BAvn Bachelor of Aviation Bachelor of Aviation Theory of Flight 4 — Questions and Answers
Question 1: What is 'aeroelastic divergence' and under what condition does it typically occur?
- Aileron reversal caused by wing twist exceeding aerodynamic restoring moments at high dynamic pressure (Correct answer)
- Structural failure of the empennage due to flutter at Vne
- Loss of control authority due to ice contamination on the leading edge
- Wing bending that causes the engines to rotate into the airstream
Correct answer: Aileron reversal caused by wing twist exceeding aerodynamic restoring moments at high dynamic pressure
Divergence occurs when aerodynamic twisting moments exceed the wing's structural torsional stiffness, causing progressive uncontrolled twisting, typically at high dynamic pressure.
Question 2: How does ground effect influence an aircraft's induced drag during landing?
- Ground effect increases induced drag, requiring more thrust to maintain approach speed
- Ground effect reduces induced drag by disrupting wingtip vortex formation near the surface (Correct answer)
- Ground effect has no measurable influence on induced drag below 50 feet AGL
- Ground effect increases parasite drag, partially offsetting the reduction in induced drag
Correct answer: Ground effect reduces induced drag by disrupting wingtip vortex formation near the surface
Proximity to the ground inhibits the downward development of wingtip vortices, reducing induced drag and causing the aircraft to 'float' during flare.
Question 3: What is the relationship between angle of attack and the coefficient of lift (CL) for a conventional airfoil below the stall?
- CL decreases linearly with increasing angle of attack
- CL increases approximately linearly with increasing angle of attack (Correct answer)
- CL increases exponentially with increasing angle of attack
- CL is independent of angle of attack below 10 degrees
Correct answer: CL increases approximately linearly with increasing angle of attack
Below the stall, CL increases approximately linearly with angle of attack at a rate of about 0.1 per degree for thin airfoils in subsonic flow.
Question 4: Which of the following correctly describes 'propeller torque effect' and its primary correction?
- The propeller pulls the nose up; corrected by elevator trim
- Reaction torque causes the aircraft to roll opposite to propeller rotation; corrected by aileron trim (Correct answer)
- Gyroscopic precession causes a yaw when the nose pitches; corrected by rudder input
- P-factor causes accelerated slipstream on one blade; corrected by engine offset
Correct answer: Reaction torque causes the aircraft to roll opposite to propeller rotation; corrected by aileron trim
Newton's third law means a clockwise-rotating propeller (viewed from behind) produces a counterclockwise rolling tendency in the airframe, corrected by aileron trim.
Question 5: What is the primary aerodynamic purpose of leading-edge slats on a high-lift system?
- Increase the camber of the wing to generate more lift at cruise speeds
- Allow the wing to operate at a higher angle of attack before stalling by re-energizing boundary layer flow (Correct answer)
- Reduce the stall speed by decreasing the wing's angle of incidence
- Increase parasite drag to act as an air brake during descent
Correct answer: Allow the wing to operate at a higher angle of attack before stalling by re-energizing boundary layer flow
Slats extend forward and down, allowing high-energy air to flow through the slot and re-energize the boundary layer, delaying separation to a higher angle of attack.
Question 6: At what point on the V-n (velocity-load factor) diagram is the aircraft simultaneously at maximum structural load and minimum possible airspeed for that load?
- VNO (normal operating speed)
- VA (maneuvering speed) (Correct answer)
- VD (design dive speed)
- VF (design flap speed)
Correct answer: VA (maneuvering speed)
Maneuvering speed (VA) is the corner velocity where the positive limit load factor is reached exactly at the stall, combining maximum G with minimum speed.
Question 7: What distinguishes laminar flow from turbulent flow in boundary layer aerodynamics?
- Laminar flow has higher skin friction drag but delays separation better than turbulent flow
- Turbulent flow is more resistant to adverse pressure gradients but produces higher skin friction drag than laminar flow (Correct answer)
- Laminar flow produces higher drag and separates earlier, making it undesirable on wings
- Turbulent flow always separates earlier under adverse pressure gradients
Correct answer: Turbulent flow is more resistant to adverse pressure gradients but produces higher skin friction drag than laminar flow
Turbulent boundary layers have higher momentum near the surface, making them more resistant to separation under adverse pressure gradients, at the cost of greater skin friction.
BAvn Bachelor of Aviation Bachelor of Aviation Theory of Flight 4
What is 'aeroelastic divergence' and under what condition does it typically occur?