Die Lösungen müssen manuell überpüft werden. Die Buchstaben stimmen nicht mehr überein.

HELI Final Test 2015, Winterthur 17.06.2015 NAME: Mark the best answer. A B C D A B C D Die Lösungen müssen manuell überpüft werden. Die Buchstaben stimmen nicht mehr überein. 1

1 Principles of Flight 1.1 Generation of a Lift Force / Induced Velocity 1. How could we justify that low Disc Loading provides high aerodynamic efficiency in hover flight? (A) Power Loading, a measure of aerodynamic efficiency, decreases when Disc Loading decreases. (B) Power Loading, a measure of helicopter performance, increases when Disc Loading decreases. (C) Power Loading, a measure of aerodynamic efficiency, increases when Disc Loading increases. (D) Power Loading, a measure of aerodynamic efficiency, increases when Disc Loading decreases. 2. What is the relation between Induced Velocity and Disc Loading? (A) Induced Velocity is independent of Disc Loading. (B) Induced Velocity is proportional to the square root of Disc Loading. (C) Induced Velocity is inversely proportional to the square root of Disc Loading. (D) Induced Velocity is proportional to the square root of Disc Loading but only in forward flight. 3. What is the best definition of Figure of Merit (FM) of a rotor? (A) FM compares the power required by a rotor to the power required by an ideal rotor without losses. (B) FM compares the power required by a rotor to the power required by an ideal rotor without Induced Velocity. (C) FM compares the power required by a rotor to the power required by a rotor with infinite radius. (D) FM compares the power required by a rotor to the power required by a wing in order to generate the same Lift force. 4. What is the relation between the Induced Velocity and the horizontal speed of a helicopter? (A) Induced Velocity tends to decrease with increasing horizontal helicopter speed but increases with increasing vertical helicopter speed. (B) Induced Velocity is independent of helicopter speed. (C) Induced Velocity tends to decrease with increasing helicopter speed. (D) Induced Velocity tends to increase with increasing helicopter speed. 5. How could the Vortex Ring (VR) flight condition be described best? (A) VR refers to a dangerous but stable rotor condition where irregular air re-circulation through the rotor disc is due to the fact that Induced Velocity and Rate of Descent have a comparable magnitude. (B) VR refers to an unstable rotor condition where irregular air re-circulation through the rotor disc is due to the fact that Induced Velocity and Rate of Descent have a comparable magnitude. (C) VR refers to an unstable rotor condition where mast bumping is due to the fact that Induced Velocity and Rate of Descent have a comparable magnitude. (D) VR refers to an unstable rotor condition where irregular air re-circulation through the rotor disc is due to the fact that Induced Velocity and horizontal speed have a comparable magnitude. 2

6. Tail wind during the approach may cause the helicopter to enter the Vortex Ring condition. This is due to tail wind increasing the amount of air flowing through the rotor disc upwards (from below the rotor disc to above it). How could this lead to Vortex Ring? (A) Tail wind artificially increases the rate of descent. (B) Tail wind increases helicopter speed. (C) Tail wind artificially decreases the rate of descent. (D) Wind may be turbulent. 7. How can the Windmilling state be best described? (A) Blade flapping angles and rate of descent are such that the aerodynamic forces generated drives the rotor. (B) Blade pitch angle and rate of descent are such that the aerodynamic forces are zero. (C) Blade pitch angle and rate of descent are such that the aerodynamic forces generated drives the rotor. (D) Blade pitch angle and rate of descent are such that the aerodynamic forces generates the lift required. 1.2 Main Rotor Aerodynamics 8. What is at the origin of the asymmetry of aerodynamic forces in forward flight? (A) The combination of rotation and rate of descent, observed in a frame of reference rotating with the blade. (B) The combination of rate of descent and forward speed, observed in a frame of reference rotating with the blade. (C) The combination of rotation and forward speed, observed in a frame of reference rotating with the blade. (D) The combination of rotation and forward speed. 9. What is the relation between flapping and a blade s angle of attack? (A) The angle of attack decreases, when a blade flaps upwards, but only in hover flight. (B) The angle of attack does not depend on flapping. (C) The angle of attack decreases, when a blade flaps upwards. (D) The angle of attack increases, when a blade flaps upwards. 10. What are the causes of the so-called flapback of the rotor in forward flight? (A) Flapback normally indicates the excessive flapping of the blades due to lift asymmetry in forward flight. (B) Flapback normally indicates the tilting backwards of the rotor disc due to lift asymmetry in forward flight. (C) Flapback normally indicates the tilting backwards of the rotor disc due to compressibility effects. (D) Flapback normally indicates the tilting backwards of the rotor disc due to the pilot operating on the longitudinal cyclic pitch control. 3

