CPL Aerodynamics 2 — Questions and Answers
Question 1: Which factor primarily determines the critical angle of attack for a given airfoil?
- Airspeed
- Airfoil shape and camber (Correct answer)
- Aircraft gross weight
- Flap setting
Correct answer: Airfoil shape and camber
Critical angle of attack is a fixed aerodynamic property of the airfoil's shape and camber, not affected by speed or weight.
Question 2: What happens to induced drag when an aircraft's airspeed is doubled at the same altitude and weight?
- It doubles
- It quadruples
- It is reduced to one-quarter (Correct answer)
- It remains unchanged
Correct answer: It is reduced to one-quarter
Induced drag varies inversely with the square of airspeed, so doubling speed reduces induced drag to one-quarter of its original value.
Question 3: Ground effect reduces induced drag primarily because it:
- Increases air density below the wing
- Restricts the formation of wingtip vortices (Correct answer)
- Increases the effective angle of attack
- Reduces parasite drag
Correct answer: Restricts the formation of wingtip vortices
Ground effect limits downwash and vortex formation near the ground, reducing induced drag significantly during takeoff and landing.
Question 4: An aircraft experiencing 'Dutch roll' is showing instability about which axes?
- Longitudinal and vertical
- Lateral only
- Longitudinal only
- Lateral and vertical simultaneously (Correct answer)
Correct answer: Lateral and vertical simultaneously
Dutch roll is an oscillatory coupling of roll and yaw (lateral and vertical axes) common in swept-wing aircraft with high dihedral.
Question 5: What is the effect of increasing aspect ratio on an aircraft's aerodynamic efficiency?
- Increases parasite drag
- Reduces induced drag (Correct answer)
- Reduces lift coefficient
- Increases stall speed
Correct answer: Reduces induced drag
A higher aspect ratio reduces wingtip vortex strength per unit span, decreasing induced drag and improving the lift-to-drag ratio.
Question 6: Which condition most accurately describes 'coffin corner' in high-altitude flight?
- The margin between Mmo and Vs narrows until they converge (Correct answer)
- The autopilot disengages at high altitude
- Cabin pressurization becomes ineffective
- Engine thrust exceeds structural limits
Correct answer: The margin between Mmo and Vs narrows until they converge
At coffin corner, the indicated stall speed and the maximum operating Mach speed converge, leaving almost no usable speed range.
Question 7: Dihedral in a wing design primarily provides stability about which axis?
- Vertical (yaw)
- Longitudinal (roll) (Correct answer)
- Lateral (pitch)
- All three axes equally
Correct answer: Longitudinal (roll)
Dihedral creates a self-correcting rolling moment when one wing drops, providing positive lateral (roll) stability.
CPL Aerodynamics 2
Which factor primarily determines the critical angle of attack for a given airfoil?