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Aileron flutter can be caused by ? [ Formation assignment ]

Question 233-1 : Cyclic deformations generated by aerodynamic inertial and elastic loads on the wing the elastic centre of the wing section coinciding with the centre of gravity of that wing section continuous deformations in one direction generated by bending and twisting of the wing aileron reversal

exemple 333 Cyclic deformations generated by aerodynamic, inertial and elastic loads on the wing.Cyclic deformations generated by aerodynamic, inertial and elastic loads on the wing.

Regarding the transonic speed range ?

Question 233-2 : Both subsonic and supersonic speeds exist in the flow around the aeroplane it starts at a mach number just above 1 it starts at a mach number equal to 1 it starts at mcrit and extends to mach number equal to 1

.subsonic range is from 0 and ends at mcrit .transonic range starts at mcrit up to mach 1 3 .supersonic range is from mach 1 3 to approximately mach 5 .above mach 5 the hypersonic speed range exemple 337 Both subsonic and supersonic speeds exist in the flow around the aeroplane.Both subsonic and supersonic speeds exist in the flow around the aeroplane.

The subsonic speed range ?

Question 233-3 : Ends at mcrit ends at a mach number just above m = 1 ends at m = 1 implies both subsonic and supersonic speeds exist in the flow around the aeroplane

.subsonic range is from 0 and ends at mcrit .transonic range starts at mcrit up to mach 1 3 .supersonic range is from mach 1 3 to approximately mach 5 .above mach 5 the hypersonic speed range exemple 341 Ends at mcrit.Ends at mcrit.

Which of these statements about the supersonic speed range is correct ?

Question 233-4 : The airflow everywhere around the aeroplane is supersonic the supersonic speed range starts at a mach number below m = 1 and extends to mach numbers above m = 1 the airflow around the aeroplane is transonic the supersonic speed range starts at m = 1 and ends at mcrit

.subsonic range is from 0 and ends at mcrit .transonic range starts at mcrit up to mach 1 3 .supersonic range is from mach 1 3 airflow everywhere around the aeroplane is supersonic to approximately mach 5 .above mach 5 the hypersonic speed range exemple 345 The airflow everywhere around the aeroplane is supersonic.The airflow everywhere around the aeroplane is supersonic.

Which of these statements about an oblique shock wave are correct or incorrect ?

Question 233-5 : I is correct ii is correct i is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is incorrect

exemple 349 I is correct, ii is correct.I is correct, ii is correct.

Which of these statements about an oblique shock wave are correct or incorrect ?

Question 233-6 : I is correct ii is correct i is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is incorrect

exemple 353 I is correct, ii is correct.I is correct, ii is correct.

Which of these statements about an oblique shock wave are correct or incorrect ?

Question 233-7 : I is correct ii is correct i is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is incorrect

. /com en/normal and oblic shock wave jpg.air is warmer behind the shock wave thus local speed of sound is higher lss is directly proportional to air temperature exemple 357 I is correct, ii is correct.I is correct, ii is correct.

Which of these statements about 'tuck under' are correct or incorrect .i a ?

Question 233-8 : I is incorrect ii is incorrect i is correct ii is incorrect i is incorrect ii is correct i is correct ii is correct

.'tuck under' is the tendency to nose down when speed is increased into the transonic flight regime as the mach number inscreases in the transonic range the centre of pressure will move aft . /com en/com080 418 jpg.'tuck under' is caused by a reduction in the downwash angle at the location of the horizontal stabiliser exemple 361 I is incorrect, ii is incorrect.I is incorrect, ii is incorrect.

Which of these statements about an oblique shock wave are correct or incorrect ?

Question 233-9 : I is correct ii is correct i is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is incorrect

. oblique/normal wave . /com en/normal and oblic shock wave jpg. exemple 365 I is correct, ii is correct.I is correct, ii is correct.

The speed range from approximately m=1 3 to approximately m=5 is called the ?

Question 233-10 : Supersonic range transonic range hypersonic range subsonic range

.subsonic range is from 0 and ends at mcrit .transonic range starts at mcrit up to mach 1 3 .supersonic range is from mach 1 3 to approximately mach 5 .above mach 5 the hypersonic speed range exemple 369 Supersonic range.Supersonic range.

What is the highest speed possible without supersonic flow over the wing ?

Question 233-11 : Critical mach number tuck under speed m = 1 initial mach buffet speed

.the critical mach number of an aerofoil is the free stream mach number at which sonic speed m=1 is first reached on the upper surface . /com en/com080 152 jpg. exemple 373 Critical mach number.Critical mach number.

When the speed over an aerofoil section increases from subsonic to supersonic ?

