MODULE 1: AERODYNAMICS & AIRFOILS
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Câu 1. The angle of attack is the angle determined by the...
- A. Chord line and the Relative airflow.
- B. Rotor speed plus the speed of the helicopter.
- C. Aerofoil chord and the reference plane.
- D. Chord line and the shaft axis.
Câu 2. Thickness/chord ratio of an aerofoil section is expressed in percentage of...
- A. chord.
- B. Blade surface.
- C. Wingspan.
- D. Thickness.
Câu 3. The SI unit of work is?
- A. N.
- B. N/m.
- C. J.
- D. Pa.
Câu 4. On approach to land, you encounter a parcel of air subjected to a temperature inversion. How could that affect your performance?
- A. Lower temperature than expected, higher performance.
- B. Higher temperature than expected, so Lower aerodynamic Performance with possible sinking below desired Approach path.
- C. Higher temperature, higher performance.
- D. Lower temperature, lower performance.
Câu 5. Parasite and profile drag change...?
- A. proportionally to V.
- B. inversely to V2.
- C. inversely to V.
- D. Proportionally to V2.
Câu 6. Which of the following is the greatest factor causing lift?
- A. Increased pressure below aerofoil.
- B. Suction above the Aerofoil.
- C. Increased airflow velocity below the aerofoil.
- D. Decreased airflow velocity above the aerofoil.
Câu 7. The camber line of a biconvex symmetrical section is...
- A. curved towards the upper surface.
- B. a circular arc. 1 / 16 A.
- C. curved towards the lower surface.
- D. common with the Chord Line.
Câu 8. Induced drag is created by...
- A. the effect of the rotor downwash on the upper part of the fuselage.
- B. the vortices that are produced at the tips of the blades.
- C. accelerating the fuselage through air.
- D. the pressure differential between upper and lower Aerofoil surfaces.
Câu 9. The transition point on a helicopter blade is the point where the...
- A. smooth flow becomes turbulent.
- B. turbulent flow becomes separated.
- C. laminar flow becomes turbulent.
- D. smooth flow becomes disturbed.
Câu 10. Profile drag is caused by...
- A. differences in pressure between stagnation point and trailing edge.
- B. the action of the Blades moving through the air.
- C. differences in pressure between upper and lower surfaces.
- D. tip vortices.
Câu 11. What is the formula for lift?
- A. L = CL2 rho2 VS.
- B. L = CL 1/2 rho V2 S.
- C. L = CL rho V2 S.
- D. L = CL2 rho V2 S.
Câu 12. In the case of a symmetrical aerofoil...
- A. its characteristics make it totally unsuitable for main rotor.
- B. induced drag will not be generated at any angle of attack.
- C. pitching moment variations due to Centre of pressure Movement are small.
- D. there is no downwash at any angle of attack.
Câu 13. The total reaction created by air flowing over a helicopter blade is resolved into two forces. These two forces are...
- A. lift and rotor thrust.
- B. lift and rotor drag.
- C. lift and drag.
- D. Rotors drag and Rotor thrust.
Câu 14. Interference drag is a component of...
- A. skin friction drag. 2 / 16 A.
- B. induced drag.
- C. Parasite drag.
- D. form drag.
Câu 15. Rotor blade sections are designed so that the centre of pressure...
- A. has a large degree of movement.
- B. Is normally positioned close to the feathering axis.
- C. moves forward and backward according to rotor speed.
- D. can move forward rapidly.
Câu 16. Which statement is true regarding velocity and induced drag of an aerofoil?
- A. Induced drag decreases as Velocity increases.
- B. Induced drag remains constant as velocity increases.
- C. Induced drag remains constant.
- D. Induced drag increases as velocity increases.
Câu 17. How does the aspect ratio of a blade influence induced drag?
- A. experiences less induced drag.
- B. A high aspect ratio increases induced drag.
- C. Aspect ratio has no effect on induced drag.
- D. Low aspect ratio produces less tip vortices.
Câu 18. Washout may be used to balance aerodynamic loads across the blade span. It...
- A. high angle of attack at root and low at tip.
- B. low angle of incidence at root and high at tip.
- C. low angle of attack at root and high at tip.
- D. has a high angle of incidence at the root and a low angle of Incidence at the tip.
Câu 19. Why is it important to keep a blade's surface clean?
- A. A clean blade is smoother, transition point occurs aft, increasing laminar boundary.
- B. Transition point moves forward quickly.
- C. Increases boundary layer thickness.
- D. Reduces structural weight.
Câu 20. MODULE 2: HIGH-SPEED FLIGHT & COMPRESSIBILITY The purpose of the swept back tip region in some modern rotor blade designs is to...
- A. reduce blade tip stresses.
- B. improve high Speed Performance.
- C. reduce blade tip vortices.
- D. reduce the amount of flapping up.
Câu 21. How is Mach Number determined?
- A. Air speed and Air Temperature (TAS / Local Speed of Sound).
- B. Air pressure and air temperature.
- C. Air speed and air pressure.
- D. Air speed and air density.
Câu 22. The appearance of a shockwave on a blade element...
- A. increases the Drag and Decreases the lift.
- B. increases drag and increases lift.
- C. decreases drag and increases lift.
- D. decreases drag and decreases lift.
Câu 23. What happens to the centre of pressure of an aerofoil after a shockwave forms on the upper surface?
- A. Unchanged.
- B. Moves Rearward.
- C. Moves forward.
- D. Disappears.
Câu 24. To increase the critical Mach number of a conventional aerofoil section...
- A. increase leading edge radius.
- B. thickness to chord ratio Should be Reduced.
- C. increase camber.
- D. fly at higher angle of attack.
Câu 25. Why is sweep back often applied to the tip of modern rotor blades?
- A. To reduce compressibility effects on retreating blade.
- B. To reduce loss of thrust in hover.
- C. To reduce the Mach effects on the Advancing Blade.
- D. To reduce crosswind susceptibility.
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