A free Premium account on the FCL.055 website! Read here
Sign up to unlock all our services and 15164 corrected and explained questions.
Question 279-1 : The induced flow component of airflow through the rotor disc ? [ Analysis topography ]
Decreases with forward flight
Question 279-2 : During a transition into forward flight from the hover and maintaining level flight ?
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 increasesTotal rotor thrust decreases. total rotor thrust and power increase. power increases but total rotor thrust decreases.
Question 279-3 : 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.
The flow through the disc will be at a maximum. for a particular blade pitch angle the angle of attack will be at a minimum. maximum power will be required, to maintain the correct rotor r.p.m.
Question 279-4 : With weight on the wheelsskids and take off rotor rpm set ?
The only power required to drive the main rotor is the profile power.
The induced power is high. parasite power plus induced power equals rotor profile power. rotor profile power is at a maximum.
Question 279-5 : The parasite power required by a helicopter ?
Is a minimum at the hover.
Is a minimum when total power required is a minimum. increases in direct proportion to forward speed. is a minimum at mean sea level.
Question 279-6 : The total power required curve is the resultant of ?
Induced power + rotor profile power + parasite power.
Induced power - parasite power - rotor profile power. induced power + rotor profile power - parasite power. power required + power in hand.
Question 279-7 : 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.
Noting the speed on the graph at which the power required is a minimum. drawing a line tangential to the power required curve from the power available origin. noting the speed on the graph where the ratio of power in hand to forward speed is greatest.
Question 279-8 : An overpitched situation is most likely to occur ?
When manoeuvring at the hover.
When induced power is increasing. when power required is low. when carrying out a flare manoeuvre.
Question 279-9 : Parasite power ?
Is parasite drag x velocity.
Varies as drag². varies as velocity². is always the largest percentage of total power required in straight level flight.
Question 279-10 : The minimum of the power required curve in level flight determines ?
Tas for endurance piston engine .
T.a.s. for maximum range (piston engine). t.a.s. for maximum angle of climb. the aircrafts' v.n.o.
Question 279-11 : In a level turn compared to a straight and level flight at the same speed ?
The induced power increases.
The parasite power increases. the rotor profile power decreases. the total power requirement is unchanged.
Question 279-12 : Recovery from retreating blade stall is made by ?
Lowering the collective.
Flaring the aircraft to reduce speed. turning away from the wind. moving the cyclic further to increase speed.
Question 279-13 : The retreating blade will stall at ?
A lower ias for an increase of auw or increased altitude.
A higher i.a.s. for increased all up weight but at the same i.a.s. for an increase in altitude. a higher i.a.s. for an increase of auw or increased altitude. a lower i.a.s. for increased all up weight but at the same i.a.s. for an increase in altitude.
Question 279-14 : With respect only to blade design forward speed is limited by ?
Airflow reversal retreating blade stall and compressibility effects.
Availability of cyclic in counter-acting flapback. the power required against power available. availability of cyclic in counter-acting inflow roll.
Question 279-15 : Retreating blade stall ?
Starts at the tip region and develops inboard.
Starts about mid span and develops outboard to the tips. starts at the blade root and develops outboard to the tip. starts at the blade root because of the larger blade pitch angle.
Question 279-16 : The lift coefficient of an aerofoil section ?
Increases with an increase in angle of attack up to the stall.
Is at its maximum value at that angle of attack giving the maximum lift to drag ratio. changes with density. changes with the velocity of the airflow, squared.
Question 279-17 : Typically the clcd ratio is ?
Maximum at an angle of attack of 4°.
Maximum at an angle of attack of 16°. minimum at an angle of attack of 4°. minimum at an angle of attack of 16°.
Question 279-18 : What is the formula for lift ?
L = cl½rhov²s.
Where cl = lift coefficientrho = densityv = tas in ms s = surfaceL = cl2rhov²s. l = cl½ rho²vs. l = clrhov ²s.
Question 279-19 : Longitudinal stability refers to movement about the ?
Lateral axis.
Longitudinal axis. axis of the tail rotor. axis perpendicular on the vertical axis.
Question 279-20 : 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.
It produces no lift at zero degrees angle of attack. it has good stalling characteristics. for a given angle of attack, it has a greater cl than other aerofoil sections.
Question 279-21 : The virtual plane of rotation is the plane through the centre of the rotor hub parallel to ?
