Parasite power ? [ Question security ]

Question 249-1 : Is parasite drag x velocity varies as drag² varies as velocity² is always the largest percentage of total power required in straight level flight

The minimum of the power required curve in level flight determines ?

Question 249-2 : T a s 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

In a level turn compared to a straight and level flight at the same speed ?

Question 249-3 : The induced power increases the parasite power increases the rotor profile power decreases the total power requirement is unchanged

Recovery from retreating blade stall is made by ?

Question 249-4 : Lowering the collective flaring the aircraft to reduce speed turning away from the wind moving the cyclic further to increase speed

The retreating blade will stall at ?

Question 249-5 : A lower i a s 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

With respect only to blade design forward speed is limited by ?

Question 249-6 : 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

Retreating blade stall ?

Question 249-7 : 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

The lift coefficient of an aerofoil section ?

Question 249-8 : 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

Typically the cl/cd ratio is ?

Question 249-9 : 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°

What is the formula for lift ?

Question 249-10 : L = cl½rhov²s l = cl2rhov²s l = cl½ rho²vs l = clrhov ²s

Longitudinal stability refers to movement about the ?

Question 249-11 : Lateral axis longitudinal axis axis of the tail rotor axis perpendicular on the vertical axis

What is the advantage of the biconvex symmetrical aerofoil section as related ?

Question 249-12 : 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

The virtual plane of rotation is the plane through the centre of the rotor hub ?

Question 249-13 : The tip path plane the relative airflow the main rotor hubplane the horizon

Blade loading is ?

Question 249-14 : 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%

Which factors determine the magnitude and direction of the relative airflow in ?

Question 249-15 : Induced flow velocity and blade section velocity lift and rotor drag total rotor thrust and rotor drag lift and total aerodynamic forces

The coning angle is determined by ?

Question 249-16 : 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

The centrifugal turning moment acting on the blade of a helicopter ?

Question 249-17 : Tends to decrease the blade pitch angle tends to roll the aircraft towards the advancing blades tends to increase the blade pitch angle is only caused by the balance weights attached to the helicopter blade

Washout and its objective are ?

Question 249-18 : 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 a 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

Blade counterweights are sometimes used in order to ?

Question 249-19 : 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

Tail rotor drift is corrected by ?

Question 249-20 : 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'

In forward flight the cyclic pitch is continuously varied throughout the rotor ?

Question 249-21 : 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

If the right skid of a helicopter touches down first due to tail rotor roll ?

Question 249-22 : 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

Coriolis effect is ?

Question 249-23 : 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

Dragging of a blade always takes place ?

Question 249-24 : 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

The negative range of tail rotor pitch is ?

Question 249-25 : For control in autorotation to counteract tail rotor drift to elimate tail rotor flapping for control when carrying out a pro torque spot turn

In a steady vertical climb and ignoring the parasite drag of the fuselage ?

Question 249-26 : Rotor thrust balances weight but rotor required power is greater than that at the hover rotor thrust is greater than weight and rotor required power is greater than that at the hover rotor thrust balances weight and rotor required power is the same as that at the hover rotor thrust is greater than weight and rotor required power is the same as that at the hover

Compared with a hover in ground effect a helicopter when hovering out of ground ?

Question 249-27 : 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

Teetering rotor heads have pre set coning angles at the hub ?

Question 249-28 : 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

Ground effect is most effective when hovering at a skid height ?

Question 249-29 : Below 4 ft at normal 4 ft at approximately 3/4 of the rotor diameter over tall grass

The advance angle of a particular helicopter is 74° the phase lag for that ?

Question 249-30 : 90° 16° 106° 164°

Ground resonance is due to ?

Question 249-31 : 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

The induced flow component of airflow through the rotor disc ?

Question 249-32 : 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

Induced power ?

Question 249-33 : Is a maximum at the hover in still air increases with forward speed decreases in direct proportion to forward speed is affected only by change of speed

The maximum range speed for piston engine helicopters in zero wind conditions ?

Question 249-34 : Drawing a line tangential to the power required curve from the point of origin of the graph the point on the graph at which the required power is a minimum drawing the tangent to the power curve from the power available origin drawing the tangent to the power required curve from the point of hover power

With reference to rotor design forward speed is limited by ?

Question 249-35 : Retreating blade stall and relative airspeed tail rotor control availability engine power availability lack of forward cyclic control

A helicopter is most likely to encounter vortex ring under conditions of ?

Question 249-36 : Low airspeed with power rate of descent greater than 300 ft/min zero airspeed with power rate of descent less than 200 ft/min cruising airspeed with power rate of descent 500 ft/min a vertical or low airspeed autorotation

In autorotation when aft cyclic is applied the effect will be ?

Question 249-37 : A decrease in airspeed and rate of descent a decrease in speed only a decrease in airspeed and rotor r p m an increase in airspeed and rotor r p m

A stable static stability is ?

Question 249-38 : The tendency of an aircraft to return to its original condition of flight after a disturbance the ability of an aircraft to turn about its axes the ability of an aircraft to climb after being disturbed most difficult to achieve in the yawing plane in forward flight

With a tail rotor positioned below the line of the main rotor a helicopter at ?

Question 249-39 : Fly left side low if main rotor rotates anti clockwise viewed from above fly right side low if main rotor rotates anti clockwise viewed from above fly left or right side low depending on which side of the helicopter the tail rotor is positioned maintain a level attitude

Ground effect is caused by ?

Question 249-40 : A decreased induced flow velocity recirculation of the air through the disc giving greater mass flow an increased induced flow velocity a decrease in pressure below the disc