ATPL Principles of Flight and Aerodynamics 3

Question 1

The critical Mach number is defined as the free-stream Mach number at which:

Accepted Answer

Sonic airflow first appears somewhere on the aircraft

Answer

The critical Mach number is the free-stream speed at which local airflow first reaches Mach 1.0 on the aircraft — typically over the upper wing surface at its thickest point.

Question 2

Mach tuck (tuck-under) experienced in transonic flight is primarily caused by:

Accepted Answer

Rearward shift of the center of pressure due to shock wave formation

Answer

As Mach number increases into the transonic range, shock wave formation causes a rearward migration of the center of pressure, generating a strong nose-down pitching moment.

Question 3

Vortex generators are small devices attached to wing surfaces primarily to:

Accepted Answer

Re-energize the boundary layer to delay flow separation

Answer

Vortex generators mix high-energy free-stream air with the slower boundary layer, increasing its momentum and delaying separation to higher angles of attack.

Question 4

When operating in ground effect, an aircraft experiences:

Accepted Answer

Decreased induced drag and increased effective lift for the same AOA

Answer

Ground effect suppresses wingtip vortex formation, reducing induced drag and the downwash angle, which effectively increases the lift curve slope and produces more lift for the same AOA.

Question 5

The load factor (n) is defined as the ratio of:

Accepted Answer

Total aerodynamic lift to aircraft weight

Answer

Load factor n = Lift / Weight and represents the number of 'g's the structure experiences; in straight-and-level unaccelerated flight n = 1.0.

ATPL - Airline Transport Pilot License Practice Test

ATPL - Airline Transport Pilot License Practice Test

ATPL Principles of Flight and Aerodynamics 3