The tip path plane.
The relative airflow. the main rotor hubplane. the horizon.
Question 279-22 : Blade loading is ?
The weight of the helicopter divided by the total area of all the blades.
The weight of the helicopter, divided by the disc area. the disc area, divided by the weight of the helicopter. the blade area, divided by the disc area x 100%.
Question 279-23 : Which factors determine the magnitude and direction of the relative airflow in a still air hover ?
Induced flow velocity and blade section velocity.
Lift and rotor drag. total rotor thrust and rotor drag. lift and total aerodynamic forces.
Question 279-24 : The coning angle is determined by ?
Blade lift and centrifugal force.
The aerodynamic lift and drag produced by a blade. centrifugal force and rotor r.p.m. rotor thrust and rotor drag.
Question 279-25 : The centrifugal turning moment acting on the blade of a helicopter ?
Tends to decrease the blade pitch angle.
Question 279-26 : 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.
1622A reduction in the blade section pitch angle towards the tip to reduce the chances of retreating blade stall. a reduction in the blade section pitch angle towards the tip to delay the effects of compressibility. the difference between the blade section pitch angle and the angle of attack at any point along the blade.
Question 279-27 : Blade counterweights are sometimes used in order to ?
Reduce the centrifugal turning moment or feathering moment.
Reduce the aerodynamic pitching moment. adjust the cg. position on the blade. increase the centrifugal turning moment or feathering moment.
Question 279-28 : Tail rotor drift is corrected by ?
Tilting the main rotor disc in the opposite direction to the drift.
Fitting delta three hinges to the tail rotor. designing the tail rotor to be level with the main rotor. fitting the tail rotor as a 'tractor type' as opposed to a 'pusher type'.
Question 279-29 : 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.
Obtain less pitch on the retreating side and more pitch on the advancing side. assist in flap back of the rotor disc. obtain more pitch in the front and less on the rear of the disc.
Question 279-30 : If the right skid of a helicopter touches down first due to tail rotor roll then the main rotation seen from above ?
Is clockwise.
Is anti-clockwide. could be either way. tail rotor roll depends only on degree of yaw pedal required. could be either way, depending upon the vertical distance of the tail rotor from the main rotor.
Question 279-31 : Coriolis effect is ?
That effect which tends to accelerate or decelerate a blade as it flaps up or down.
The force that causes tail rotor flapping another term for phase lag. cancelled by a delta three hinge.
Question 279-32 : Dragging of a blade always takes place ?
In the plane of rotation.
In the horizontal plane rotating about the vertical axis. in the vertical plane rotating about the axis of rotation. in the horizontal plane rotating about the shaft axis.
Question 279-33 : The negative range of tail rotor pitch is ?
For control in autorotation.
To counteract tail rotor drift. to elimate tail rotor flapping. for control when carrying out a pro-torque spot turn.
Question 279-34 : 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.
Question 279-35 : 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.
Has the same total rotor thrust and rotor required power. has increased total rotor thrust and increased rotor required power. has increased total rotor thrust and the same rotor required power.
Question 279-36 : Teetering rotor heads have pre set coning angles at the hub ?
To relieve bending loads in the plane of rotation.
To relieve dragging forces. to give greater clearance from the fuselage. to allow the blades to flap in the absence of flapping hinges.
Question 279-37 : Ground effect is most effective when hovering at a skid height ?
Below 4 ft .
At normal 4 ft. at approximately 3/4 of the rotor diameter. over tall grass.
Question 279-38 : The advance angle of a particular helicopter is 74° the phase lag for that particular helicopter will be approximately ?
90°.
16°. 106°. 164°.
Question 279-39 : Ground resonance is due to ?
A coupling between the rotor imbalance frequency and the natural frequency of the undercarriage.
The rotor downwash affecting the tail rotor when on or close to the ground. a high frequency, low amplitude vibration emanating from thin skinned areas such as doors and panels. a rate of roll which cannot be arrested with full opposite cycle.
Question 279-40 : The induced flow component of airflow through the rotor disc ?
Decreases with forward flight so influencing the angle of attack.
Increases with forward speed to increase the mass flow. in forward flight is evenly distributed about the disc. remains constant throughout the helicopters speed range.
Exclusive rights reserved. Reproduction prohibited under penalty of prosecution.