11. Which physical phenomena may be listed among the compressibility effects on the advancing blade? (A) Generation of shock waves along the blade and strong increase of Induced Velocity. (B) Stall due to excessive angle of attack of the outboard part of the blade and significant increase of the drag force. (C) Generation of a shock wave on the inboard part of the blade, significant increase of the drag force and possibly separation of the boundary layer. (D) Generation of a shock wave on the outboard part of the blade, significant increase of the drag force and possibly separation of the boundary layer. 12. Are compressibility effects relevant on the retreating blade? (A) Not in the normal range of helicopter speed, even if Mach number on the retreating blade may also reach values of 0.7-0.8. (B) As the helicopter approaches its max horizontal speed, Mach number on the retreating blade may be close to 1.0. (C) Not in the normal range of helicopter speed, as the flow on the whole retreating blade is always stalled. (D) Not in the normal range of helicopter speed, as Mach number on the retreating blade is limited. 13. What is the action of the collective pitch control on the blades angle of attack? (A) Collective pitch control increases the pitch angle on the retreating blade and hence also the angle of attack on that blade. (B) Collective pitch control increases the pitch angle on all blades simultaneously and hence it decreases the angle of attack. (C) Collective pitch control increases the pitch angle on all blades simultaneously and hence also the angle of attack. (D) Collective pitch control does not affect the angle of attack but only the pitch angle. 14. The tip of the advancing blade is the rotor area where the highest relative airspeed is observed in forward flight. What might be the phenomena affected by the tip geometry at high speed? (A) Separation of the boundary layer. (B) Strength and position of the shock wave and the position of the tip vortex. (C) Strength and position of the shock wave. (D) Strength and the position of the tip vortex. 4

15. As a results of the physical phenomena mentioned in the previous question, which environmental aspects may be strongly affected by the blade tip geometry? (A) Autorotation performance. (B) Generation of noise. (C) Generation of noise and safety for ground personnel. (D) Generation of noise, safety for ground personnel and Autorotation performance. 1.3 Rotor Dynamics 16. What are the causes of the blade rotation about the lead/lag hinge? (A) The flapping of the blade (due to gyroscopic effects) and the drag force. (B) The pitching of the blade (due to gyroscopic effects) and the drag force. (C) The cyclic pitch control. (D) The flapping of the blade. 17. How can the rotor disc (tip-path-plane) be oriented by the pilot? (A) By means of the cyclic pitch control which lets the blades lead/lagging. (B) By means of the collective pitch control which lets the blades flapping. (C) By means of the cyclic pitch control which lets the blades flapping. (D) By means of the cyclic pitch control which lets the blades rotate about the pitch axis. 18. Is the rotation of the main rotor blades about the flapping hinges free or constrained (= fixed) during the flight? (A) Mechanically constrained, otherwise the blades would flap excessively. (B) Mechanically constrained. The moment of aerodynamic forces about the flapping hinge is balanced by the centrifugal forces. (C) Free. The moment of the aerodynamic forces about the flapping hinge is balanced by Coriolis forces. (D) Free. The moment of the aerodynamic forces about the flapping hinge is balanced by the centrifugal forces. 19. How is the amplitude of longitudinal flapping of tail rotors blades in forward flight normally kept within a reasonable range (= limited)? (A) By manually operating the tail rotor longitudinal cyclic pitch control. (B) By the use of an electronic control system. (C) By mechanically coupling flapping and pitching so that flap-up causes a pitch angle reduction. (D) By reducing the helicopter speed. 5

