POF 04

1. The initial response (or initial tendency) of an object, once the force that displaced it from equilibrium has been removed, determines the aircraft's __________ stability. The subsequent response of an object over a period of time, after it has been displaced from equilibrium by a disturbing force and after the disturbing force has been removed, determines the aircraft's __________ stability. A) static; dynamic. B) static; static. C) dynamic; dynamic. D) dynamic; static.

2. The more statically stable an aircraft is, the __________ manoeuvrable it is. A) less. B) more.

3. The essential pre-requisite for dynamic stability is __________ __________. A) static stability B) speed stability

4. An object with __________ static stability begins to move back towards equilibrium after being displaced. A) positive. B) neutral. C) negative. D) no.

5. An object with __________ static stability shows no tendency to move back to, or further diverge from, equilibrium after being displaced. A) neutral. B) positive. C) negative.

6. An object with __________ static stability diverges further from equilibrium after being displaced. A) negative. B) positive. C) neutral. D) no.

7. Study the diagram, then identify which 3 of the following statements are correct. [Abbildung erforderlich: siehe Original-PDF, Seite 2. Grafik nicht in dieser CSV enthalten.] A) Both A and B demonstrate positive static stability. B) Both A and B demonstrate positive dynamic stability. C) Both A and B are examples of periodic motion. D) A shows greater dynamic stability than B. E) B shows significantly greater static stability than A.

8. If an aircraft is to return to equilibrium after an initial disturbance, it must have __________ dynamic stability and it __________ positive static stability. A) positive; must have. B) positive; need not have. C) negative; must have. D) neutral; must have. E) negative; need not have.

9. The __________ is a point on an aerofoil where the size of the wing moment remains approximately constant at all angles of attack. A) aerodynamic centre B) MAC C) centre of pressure

10. The aerodynamic moment:Is zero at all angles of attack for a __________ aerofoil.Is negative for a __________ cambered aerofoil. A) symmetrical; positively. B) cambered; positively. C) symmetrical; negatively. D) cambered; negatively.

11. The principal contributor to longitudinal stability is the horizontal stabiliser. This device acts around the aircraft's __________ axis. A) lateral. B) normal. C) longitudinal.

12. The CG is normally __________ of the AC. This produces a __________ pitching moment. A) forward; nose-down. B) forward; nose-up. C) aft; nose-up. D) aft; nose-down.

13. Under normal conditions, in straight, level and unaccelerated flight, the horizontal stabiliser produces __________ pitching moment. A) a tail-down. B) a tail-up. C) no.

14. The greater the difference between CG and AC position, the __________ the pitching moment that must be counteracted by the stabiliser.The greater the distance between the AC and the stabiliser the __________ the moment arm. A) greater; greater. B) greater; lesser. C) lesser; lesser. D) lesser; greater.

15. The __________ can provide temporary balancing pitching moments, whereas the __________ is a permenant, natural contributor to longitudinal stability. A) elevator; stabiliser B) elevator; elevator C) stabiliser; elevator D) stabiliser; stabiliser

16. For an aerofoil with a given pitching moment coefficient, the pitching moment increases if the dynamic pressure, wing area or MAC increase. Both wing area and MAC are changed by extending __________. A) flaps. B) slats. C) slots.

17. The pitching moment is much greater at higher indicated airspeeds because: A) Dynamic pressure is proportional to V². B) Of the movement of the CP. C) Of the movement of the CG. D) Dynamic pressure is proportional to V.

18. An aircraft with an __________ CG tends to be less longitudinally stable and thus more responsive to elevator inputs. A) aft. B) forward. C) positive.

19. The furthest aft position of the CG for which the aircraft is not statically unstable is called the __________ __________. Static longitudinal stability is proportional to the distance between this and the CG. A) neutral point B) static margin C) aerodynamic centre

20. At the neutral point there is no pitching moment because the __________ and aerodynamic centre of the whole aircraft are co-located. A) CG B) CP

21. Which of the following statements about longitudinal stability are correct?Mark all correct answers. A) The manufacturer's forward CG limit ensures an arm that is long enough to produce a sufficiently strong restoring moment, but not so large that longitudinal stability becomes excessively strong. B) The CG position has a strong influence on longitudinal static stability, because its position determines the length of the arm between it and the AC. C) The difference between the aft CG limit and the neutral point is the static margin. D) A forward CG increases static stability.

