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Question 254-1 : In a constant speed vertical climb outside ground effect, if the effects of parasite drag on the helicopter fuselage are ignored ? [ Explanation maintenance ]

Total rotor thrust will equal aircraft weight.

exemple 354 Total rotor thrust will equal aircraft weight.

Question 254-2 : When a helicopter is operating in ground effect ige , under the same environmental conditions as the helicopter out of ground effect oge , for all blade sections the blade section ?

Pitch angle is lower

exemple 358 Pitch angle is lower

Question 254-3 : In straight and level flight, as forward speed is increased, rotor thrust is ?

Increased

exemple 362 Increased

Question 254-4 : Ground effect is altered by wind and slope of the ground and its effect disappears at a height approximately equal to ?

The diameter of the rotor disc.

exemple 366 The diameter of the rotor disc.

Question 254-5 : Whilst hovering close to the ground, if the effect of recirculation becomes greater than ground effect ?

More power and collective pitch would be required.

.ground effect is the increased efficiency of the rotor system caused by interference of the airflow when near the ground. the air pressure or density is increased, which acts to decrease the downward velocity of air. ground effect permits relative wind to be more horizontal, lift vector to be more vertical, and induced drag to be reduced. these conditions allow the rotor system to be more efficient. maximum ground effect is achieved when hovering over smooth hard surfaces..when hovering over surfaces as tall grass, trees, bushes, rough terrain, and water, maximum ground effect is reduced..rotor efficiency is increased by ground effect to a height of about one rotor diameter measured from the ground to the rotor disk for most helicopters. since the induced flow velocities are decreased, the aoa is increased, which requires a reduced blade pitch angle and a reduction in induced drag. this reduces the power required to hover in ground effect.. 1348.when hovering over long grass the power required to hover will be greater than that required over a smooth surface. it is similar to hovering outside ground effect since there is a greater recirculation of air through the rotor disc. exemple 370 More power and collective pitch would be required.

Question 254-6 : In level flight, as forward velocity is increased, induced flow velocity ?

Decreases and the component of the horizontal airflow through the disc increases.

.the mean induced airflow velocity is perpendicular to the rotor disc. in the hover, the induced airflow velocity increases after passing through the rotor it is maximum in the hover. in level flight, as forward velocity increases, induced flow velocity and power decreases and the horizontal airflow through the disc increases, influencing the angle of attack..when the induced flow and the perpendicular component of horizontal flow are of the same magnitude, the flow through the disc will be at a minimum. exemple 374 Decreases and the component of the horizontal airflow through the disc increases.

Question 254-7 : The effects of recirculation are at their worst ?

Close to building type obstructions.

exemple 378 Close to building-type obstructions.

Question 254-8 : If the cg is aft of the rotor hub, when the helicopter lifts to the hover ?

The nose will pitch up.

exemple 382 The nose will pitch up.

Question 254-9 : A power reduction appears in translation ?

As airspeed reaches a value of approximately 10 to 20 kts

exemple 386 As airspeed reaches a value of approximately 10 to 20 kts

Question 254-10 : When the helicopter is flared to transition from forward flight to the hover, the change in relative airflow causes ?

The blade angle of attack to increase

exemple 390 The blade angle of attack to increase

Question 254-11 : Airflow reversal first occurs at the blade 1 on the 2 side of the disc ?

1 root 2 retreating

exemple 394 (1) root (2) retreating

Question 254-12 : Retreating blade stall will occur because ?

At increasing forward speed the retreating blade needs an increasingly higher angle of attack.

exemple 398 At increasing forward speed the retreating blade needs an increasingly higher angle of attack.

Question 254-13 : The symptoms of retreating blade stall are ?

Rotor roughness and vibration leading to a possible pitch up and roll to the retreating side

exemple 402 Rotor roughness and vibration leading to a possible pitch up and roll to the retreating side

Question 254-14 : When the helicopter is in level, forward flight ?

The induced flow velocity is smallest at the front of the disc

exemple 406 The induced flow velocity is smallest at the front of the disc

Question 254-15 : Inflow roll ?

Causes a roll towards the advancing side

exemple 410 Causes a roll towards the advancing side

Question 254-16 : The degree of control available through the cyclic stick is affected by aircraft ?

Aum, altitude and cg

Aum = all up mass. exemple 414 Aum, altitude and cg

Question 254-17 : Induced power ?

Decreases as forward speed increases.

exemple 418 Decreases as forward speed increases.

Question 254-18 : The flight speed to achieve maximum endurance in a helicopter is ?

