territory. The other options don’t describe this primary effect: increased fuel flow is a consequence of needing more thrust to overcome the higher drag, not the fundamental compressibility phenomenon itself; cabin pressure variation isn’t the key compressibility issue at this speed; and claiming no change in handling characteristics ignores the common shock-induced changes in aerodynamics. Drag increases is the best description of the compressibility effect.

As Mach approaches and passes the critical Mach, compressibility effects become significant as shock waves form on the aircraft surfaces. These shocks disrupt the smooth pressure distribution, causing a large increase in drag known as wave drag. This drag rise occurs even if the lift doesn’t grow correspondingly, so the overall drag increases as speed crosses into transonic territory. The other options don’t describe this primary effect: increased fuel flow is a consequence of needing more thrust to overcome the higher drag, not the fundamental compressibility phenomenon itself; cabin pressure variation isn’t the key compressibility issue at this speed; and claiming no change in handling characteristics ignores the common shock-induced changes in aerodynamics. Drag increases is the best description of the compressibility effect.