22. Study the diagram. Identify which 2 of the following statements are correct. [Abbildung erforderlich: siehe Original-PDF, Seite 5. Grafik nicht in dieser CSV enthalten.] A) The most stable condition is shown by curve D and CG position 1. B) Neutral stability is shown in curve B. C) The most stable condition is shown by curve A and CG position 1. D) The most stable condition is shown by curve A and CG position 5.

23. Study the diagram. Identify which of the following statements are correct.Mark all correct answers. [Abbildung erforderlich: siehe Original-PDF, Seite 5. Grafik nicht in dieser CSV enthalten.] A) C, B and D identify trim positions at various forward speeds. B) A shows the stability curve for a given elevator deflection. C) B shows the trim position for 15° of up elevator. D) C shows a trim position for relative high forward speed (high alpha)

24. Which 2 of the following statements are correct? A) The horizontal stabiliser is by far the most important contributor to longitudinal static stability. B) An excessively aft CG reduces stick force stability. C) The wing contributes to longitudinal static stability because the AC is forward of the CG. D) The fuselage has a stable pitching moment because its CP almost always lies ahead of its CG. E) Increased wing camber increases longitudinal stability.

25. For manual controls, the amount of force needed to change elevator deflection __________ with IAS and __________ with altitude. A) increases; decreases. B) decreases; decreases. C) increases; increases. D) decreases; increases.

26. Stick force per g is the amount of control column force required to generate a given amount of __________. A) vertical acceleration. B) pitch. C) roll. D) trim force.

27. The danger of designing an aircraft with low stick force per g is that: A) It is very easy to overstress the aircraft. B) It affects longitudinal static stability. C) The aircraft becomes too stable. D) There is no feel.

28. Longitudinal stability __________ with altitude. A) reduces. B) increases. C) remains constant.

29. Stick force per g __________ with forward CG position. Stick force per g will be __________ under negative g if the aircraft is out of trim. A) increases; greater. B) decreases; greater. C) increases; less. D) decreases; less.

30. Which of the following are characteristics of short-period oscillations:Mark all correct answers. A) Large rates of change of pitch attitude, and angle of attack. B) Period can be anything from about 1 second to a few seconds. C) Little change in the airspeed or altitude. D) Dangerous because it can result in large load factors. E) Little change in alpha.

31. Which of the following are characteristics of long-period oscillations.Mark 2 correct answers. A) Large changes in altitude and speed (if not corrected). B) Little change in alpha. C) Period is several seconds. D) Large changes in load factor.

32. Static and dynamic stability decrease with altitude because of the reduced effect of __________ __________. A) aerodynamic damping B) the elevators

33. Positive static directional stability is the initial tendency to return to straight flight after a disturbance in __________ about the __________ axis. A) yaw; normal. B) roll; normal. C) pitch; normal.

34. Sideslip or yaw angle (β) is the angle between the __________ axis and the relative air flow. A) longitudinal B) lateral

35. If positive static directional stability is very strong it will be __________ to change the aircraft’s direction. A) difficult. B) easy. C) simple.

36. The coefficient of yawing moment (__________) is the yawing moment per unit of dynamic pressure (q), wing area (S) and wing span (b). A) CN B) CM C) CP

37. With positive directional static stability, as β becomes positive so too does CN. The aircraft yaws towards the relative air flow. As β becomes negative so too will CN. This is known colloquially as the __________ effect (named for a traditional wind direction indicating device). A) weathercock B) wind C) secondary

38. Aircraft with positive static directional stability create yawing moments in the __________ direction as the sideslip. A) same B) opposite C) parallel D) perpendicular

39. The principal design element contributing to directional stability is __________. A) the fin. B) dihedral. C) the rudder.

40. Study the diagram, identify which of the following statements is accurate. [Abbildung erforderlich: siehe Original-PDF, Seite 9. Grafik nicht in dieser CSV enthalten.] A) Curve B shows positive directional stability. B) Curve C shows positive directional stability. C) Curve B shows the effect of altitude on directional stability. D) Curve A shows positive directional stability.

41. At the trim point CN is zero. Provided there is no asymmetric thrust, or other aerodynamic loading, then β will be __________. A) zero. B) positive. C) negative.

42. Disregarding the restoring effect of fuselage area behind the CG, an increased distance between the fuselage CP and the CG is __________. A) destabilising. B) stabilising.

