HELI

Introduction to Rotary Wing Aircraft, Vorlesung an der ZHAW SoE, Studiengang Aviatik

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About these flashcards

These flashcards delve into the intricate mechanics and dynamics of helicopter flight, covering topics like rotor aerodynamics, blade pitch control, and engine power management. They explore the challenges of scaling down helicopter designs, the physics behind autorotation, and the nuances of ground effect. This set is invaluable for university students and engineers studying aeronautical engineering, offering a deep understanding of helicopter operations and the forces at play during flight.

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246

Students

Language

English

Category

Technology

Level

University

Created / Updated

13.06.2018 / 20.06.2018

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What are the difficulties met by the designers of a helicopter main gearbox? (A) Accommodate a reduction ratio (Untersetzung) of about 100 in limited space and mass. (B) Accommodate a reduction ratio (Untersetzung) of about 100 in limited space and mass. Additionally, the design must minimize maintenance and maximize reliability. (C) Accommodate a reduction ratio (Untersetzung) of about 100 at a limited cost. (D) Accommodate a reduction ratio (Untersetzung) of about 100 in limited space and mass. Additionally, the design must keep noise level to a minimum.

(B) Accommodate a reduction ratio (Untersetzung) of about 100 in limited space and mass. Additionally, the design must minimize maintenance and maximize reliability.

How can the reliability of the helicopter gearboxes be improved and the maintenance costs reduced? (A) By the introduction of a control system which reduces vibrations. (B) By the introduction of better suited metallic materials. (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.

(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.

What are the differences between Category A and Category B helicopters? (A) Cat A helicopters, unlike cat B, have a certain stay-up capability in case of engine failure. (B) Cat A helicopters, unlike cat. B, are always multi engine. (C) Cat A helicopters, unlike Cat. B, have a significant excess power. (D) Cat. B helicopters are always single engine.

(A) Cat A helicopters, unlike cat B, have a certain stay-up capability in case of engine failure.

Why are all single engine helicopters Cat. B? (A) Because they are less reliable. (B) Because they have less available power. (C) Because they have no stay-up capability in case of engine failure. (D) Because they have less excess power.

C) Because they have no stay-up capability in case of engine failure.

What are Performance Class 1 operations? (A) 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. (B) Flights, or portion of flights, during which an emergency landing may be required in the presence of an engine failure. (C) Flights, or portion of flights, during which an emergency landing is always required in the presence of an engine failure. (D) Flights, or portion of flights, during which an emergency landing is never required in the presence of an engine failure.

(D) Flights, or portion of flights, during which an emergency landing is never required in the presence of an engine failure.

What are Performance Class 2 operations? (A) Flights, or portion of flights, during which an emergency landing is never required in the presence of an engine failure. (B) Flights, or portion of flights, during which an emergency landing may be required in the presence of an engine failure. (C) Flights, or portion of flights, during which an emergency landing is always required in the presence of an engine failure. (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.

(B) Flights, or portion of flights, during which an emergency landing may be required in the presence of an engine failure.

What are Performance Class 3 operations? (A) Flights, or portion of flights, during which an emergency landing is always required in the presence of an engine failure. (B) Flights, or portion of flights, during which an emergency landing is never required in the presence of an engine failure. (C) Flights, or portion of flights, during which an emergency landing may be required in the presence of an engine failure. (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.

(A) Flights, or portion of flights, during which an emergency landing is always required in the presence of an engine failure.

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.

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 50% 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) It may require up to approximately 1% of the total power required, depending on the flight condition. (D) Tail Rotor normally works in windmilling condition and does not require any power to work.

(B) It may require up to approximately 10% of the total power required, depending on the flight condition.

What are the main contributions to the power required of a helicopter? (A) Induced power, parasitic power, viscous losses, losses in the gearboxes. (B) Induced power, parasitic power, air conditioning, anti-torque system power, transmission losses. (C) Induced power, parasitic power, viscous losses, anti-torque system power, transmission losses. (D) Induced power, parasitic power, viscous losses, air conditioning, hydraulic power, transmission losses.

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.

(B) Induced power.

What is Ground Effect (GE) in a conventional helicopter and what are the consequences on power required? (A) GE generates high-energy vortexes between rotor and ground. As a consequence, the power required to generate a Thrust force T is normally smaller. (B) 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. (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.

(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.

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 opposite sides (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 the same side (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.

(A) 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.

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.

(C) Engine(s) disconnection, reduction of collective pitch until rate of descent stabilises, stabilized descent, final flare, touchdown with (small) residual kinetic energy

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.

