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Question 255-1 : 'dynamic roll over' may be caused by ? [ Explanation maintenance ]

An excessive rolling movement developing about a skid or wheel in contact with a slope or uneven ground.

exemple 355 An excessive rolling movement developing about a skid or wheel in contact with a slope or uneven ground.

Question 255-2 : A main rotor blade may be twisted along its span to ensure ?

A more desirable lift distribution.

exemple 359 A more desirable lift distribution.

Question 255-3 : The maximum speed during backwards is lower than in forward flight, this is due to ?

The reduced control range in the rearward direction and the directional stability of the airframe

exemple 363 The reduced control range in the rearward direction and the directional stability of the airframe

Question 255-4 : When in the hover, movement of the collective lever upwards will change the pitch angle of the main rotor blades ?

By an equal amount throughout 360 of rotation

exemple 367 By an equal amount throughout 360 of rotation

Question 255-5 : In a tail rotor, asymmetry of lift ?

May be reduced by allowing blade flapping

exemple 371 May be reduced by allowing blade flapping

Question 255-6 : A helicopter having an anti clockwise rotating main rotor when seen from above , with power on, will have a tendency to drift ?

To the right.

exemple 375 To the right.

Question 255-7 : In a hingeless main rotor there are ?

Feathering bearing but no dragging or flapping hinges.

exemple 379 Feathering bearing but no dragging or flapping hinges.

Question 255-8 : In a shrouded tail rotor fenestron the blades ?

Respond to tail rotor collective pitch control.

The control of the tail rotor thrust is achieved by collective variation of the pitch angle of the blades...the pitch control tail rotor blades system is connected to the rudder pedals. exemple 383 Respond to tail rotor collective pitch control.

Question 255-9 : Ground resonance can be prevented from developing to a critical point, if action is taken early enough, by ?

Applying collective pitch control and lifting off.

exemple 387 Applying collective pitch control and lifting off.

Question 255-10 : The three main features which define the maximum speed of a helicopter are ?

Compressibility limit of advancing blade, retreating blade stall and design limits of cyclic control

exemple 391 Compressibility limit of advancing blade, retreating blade stall and design limits of cyclic control

Question 255-11 : During autorotative flight ?

The fuselage will tend to rotate in the same direction as the rotor.

exemple 395 The fuselage will tend to rotate in the same direction as the rotor.

Question 255-12 : Blade sailing, with the attendant possibility of a blade strike on the tail boom or rear fuselage, is most likely to occur ?

During very low rotor rpm conditions, particularly whilst starting or stopping the engine in gusty conditions

exemple 399 During very low rotor rpm conditions, particularly whilst starting or stopping the engine in gusty conditions

Question 255-13 : The primary factor which prevents the main rotor blade coning upwards on an articulated rotor head is ?

The centrifugal force acting on the blades.

exemple 403 The centrifugal force acting on the blades.

Question 255-14 : Blades with a positive coning angle flapping upwards tend to ?

Increase rotational speed.

exemple 407 Increase rotational speed.

Question 255-15 : An increase in angle of attack of a rotor blade element, below the stall angle, causes an increase in ?

Drag and lift forces.

exemple 411 Drag and lift forces.

Question 255-16 : A shrouded tail rotor fenestron ?

Largely removes lift dissymmetry and the attendant need for cyclic feathering of the tail rotor

exemple 415 Largely removes lift dissymmetry and the attendant need for cyclic feathering of the tail rotor

Question 255-17 : During an autorotative descent the maximum gliding distance will be obtained at ?

A speed greater than that associated with the minimum rate of descent

exemple 419 A speed greater than that associated with the minimum rate of descent

Question 255-18 : In forward flight the lift produced by a given blade element is dependent upon ?

Angle of attack and the square of its air speed

exemple 423 Angle of attack and the square of its air speed

Question 255-19 : When the cyclic pitch control is forward, a main rotor blade will reach its maximum pitch ?

On the retreating side.

exemple 427 On the retreating side.

Question 255-20 : Blade hinges arranged with a 'delta three' hinge effect ?

Decrease their pitch angle with flap up.

exemple 431 Decrease their pitch angle with flap up.

