At high speeds near or beyond the critical Mach, which event can occur as a compressibility effect, with the correct choice being the second option?

• A. Increased Fuel Consumption
• B. Drag Increases
• C. Enhanced Stability
• D. Zero Effect on Airflow

Answer: (B)

When speeds approach the critical Mach, air starts behaving as a compressible medium rather than a simple incompressible flow. Local flow around surfaces can reach Mach 1, producing shock waves. These shocks cause a sudden rise in pressure on the surfaces and create wave drag, so the overall drag increases sharply in the transonic range. This compressibility effect is the primary reason drag goes up as you near or exceed the critical Mach. The other choices don’t describe what directly happens: while higher drag can lead to more fuel burn, the fundamental event at this speed regime is the drag rise from shock waves; enhanced stability isn’t guaranteed and is not the marked compressibility effect, and zero effect on airflow contradicts the basic physics of shock formation.