(D) Kinetic energy of the helicopter and of the rotor is kept constant, whereas potential energy reduces.

In which of the following cases must an emergency landing be performed? (A) Engine failure in a twin engined helicopter. (B) Engine failure in a twin engined helicopter during take-off. (C) Tail rotor complete failure in a twin engined helicopter. (D) Engine failure in a twin engined helicopter during landing.

(B) Engine failure in a twin engined helicopter during take-off.

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) Help the pilot avoiding inefficient flight conditions. (B) Indicate the height-speed combinations, where flight is legal. (C) Indicate the height-speed combinations, where an emergency landing would prove difficult for the average pilot. (D) Indicate the height-speed combinations, where an emergency landing would be easy even for the inexperienced pilot.

What must be the pilot’s reaction to the development of Ground Resonance? (A) Immediately interrupt the contact with the ground, if the rotor RPM are high enough, otherwise stop the rotor. (B) Immediately switch on the stability augmentation system. (C) Immediately reduce collective pitch. (D) Immediately stop the rotor by starting the rotor brake.

(A) Immediately interrupt the contact with the ground, if the rotor RPM are high enough, otherwise stop the rotor.

Speaking of scaling down an aircraft design, we might recall that the mass are proportional to the cube of the scale of length, l3; the aerodynamic forces are proportional to l2. What can be said about the development of smaller scale helicopters? (A) Sizing of load-carrying components may become impossible. (B) Sizing of load-carrying components is more problematic. (C) Sizing of load-carrying components is less problematic. (D) Sizing of load-carrying components is trivial.

What can be said about the aerodynamics of smaller scale helicopters as compared to full scale ones? (A) Since Reynolds number is much smaller, the aerodynamic effects may also be very different. (B) Since Reynolds number is much bigger, the aerodynamic effects may also be very different. (C) Given the special nature of helicopters, no significant changes are expected. (D) Since Reynolds number does not change much, no significant changes are expected.

(A) Since Reynolds number is much smaller, the aerodynamic effects may also be very different.

Why is the generation of an induced velocity a consequence of the generation of lift (by a heli rotor)?A. Because of the conservation of momentum B. Because of the conservation of energy C. Because of air viscosity D. Because of rotation speed Omega

Keyboard commands:

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A. Because of the conservation of momentum

In hover, induced velocity is inversely proportional to rotor area. This means, with respect to a reference radius: A. That a rotor with a smaller radius will generate a higher induced velocity but will have the same efficiency – while generating the same thrust force B. That a rotor with a smaller radius will generate a smaller induced velocity – while generating the same thrust force C. That a rotor with a smaller radius will generate the same induced velocity – while generating the same thrust force D. That a rotor with a smaller radius will generate a higher induced velocity – while generating the same thrust force

Keyboard commands:

= turn,

= for-/backward,

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D. That a rotor with a smaller radius will generate a higher induced velocity – while generating the same thrust force

Induced velocity in autorotation is: A. Zero B. Equal to descent velocity, without considering the final flare C. Smaller than descent velocity, without considering the final flare D. Larger than descent velocity, without considering the final flare

Keyboard commands:

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= for-/backward,

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C. Smaller than descent velocity, without considering the final flare

Induced velocity in autogyrus / gyroplanes is: A. Zero because the rotor is windmilling B. Non-zero because the rotor does generate lift C. Zero because the rotor is not driven by the engine D. Non-zero because the rotor turns

Keyboard commands:

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B. Non-zero because the rotor does generate lift

What is normally meant by “vortex ring”? A. A working state of a rotor characterized by stable re-circulation through rotor disc B. A working state of a rotor characterized by a strong wake C. A working state of a rotor characterized by circulation D. A working state of a rotor characterized by unstable re-circulation through rotor disc

Keyboard commands:

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D. A working state of a rotor characterized by unstable re-circulation through rotor disc

What is meant with the term windmilling? A. Windmilling is the working state of a rotor in which the flow gives energy to the rotor system – i.e it is the state in which wind turbines work when they generate power B. Windmilling is the working state of a rotor in which the rotor accelerates its rotation speed C. Windmilling is the working state of a rotor in which the rotor system gives energy to the flow- i.e it is the state in which wind turbines work when they generatie power D. WIndmilling is the working state of a rotor in which the flow gives energy to the rotor system – i.e it is the state in which helicopter rotors work

Keyboard commands:

= turn,

= for-/backward,

= scroll

A. Windmilling is the working state of a rotor in which the flow gives energy to the rotor system – i.e it is the state in which wind turbines work when they generate power

