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Helicopter gearboxes are complex mechanical devices. The complexity is a consequence of . . .

...the presence of numerous monitoring devices,

. . . the fact that gearboxes are air cooled,

. . the large transmission ratio between input and output shafts,

. . the small transmission ratio between input and output shafts,

A gearbox is a device which allows changing the direction and the rotation speed of a shaft. How many gearboxes are there on a conventional helicopter (i.e. with a main rotor and a tail rotor)?

Only one: main gearbox,

Two: main and tail gearboxes,

Two: main and intermediate gearboxes,

Three: main, intermediate and tail gearboxes,

What is the function of the intermediate gearbox?

Change the direction of the shaft and also reduce the rotation speed,

Reduce the rotation speed,

Connect the engines to the main rotor,

Change the direction of the shaft,

Gearboxes are flight critical systems. In case of a gearbox failure, the pilot may need to:

reduce forward speed and land vertically in order to reduce power required

perform an emergency landing in the case the helicopter has only one gearbox,

perform an emergency landing only if the helicopter is Category B,

switch off the engines and perform an emergency landing,

Which statement is true about helicopter engines?

Helicopter engines are air-cooled,

Helicopter engines are designed to be installed on helicopters only,

Helicopter engines are conventional engines that may be installed on helicopters and on fixed wing aircraft,

Helicopter engines are more powerful than those installed in fixed wing aircraft,

What are typical requirements for helicopter engines?

Oil cooled, able to sustain high power settings and/or large pitch and bank angles,

Oil cooled, able to sustain high power settings for longer times and/or large pitch and bank angles,

Air cooled, able to sustain high power settings for longer times and/or large pitch and bank angles,

Air cooled, able to sustain high power settings and/or large yaw angles,

Does the helicopter pilot need to control the power manually, on modern turbine helicopters?

Yes, the pilot controls the engines power setting, an automatic systems adjusts the attitude of the helicopter,

No, the pilot only controls the rotor, an automatic systems adjusts the power setting so that the pitch angle of the blades are maintained,

Yes,thepilotcontrolstheenginespowersetting,anautomaticsystemsadjuststhepitchangles of the blades,

No, the pilot only controls the rotor, an automatic systems adjusts the power setting so that the rotation speed of the rotor is maintained,

The function of a helicopter turboshaft engine is to provide mechanical power . . .

..to the rotors through the gearbox,

..to the FADEC system,

..to the rotors

. to the rotor in the air and to the landing gear on the ground,

Engines are installed on the roof of the helicopter; the engineers optimize the design of the installation in order to minimize mainly . . .

.the manufacturing costs

.the Coriolis forces

.the aerodynamic drag force

.the aerodynamic lift force

A wheeled landing gear allows . .

...easier taxiing,

...a more comfortable taxiing,

. . easier hangaring, taxiing, rolling take-off and landing,

. . easier hangaring, safe landing on unprepared surfaces,

A skid landing gear allows the designers to .

. . increase the cost and the weight of the helicopter,

.make the helicopter fly more comfortably,

...save cost and weight,

..make the helicopter look cool,

Can landing gear design affect ground resonance?

No, ground resonance only depends on the stiffness of the fuselage,

Yes, landing gear design determines the dynamics of the helicopter on the ground,

No, ground resonance only depends on the stiffness of the rotor blades,

Yes, landing gear design influences the kinematics of the rotor blades,

A good reason to install a skid landing gear could be:

allowing the helicopter to land on rough terrain,

making hangaring easier

allowing taxiing,

providing a support for passengers climbing in and out of the fuselage,

Most wheeled landing gear are equipped with dampers; this is necessary to prevent . .

...stability,

.uncomfortable taxiing,

.damages to the fuselage while taxiing

...ground resonance,

In some cases, skid landing gear are not equipped with dampers; how can energy be dissipated and stability guaranteed?

by special devices installed in the main gearbox,

through friction between skid and ground,

through collective and cyclic pitch controls,

by allowing automatic systems to control the helicopter,

What could be a good definition for ground resonance?