Question 255-21 : Some tail rotor hinges are not perpendicular to the feathering axis in order to ?

Reduce the effects of dissymmetry of lift with forward speed

.since the tail rotor is subjected to dissymmetry of rotor thrust it is often fitted with flapping hinges. normally they have delta 3 hinges that decrease the angle of attack when the blade flaps up and vice versa. exemple 435 Reduce the effects of dissymmetry of lift with forward speed

Question 255-22 : The normal or yaw axis of a helicopter is a straight line ?

Passing through the centre of gravity perpendicular to the longitudinal and lateral axes

exemple 439 Passing through the centre of gravity perpendicular to the longitudinal and lateral axes

Question 255-23 : The angle of attack of an aerofoil section is the angle between the ?

Chord line and the relative airflow

exemple 443 Chord line and the relative airflow

Question 255-24 : A helicopter is statically stable when it exhibits the ?

Tendency to return to its original attitude after a disturbance

exemple 447 Tendency to return to its original attitude after a disturbance

Question 255-25 : The amount of lift produced by a given helicopter rotor blade element is dependent upon ?

The angle of attack of the blade, the square of the air velocity relative to the blade element and the air density

exemple 451 The angle of attack of the blade, the square of the air velocity relative to the blade element and the air density

Question 255-26 : Phase lag is the ?

Azimuthal angle through which a blade moves between a pitch value input and the corresponding flapped position

exemple 455 Azimuthal angle through which a blade moves between a pitch value input and the corresponding flapped position

Question 255-27 : As speed increases the parasite drag of a helicopter fuselage will ?

Tend to cause the nose to pitch down

exemple 459 Tend to cause the nose to pitch down

Question 255-28 : 'coning angle' is defined as the angle between the rotor blade's longitudinal axis and the ?

Tip path plane.

. 2407 exemple 463 Tip path plane.

Question 255-29 : Disc loading is defined as the ?

Ratio of the total weight of the helicopter, per unit of the disc area

exemple 467 Ratio of the total weight of the helicopter, per unit of the disc area

Question 255-30 : In order to reduce the effects of retreating blade stall on a helicopter in flight, the ?

Collective pitch should be lowered to decrease pitch

exemple 471 Collective pitch should be lowered to decrease pitch

Question 255-31 : If a helicopter is loaded for flight and the centre of gravity is within limits for take off ?

The centre of gravity position needs to be calculated for landing


Question 255-32 : In order to produce a stable teetering rotor it may be necessary to ?

Stabilise it by use of rotating masses

exemple 479 Stabilise it by use of rotating masses

Question 255-33 : A tilt of the rotor disc plane will cause the helicopter to accelerate ?

In the direction of tilt

exemple 483 In the direction of tilt

Question 255-34 : The avoid areas in a 'height velocity diagram' define the height/velocity combination ?

From which safe autorotative descent and landing after engine failure may not easily be accomplished

exemple 487 From which safe autorotative descent and landing after engine failure may not easily be accomplished

Question 255-35 : In a hingeless rotor head, flapping movements ?

Are accommodated for by the rotor blades flexible attachements to the hub.

exemple 491 Are accommodated for by the rotor blades flexible attachements to the hub.

Question 255-36 : When a cyclic control input has been made, the rotor blade pitch will be ?

Increasing for one half revolution and decreasing for the next half

exemple 495 Increasing for one half revolution and decreasing for the next half

Question 255-37 : What effect does an increase in density altitude have on the amount of anti torque pedal required to maintain heading in the hover and why ?

Increased because power required increases and the tail rotor is less effective

exemple 499 Increased because power required increases and the tail rotor is less effective

Question 255-38 : If the centre of gravity is at the rear limit ?

Then forward cyclic travel is reduced.

exemple 503 Then forward cyclic travel is reduced.

Question 255-39 : With a centre of gravity position near the front limit what will be the effect upon fuselage attitude and cyclic stick position, in a still air hover ?

Nose down, cyclic stick back.

. 2411 exemple 507 Nose down, cyclic stick back.

Question 255-40 : The principal forces acting on a helicopter in forward flight are ?

Main rotor thrust, weight, parasite drag and main rotor profile drag.



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