43. Which of the following statements about directional stability are correct?Mark all correct answers. A) Static directional stability increases with sweepback angle. B) A straight wing has a very small effect on directional stability. C) Fuselage pitch angle has little effect on directional stability. D) The fuselage becomes destabilising at large β angles. E) Directional stability increases slightly with fin sweepback.

44. An aircraft has positive static __________ stability if, after a displacement in roll, its initial tendency is to return to wings level. A) lateral B) directional C) perpendicular

45. Study the diagram. Identify which of the following statements about lateral stability are correct:Mark all correct answers. [Abbildung erforderlich: siehe Original-PDF, Seite 10. Grafik nicht in dieser CSV enthalten.] A) Curve C indicates instability. B) Curve B indicates stability. C) Curve B could indicate the effect of altitude when compared with Curve A. D) A horizontal curve indicates neutral stability. E) Curve A indicates stronger stability than Curve B.

46. Which of the following statements are correct?Mark all correct answers. A) Dihedral increases static lateral stability. Anhedral reduces it. B) A high wing increases static lateral stability. A low wing reduces it. C) Sweep angle increases lateral static stability. D) A high vertical fin increases static lateral stability. E) A dorsal fin reduces dihedral effect, a ventral fin contributes to it.

47. An uncoordinated displacement in roll results in __________. A) sideslip. B) pitch down moments.

48. __________ instability can occur when directional stability is strong and lateral stability is weak. A) Spiral B) Turning

49. Because of the risk of Dutch Roll, an aircraft must not be dispatched if its __________ is unserviceable. A) yaw damper B) autopilot C) flight director

50. Increased Mach number __________ the tendency for Dutch roll because __________ compressibility effects create higher asymmetric drag on the wings. A) increases; increased B) increases; reduced C) decreases; increased D) decreases; reduced

51. __________ angle is the angle at which an aircraft is inclined about its longitudinal axis with respect to the horizontal. A) Bank B) Yaw C) Sideslip

52. What happens following the deployment of leading edge devices, while the trailing edge flaps remain retracted?

53. Why are Vortex generators mounted on the upper wing surface?

54. When an aircraft's Centre of Gravity (CG) is at the forward limit, the longitudinal static stability is (1) _____ and the pitch control forces are (2) _____ than when the CG is at the aft limit.

55. Considering the longitudinal stability of an aeroplane, why does the stick force per 'g' decrease with pressure altitude, at a given IAS?

56. Longitudinal static stability is created by the fact that the:

57. Flying an aircraft with a joystick, if a small displacement of the joystick results in a large change in pitch/bank angle, the aeroplane is described as being:

58. When an aeroplane has zero static longitudinal stability, the pitching moment coefficient CM versus angle of attack line:

59. As the stability of an aeroplane decreases:

60. An aeroplane which has low static lateral stability is more prone to have controllability problems in:

61. Positive static lateral stability is the tendency of an aeroplane to:

62. Static lateral stability will be increased by:

63. Consider two elevator control systems: 1 is fitted with a trim tab. 2 is fitted with fully powered hydraulic controls and an adjustable horizontal stabiliser. For both cases and starting from a trimmed condition, how will the neutral position of the control column change, after trimming for a speed increase?

64. Aeroplane manoeuvrability increases for a given control surface deflection when:

65. The pilots prepare and trim the aircraft for take-off, setting the trim for a CG position at 12% of the MAC. But due to an error, the real position of the CG is at 24% of the MAC. What could this cause?

66. Rotation around the longitudinal axis is called:

67. On an airliner with stabiliser trim, an extra baggage container is loaded into the front hold, forward of the CG. When the pilot makes an adjustment to the take-off trim, how will the stabiliser move?

68. In a skidding turn (the nose pointing inwards), compared with a co-ordinated turn, the bank angle (i) and the "ball" or slip indicator (ii) are respectively:

69. The pilot of an aircraft changes its heading to the right, from 214° to 334° and makes a rate-1 turn. The duration of this manoeuvre is:

70. You are departing an airfield surrounded by mountainous terrain on three sides. The departure procedures after take-off from the active runway require a 180 degree turn onto the reciprocal of runway heading. Assuming the turn is made with the maximum allowed bank angle of 30 degrees, the pilot should ensure terrain clearance by:

71. Two identical aeroplanes A and B, with the same mass, are flying steady level co- ordinated 20 degree bank turns. If the TAS of A is 130 kt and the TAS of B is 200 kt: