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Question 277-1 : Ground effect is altered by wind and slope of the ground and its effect disappears at a height approximately equal to ? [ Analysis topography ]

The diameter of the rotor disc.

exemple 377 The diameter of the rotor disc.

Question 277-2 : 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 381 More power and collective pitch would be required.

Question 277-3 : 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 385 Decreases and the component of the horizontal airflow through the disc increases.

Question 277-4 : The effects of recirculation are at their worst ?

Close to building type obstructions.

exemple 389 Close to building-type obstructions.

Question 277-5 : If the cg is aft of the rotor hub, when the helicopter lifts to the hover ?

The nose will pitch up.

exemple 393 The nose will pitch up.

Question 277-6 : A power reduction appears in translation ?

As airspeed reaches a value of approximately 10 to 20 kts

exemple 397 As airspeed reaches a value of approximately 10 to 20 kts

Question 277-7 : 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 401 The blade angle of attack to increase

Question 277-8 : Airflow reversal first occurs at the blade 1 on the 2 side of the disc ?

1 root 2 retreating

exemple 405 (1) root (2) retreating

Question 277-9 : Retreating blade stall will occur because ?

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

exemple 409 At increasing forward speed the retreating blade needs an increasingly higher angle of attack.

Question 277-10 : The symptoms of retreating blade stall are ?

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

exemple 413 Rotor roughness and vibration leading to a possible pitch up and roll to the retreating side

Question 277-11 : When the helicopter is in level, forward flight ?

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

exemple 417 The induced flow velocity is smallest at the front of the disc

Question 277-12 : Inflow roll ?

Causes a roll towards the advancing side

exemple 421 Causes a roll towards the advancing side

Question 277-13 : The degree of control available through the cyclic stick is affected by aircraft ?

Aum, altitude and cg

Aum = all up mass. exemple 425 Aum, altitude and cg

Question 277-14 : Induced power ?

Decreases as forward speed increases.


Question 277-15 : 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 433 Near the speed corresponding to the lowest point of the power required curve

Question 277-16 : 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 437 (1) decrease (2) increase.

Question 277-17 : 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.


Question 277-18 : 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


Question 277-19 : If the rotor is overpitched, the corrective action is to ?

Reduce collective pitch and leave engine power constant

exemple 449 Reduce collective pitch and leave engine power constant

Question 277-20 : If the helicopter forward speed increases then ?

Parasite drag from the fuselage and its components increases.

exemple 453 Parasite drag from the fuselage and its components increases.

Question 277-21 : 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.

Question 277-22 : To maintain constant rotor rpm during autorotation ?

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

exemple 461 The autorotative moment must be greater than the moment of the blades drag.

Question 277-23 : The autorotative section of a rotor blade in vertical autorotation is ?

In the centre span section of the blade.

. 2408 exemple 465 In the centre span section of the blade.

Question 277-24 : 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


Question 277-25 : In an autorotation with normal forward speed, compared with a vertical autorotation in still air, the rate of descent is ?

Always lower.

exemple 473 Always lower.

Question 277-26 : 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 477 (1) decrease (2) decrease

Question 277-27 : 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

exemple 481 To prevent the fuselage rotating in the same direction as the main rotor blades

Question 277-28 : 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 485 And rate of descent will decrease.

Question 277-29 : 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 489 A deliberate or unintentional oscillation of the helicopter in contact with or resting on the ground

Question 277-30 : The most likely causes of rotor head vibration are ?

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

exemple 493 Faulty drag dampers, incorrect blade tracking and blades of unequal weight or balance.

Question 277-31 : 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 497 To take-off if rotor rpm sufficient, to shut down and apply rotor brake if rotor rpm insufficient

Question 277-32 : 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 501 30 kts and the rate of descent is greater than 300 fpm

Question 277-33 : The loss of lift leading to retreating blade stall will commence ?

Near the tip.

exemple 505 Near the tip.

Question 277-34 : Autorotative moment of the aerodynamic forces ?

Drives the rotor during autorotation

exemple 509 Drives the rotor during autorotation

Question 277-35 : At a given power setting, ground effect is most effective when hovering ?

Over a hard level surface.

exemple 513 Over a hard level surface.

Question 277-36 : A fully articulated rotor permits the blades to ?

Flap, drag and feather.

exemple 517 Flap, drag and feather.

Question 277-37 : Should a helicopter suffer from retreating blade stall in flight, to reduce the effects ?

The collective pitch should be lowered to decrease pitch.

exemple 521 The collective pitch should be lowered to decrease pitch.

Question 277-38 : 'dynamic roll over' may be caused by ?

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

exemple 525 An excessive rolling movement developing about a skid or wheel in contact with a slope or uneven ground.

Question 277-39 : A main rotor blade may be twisted along its span to ensure ?

A more desirable lift distribution.

exemple 529 A more desirable lift distribution.

Question 277-40 : 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 533 The reduced control range in the rearward direction and the directional stability of the airframe


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