20. How can Ground Resonance (GR) be best described? (A) GR is a dynamic instability caused by the oscillations of the helicopter on the landing gear, on the ground. (B) GR is a dynamic instability caused by a coupling of the rotor head motion and the oscillations of the helicopter on the landing gear, on the ground. (C) GR is a dynamic instability caused by a coupling of the blades lead/lag motion and the oscillations of the helicopter in flight. (D) GR is a dynamic instability caused by a coupling of the blades lead/lag motion and the oscillations of the helicopter on the landing gear, on the ground. 21. How is Ground Resonance generally prevented on modern helicopters? (A) Hydraulic dampers are installed on the main rotor head (about the lead/lag hinges), on the landing gear suspensions as well as on the tail rotor head (about the flapping hinge). (B) Hydraulic dampers are installed on the main rotor head (about the lead/lag hinges) as well as on the landing gear suspensions. (C) Hydraulic dampers are installed on the landing gear suspensions. (D) Hydraulic dampers are installed on the main rotor head (about the lead/lag hinges). 22. What are the functions of Swashplates (= Taumelscheiben)? (A) Swashplates position and orientation determine the angle of attack of all blades. (B) Swashplates rotation around the rotor mast determines the pitch angles of all blades. (C) The fixed swashplate determines the collective pitch angle, the rotating swashplate determines the cyclic pitch angle. (D) Swashplates position and orientation determine the pitch angles of all blades. 23. Can Ground Resonance also occur on helicopters without a semi-rigid rotor head (see-saw)? (A) Yes. (B) Yes, but only if one or more hydraulic dampers are defective. (C) It depends on the type of landing gear. (D) No. 24. Why are Tail Rotors normally equipped with collective pitch control? (A) To control the orientation of the Tail Rotor disc. (B) To control the longitudinal flapping of the Tail Rotor. (C) To control the force generated by the Tail Rotor. (D) To control the power required by the Tail Rotor. 25. What is the phase delay between flapping and lead/lagging (lead/lagging following flapping)? 6

(A) Normally approximately 90. (B) Normally approximately 180. (C) Almost zero. (D) Normally approximately 45. 26. Flap and lead/lag hinges have been introduced also to limit the mechanical stresses in the blade root area. How does this happen? (A) The centrifugal forces balance the aerodynamic forces. (B) The hinges allow the rotation about their axis: the bending moment is consequently zero. (C) The hinges allow the rotation about their axis: all forces are consequently zero in correspondence of the hinge. (D) The aerodynamic forces are much lower thanks to the introduction of the flapping hinge. 1.4 Rotor stability and control 27. Is an isolated rotor stable with respect to longitudinal translations? (Assumption: the rotor rotates on a horizontal plane; a longitudinal velocity disturbance is considered). (A) The isolated rotor is statically unstable but dynamically stable. (B) The isolated rotor is statically and dynamically stable. (C) The isolated rotor is statically and dynamically unstable. (D) The isolated rotor is statically stable but dynamically unstable. 28. Is an isolated rotor stable with respect to lateral translations? (Assumption: the rotor rotates on a horizontal plane; a lateral velocity disturbance is considered). (A) The isolated rotor is statically and dynamically unstable. (B) The isolated rotor is statically and dynamically stable. (C) The isolated rotor is statically stable but dynamically unstable. (D) The isolated rotor is statically unstable but dynamically stable. 29. What can be said about the directional stability (yaw) of helicopters? (A) Helicopters are statically and dynamically stable. (B) Helicopters are statically and dynamically unstable. (C) Helicopters are statically stable and may also be dynamically stable. (D) Helicopters are statically unstable and may also be dynamically unstable. 7