Why is a rotor less efficient than a wing in forward flight at high speed, at an advance ratio mü=V/(Omega x R) = 0.40 for instance? A. Because the flow around the retreating blade is disturbed by compressibility effects and the advancing blade experiences inverse flow or very high angle of attack B. Because the flow around the blades is disturbed by compressibility effects C. Because the flow around the advancing blade is disturbed by compressibility effects and the retreating blade experiences inverse flow or very high angle of attack D. Because wing increase their efficiency as speed increases

Keyboard commands:

= turn,

= for-/backward,

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C. Because the flow around the advancing blade is disturbed by compressibility effects and the retreating blade experiences inverse flow or very high angle of attack

What is the physical phenomenon at the origin of ground effect? A. While flying close to the ground a high-pressure cushion appears between rotor and ground B. While flying close to the ground a high-pressure cushion appears above the rotor C. While flying close to the ground a high-pressure cushion appears between rotor and ground D. While flying close to the ground a high-pressure cushion appears above the rotor

Keyboard commands:

= turn,

= for-/backward,

= scroll

A. While flying close to the ground a high-pressure cushion appears between rotor and ground

How would you describe the effects of ground effect on a helicopter performances? A. Power required and lift decrease proportionally B. Power required decreases while generating the same lift C. Power required increases while generating the same lift D. Power required and lift increase proportionally

Keyboard commands:

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= for-/backward,

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B. Power required decreases while generating the same lift

Why is forward speed of conventional helicopter limited about 150 – 160kt? A. Fuselage drag B. Compressibility effects on retreating blade and stall of advancing blade C. Fuselage drag and tail rotor stall D. Compressibility effects on advancing blade and stall of retreating blade

Keyboard commands:

= turn,

= for-/backward,

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D. Compressibility effects on advancing blade and stall of retreating blade

Why does the above limitation not apply to tilt-rotors such as Bell-Boeing MV22? A. Because the rotors are tilted forward at high-speed B. Because the fuselage has a much smaller drag coefficient C. Because the radius of the rotors is much smaller than a conventional helicopter D. Because the rotors are tilted forward at high-speed interference between rotor downwash and fuselage is reduced

A. Because the rotors are tilted forward at high-speed

Why does the above limitation not apply to compound helicopters such as the Eurocopter X3 (= helicopters with a main rotor but also a small wing and propellers)? A. Because at high speed the main rotor is partially unloaded since wing and propellers generate most of the necessary forces (forward thrust) B. Because at high speed the main rotor is partially unloaded since wing and propellers generate most of the necessary forces (lift) C. Because at high speed the main rotor is partially unloaded since wing and propellers generate most of the necessary forces (forward thrust and lift) D. Because at high speed the main rotor is partially unloaded since wing and propellers generate most of the necessary forces (drag and lift)

C. Because at high speed the main rotor is partially unloaded since wing and propellers generate most of the necessary forces (forward thrust and lift)

The main rotor head types are: A. Semi-rigid (also called “see-saw”), semi articulated, articulated, hingeless and bearlingless B. Semi-rigid (also called “see-saw”), articulated, hingeless and bearingless C. Semi-rigid (also called “see-saw”), articulated, hingeless D. Rigid, hingeless and bearingless

B. Semi-rigid (also called “see-saw”), articulated, hingeless and bearingless

What are hingeless rotor heads? A. Rotor heads without mechanical hinges around flap and lead/lag axes B. Rotor heads without hinges around flap and lead/lad axes C. Rotor heads with rigid connections to blades, like propellers D. Rotor heads without mechanical hinges

A. Rotor heads without mechanical hinges around flap and lead/lag axes

What are bearingless rotor heads? A. Rotor heads without hinges around flap and lead/lag axes B. Rotor heads without mechanical hinges around flap and lead/lag axes C. Rotor heads with rigid connections to blades, like propellers D. Rotor heads without mechanical hinges

D. Rotor heads without mechanical hinges

Which type of rotor head provide the highest control moments? (A) Hingeless and bearingless, because these constructions (Bauweise) accommodate large hinge offset more conveniently. (B) Hingeless and bearingless, because these constructions (Bauweise) accommodate small hinge offset more conveniently. (C) Hingeless and bearingless, because these constructions (Bauweise) are more suitable to large size helicopters. (D) Hingeless and bearingless, because these constructions (Bauweise) do not have mechanical hinges.

A) Hingeless and bearingless, because these constructions (Bauweise) accommodate large hinge offset more conveniently.

