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Question 259-1 : Drag damping may be achieved by means of ? [ Explanation maintenance ]

Oil or mechanical friction.

exemple 359 Oil or mechanical friction.

Question 259-2 : With regard to an intermeshing rotor helicopter synchropter.i. the full power available can be used for lifting..ii this helicopter has good directional stability. ?

I true, ii false.

. 1349.you 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 efficiency..yaw is accomplished through varying torque, which is done simply by increasing collective pitch on one of the blade sets, directional stability is not optimal. exemple 363 I true, ii false.

Question 259-3 : In a stationary hover relative to the ground , the position of the advancing blade relative to the pilot ?

Depends on the direction of rotation of the main rotor and wind direction.

exemple 367 Depends on the direction of rotation of the main rotor and wind direction.

Question 259-4 : The effect of a delta three hinge on a tail rotor is that the blade pitch ?

Decreases when the blade flaps in the direction of the thrust vector.

exemple 371 Decreases when the blade flaps in the direction of the thrust vector.

Question 259-5 : Flapping of the tail rotor in forward flight is reduced by the use of ?

Delta three flapping hinges.

exemple 375 Delta three flapping hinges.

Question 259-6 : Which of the following ground surfaces gives the best ground cushion ?

Ice covered level concrete.

exemple 379 Ice covered level concrete.

Question 259-7 : The onset of vortex ring state settling with power can be identified by ?

Vibration, cyclic stick shake, random yawing, increased rate of descent

exemple 383 Vibration, cyclic stick shake, random yawing, increased rate of descent

Question 259-8 : The recommended recovery action from overpitching is ?

Lower the collective lever to increase rotor rpm

exemple 387 Lower the collective lever to increase rotor rpm

Question 259-9 : Tail rotor blade counterweights are sometimes used in order to ?

Prevent the blades from going to minimum pitch in case of control failure.

exemple 391 Prevent the blades from going to minimum pitch in case of control failure.

Question 259-10 : Maximum rotor rpm in powered flight is limited by ?

Blade and hub strength.

exemple 395 Blade and hub strength.

Question 259-11 : The correct tyre pressure of the undercarriage is important to prevent ground resonance when ?

Engaging a fully articulated rotor.

exemple 399 Engaging a fully-articulated rotor.

Question 259-12 : One feature that compensates for phase lag is ?

The advance angle.

exemple 403 The advance angle.

Question 259-13 : Which moments or motions interact in a dutch roll ?

Rolling and yawing.

exemple 407 Rolling and yawing.

Question 259-14 : The tendency to dutch roll increases when ?

The static lateral stability increases.

Cqb15 december 2011. exemple 411 The static lateral stability increases.

Question 259-15 : An example of a combined lateral and directional periodic motion is a ?

Dutch roll.

Cqb15 december 2011. exemple 415 Dutch roll.

Question 259-16 : The formula for the mach number is a= speed of sound ?

M= tas / a

exemple 419 M= tas / a

Question 259-17 : The speed of sound is determined only by ?

Temperature.

Cqb15 december 2011... varegar.tricky, but you should focus in the formula..lss local speed of sound = 38,95 which is a constant x square root of temperature in kelvin.. it is obvious that temperature affects density and therefore density affects sound speed, but keep focus in the previous formula. exemple 423 Temperature.

Question 259-18 : In a stationary subsonic streamline flow pattern, if the streamlines converge, in this part of the pattern, the static pressure i will...and the velocity ii will... ?

I decrease, ii increase.

. 1466.static pressure decreases in a venturi, and airflow speed increases. exemple 427 (i) decrease, (ii) increase.

Question 259-19 : The si units of air density i and force ii are ?

I kg / m³, ii n.

.the use of units follow the international rules and style conventions.pdf668 exemple 431 (i) kg / m³, (ii) n.

Question 259-20 : The unit of dynamic pressure 'q' is ?

N / m².

.the use of units follow the international rules and style conventions.pdf668 exemple 435 N / m².

Question 259-21 : Which formula or equation describes the relationship between force f , acceleration a and mass m ?

