Question 277-1 : In straight and level flight as forward speed is increased rotor thrust is ? [ Analysis topography ]

Question 277-2 : 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.

Question 277-3 : 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 surfaceswhen hovering over surfaces as tall grass trees bushes rough terrain and water maximum ground effect is reducedrotor 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 1348when 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

Question 277-4 : 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 attackwhen 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

Question 277-5 : The effects of recirculation are at their worst ?

Close to building type obstructions.

Question 277-6 : If the cg is aft of the rotor hub when the helicopter lifts to the hover ?

The nose will pitch up.

Question 277-7 : A power reduction appears in translation ?

As airspeed reaches a value of approximately 10 to 20 kts.

Question 277-8 : 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.

Question 277-9 : Airflow reversal first occurs at the blade 1 on the 2 side of the disc ?

1 root 2 retreating.

Question 277-10 : Retreating blade stall will occur because ?

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

Question 277-11 : The symptoms of retreating blade stall are ?

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

Question 277-12 : When the helicopter is in level forward flight ?

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

Question 277-13 : Inflow roll ?

Causes a roll towards the advancing side.

Question 277-14 : The degree of control available through the cyclic stick is affected by aircraft ?

Question 277-15 : Induced power ?

Decreases as forward speed increases.

Question 277-16 : The flight speed to achieve maximum endurance in a helicopter is ?

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

Question 277-17 : With an increase in altitude 1 normally aspirated piston engine power will 2 in the hover rotor power required will ?

Question 277-18 : 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 ?

Question 277-19 : 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 277-20 : If the rotor is overpitched the corrective action is to ?

Reduce collective pitch and leave engine power constant.

Question 277-21 : If the helicopter forward speed increases then ?

Question 277-22 : 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 277-23 : To maintain constant rotor rpm during autorotation ?

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

Question 277-24 : The autorotative section of a rotor blade in vertical autorotation is ?

Question 277-25 : In autorotation for maximum range the helicopter must be flown at a speed ?

Found by drawing a tangent from the origin to the tasrate of descent curve.

Question 277-26 : In an autorotation with normal forward speed compared with a vertical autorotation in still air the rate of descent is ?

Always lower.

Question 277-27 : 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.

Question 277-28 : 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 277-29 : 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.

Question 277-30 : 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.

Question 277-31 : The most likely causes of rotor head vibration are ?

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

Question 277-32 : 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.

Question 277-33 : 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.

Question 277-34 : The loss of lift leading to retreating blade stall will commence ?

Near the tip.

Question 277-35 : Autorotative moment of the aerodynamic forces ?

Drives the rotor during autorotation.

Question 277-36 : At a given power setting ground effect is most effective when hovering ?

Over a hard level surface.

Question 277-37 : A fully articulated rotor permits the blades to ?

Flap drag and feather.

Question 277-38 : Should a helicopter suffer from retreating blade stall in flight to reduce the effects ?

The collective pitch should be lowered to decrease pitch.

Question 277-39 : '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.

Question 277-40 : A main rotor blade may be twisted along its span to ensure ?

A more desirable lift distribution.