A stable mode involving the motion of the blades around the lead/lag hinge,

An unstable mode involving the oscillations of the helicopter on the ground and the motion of the blades around the lead/lag hinges,

An unstable mode involving the oscillations of the helicopter on the ground and the rotation of the rotor,

An unstable mode involving the oscillations of the helicopter on the ground,

How is ground resonance prevented on most helicopters ?

By installing dampers on rotor blades,

By installing springs on landing gear and rotor blades,

By installing dampers on landing gear,

By installing dampers on the landing gear and rotor blades,

The Fenestron is an anti-torque system consisting of a rigid rotor surrounded by a shroud; what are the advantages of this particular design?

Greater safety for ground personnel,

Smaller acoustic footprint (= less noisy), safety when operating on ships,

Smaller acoustic footprint (= less noisy), greater safety for ground personnel,

Smaller acoustic footprint (= less noisy),

What is the function of the shroud in a Fenestron system, beside protecting the tail rotor?

Generate an additional lateral aerodynamic force,

Provide a contact point for landing,

None,

Protect components of the drive system (shafts and tail gearbox),

NOTAR is an acronym for NO TAil Rotor. The device with this name consists of low-pressure air flowing through the tailboom, which is expelled through lateral openings generating a lateral force by deviating the rotor downwash. What are the main advantages of this system with respect to a conventional tail rotor?

Smaller acoustic footprint (= less noisy), reduced safety for ground personnel,

Smaller acoustic footprint (= less noisy), greater safety for ground personnel,

Smaller acoustic footprint (= less noisy),

Greater safety for ground personnel,

How is the main rotor downwash deviated in a NOTAR system, in order to generate a lateral force, aerodynamically?

Exploiting ground resonance,

Exploting ground effect,

With an additional rotor,

Exploiting the so-called Coanda effect,

A conventional tail rotor system consists of a rotor equipped with flapping hinges and collective pitch control. What are the advantages of a such a system with respect to a Fenestron-like (= shrouded rotor) system?

Smaller acoustic footprint (= less noisy), greater safety for ground personnel,

Smaller acoustic footprint (= less noisy),

A better aerodynamic efficiency in most of the flight envelope,

Greater safety for ground personnel,

How is a Category A helicopter defined, according to European Air OPS regulations?

There is no such thing as a Category A helicopter,

A helicopter with stay-up capability in case of power unit failure,

A helicopter without stay-up capability in case of power unit failure,

A helicopter with stay-up capability in case of tail rotor failure,

How could be described the stay-up capability, mentioned in the previous question, according to European Air OPS regulations?

The helicopter can safely continue flying in case of engine failure and also gearbox or tail rotor failure,

Even though one engine is malfunctioning or has been switched off, the power available is sufficient to hover in and out of ground effect,

The power generated by the working engines is sufficient to fly at best-endurance speed,

ven though all the engines are malfunctioning or have been switched off, the power available is sufficient to hover in and out of ground effect,

How is a Category 1 helicopter defined, according to European Air OPS regulations?

A helicopter with stay-up capability in case of power unit failure,

A helicopter without stay-up capability in case of power unit failure,

A helicopter with stay-up capability in case of tail rotor failure,

There is no such thing as a Category 1 helicopter,

What is a trivial consequence of the definitions given above, with regard to single engined heli- copters?

Single engined helicopters can stay-up after an engine failure,

A single engined helicopter cannot be Category A,

A single engined helicopter may be Category A,

Single engined helicopters are unsafe,

What is a trivial consequence of the definitions given above, with regard to multi-engine helicopters?

Multi-engine helicopters cannot stay-up after an engine failure,

Multi-engine helicopters may be Category A,

Multi-engine helicopters are Category A,

Multi-engine helicopters are safe,

Rotor head design can influence the manoeuvrability of the helicopter (manoeuvrability may be defined as ratio between the rotation rate, as output, and the amount of cyclic control provided by the pilot, as input). How can this relation be described?

