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Question 256-1 : A nose down pitch attitude in forward flight is caused by ? [ Explanation maintenance ]

The horizontal component of total rotor thrust acting above parasite drag.

exemple 356 The horizontal component of total rotor thrust acting above parasite drag.

Question 256-2 : To increase forward speed in straight and level flight ?

Total rotor thrust must be increased.

exemple 360 Total rotor thrust must be increased.

Question 256-3 : The induced flow component of airflow through the rotor disc ?

Decreases with forward flight.

exemple 364 Decreases with forward flight.

Question 256-4 : During a transition into forward flight from the hover, and maintaining level flight ?

Total rotor thrust increases.

exemple 368 Total rotor thrust increases. — .while transitioning to forward flight at about 16 to 24 kt, the helicopter goes through effective translational lift etl. the rotor blades become more efficient as forward airspeed increases. the rotor system completely outruns the recirculation of old vortices and begins to work in relatively undisturbed air. the flow of air through the rotor system is more horizontal therefore, induced flow and induced drag are reduced. the angle of attack is effectively increased, which makes the rotor system operate more efficiently, total rotor thrust increases.

Question 256-5 : When the induced flow and the perpendicular component of horizontal flow are of the same magnitude ?

The flow throught the disc will be at a minimum.

exemple 372 The flow throught the disc will be at a minimum.

Question 256-6 : With weight on the wheels/skids, and take off rotor rpm set ?

The only power required to drive the main rotor is the profile power.

Question 256-7 : The parasite power required by a helicopter ?

Is a minimum at the hover.

exemple 380 Is a minimum at the hover.

Question 256-8 : The total power required curve is the resultant of ?

Induced power + rotor profile power + parasite power.

Question 256-9 : The maximum range speed for piston engine helicopters in zero wind conditions is found by ?

Drawing a line tangential to the power required curve from the point of origin of the graph.

exemple 388 Drawing a line tangential to the power required curve from the point of origin of the graph.

Question 256-10 : An overpitched situation is most likely to occur ?

When manoeuvring at the hover.

exemple 392 When manoeuvring at the hover.

Question 256-11 : Parasite power ?

Is parasite drag x velocity.

exemple 396 Is parasite drag x velocity.

Question 256-12 : The minimum of the power required curve in level flight determines ?

T.a.s. for endurance piston engine.

exemple 400 T.a.s. for endurance (piston engine).

Question 256-13 : In a level turn compared to a straight and level flight at the same speed ?

The induced power increases.

exemple 404 The induced power increases.

Question 256-14 : Recovery from retreating blade stall is made by ?

Lowering the collective.

exemple 408 Lowering the collective.

Question 256-15 : The retreating blade will stall at ?

A lower i.a.s. for an increase of auw or increased altitude.

exemple 412 A lower i.a.s. for an increase of auw or increased altitude.

Question 256-16 : With respect only to blade design, forward speed is limited by ?

Airflow reversal, retreating blade stall and compressibility effects.

exemple 416 Airflow reversal, retreating blade stall and compressibility effects.

Question 256-17 : Retreating blade stall ?

Starts at the tip region and develops inboard.

exemple 420 Starts at the tip region and develops inboard.

Question 256-18 : The lift coefficient of an aerofoil section ?

Increases with an increase in angle of attack up to the stall.

exemple 424 Increases with an increase in angle of attack up to the stall.

Question 256-19 : Typically the cl/cd ratio is ?

Maximum at an angle of attack of 4°.

exemple 428 Maximum at an angle of attack of 4°.

Question 256-20 : What is the formula for lift ?

L = cl½rhov²s.

exemple 432 L = cl½rhov²s. — .where.cl = lift coefficient.rho = density.v = tas in m/s.s = surface.

Question 256-21 : Longitudinal stability refers to movement about the ?

Lateral axis.

exemple 436 Lateral axis.

Question 256-22 : What is the advantage of the biconvex symmetrical aerofoil section as related to helicopter blade design ?

The centre of pressure moves little in the normal angle of attack range.

exemple 440 The centre of pressure moves little in the normal angle of attack range.

Question 256-23 : The virtual plane of rotation is the plane through the centre of the rotor hub parallel to ?

The tip path plane.

exemple 444 The tip path plane.

Question 256-24 : Blade loading is ?

The weight of the helicopter, divided by the total area of all the blades.

exemple 448 The weight of the helicopter, divided by the total area of all the blades.

Question 256-25 : Which factors determine the magnitude and direction of the relative airflow in a still air hover ?

Induced flow velocity and blade section velocity.

exemple 452 Induced flow velocity and blade section velocity.

Question 256-26 : The coning angle is determined by ?

Blade lift and centrifugal force.

exemple 456 Blade lift and centrifugal force.

Question 256-27 : The centrifugal turning moment acting on the blade of a helicopter ?

Tends to decrease the blade pitch angle.

exemple 460 Tends to decrease the blade pitch angle.

Question 256-28 : Washout and its objective are ?

A reduction in the blade section pitch angle towards the tip to give a more even distribution of lift along the span of the blade.

exemple 464 A reduction in the blade section pitch angle towards the tip to give a more even distribution of lift along the span of the blade. — . 1622

Question 256-29 : Blade counterweights are sometimes used in order to ?

Reduce the centrifugal turning moment or feathering moment.

Question 256-30 : Tail rotor drift is corrected by ?

Tilting the main rotor disc in the opposite direction to the drift.

exemple 472 Tilting the main rotor disc in the opposite direction to the drift.

Question 256-31 : In forward flight the cyclic pitch is continuously varied throughout the rotor revolution to ?

Obtain more pitch on the retreating side and less pitch on the advancing side.

exemple 476 Obtain more pitch on the retreating side and less pitch on the advancing side.

Question 256-32 : If the right skid of a helicopter touches down first due to tail rotor roll, then the main rotation seen from above ?

Is clockwise.

exemple 480 Is clockwise.

Question 256-33 : Coriolis effect is ?

That effect which tends to accelerate or decelerate a blade as it flaps up or down.

exemple 484 That effect which tends to accelerate or decelerate a blade as it flaps up or down.

Question 256-34 : Dragging of a blade always takes place ?

In the plane of rotation.

exemple 488 In the plane of rotation.

Question 256-35 : The negative range of tail rotor pitch is ?

For control in autorotation.

exemple 492 For control in autorotation.

Question 256-36 : In a steady vertical climb and ignoring the parasite drag of the fuselage ?

Rotor thrust balances weight but rotor required power is greater than that at the hover.

exemple 496 Rotor thrust balances weight but rotor required power is greater than that at the hover.

Question 256-37 : Compared with a hover in ground effect, a helicopter when hovering out of ground effect ?

Has the same total rotor thrust and increased rotor required power.

exemple 500 Has the same total rotor thrust and increased rotor required power.

Question 256-38 : Teetering rotor heads have pre set coning angles at the hub ?

To relieve bending loads in the plane of rotation.

exemple 504 To relieve bending loads in the plane of rotation.

Question 256-39 : Ground effect is most effective when hovering at a skid height ?

Below 4 ft.

exemple 508 Below 4 ft .

Question 256-40 : The advance angle of a particular helicopter is 74°. the phase lag for that particular helicopter will be approximately ?

90°.

exemple 512 90°.

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