30. What can play a major role in the different behaviour of helicopter and isolated rotors, also in this case with respect to directional stability (yaw)? (A) The presence of the Tail Rotor. (B) The presence of a fin (Seitenflosse). (C) The fuselage inertia. (D) The presence of a tailplane (Höhenflosse). 31. How can helicopter stability be improved? (A) By means of control systems which use sensors to capture the helicopter motion and have small authority on cyclic and collective controls. (B) By modifying of the rotor head geometry. (C) By increasing the flapping hinge offset. (D) By means of control systems which use sensors to capture the helicopter motion and move a small rudder accordingly. 32. How is directional control (yaw) obtained in (conventional) helicopters? (A) Main Rotor longitudinal cyclic pitch control. (B) Main Rotor collective pitch control. (C) Tail Rotor collective pitch control. (D) Main Rotor directional cyclic pitch control. 33. How is longitudinal control (pitch) axis obtained in (conventional) helicopters? (A) Main Rotor collective pitch control. (B) Tail Rotor longitudinal cyclic pitch control. (C) Tail Rotor collective pitch control. (D) Main Rotor longitudinal cyclic pitch control. 34. How is longitudinal control (pitch) obtained on tandem helicopters? (A) Differential collective pitch control (applying the same change in collective pitch on front and rear rotors). (B) Deflection of the elevator. (C) Longitudinal cyclic control (applying the same change in longitudinal cyclic pitch on front and rear rotor). (D) Differential collective pitch control (applying opposite changes in collective pitch on front and rear rotors). 8

2 Aircraft General Knowledge 2.1 Main Rotor System 35. Which are the main types of rotor head? (A) Semi-rigid (see-saw), articulated, hingeless, headless. (B) Semi-rigid (see-saw), articulated, elastomeric. (C) Semi-rigid (see-saw), articulated, hingeless, bearingless. (D) Rotor with pitch control, rotor heads without pitch control. 36. What is the flapping hinge offset? (A) It is the distance between the flapping hinge and feathering hinge axes. (B) It is the distance between the flapping hinge and lead/lag hinge axes. (C) It is the distance between the flapping hinge axis and the centre of the rotor mast. (D) It is the distance between the flapping hinge and rotating swashplate. 37. What is the relevance of the flapping hinge offset with respect to flight dynamics? (A) None. (B) The larger the flapping hinge offset, the smaller the control moments available to the pilot. (C) The larger the flapping hinge offset, the more dynamically stable is the rotor. (D) The larger the flapping hinge offset, the larger the control moments available to the pilot. 38. What are the consequences for the control moments if a low-g helicopter manoeuvre is performed with a semirigid rotor head (flapping hinge offset = 0)? (A) Control moments are slightly smaller but there are significant consequences. (B) The rotor thrust is small and so are the control moments which the pilot can generate. (C) No differences with respect to level flight or high-g manoeuvres. (D) The rotor thrust is large and so are the control moments which the pilot can generate. 39. Do hingeless or bearingless rotor heads have flapping hinges? (A) Yes. However, the rotation of the blade is accommodated by special elastomeric bearings (Lager). (B) No. However, they have lead/lag hinges only. (C) No, blades are rigidly attached to the rotor head. (D) Yes. However, we speak of virtual hinges since the rotation of the blade is allowed by the elastic deformation of the blade root to rotor head attachments. 9

