HELI

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

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C. H.

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C. H.

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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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Englisch

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Technik

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Erstellt / Aktualisiert

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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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What is the relation between the so-called flapping hinge offset and the maximal control moments around the pitch and roll helicopter axes available to the pilot? (A) None, control moments only depend on cyclic pitch excursion (range). (B) The bigger the flapping hinge offset, the smaller the max control moments. (C) None, control moments only depend on available power. (D) The bigger the flapping hinge offset, the bigger the max control moments.

(D) The bigger the flapping hinge offset, the bigger the max control moments.

What is the relation between the flapping hinge offset and the type of rotor head? (A) Hingeless and bearingless rotor heads are a better solution for large hinge offset designs, because the lack of mechanical hinges makes the rotor head lighter and less draggy. (B) Hingeless and bearingless rotor heads are a better solution for large hinge offset designs, because the lack of mechanical hinges makes the blade stiffer. (C) Articulated rotor heads are a better solution for large hinge offset designs, because the presence of mechanical hinges makes the rotor lighter and less draggy. (D) Articulated rotor heads are a better solution for large hinge offset designs, because mechanical hinges require less maintenance.

(A) Hingeless and bearingless rotor heads are a better solution for large hinge offset designs, because the lack of mechanical hinges makes the rotor head lighter and less draggy.

What is a virtual flapping hinge? (A) It is a flapping hinge with lubrication. (B) It is an idealized hinge, made by a rigid blade-to-hub attachment. (C) It is an idealized hinge, made by a flexible blade-to-hub attachment. (D) It is a flapping hinge with a very small hinge offset.

Is tail rotor effective in autorotation? (A) Yes, it is driven by the engine. (B) Yes, it is driven by the main rotor. (C) Yes, it is driven by an auxiliary power unit. (D) No, there are sources of power to drive it.

(B) Yes, it is driven by the main rotor.

What are the main disadvantages of the conventional tail rotor with respect to solutions such as Fenestron and NOTAR? (A) Higher weight and mechanical complexity. (B) Risk of accidents on the ground. (C) Acoustic footprint (noise) and risk of accidents on the ground. (D) Acoustic footprint (noise).

The NOTAR system is: (A) Very noisy. (B) Highly scalable. (C) Very efficient at high speed. (D) Very quiet.

(D) Very quiet.

The Fenestron system is: (A) Very safe for ground operations. (B) Highly scalable. (C) Very noisy. (D) Equipped with cyclic control.

(A) Very safe for ground operations.

Is a separate anti-torque system installed on helicopters with co-axial rotors? (A) No, because the rotors are counter rotating. (B) No, because the rotors both rotate in the same direction. (C) No, because helicopters with coaxial rotors are extremely slow. (D) No, because torque is controlled with lateral cyclic.

(A) No, because the rotors are counter rotating.

Why is it that on helicopters with coaxial rotors, while performing an autorotation, yaw control inputs are reversed with respect to the normal working state of the rotor? (A) Because in autorotation the energy flow is reversed: from the gearbox to the rotors. (B) Because it is artificially reversed by a mechanical system to reduce the pilot’s workload. (C) Because in autorotation the energy flow is reversed: from the rotors to the gearbox. (D) Because in coaxial helicopters the energy flow is reversed in all flight conditions: from the rotors to the engines.

Could a turboshaft engine designed for fixed wing aircraft always be considered for installation on a helicopter? (A) No, helicopter engines have two output shafts: one to the main rotor and one to the tail rotor. (B) No, the requirements for helicopter engines are very different from those of fixed wing aircraft. (C) No, helicopter engines have centrifugal compressors, fixed wing engines only have axial compressors. (D) No, helicopter engines have a higher number of turbine stages.

(B) No, the requirements for helicopter engines are very different from those of fixed wing aircraft.

Why do helicopter gearboxes need intensive maintenance? (A) Because of the large number of moving mechanical parts subject to wear and tear (D:wear and tear = Verschleiss). (B) Because of the difficulty of lubricating moving mechanical parts. (C) Because of the long percentage of flight hours spent in hover flight. (D) Because of the large torque generated by the engine.

(A) Because of the large number of moving mechanical parts subject to wear and tear (D:wear and tear = Verschleiss).

What should the pilot do in case of a failure of the tail rotor transmission? (A) Continue flying. (B) Disconnect the main rotor from the engines. (C) Disconnect the tail rotor from the engines. (D) Disconnect the main rotor from the engines and perform an emergency landing.

