Question 280-1 : Induced power ? [ Attainment AIM ]

Question 280-2 : 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.

1350at the contact point total drag is at a minimum it gives the speed for maximum range

Question 280-3 : With reference to rotor design forward speed is limited by ?

Retreating blade stall and relative airspeed.

Question 280-4 : A helicopter is most likely to encounter vortex ring under conditions of ?

Low airspeed with power rate of descent greater than 300 ftmin.

Question 280-5 : In autorotation when aft cyclic is applied the effect will be ?

A decrease in airspeed and rate of descent.

Question 280-6 : A stable static stability is ?

The tendency of an aircraft to return to its original condition of flight after a disturbance.

Question 280-7 : With a tail rotor positioned below the line of the main rotor a helicopter at the hover will ?

Fly left side low if main rotor rotates anti clockwise viewed from above.

A tail rotor positioned on the same line of the main rotor will reduce the tail rotor roll 1352

Question 280-8 : Ground effect is caused by ?

A decreased induced flow velocity.

Question 280-9 : In a still air hover induced flow velocity is affected by ?

Disc loading and density.

Question 280-10 : What are the conditions necessary for ground resonance in addition to having a helicopter in contact with the ground ?

An out of balance force at the rotor head.

Question 280-11 : Dynamic roll over is ?

A condition whereby a rolling motion with wheels in contact with the ground cannot be restrained by cyclic control.

Question 280-12 : The minimum value of the power required curve determines ?

The tas for maximum rate of climb speed.

1356at minimum value of the power required curve where the gap between power available and the maximum power available is greatest you will find the tas for maximum rate of climb speed

Question 280-13 : In a level balanced turn ?

Retreating blade stall will occur at a lower ias than in straight and level flight.

Question 280-14 : With forward flight thrust on the advancing side of a tail rotor system ?

Is kept approximately constant because movement of the blade about its flapping axis reduces the angle of attack.

Question 280-15 : On a main rotor if the flapping hinge is offset ?

It improves cyclic control response.

Question 280-16 : The centre of pressure is the point on an aerofoil section ?

Through which the resultant aerodynamic force acts.

Question 280-17 : In autorotation the tail rotor thrust on a helicopter with anti clockwise main rotor rotation as seen from above is ?

To the left.

Think back to basic vector diagrams of the main rotor which way does total rotor thrust act answer = upok a tail rotor is exactly the same just on its side when we enter auto we are removing all the torque from the main rotor in an anti clockwise rotor with power applied this normally wants to spin us round to the right viewed inside the cockpit that is what would happen if the tail rotor failed remove tq and the fuselage is effectively now going to move in the opposite direction to the main rotor newtons laws equal and opposite blah it is not anywhere near as significant though as there is no tq to really drive it it is just trying to follow the main rotor but there will be an amount of left yaw the tail assembly design will assist with directional stability in this instance but we will still need a little extra help from the tail rotoraircraft nose wants to go left or anti clockwise viewed from above and tail wants to go right we just need to counter this remember here we have created a moment and we need to balance it as i said before think about your vector diagram and which direction does the thrust need to act up or in this case the rotor is on its side so to the left in order to pull the tail back and push the nose back to the righttherefore we need a little thrust to the left to do this the key is the fact that the aircraft wants to follow the main rotor once we have removed all the torque

Question 280-18 : Induced power ?

Is a maximum at the hover without wind.

Question 280-19 : In the flare the resultant aerodynamic forces on the blades ?

Moves forward towards the axis of rotation.

Question 280-20 : The camber line of a biconvex symmetrical section is ?

Common with the chord line.

Question 280-21 : The angle of attack of an aerofoil is the angle between ?

The chord line and the relative air flow.

Question 280-22 : A reduction in blade section pitch angle towards the tip is termed ?

Washout.

Question 280-23 : The force which acts at right angles to the relative airflow is ?

Question 280-24 : The point at which the resultant of lift forces acts is ?

Centre of pressure.

Question 280-25 : On a symmetrical blade element with a positive angle of attack lift is produced by ?

Airflow velocity increasing over upper surface giving decreased pressure and velocity decreasing over lower surface giving increased pressure.

Question 280-26 : Bernoulli's' theorem indicates that ?

The sum of pressure energy and dynamic energy is constant.

Question 280-27 : The point where a laminar boundary layer becomes turbulent is called ?

The transition point.

Transition point the point on the surface of an aerofoil where laminar airflow becomes turbulent the point moves forward as airspeed increasesthe separation point point where airflow leaves the surface of an aerofoil

Question 280-28 : The expression 'in a streamlined flow of fluid the sum of all energies is a constant' derives from ?

Bernoulli's theorem.

Question 280-29 : Cl varies with ?

Angle of attack.

Question 280-30 : Within the normal operating angles of attack the centre of pressure of a biconvex symmetrical aerofoil section ?

Moves very little.

Question 280-31 : That point where airflow leaves the surface of an aerofoil is known as ?

The separation point.

The separation point point where airflow leaves the surface of an aerofoiltransition point the point on the surface of an aerofoil where laminar airflow becomes turbulent the point moves forward as airspeed increases

Question 280-32 : For a rotor which turns in an anti clockwise direction seen from above with a sideways flight to the left with zero wind the pilot will have the advancing blade ?

In front of him.

Question 280-33 : The power requirement of the tail rotor is greatest during ?

A hover turn oge in the same direction as the main rotor.

Question 280-34 : 'a line connecting the leading and trailing edge midway between the upper and lower surface of a aerofoil' this definition is applicable for ?

The camber line.

Question 280-35 : What is the effect on induced drag of an increase in aspect ratio ?

Induced drag decreases because the effect of tip vortices decreases.

Induced drag varies with lift speed and aspect ratio is inversely proportional to aspect ratio and v² so multiply by 1v² and directly proportional to lift²cl²weight²

Question 280-36 : What is the stagnation point ?

The point where the velocity of the relative airflow is reduced to zero.

Question 280-37 : When an aerofoil section has accelerated from subsonic to supersonic speeds its aerodynamic centre will have ?

Shifted from approximately 25% to about 50% of the chord.

Question 280-38 : Which boundary layer when considering its velocity profile perpendicular to the flow has the greatest change in velocity close to the surface ?

Turbulent boundary layer.

Question 280-39 : The si unit of measurement for pressure is ?

Nm².

Icao annex 5 units of measurement attachment b 2 mass force and weight 21 the principal departure of si from the gravimetric system of metric engineering units is the use of explicitly distinct units from mass and force in si the name kilogram is restricted to the unit of mass and the kilogram force from which the suffix force was in practice often erroneously dropped is not to be used in its place the si unit of force the newton is used likewise the newton rather than the kilogram force is used to form derived units which include force for example pressure or stress nm² = pa energy nm = j and power nms = w

Question 280-40 : The polar curve of an aerofoil section is a graphic relationship between ?

Lift coefficient cl and drag coefficient cd.