40. Do hingeless rotor heads have a feathering hinge (the axis about which the blade pitch can be controlled)? (A) No, the angle of attack can be modified by flapping the blades only. (B) No, the pitch angle is adjusted by aerodynamic tabs. (C) No, the blades have a fixed pitch angle in this case. (D) Yes. 41. Do bearingless rotor heads have a feathering hinge (the axis about which the blade pitch can be controlled)? (A) No, the blades have a fixed pitch angle in this case. (B) No, the pitch angle is adjusted by aerodynamic tabs. (C) No, the angle of attack can be modified by flapping the blades only. (D) Yes but a virtual one, since feathering of the blade is accommodated by the torsion of the blade root to rotor head attachment. 2.2 Anti Torque System 42. What are the main advantages of the Fenestron tail rotor type? (A) Low noise level. (B) Safety for ground personnel. (C) Safety for ground personnel, low noise level. (D) Safety for ground personnel, low noise level, aerodynamic efficiency. 43. What are the main advantages of a conventional tail rotor (with respect to Fenestron and NOTAR)? (A) Higher aerodynamic efficiency, lower noise level, higher safety for ground personnel. (B) Higher aerodynamic efficiency, lower noise level. (C) Higher aerodynamic efficiency, higher control power at high speed. (D) Higher aerodynamic efficiency, higher control power at high speed, lower noise level. 44. The NOTAR system is a particular type of anti-torque system. How could it be described? (A) Pressurized air is blown into the tail boom. Lateral force is obtained by means of an orientable rudder. (B) Pressurized air is blown into the tail boom. Lateral force is obtained by means of an orientable air outlet. (C) Pressurized air is blown into the tail boom. Lateral force is obtained by deviating the freestream airflow through the so-called Coanda effect. (D) Pressurized air is blown into the tail boom. Lateral force is obtained by means of an orientable air outlet and deviating of the main rotor downwash through the so-called Coanda effect. 10

45. Co-axial helicopters normally counter rotating rotors and do not have a tail rotor. How could this be explained? (A) The tail rotor would provide an excessive mechanical complexity. (B) The engine exhaust is normally deviated laterally in order to generate a sufficiently large anti-torque moment. (C) The directional control can be obtained by differential collective pitch. (D) The torque exchanged between each of the rotors and the gearbox has opposite sign. If the two contributions are equal, the total torque is zero. 46. Do helicopters need the anti-torque system also during Autorotation (AR)? (A) No, because engines are not providing any power. (B) Yes, because engines may provide some residual amount of power to the rotor. (C) No, because the tail rotor is disengaged during AR. (D) Yes, because the torque exchanged between rotor and gearbox is not exactly zero during AR; the rotor does provide a small amount of power to the gearbox e.g. to keep hydraulics running. 47. What is the action of the the pilot using the pedals during normal flight? (A) Controlling Main Rotor collective pitch. (B) Controlling Tail Rotor longitudinal cyclic pitch. (C) Controlling Tail Rotor blades angle of attack. (D) Controlling Tail Rotor collective pitch. 2.3 Engines and Transmission 48. What are the special requirements for a turboshaft engines to be installed on a helicopter (with respect to the installation on a fixed wing aircraft)? (A) Large bank and pitch angles, no easy accessible undisturbed airflow for cooling, max continuous power never required thanks to ground effect. (B) Long periods of time at high power setting, large bank and pitch angles, FADEC absolutely necessary. (C) Long periods of time at high power setting, large bank and pitch angles, no easy accessible undisturbed airflow for cooling. (D) Large bank and pitch angles, no easy accessible undisturbed airflow for cooling, very high max continuous power for hover in ground effect. 49. How many gearboxes can one normally find on a conventional helicopter? (A) Main gearbox, intermediate gearbox, tail gearbox. Additionally, engines may have auxiliary gearboxes. (B) Main gearbox, intermediate gearbox, tail gearbox. (C) Main gearbox, intermediate gearbox, central gearbox, tail gearbox. (D) Main gearbox, tail gearbox. Additionally, engines may have auxiliary gearboxes. 11

50. Are helicopters gearboxes maintenance intensive (= does gearbox maintenance involve a large workload and high costs)? (A) Yes, but only the ones not equipped with electronic monitoring systems. (B) No. (C) Only in multi-engined helicopters. (D) Yes. 51. What are the consequences of a mechanical failure in the main gearbox? (A) If the helicopter is multi-engined and Cat. A, the pilot can continue flying. (B) It may force the pilot to disconnect the Tail Rotor. (C) It may force the pilot to perform an emergency landing by Autorotation. (D) None. The pilot must only disconnect the main gearbox and continue flying. 52. What are the difficulties met by the designers of a helicopter main gearbox? (A) Accommodate a reduction ratio (Untersetzung) of about 100 at a limited cost. (B) Accommodate a reduction ratio (Untersetzung) of about 100 in limited space and mass. (C) Accommodate a reduction ratio (Untersetzung) of about 100 in limited space and mass. Additionally, the design must keep noise level to a minimum. (D) Accommodate a reduction ratio (Untersetzung) of about 100 in limited space and mass. Additionally, the design must minimize maintenance and maximize reliability. 53. How can the reliability of the helicopter gearboxes be improved and the maintenance costs reduced? (A) By the introduction of better suited metallic materials. (B) By the introduction of a control system which reduces vibrations. (C) By the introduction of a monitoring system, which measures wear and tear (Verschleiss) in the various components and sends warnings as soon as one needs replacement. (D) By the introduction of a monitoring system, which measures vibrations in the various components and counterbalances them with small shakers. 12