F=m.a

.force energy brought to bear, which tends to cause a motion or change...mass a measure of the amount of material contained in a body...acceleration rate of change of velocity velocity + time or distance + time². exemple 439 F=m.a

Question 259-22 : Static pressure is acts ?

In all directions.

.static pressure is atmospheric pressure measured at a point where there is no external disturbance, and the flow of air over the surface is perfectly smooth. exemple 443 In all directions.

Question 259-23 : Which one of the following statements about bernoulli's theorem is correct ?

The dynamic pressure increases as static pressure decreases.

.pt total pressure..ps static pressure..pd dynamic pressure 1/2 x density x tas²...bernoulli's theorem is..pt = ps + pd..then, if pd inscreases, ps decreases, as pt always remains constant. exemple 447 The dynamic pressure increases as static pressure decreases.

Question 259-24 : If in a two dimensional incompressible and subsonic flow, the streamlines converge the static pressure in the flow will ?

Decrease.

. 1466.static pressure decreases in a venturi, and airflow speed increases. exemple 451 Decrease.

Question 259-25 : Bernoulli's equation can be written as. pt= total pressure, ps = static pressure and q=dynamic pressure ?

Pt = ps + q

.pt total pressure..ps static pressure..pd 'q' dynamic pressure 1/2 x density x tas²..bernoulli's theorem is pt = ps + pd exemple 455 Pt = ps + q

Question 259-26 : Which of the following statements about boundary layers is correct ?

The turbulent boundary layer has more kinetic energy than the laminar boundary layer.

exemple 459 The turbulent boundary layer has more kinetic energy than the laminar boundary layer.

Question 259-27 : On an asymmetrical, single curve aerofoil main rotor blade element , in subsonic airflow, at low angle of attack, when the angle of attack is increased, the centre of pressure will ?

Move forward.

.the pressure created by an aerofoil at any point may be represented by a vector at right angles to its surface, whose length is proportional to the difference between absolute pressure at the point and the free stream static pressure..all of them can be represented by a single vector acting at a particular point, called the centre of pressure.. 669..the centre of pressure is a theoretical point on the chord line through which the resultant of all forces the total reaction is said to act..its position is usually around 25% of the way from the leading edge a quarter chord behind the leading edge , simply because more lift is generated there, but it moves steadily forward as the angle of attack is increased, until just before the stalling angle, when it moves rapidly backwards the centre of pressure's most forward point is just before the stalling angle. exemple 463 Move forward.

Question 259-28 : With increasing angle of attack, the stagnation point will move i... and the point of lowest pressure will move ii....respectively i and ii are ?

I down, ii forward.

. 1576.in red, the stagnation point will move down..in blue, the point of lowest pressure will move forward. exemple 467 (i) down, (ii) forward.

Question 259-29 : The correct drag d formula is ?

D= cd 1/2 rho v² s

.where cd = drag coefficient.rho = density.v = tas in m/s.s = surface..drag is the force that opposes the forward motion of a body through the air. it's an aerodynamic force on a body acting parallel and opposite to the relative wind. exemple 471 D= cd 1/2 rho v² s

Question 259-30 : The value of the parasite drag in straight and level flight at constant weight varies linearly with the ?

Square of the speed.

.parasite drag is present any time the helicopter is moving through the air. this type of drag increases with airspeed. non lifting components of the helicopter, such as the cabin, rotor mast, tail, and landing gear, contribute to parasite drag the tail rotor drag is also included in the parasite drag. any loss of momentum by the airstream, due to such things as openings for engine cooling, creates additional parasite drag..because of its rapid increase with increasing airspeed, parasite drag is the major cause of drag at higher airspeeds.. 2421.parasite drag varies with the square of the velocity therefore, doubling the airspeed increases the parasite drag four times...the power to overcome this drag is the parasite power..in the level flight at constant speed the main rotor induced power, the rotor profile power and the parasite power are summed to give the total power required to drive the main rotor notation 'ptot mr'.

Question 259-31 : Rotation about the lateral axis is called ?