(D) Disconnect the main rotor from the engines and perform an emergency landing.

Are the consequences of a main gearbox failure different on a Class A and on a Class B helicopter? (A) No, the failure is equally critical. (B) Yes, Class A helicopters can fly for a short time without a working gearbox. (C) Yes, on Class B helicopters it is more critical because of the lack of “stay-up” capability. (D) No, the failure is non-critical in both cases.

(A) No, the failure is equally critical.

What is the ratio (approximately) of the rotation speed of the last turbine stage to the rotation speed of the main rotor? (A) About 1000. (B) Up to 100. (C) Lower than 10. (D) 20,000.

(B) Up to 100.

What are category A and 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, are never single engine. (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.

Singe engine helicopters are: (A) Always Cat. A. (B) Either Cat. A or B depending on take off mass and power available. (C) Either Cat. A or B depending on type of rotor (co-axial rotors may be Cat. A). (D) Always Cat. B

(D) Always Cat. B

Do you always need a Cat. A helicopter for performance class 1 operations? (A) No, also multi engine Cat. B may do that. (B) Yes (C) No. (D) No, it does not depend on the helicopter category.

(B) Yes

What do performance class 1 operations involve? (A) The fact that a tail rotor failure does never impose an emergency landing. (B) The fact that one engine failure does never impose an emergency landing. (C) The fact that a gearbox failure does never impose an emergency landing. (D) The fact that one engine failure does never impose an emergency landing except in the early take off and late landing phases.

Which requirements distinguish performance class 3 operations form the other performance classes? (A) The need to perform an emergency landing whenever the tail rotor fails. (B) The need to perform an emergency landing if one engine failure occurs in the early take off or late landing phases. (C) The need to perform an emergency landing if the helicopter is single engine and the engine fails. (D) The need to perform an emergency landing if one engine failure occurs.

(D) The need to perform an emergency landing if one engine failure occurs.

What are the causes of the limited max speed of conventional helicopters? (A) Compressibility effects on advancing blade and retreating blade stall. (B) Compressibility effects on advancing blade. (C) Retreating blade stall. (D) Compressibility effects and stall of advancing blade.

(A) Compressibility effects on advancing blade and retreating blade stall.

What can we say about the power required by the tail rotor of a conventional helicopter? (A) It is normally lower at low speed. (B) It is normally lower at high speed. (C) It is normally lower in hover. (D) It depends only on main rotor collective settings.

(B) It is normally lower at high speed.

Smaller rotors are aerodynamically more efficient at high speed. Of course they also generate a higher induced velocity and hence require a higher induced power. Is this a significant problem? (A) No, induced power is negligible at all speed on helicopters. (B) No, at high speed induced velocity is normally very large. (C) No, at high speed induced velocity is normally very small. (D) No, it is an advantage: the bigger the induced velocity, the smaller the power required.

What can you say about the power required by a fixed wing aircraft and the one required by a conventional helicopter, when the two aircraft have the same payload and fly at the same height and at a speed of approximately 150 kt? (A) The power required by the fixed wing aircraft is normally smaller. (B) The power required by the helicopter is normally smaller. (C) The power required by the two aircraft is normally very similar, as it depends on speed and mass only for both of them. (D) The power required by the two aircraft is normally very similar, as it is a function of height only for both of them.

(A) The power required by the fixed wing aircraft is normally smaller.

What are the consequences of a main gearbox failure on a conventional multiengine helicopter? (A) Emergency landing by autorotation must be performed only by Cat B and C helicopters. (B) Emergency landing by autorotation must not be performed except in the early take off and late landing phases. (C) Emergency landing by autorotation does not need to be performed (D) Emergency landing by autorotation must be performed.

(D) Emergency landing by autorotation must be performed.

How must the pilot react when he or she realizes that a ground resonance episode is developing? (A) Immediately switch on the stability augmentation system. (B) Immediately interrupt the contact with the ground, if the rotor RPM are high enough, otherwise stop the rotor. (C) Immediately reduce collective pitch. (D) Immediately stop the rotor by starting the rotor brake.

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

Which statement is true about helicopter gearboxes? (A) Gearboxes are complex mechanical devices, (B) Gearboxes are very unreliable, (C) Gearboxes are the same used for fixed wing aircraft, (D) Gearboxes have a reduction ratio of over one million.