3 Performance Classes and Helicopters Categories 54. What are the differences between Category A and Category B helicopters? (A) Cat A helicopters, unlike Cat. B, have a significant excess power. (B) Cat. B helicopters are always single engine. (C) Cat A helicopters, unlike cat B, have a certain stay-up capability in case of (D) Cat A helicopters, unlike cat. B, are always multi engine. 55. Why are all single engine helicopters Cat. B? (A) Because they are less reliable. (B) Because they have less excess power. (C) Because they have less available power. (D) Because they have no stay-up capability in case of 56. What are Performance Class 1 operations? (A) Flights, or portion of flights, during which an emergency landing is never required in the presence of an (B) Flights, or portion of flights, during which an emergency landing may be required in the presence of an engine failure, but only when flying over hostile territory. (C) Flights, or portion of flights, during which an emergency landing is always required in the presence of an (D) Flights, or portion of flights, during which an emergency landing may be required in the presence of an 57. What are Performance Class 2 operations? (A) Flights, or portion of flights, during which an emergency landing is always required in the presence of an (B) Flights, or portion of flights, during which an emergency landing is never required in the presence of an (C) Flights, or portion of flights, during which an emergency landing may be required in the presence of an (D) Flights, or portion of flights, during which an emergency landing may be required in the presence of an engine failure, but only when flying over hostile territory. 13

58. What are Performance Class 3 operations? (A) Flights, or portion of flights, during which an emergency landing may be required in the presence of an (B) Flights, or portion of flights, during which an emergency landing is never required in the presence of an (C) Flights, or portion of flights, during which an emergency landing is always required in the presence of an (D) Flights, or portion of flights, during which an emergency landing may be required in the presence of an engine failure, but only when flying over hostile territory. 4 Helicopters performances 59. Which physical phenomena can limit the maximum forward speed of helicopters? (A) Retreating blade stall. (B) Compressibility effects on advancing blade. (C) Compressibility effects on advancing blade and retreating blade stall. (D) Compressibility effects and stall of advancing blade. 60. Conventional helicopters need a tail rotor for directional control. How does the power required by the tail rotor relate to the total power required? (A) It may require up to approximately 1% of the total power required, depending on the flight condition. (B) It may require up to approximately 10% of the total power required, depending on the flight condition. (C) Tail Rotor normally works in windmilling condition and does not require any power to work. (D) It may require up to approximately 50% of the total power required, depending on the flight condition. 61. What are the main contributions to the power required of a helicopter? (A) Induced power, parasitic power, viscous losses, air conditioning, hydraulic power, transmission losses. (B) Induced power, parasitic power, air conditioning, anti-torque system power, transmission losses. (C) Induced power, parasitic power, viscous losses, losses in the gearboxes. (D) Induced power, parasitic power, viscous losses, anti-torque system power, transmission losses. 62. What is the largest contribution to the power required of a helicopter in hover flight? (A) Induced power only out-of-ground-effect. Parasitic power when hovering in-ground-effect. (B) Induced power. (C) Aircraft systems (air conditioning etc). (D) Viscous losses or compressibility effects, depending on the blade section aerofoils. 14