Near the speed corresponding to the lowest point of the power required curve

exemple 422 Near the speed corresponding to the lowest point of the power required curve

Question 254-19 : With an increase in altitude,. 1 normally aspirated piston engine power will...... 2 in the hover rotor power required will..... ?

1 decrease 2 increase.

exemple 426 (1) decrease (2) increase.

Question 254-20 : When operating with limited power, the speed giving the steepest or maximum angle of climb. limited power power available is less than the hover power required ?

Is always less than the best endurance speed.

exemple 430 Is always less than the best endurance speed.

Question 254-21 : Compared to a straight and level flight to perform a coordinated turn same height and speed the collective pitch 1 and power 2 must be ?

1 increased 2 increased

exemple 434 (1) increased (2) increased

Question 254-22 : If the rotor is overpitched, the corrective action is to ?

Reduce collective pitch and leave engine power constant

exemple 438 Reduce collective pitch and leave engine power constant

Question 254-23 : If the helicopter forward speed increases then ?

Parasite drag from the fuselage and its components increases.

exemple 442 Parasite drag from the fuselage and its components increases.

Question 254-24 : Overpitching may occur as a result of ?

Applying too much collective pitch at high power settings.

.because of the downwash of the main rotor on the stabiliser fitted to the tail boom. exemple 446 Applying too much collective pitch at high power settings.

Question 254-25 : To maintain constant rotor rpm during autorotation ?

The autorotative moment must be greater than the moment of the blades drag.

exemple 450 The autorotative moment must be greater than the moment of the blades drag.

Question 254-26 : The autorotative section of a rotor blade in vertical autorotation is ?

In the centre span section of the blade.

. 2408 exemple 454 In the centre span section of the blade.

Question 254-27 : In autorotation for maximum range, the helicopter must be flown at a speed ?

Found by drawing a tangent from the origin to the tas/rate of descent curve

exemple 458 Found by drawing a tangent from the origin to the tas/rate of descent curve

Question 254-28 : In an autorotation with normal forward speed, compared with a vertical autorotation in still air, the rate of descent is ?

Always lower.

exemple 462 Always lower.

Question 254-29 : In a normal forward autorotative descent, if the collective is raised by a small amount, the rotor rpm will 1 and the rate of descent will 2 ?

1 decrease 2 decrease

exemple 466 (1) decrease (2) decrease

Question 254-30 : One of the function of the anti torque device during an autorotation is ?

To prevent the fuselage rotating in the same direction as the main rotor blades


Question 254-31 : If an autorotative descent is commenced from a high altitude and collective position is not changed, then, as altitude reduces, rotor rpm ?

And rate of descent will decrease.

exemple 474 And rate of descent will decrease.

Question 254-32 : The required condition for the initiation of ground resonance is ?

A deliberate or unintentional oscillation of the helicopter in contact with or resting on the ground

exemple 478 A deliberate or unintentional oscillation of the helicopter in contact with or resting on the ground

Question 254-33 : The most likely causes of rotor head vibration are ?

Faulty drag dampers, incorrect blade tracking and blades of unequal weight or balance.

exemple 482 Faulty drag dampers, incorrect blade tracking and blades of unequal weight or balance.

Question 254-34 : If ground resonance is encountered in a helicopter, the correct recovery action is ?

To take off if rotor rpm sufficient, to shut down and apply rotor brake if rotor rpm insufficient

exemple 486 To take-off if rotor rpm sufficient, to shut down and apply rotor brake if rotor rpm insufficient

Question 254-35 : Vortex ring settling with power will probably occur if power is applied when the airspeed is below approximately ?

30 kts and the rate of descent is greater than 300 fpm

exemple 490 30 kts and the rate of descent is greater than 300 fpm

Question 254-36 : The loss of lift leading to retreating blade stall will commence ?

Near the tip.

exemple 494 Near the tip.

Question 254-37 : Autorotative moment of the aerodynamic forces ?

Drives the rotor during autorotation

exemple 498 Drives the rotor during autorotation

Question 254-38 : At a given power setting, ground effect is most effective when hovering ?

Over a hard level surface.

exemple 502 Over a hard level surface.

Question 254-39 : A fully articulated rotor permits the blades to ?

Flap, drag and feather.

exemple 506 Flap, drag and feather.

Question 254-40 : Should a helicopter suffer from retreating blade stall in flight, to reduce the effects ?

The collective pitch should be lowered to decrease pitch.

exemple 510 The collective pitch should be lowered to decrease pitch.


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