Question 281-1 : True airspeed tas is ? [ Attainment AIM ]

Question 281-2 : Total pressure is rho = density ?

Static pressure plus dynamic pressure.

Question 281-3 : The unit of measurement for density is ?

Kgm³.

Question 281-4 : The transition point is the point where ?

The boundary layer changes from laminar to turbulent.

Question 281-5 : Considering a positively cambered aerofoil section the pitching moment when the lift coefficient cl=0 is ?

Negative nose down .

When a positively cambered airfoil is at zero lift it has to be at a small negative alpha to cancel out the camber which gives some lift at zero alpha the angle of attack has a negative value when the lift coefficient equals zero it is because the pressure distribution is producing negative lift at the front and positive lift at the back of the airfoil 1631a symmetrical aerofoil need to have a positive pitch to produce lift if the pitching moment is zero the lift is zeroa positively cambered aerofoil produces lift with a zero pitching moment thus not to produce lift it need a negative pitching moment 2416in this example lift coeffient = 0 when angle of attack = 4° the pitching moment is nose down

Question 281-6 : An aerofoil is cambered when ?

The line which connects the centres of all inscribed circles is curved.

Question 281-7 : A flat plate when positioned in the airflow at a small angle of attack will produce ?

Both lift and drag.

Question 281-8 : Positive static stability of an aeroplane means that following a disturbance from the equilibrium condition ?

The initial tendency is to return towards its equilibrium condition.

Question 281-9 : Load factor is ?

Liftweight.

Question 281-10 : Which statement is correct about an expansion wave in supersonic flow 1 the static temperature in front of an expansion wave is higher than the static temperature behind it2 the speed in front of an expansion wave is higher than the speed behind it ?

1 is correct and 2 is incorrect.

The effect on pressure temperature density and velocity is the opposite in expansion waves to obliquenormal shock waves expansion wave also known as a prandtl meyer expansion fan when a supersonic airflow passes over a surface that suddenly drops away or rounds corner an expansion fan of an infinite number of shock waves forms at the apex of the corner and diverts the airflow around the cornerairflowing through an expansion fan goes through the following changes 1the airsteam accelerates and the air behind the shock wave has higher supersonic velocity2the airflow direction follows the surface contour3the static pressure behind the expansion wave decreases4the density behind the expansion wave decreases5there is no loss of energy 2417 obliquenormal wave 2418

Question 281-11 : Which rotor system is most effective in terms of control power ?

The rigidhead.

2405

Question 281-12 : What happens as a helicopter accelerates through 12 kt ?

It passes through translational lift.

Question 281-13 : With reference to translational lift which of the following statements is true ?

Question 281-14 : When a helicopter is in an ideal free air hover the trt is acting vertically and is equal and opposite to ?

Weight and parasite drag.

Trt total rotor thrustthe parasite drag comes from the airflow blowing downwards over the fuselage it adds to the apparent weight so you need a little extra thrust to overcome itlooking at forward flight you have four main vectors 2419as you slow down and the downwash slowly changes from being rear and down to just being down the vectors move around a little lift and weight stay the same drag moves to being a bit down and thrust has to move a bit upin the hover weight and drag coincide and lift and thrust coincide so in the hover you get lift + thrust = weight + drag

Question 281-15 : As a helicopter accelerates the attitude becomes ?

Nose down.

Question 281-16 : Where on the surface of a typical aerofoil will flow separation normally start at high angles of attack ?

Question 281-17 : Lift is the ?

Question 281-18 : A helicopter is statically stable when it shows the ?

Tendency to return to its original attitude after having been displaced.

Question 281-19 : Blade sailing can occur when ?

The rotor is starting up or slowing down in gusty wind conditions.

Question 281-20 : Which statement is correct regarding the coning angle ?

Question 281-21 : Dissymmetry of lift due to forward flight is compensated for by the ?

Advancing blade flapping up and reducing its angle of attack and the retreating blade flapping down and increasing its angle of attack.

Question 281-22 : The rotor disc plane is always ?

Perpendicular to the rotor thrust.

Question 281-23 : The main induced air flow velocity is considered perpendicular to the ?

Question 281-24 : For a rotor which turns in a clockwise direction seen from above in a backward flight with zero wind the pilot will have the advancing blade ?

On his right.

Question 281-25 : For a rotor which turns in an anti clockwise direction seen from above in a backward flight with zero wind the pilot will have the retreating blade ?

On his right.

Question 281-26 : For a rotor which turns in a clockwise direction seen from above in a backward flight with zero wind the pilot will have the retreating blade ?

On his left.

Question 281-27 : Separation of the airflow from a blade ?

Occurs with increasing mach number at decreasing angle of attack.

Question 281-28 : Drag dampers in a rotor system ?

May use the principle of damping by friction.

Question 281-29 : The main reason for the negative range of tail rotor pitch is ?

For yaw control in autorotation.

Question 281-30 : Why is sweep back often applied to the tip of modern rotor blades ?

To reduce the mach effects on the advancing blade.

Question 281-31 : One reason for increased rotor rpm in the flare is ?

Conservation of angular momentum coriolis effect.

Question 281-32 : The advance angle is ?

Used to compensate for phase lag.

Question 281-33 : The ground effect is affected by 1 the hover height2 the length of the helicopter3 the ground texture4 the diameter of the main rotorthe combination of correct statements is ?

1 3 and 4.

Question 281-34 : As a result of a positive 'g' manoeuvre in a helicopter there is ?

An increase in coning angle.

Question 281-35 : Drag dampers in a rotor system ?

May use the principle of damping by means of oil.

Question 281-36 : The forces and moments caused by the dragging of the rotor blades on a hingeless rotor head are absorbed ?

Through bending at the blade root.

Question 281-37 : The recommended recovery action from vortex ring settling with power is to ?

Cyclic forward to increase airspeed pause for airspeed then apply power.

Question 281-38 : The centre of gravity of a single rotor helicopter will be ?

Close to the main rotor axis.

Question 281-39 : Drag damping may be achieved by means of ?

Oil or mechanical friction.

Question 281-40 : With regard to an intermeshing rotor helicopter synchropter i the full power available can be used for liftingii this helicopter has good directional stability ?

I true ii false.

1349you do not have to counteract a torque reaction on a synchropter the two rotors turn in opposite directions this arrangement allows the helicopter to function without the need for a tail rotor which saves power however neither rotor lifts directly vertically which reduces efficiencyyaw is accomplished through varying torque which is done simply by increasing collective pitch on one of the blade sets directional stability is not optimal