Do rotor heads with large hinge offsets provide a lower “comfort” for passengers when flying in turbulence? (A) No, because turbulence might cause a non-symmetric loading on the rotor blades. (B) No, because aerodynamic forces generated by turbulence on the blades are transmitted to the fuselage through the rotor head. (C) Yes, because aerodynamic forces generated by turbulence on the blades are transmitted to the fuselage through the rotor head. (D) No, because turbulence does not alter (ändert) the distribution of aerodynamic forces.

(C) Yes, because aerodynamic forces generated by turbulence on the blades are transmitted to the fuselage through the rotor head.

Why is a helicopter equipped with a semi-rigid (“see-saw”) rotor slower than other rotor head types to react to pilot’s inputs? (A) Because semi-rigid rotors have large hinge offsets. (B) Because semi-rigid rotors are an old solution. (C) Because semi-rigid rotors have mechanical hinges. (D) Because the hinge offset of semi-rigid rotors is zero.

(D) Because the hinge offset of semi-rigid rotors is zero.

Which materials are commonly used on modern helicopters to manufacture main rotor blades? (A) Carbon fibers and glass fibers composite. (B) Aluminum. (C) Carbon fibers composite. (D) Wood.

(A) Carbon fibers and glass fibers composite.

What is the function of the tail rotor system? (A) Provide control around the pitch axis. (B) Preventing the helicopter from spinning around. (C) Provide control around the yaw axis. (D) Provide control around the roll axis.

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Flashcards

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 aerodynamic forces are much lower thanks to the introduction of the flapping hinge. (B) The centrifugal forces balance the aerodynamic forces. (C) The hinges allow the rotation about their axis: the bending moment is consequently zero. (D) The hinges allow the rotation about their axis: all forces are consequently zero in correspondence of the hinge.

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 stable but dynamically unstable. (B) The isolated rotor is statically and dynamically stable. (C) The isolated rotor is statically and dynamically unstable. (D) The isolated rotor is statically unstable but dynamically stable.

(A) The isolated rotor is statically stable but dynamically unstable.

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.

What can be said about the directional stability (yaw) of helicopters? (A) Helicopters are statically unstable and may also be dynamically unstable. (B) Helicopters are statically and dynamically unstable. (C) Helicopters are statically and dynamically stable. (D) Helicopters are statically stable and may also be dynamically stable.

(D) Helicopters are statically stable and may also be dynamically stable.

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 fuselage inertia. (B) The presence of a tailplane (Höhenflosse). (C) The presence of a fin (Seitenflosse). (D) The presence of the Tail Rotor.

How can helicopter stability be improved? (A) By modifying of the rotor head geometry. (B) By means of control systems which use sensors to capture the helicopter motion and have small authority on cyclic and collective controls. (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.

(B) By means of control systems which use sensors to capture the helicopter motion and have small authority on cyclic and collective controls.

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.

How is longitudinal control (pitch) axis obtained in (conventional) helicopters? (A) Main Rotor longitudinal cyclic pitch control. (B) Main Rotor collective pitch control. (C) Tail Rotor collective pitch control. (D) Tail Rotor longitudinal cyclic pitch control.

(A) Main Rotor longitudinal cyclic pitch control.

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) Differential collective pitch control (applying opposite changes in collective pitch on front and rear rotors). (C) Longitudinal cyclic control (applying the same change in longitudinal cyclic pitch on front and rear rotor). (D) Deflection of the elevator.

(B) Differential collective pitch control (applying opposite changes in collective pitch on front and rear rotors).

Which are the main types of rotor head? (A) Rotor with pitch control, rotor heads without pitch control. (B) Semi-rigid (see-saw), articulated, elastomeric. (C) Semi-rigid (see-saw), articulated, hingeless, headless. (D) Semi-rigid (see-saw), articulated, hingeless,bearingless.

(D) Semi-rigid (see-saw), articulated, hingeless, bearingless.

What is the flapping hinge offset? (A) It is the distance between the flapping hinge and lead/lag hinge axes. (B) It is the distance between the flapping hinge axis and the centre of the rotor mast. (C) It is the distance between the flapping hinge and feathering hinge axes. (D) It is the distance between the flapping hinge and rotating swashplate.

(B) It is the distance between the flapping hinge axis and the centre of the rotor mast.

What is the relevance of the flapping hinge offset with respect to flight dynamics? (A) The larger the flapping hinge offset, the larger the control moments available to the pilot. (B) The larger the flapping hinge offset, the smaller the control moments available to the pilot. (C) None. (D) The larger the flapping hinge offset, the more dynamically stable is the rotor.