63. What is Ground Effect (GE) in a conventional helicopter and what are the consequences on power required? (A) GE generates a low-pressure air cushion between rotor and ground. As a consequence, the power required to generate a Thrust force T is normally smaller. (B) GE generates high-energy vortexes between rotor and ground. As a consequence, the power required to generate a Thrust force T is normally smaller. (C) GE generates a high-pressure air cushion between rotor and ground. As a consequence, the power required to generate a Thrust force T is normally larger. (D) GE generates a high-pressure air cushion between rotor and ground. As a consequence, the power required to generate a Thrust force T is normally smaller. 64. What may be the most important advantage - beside the absence of a Tail Rotor - of co-axial rotors in forward flight at high advance ratio? (A) The retreating blades of each rotor happen to be on the same side (left / right), causing the asymmetric lift distribution over the two rotor discs to compensate each other. (B) The compressibility effects on the advancing blades of each rotor are much smaller due to the rotors geometry. (C) The retreating blades of each rotor happen to be on opposite sides (left / right), causing the asymmetric lift distribution over the two rotor discs to compensate each other. (D) The retreating blades of each rotor happen to be on opposite sides (left / right), causing the problems due to excessive flapping to compensate each other. 5 Operations 65. In which phases can Autorotation be broken down into (sequence is relevant)? (A) Engine(s) disconnection, violent collective pull-up, stabilized descent, final flare, touchdown with (small) residual kinetic energy. (B) Reduction of collective pitch until rate of descent stabilises, stabilized descent, engine(s) disconnection, final flare, touchdown with (small) residual kinetic energy. (C) Engine(s) disconnection, reduction of collective pitch until rate of descent stabilises, stabilized descent, final flare, touchdown with (small) residual kinetic energy. (D) Engine(s) disconnection, activation of the automatic autorotative system, stabilized descent, final flare, touchdown with large residual kinetic energy. 66. During the stabilized descent phase of an Autorotation, what can be said about potential and kinetic energy? (A) Kinetic energy is zero during Autorotation, as engines are shut off. (B) Kinetic energy of the helicopter and of the rotor, as well as the potential energy, continuously decrease. (C) All energies remain constant at all times. (D) Kinetic energy of the helicopter and of the rotor is kept constant, whereas potential energy reduces. 15

67. In which of the following cases must an emergency landing be performed? (A) Engine failure in a twin engined helicopter during take-off. (B) Engine failure in a twin engined helicopter during landing. (C) Tail rotor complete failure in a twin engined helicopter. (D) Engine failure in a twin engined helicopter. 68. Every point in the AVOID areas in the Height-Velocity diagrams (also said dead man curves ) indicate a combination of height and horizontal speed. What is the use of such a diagramme? (A) Indicate the height-speed combinations, where an emergency landing would prove difficult for the average pilot. (B) Indicate the height-speed combinations, where an emergency landing would be easy even for the inexperienced pilot. (C) Help the pilot avoiding inefficient flight conditions. (D) Indicate the height-speed combinations, where flight is legal. 69. What must be the pilot s reaction to the development of Ground Resonance? (A) Immediately switch on the stability augmentation system. (B) Immediately reduce collective pitch. (C) Immediately interrupt the contact with the ground, if the rotor RPM are high enough, otherwise stop the rotor. (D) Immediately stop the rotor by starting the rotor brake. 6 Rotary Wing Drones 70. Speaking of scaling down an aircraft design, we might recall that the mass are proportional to the cube of the scale of length, l 3 ; the aerodynamic forces are proportional to l 2. What can be said about the development of smaller scale helicopters? (A) Sizing of load-carrying components is trivial. (B) Sizing of load-carrying components is more problematic. (C) Sizing of load-carrying components may become impossible. (D) Sizing of load-carrying components is less problematic. 71. What can be said about the aerodynamics of smaller scale helicopters as compared to full scale ones? (A) Given the special nature of helicopters, no significant changes are expected. (B) Since Reynolds number is much smaller, the aerodynamic effects may also be very different. (C) Since Reynolds number is much bigger, the aerodynamic effects may also be very different. (D) Since Reynolds number does not change much, no significant changes are expected. 16