The larger the flapping hinge offset, the larger the manoeuvrability,

Manoeuvrability is proportional to the distance between the rotating swashplate and the rotor head,

The larger the flapping hinge offset, the smaller the manoeuvrability,

The smaller the flapping hinge offset, the larger the manoeuvrability,

Articulated rotors are those, in which the blades can flap, lead/lag and feather (= pitch). How are these degrees of freedom practically implemented in the design of the rotor head?

Exploiting material elasticity,

Exploiting deformation of the blade attachments: bending and twisting,

Introducing flapping, lead-lagging and feathering hinges,

Letting the rotor head move around a spherical hinge (the blades are rigidly attached to the rotor head),

Hingeless rotors also have blades which can flap, lead/lag and feather (= pitch). How are these degrees of freedom practically implemented in the design of the rotor head?

By introducing flapping, lead-lagging and feathering hinges,

By designing blade attachments (to the rotor head) which can deform substantially, in bending and twisting,

By designing blade attachments (to the rotor head) which can deform substantially, in twisting, and, additionally, flapping and lead/lag hinges,

By designing blade attachments (to the rotor head) which can deform substantially, in bending, and, additionally, a feathering hinge,

Bearingless rotors also have blades which can flap, lead/lag and feather (= pitch). How are these degrees of freedom practically implemented in the design of the rotor head?

By introducing flapping, lead-lagging and feathering hinges,

By designing blade attachments (to the rotor head) which can deform substantially, in bending, and, additionally, a feathering hinge,

By designing blade attachments (to the rotor head) which can deform substantially, in twisting, and, additionally, flapping and lead/lag hinges,

By designing blade attachments (to the rotor head) which can deform substantially, in bending and twisting,

Rotor heads with larger hinge offsets may respond to unsteady airloads (gusts or turbulence) . . .

..with an unstable motion,

..by generating non-negligible moments on the fuselage and consequently affecting the comfort of passengers negatively,

by flapping excessively, and consequently affecting the comfort of passengers negatively,

. by generating moments on the fuselage, which are smaller than those generated by articu- lated rotors,

The so-called see-saw rotors have one single flapping hinge for both blades and, consequently, zero hinge offset. The helicopter is therefore more difficult to control when performing manoeuvres with ...

.lateral wind,

.a load factor of 1,

..a large positive load factor,

..small or zero load factor,

What is the physics behind the previous question?

(The so-called see-saw rotors have one single flapping hinge for both blades and, consequently, zero hinge offset. The helicopter is therefore more difficult to control when performing manoeuvres with)

If hinge offset is zero, then control moments can only be obtained by tilting the thrust vector; when thurst is small or zero, then control moments are also small,

If hinge offset is zero, then control moments may only be generated by changing the direction of gravity force,

If hinge offset is zero, then control moments may not be generated,

If hinge offset is zero, then control moments are proportional to cyclic pitch control input,

Helicopters with large hinge offset have high manoeuvrability also when rotor thrust is small. This is of great help when performing manoeuvres at low load factor. What is the physics behind this?

Control moments are proportional to load factor,

Control moments are proportional to rotor torque,

Control moments are always proportional to collective pitch control inputs,

Control moments have a component which is proportional to cyclic pitch control input,

See-saw rotors have zero hinge offset. Therefore, they are not suitable for helicopters which need to be very manoeuvrable, because . . .

..control moments are very large,

. the rotor does not have flapping hinges,

.control moments are very small

. . the helicopter is not controllable at high load factor,

Hingeless and bearingless rotors may have large hinge offset. In this case, they provide high ma- noeuvrability, because . . .

.control moments are small,

..the blades do not flap,

..control moments are large,

...the blades are structurally rigid,

The pilot controls the thrust generated by the main rotor by means of . . .

.the collective pitch lever,

..the pedals,

.the power throttle

..the cyclic pitch lever (stick),

The pilot controls the orientation of the trust force vector generated by the rotor by means of . .

.the collective pitch lever,

.the pedals

.the power throttle

..the cyclic pitch lever (stick),

When the pilot acts on the pedals, he/she controls the tail rotor thrust through . .

..the tail rotor cyclic pitch,

.the main rotor collective pitch

.the in main rotor cyclic pitch

.the tail rotor collective pitch

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