(A) The larger the flapping hinge offset, the larger the control moments available to the pilot.

What are the consequences for the control moments if a low-g helicopter manoeuvre is performed with a semi-rigid rotor head (flapping hinge offset = 0)? (A) No differences with respect to level flight or high-g manoeuvres. (B) The rotor thrust is large and so are the control moments which the pilot can generate. (C) The rotor thrust is small and so are the control moments which the pilot can generate. (D) Control moments are slightly smaller but there are significant consequences.

Do hingeless or bearingless rotor heads have flapping hinges? (A) No. However, they have lead/lag hinges only. (B) No, blades are rigidly attached to the rotor head. (C) Yes. However, the rotation of the blade is accommodated by special elastomeric bearings (Lager). (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.

(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.

Do hingeless rotor heads have a feathering hinge (the axis about which the blade pitch can be controlled)? (A) No, the pitch angle is adjusted by aerodynamic tabs. (B) No, the blades have a fixed pitch angle in this case. (C) Yes. (D) No, the angle of attack can be modified by flapping the blades only.

Do bearingless rotor heads have a feathering hinge (the axis about which the blade pitch can be controlled)? (A) Yes but a “virtual” one, since feathering of the blade is accommodated by the torsion of the blade root to rotor head attachment. (B) No, the blades have a fixed pitch angle in this case. (C) No, the pitch angle is adjusted by aerodynamic tabs. (D) No, the angle of attack can be modified by flapping the blades only.

(A) Yes but a “virtual” one, since feathering of the blade is accommodated by the torsion of the blade root to rotor head attachment.

What are the main advantages of the Fenestron tail rotor type? (A) Safety for ground personnel, low noise level, aerodynamic efficiency. (B) Safety for ground personnel. (C) Low noise level. (D) Safety for ground personnel, low noise level.

(D) Safety for ground personnel, low noise level.

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, higher control power at high speed, lower noise level. (C) Higher aerodynamic efficiency, higher control power at high speed. (D) Higher aerodynamic efficiency, lower noise level.

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 deviating the freestream airflow through the so-called Coanda effect. (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 means of an orientable rudder. (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.

(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.

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 torque exchanged between each of the rotors and the gearbox has opposite sign. If the two contributions are equal, the total torque is zero. (C) The directional control can be obtained by differential collective pitch. (D) The engine exhaust is normally deviated laterally in order to generate a sufficiently large anti-torque moment.

(B) 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.

Do helicopters need the anti-torque system also during Autorotation (AR)? (A) 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. (B) Yes, because engines may provide some residual amount of power to the rotor. (C) No, because engines are not providing any power. (D) No, because the tail rotor is disengaged during AR.

(A) 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.

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 collective pitch. (D) Controlling Tail Rotor blades angle of attack.

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) Long periods of time at high power setting, large bank and pitch angles, no easy accessible undisturbed airflow for cooling. (B) Long periods of time at high power setting, large bank and pitch angles, FADEC absolutely necessary. (C) Large bank and pitch angles, no easy accessible undisturbed airflow for cooling, max continuous power never required thanks to ground effect. (D) Large bank and pitch angles, no easy accessible undisturbed airflow for cooling, very high max continuous power for hover in ground effect.

(A) Long periods of time at high power setting, large bank and pitch angles, no easy accessible undisturbed airflow for cooling.

How many gearboxes can one normally find on a conventional helicopter? (A) Main gearbox, tail gearbox. Additionally, engines may have auxiliary gearboxes. (B) Main gearbox, intermediate gearbox, tail gearbox. (C) Main gearbox, intermediate gearbox, tail gearbox. Additionally, engines may have auxiliary gearboxes. (D) Main gearbox, intermediate gearbox, central gearbox, tail gearbox.

Are helicopters gearboxes maintenance intensive (= does gearbox maintenance involve a large workload and high costs)? (A) No. (B) Yes. (C) Only in multi-engined helicopters. (D) Yes, but only the ones not equipped with electronic monitoring systems.

(B) Yes.

What are the consequences of a mechanical failure in the main gearbox? (A) It may force the pilot to disconnect the Tail Rotor. (B) None. The pilot must only disconnect the main gearbox and continue flying. (C) If the helicopter is multi-engined and Cat. A, the pilot can continue flying . (D) It may force the pilot to perform an emergency landing by Autorotation.

(D) It may force the pilot to perform an emergency landing by Autorotation.