ATPL Principles of Flight and Aerodynamics 1 — Questions and Answers
Question 1: According to Bernoulli's principle, what happens to static pressure when airflow velocity increases over an airfoil?
- Static pressure increases proportionally
- Static pressure decreases (Correct answer)
- Static pressure remains constant
- Dynamic pressure decreases
Correct answer: Static pressure decreases
Bernoulli's principle states that as fluid velocity increases, static pressure decreases, creating the pressure differential across the wing that generates lift.
Question 2: The angle of attack (AOA) is defined as the angle between:
- The wing chord line and the aircraft's longitudinal axis
- The relative wind and the chord line of the wing (Correct answer)
- The flight path and the horizon
- The aircraft pitch attitude and the horizon
Correct answer: The relative wind and the chord line of the wing
Angle of attack is measured between the free-stream relative wind and the chord line of the airfoil, regardless of the aircraft's pitch attitude.
Question 3: Which type of aerodynamic drag increases as airspeed increases?
- Induced drag
- Parasite drag (Correct answer)
- Vortex drag
- Profile drag at low speed
Correct answer: Parasite drag
Parasite drag (including form, interference, and skin friction drag) increases proportionally with the square of airspeed.
Question 4: Induced drag is directly associated with:
- Wing surface area only
- Airspeed squared
- Lift production (Correct answer)
- Fuselage cross-sectional shape
Correct answer: Lift production
Induced drag is a byproduct of lift generation, caused by wingtip vortices that create a rearward tilting of the lift vector.
Question 5: A stall of an airfoil occurs when:
- Airspeed drops below a specific fixed value for all conditions
- The critical angle of attack is exceeded (Correct answer)
- Aircraft weight exceeds maximum available lift coefficient
- Engine power is reduced below a threshold
Correct answer: The critical angle of attack is exceeded
A stall occurs when the critical angle of attack is exceeded, causing boundary layer separation and a dramatic loss of lift regardless of airspeed.
Question 6: Which flap type produces the greatest increase in both lift coefficient and wing area?
- Plain flap
- Fowler flap (Correct answer)
- Split flap
- Krueger flap
Correct answer: Fowler flap
Fowler flaps both extend rearward (increasing wing chord and area) and deflect downward, producing the greatest increase in lift with significant drag.
Question 7: The lift coefficient (CL) of an airfoil at subsonic speeds is primarily controlled by:
- True airspeed
- Air density altitude
- Angle of attack (Correct answer)
- Wing aspect ratio
Correct answer: Angle of attack
The lift coefficient is primarily determined by the angle of attack, which controls the pressure distribution and circulation around the airfoil.
ATPL Principles of Flight and Aerodynamics 1
According to Bernoulli's principle, what happens to static pressure when airflow velocity increases over an airfoil?