Question 233-12 : Moves from approximately 25% to about 50% of the chord moves aft by approximately 10% of the chord does not move moves slightly forward

.the aerodynamic center is a point somewhere between the leading edge and the trailing edge where there will be no change in the pitching moment of the aerofoil as the pressure pattern on the aerofoil changes this point on the aerofoil does not move as you change angle of attack and the pitching moment of a wing is always constant about it ..in the transonic region the formation of shock waves on the wing surface and the resulting separated flow causes movement of the wing aerodynamic center .the magnitude of the aerodynamic center movement depends on the design parameters of the wing the aft shift of the aerodynamic center results in an increase in longitudinal stability at a constant mach number or an increase in angle of attack stability the aft shift of the aerodynamic center is analogous to moving the airplane center of gravity forward exemple 377 Moves from approximately 25% to about 50% of the chord.Moves from approximately 25% to about 50% of the chord.

What is the value of the mach number if the mach angle equals 45° ?

Question 233-13 : 1 4 2 0 7 1 2

The formula is .mach angle = sin^&8722 1 x 1/machnumber .45° = sin^ 1 x 1/m .sin 45° = 1/m.m = 1 41 exemple 381 1.41.4

If the mach number is 0 8 and the tas is 480 kt what is the speed of sound ?

Question 233-14 : 600 kt 384 kt 750 kt 560 kt

Jamacof .m = tas lss.0 8 = 480 lss.lss = 600 exemple 385 600 kt.600 kt.

One advantage of a supercritical wing aerofoil over a conventional one is ?

Question 233-15 : It allows a wing of increased relative thickness to be used for approximately the same cruise mach number a lower value of mcrit at the same relative thickness improved dutch roll damping at cruise altitude that there is no need for spoilers

exemple 389 It allows a wing of increased relative thickness to be used for approximately the same cruise mach number.It allows a wing of increased relative thickness to be used for approximately the same cruise mach number.

The sonic boom of an aeroplane flying at supersonic speed is created by ?

Question 233-16 : Shock waves around the aeroplane aerodynamic heating the expansion flow behind the aeroplane the centre of pressure which is moving aft on the aerofoil

exemple 393 Shock waves around the aeroplane.Shock waves around the aeroplane.

A supercritical wing ?

Question 233-17 : Will develop no noticeable shock waves when flying just above mcrit always cruises at mcrit will be free of mach buffet in the transonic range will develop no transonic flow just above mcrit

Celsohernandez .what is a supercritical wing ..when the speed of an aircraft approaches the speed of sound the local airflow about the airplane particularly above the upper surface of the wing may exceed the speed of sound such a condition is called supercritical flow on previous aircraft this supercritical flow resulted in the onset of a strong local shock wave above the upper surface of the wing illustration 'a' this local wave caused an abrupt increase in the pressure on the surface of the wing which may cause the surface boundary layer flow to separate from the surface with a resulting severe increase in the turbulence of the flow the increased turbulence leads to a severe increase in drag and loss in lift with a resulting decrease in flight efficiency . /com en/com080 969 jpg.supercritical airfoils are shaped to substantially reduce the strength of the shock wave and to delay the associated boundary layer separation illustration 'b' since the airfoil shape allows efficient flight at supercritical flight speeds a wing of such design is called a supercritical wing .just above mcrit a supercritical wing will develop no noticeable shock waves exemple 397 Will develop no noticeable shock waves when flying just above mcrit.Will develop no noticeable shock waves when flying just above mcrit.

The aft movement of the centre of pressure during the acceleration through the ?

Question 233-18 : Increase in static longitudinal stability decrease the longitudinal stability decrease the static lateral stability increase the static lateral stability

Transonic flight regime between sonic and supersonic speeds only part of the airflow over the wing is above the speed of sound .the aft movement of the centre of pressure during the acceleration through the transonic flight regime will increase the static longitudinal stability .as the mach number increases in the transonic range the centre of pressure will move aft .a corrective pitch up input on the stabiliser is required . 685.to maintain equilibrium an increase in downward force is required the blue arrow vector of the total aerodynamic lift vertical to the centre of pressure moves aft red point is the centre of gravity .transonic range starts at mcrit up to mach 1 3 .the aft movement of the centre of pressure will increase the initial tendency to return to the original state of equilibrium after being disturbed on the lateral axis longitudinal stability because more down force on the tail is required to maintain level flight thus a more important force will be necessary for disturbing this equilibrium the static longitudinal stability is increased . 686.an aeroplane exhibits static longitudinal stability if when the angle of attack changes the change in total aeroplane lift acts aft of the centre of gravity .notice lateral stability decreases in the transonic range but it is not caused by the centre of pressure shift it is caused by asymmetric shock wave generation on either wing exemple 401 Increase in static longitudinal stability.Increase in static longitudinal stability.