(A) Gearboxes are complex mechanical devices,

How many and which gearboxes are there on a conventional helicopter (i.e. with a main rotor and a tail rotor)? (A) Two: main and tail gearboxes, (B) Only one: main gearbox, (C) Three: main, intermediate and tail gearboxes, (D) Two: left and right gearboxes,

Are gearboxes flight critical systems? (A) Yes, but only the main gearbox, tail gearbox failure has no consequences, (B) Yes, but only on single engine helicopters, (C) Yes, but only on piston engine helicopters, (D) Yes, if a gearbox fails, an emergency landing is normally required,

(D) Yes, if a gearbox fails, an emergency landing is normally required,

Which statement is true about helicopter engines? (A) Helicopter engines are turboprop engines designed for use on helicopters, (B) Helicopter engines are turboshaft engines designed for use on helicopters, (C) Helicopter engines are turboshaft engines, identical to those used on fixed wing aircraft, (D) Helicopter engines are piston engines designed for use on helicopters,

(B) Helicopter engines are turboshaft engines designed for use on helicopters,

What are typical requirements for helicopter engines? (A) No air cooling available, low power setting for long time, large pitch and bank angles, (B) No air cooling available, high power setting for long times, large pitch and bank angles, (C) Air cooling instead of oil cooling, large pitch and bank angles, (D) Air cooling instead of oil cooling, large pitch and bank angles, low power settings,

(B) No air cooling available, high power setting for long times, large pitch and bank angles,

Does a helicopter pilot need to control the power setting manually, on modern turbine helicopters? (A) No, power setting is fixed on helicopters, (B) Yes, like on fixed wing aircraft, (C) No, a control system called FADEC controls the engines power setting, (D) Yes, with the throttle installed on the collective pitch lever,

What is the function of a helicopter turboshaft engine? (A) Providing mechanical power to the rotors through the gearbox, (B) Providing mechanical power to the main rotor, (C) Providing mechanical power to main and tail rotor, (D) Providing mechanical power to the turbine,

(A) Providing mechanical power to the rotors through the gearbox,

Where are helicopters engines installed? (A) Usually on the upper side of the fuselage (helicopter roof), close to the main gearbox, (B) Usually inside the helicopter cabin (fuselage) for balance reasons, (C) In the front part of the fuselage for air cooling, (D) Halfway between main and tail rotor to minimize the length of the drive system,

(A) Usually on the upper side of the fuselage (helicopter roof), close to the main gearbox,

Advantages of wheeled landing gears (with respect to skid landing gears) are: (A) Lower maintenance costs, no ground resonance, (B) Easier hangaring, lower weight, less maintenance, (C) Lower mechanical complexity, easier hangaring, comfort, (D) Easier hangaring, taxiing, rolling take off and landing, comfort,

(D) Easier hangaring, taxiing, rolling take off and landing, comfort,

Advantages of skid landing gears (with respect to wheeled landing gears) are: (A) Easier hangaring, (B) Better comfort, (C) Lower weight and maintenance costs, (D) Rolling take off possible,

Are landing gears related to ground resonance? (A) Yes, landing gears instability is the cause of ground resonance, (B) Yes, the dynamics of the helicopter on the ground also depends on the landing gear, (C) No, ground resonance only depends on the rotor, (D) No, ground resonance only depends on the blades,

(B) Yes, the dynamics of the helicopter on the ground also depends on the landing gear,

Big helicopters, over 10 tonnes of mass, never have skid landing gears. Why? (A) Hangaring and taxiing would be very difficult, (B) Ground resonance could not be avoided, (C) Passengers comfort would be disappointing, (D) Aerodynamic drag would be too high,

(A) Hangaring and taxiing would be very difficult,

Skid landing gears may also not have dampers. How is energy dissipated if the helicopter oscillates on the ground? (A) By the pilot, (B) By an electronic control system called FADEC, (C) Friction between skid and ground, (D) By the main rotor,

What is ground resonance? (A) An instability mode of the landing gear, (B) An instability mode involving the main rotor on the ground, (C) An instability mode involving the fuselage and the landing gear, (D) An instability mode involving the oscillations of the helicopter on the ground and the main rotor,

(D) An instability mode involving the oscillations of the helicopter on the ground and the main rotor,

How is ground resonance prevented, normally? (A) With dampers on the landing gear, (B) With dampers on the rotor and the landing gear, (C) With a control system called FADEC, (D) With flapping hinges,

(B) With dampers on the rotor and the landing gear,

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