In transonic speeds, which effect may occur as a result of compressibility, with the correct choice being the last option?

In transonic speeds, which effect may occur as a result of compressibility, with the correct choice being the last option?

• A. Drag Resistance Vanishes
• B. Improved Aerodynamic Efficiency at All Speeds
• C. Increased Engine Power for the Same Thrust
• D. Drag Increases

Answer: (D)

Compressibility effects at transonic speeds cause shock waves to form on surfaces like wings, which abruptly alter the pressure distribution and create wave drag. As these shocks develop and move with the flow, they add drag, so overall drag rises in the transonic regime. That’s why the correct description is that drag increases. The other statements don’t fit: drag does not vanish with compressibility; efficiency isn’t guaranteed to improve at all speeds; and engine power for the same thrust isn’t a direct consequence of transonic compressibility—it's the increased drag that changes the power required to overcome it.

Compressibility effects at transonic speeds cause shock waves to form on surfaces like wings, which abruptly alter the pressure distribution and create wave drag. As these shocks develop and move with the flow, they add drag, so overall drag rises in the transonic regime. That’s why the correct description is that drag increases. The other statements don’t fit: drag does not vanish with compressibility; efficiency isn’t guaranteed to improve at all speeds; and engine power for the same thrust isn’t a direct consequence of transonic compressibility—it's the increased drag that changes the power required to overcome it.