Pitching.

. 2422 exemple 479 Pitching.

Question 259-32 : Rolling is the rotation of the helicopter about the ?

Longitudinal axis.

. 2422 exemple 483 Longitudinal axis.

Question 259-33 : An helicopter has static directional stability, in a side slip to the right, initially the ?

Nose of the helicopter tends to move to the right.

.directional stability is accomplished by placing a vertical stabilizer or fin to the rear of the centre of gravity on the upper portion of the tail section.. 2423. fuselage and fin for directional stability. exemple 487 Nose of the helicopter tends to move to the right.

Question 259-34 : Following a disturbance, an helicopter oscillates about the lateral axis at a constant amplitude..the helicopter is ?

Statically stable dynamically neutral.

. static stability..static stability refers to the initial tendency, or direction of movement, back to equilibrium. in aviation, it refers to the initial response when disturbed from a given aoa, slip, or bank..positive static stability is the initial tendency of the helicopter to return to the original state of equilibrium after being disturbed... dynamic stability.dynamic stability refers to the helicopter response over time when disturbed from a given aoa, slip, or bank..neutral dynamic stability means, once displaced, the displaced object neither decreases nor increases in amplitude. a worn automobile shock absorber exhibits this tendency...for information. positive dynamic stability means, over time, the motion of the displaced object decreases in amplitude and, because it is positive, the object displaced returns toward the equilibrium state.. negative dynamic stability means, over time, the motion of the displaced object increases and becomes more divergent. exemple 491 Statically stable - dynamically neutral.

Question 259-35 : Compared with usual values of a blade angle of attack, the lift 1 and drag 2 in the stall change as follows ?

1 decreases 2 increases.

exemple 495 (1) decreases (2) increases.

Question 259-36 : A strake on the tailboom is employed ?

To separate airflow downwash from the main rotor on one side of the tailboom.

. 2424.on some helicopters, running the length of the tail boom are 'l' shape brackets. these are known as tail boom strakes and they act like spoilers...the strake breaks up the airflow downwash from the main rotor on one side, creating a low pressure airflow past the strake. the 'normal' higher pressure airflow on the unobstructed side of the tailboom thus turns the tailboom into a wing, and creates lift toward the strake side of the boom. this offloads the anti torque demand on the tail rotor, giving greater tail rotor authority in the hover. exemple 499 To separate airflow (downwash from the main rotor) on one side of the tailboom.

Question 259-37 : An anti torque system without tail rotor is called ?

Notar.

. 2425.notar fan housed in the aft fuselage pushes large amount of low pressured air into the tail boom. the air is released through slits cut in the starboard/right side of the tail boom and jet thruster. the air released through the slits flows along the tail boon surface by a boundary layer control called coanda effect..under the effect of main rotor downwash, tail boom acts like a wing and and produces lift toward right when observed from aft and this becomes a part of anti torque. during hovering anti torque is compensated for with thrust generated by jet thruster. exemple 503 Notar.

Question 259-38 : How are the speeds shown in the figure at point 1 and point 2 related to the relative wind/airflow v. 2426 ?

V1 = 0 and v2 > v

exemple 507 V1 = 0 and v2 > v

Question 259-39 : Which of these statements about tandem rotor helicopters are correct or incorrect.1 the two rotors turn in the same direction.2 the rear rotor is positioned higher than the front rotor ?

1 is incorrect, 2 is correct.

.boeing ch 47 chinook. 1339..vertol h 21. 1340.tandem rotor helicopters use counter rotating rotors, with each canceling out the other's torque.

Question 259-40 : When increasing the forward speed by a factor 3, the parasite power increases by a factor ?

27.

.the parasite drag fx is the drag on the helicopter fuselage including the drag of the rotor hub and all external equipment as wheels, winch, etc. the tail rotor drag is also included in the parasite drag. the power to overcome this drag is the parasite power px...fx = 1/2 rho s v² cx..px = fx x v = 1/2 rho s v3 cx..px varies as the cube of the speed. exemple 515 27.


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