What is the effect of aeroplane mass on shock wave intensity at constant mach ?

Question 233-19 : Increasing mass increases shock wave intensity decreasing mass increases shock wave intensity decreasing mass increases shock wave intensity at below standard temperatures a change in mass does not influence shock wave intensity

.shock wave intensity is determined by the aircraft design the altitude the size and weight of the aircraft the power or volume of the shock wave is dependent on the quantity of air that is being accelerated thus increasing aeroplane mass will increase the quantity of air that is being accelerated at constant mach number exemple 405 Increasing mass increases shock wave intensity.Increasing mass increases shock wave intensity.

The position of the centre of pressure on an aerofoil of an aeroplane cruising ?

Question 233-20 : Further aft further forward identical undetermined since there is no defined centre of pressure location at supersonic speeds

exemple 409 Further aft.Further aft.

Which of these statements about an oblique shock wave are correct or incorrect ?

Question 233-21 : I is incorrect ii is correct i is correct ii is correct i is incorrect ii is incorrect i is correct ii is incorrect

. /com en/normal and oblic shock wave jpg.behind a shock wave static pressure rises but speed and therefore dynamic presure falls some energy is lost in the temperature rise so total pressure static + dynamic has fallen .total pressure in front of an oblique shock wave is higher than behind it exemple 413 I is incorrect, ii is correct.I is incorrect, ii is correct.

Assuming isa conditions and a descent below the tropopause at constant mach ?

Question 233-22 : Lift coefficient decreases ias decreases tas remains constant lift coefficient increases

.'descent at constant mach number' means the tas will increase .if the tas increase at a constant mach number descent we must reduce the angle of attack to maintain lift at the same level during descent lift = 1/2 rho s v² cl thus the lift coefficient cl will be decreased exemple 417 Lift coefficient decreases.Lift coefficient decreases.

Which statement with respect to the speed of sound is correct ?

Question 233-23 : Varies with the square root of the absolute temperature increases always if the density of the air decreases is independent of altitude doubles if the temperature increases from 9° to 36° centigrade

Babar350 .why the answer ' is independent of altitude' is wrong .since the right answer is ' varies with sqr root of kelvin temp' it is indeed independent of altitude isn't it ..the speed of sound is dependent of altitude since temperature normally changes with altitude .speed of sound in kt = 39 x sqrt temperature in k° exemple 421 Varies with the square root of the absolute temperature.Varies with the square root of the absolute temperature.

For most jet transport aeroplanes the maximum operating limit speed vmo ?

Question 233-24 : Is replaced by mmo at higher altitudes is expressed as a true air speed is lower than vne is equal to vd

exemple 425 Is replaced by mmo at higher altitudes.Is replaced by mmo at higher altitudes.

Behind a normal shock wave on an aerofoil section the local mach number is ?

Question 233-25 : Less than 1 lower than before but still greater than 1 equal to 1 higher than before

Img /com en/normal and oblic shock wave jpg.

When shock stall occurs lift will decrease because ?

Question 233-26 : Flow separation occurs behind the shock wave of the existence of a shock wave being located at the trailing edge of the wing mcrit is reached the bow wave appears

exemple 433 Flow separation occurs behind the shock wave.Flow separation occurs behind the shock wave.

If ias remains constant the effect of decreasing aeroplane mass is that mcrit ?

Question 233-27 : Increases remains unchanged decreases assuming the temperature remains constant decreases as altitude increases and increases as altitude decreases

exemple 437 Increases.Increases.

Which of these statements on shock stall is correct ?

Question 233-28 : Shock stall is a stall due to flow separation caused by a shock wave shock stall is a stall due to flow separation at high angles of attack shock stall is caused by sudden loss of lift due to a rise in load factor clmax does not change as the mach number increases

Which of these statements about the transonic speed range is correct ?

Question 233-29 : The transonic speed range starts at mcrit and extends to mach numbers above m = 1 the airflow everywhere around the aeroplane is supersonic the airflow everywhere around the aeroplane is subsonic the transonic speed range starts at m = 0 5 and ends at mcrit

When an aeroplane with the centre of gravity forward of the centre of pressure ?

Question 233-30 : Downwards upwards zero because in steady flight all loads are in equilibrium downwards because it is always negative regardless of the position of the centre of gravity

Img /com en/com080 65 jpg. exemple 449 Downwards.Downwards.

On a jet aeroplane engines mounted below the low wing the thrust is suddenly ?

Question 233-31 : The elevator must be deflected downward the elevator must be deflected upwards no elevator deflection be will required because the thrust line of the engines remains unchanged the amount of elevator deflection is independent of cg location

Img /com en/com080 526 jpg.thrust line is below the center of gravity if thrust is suddenly increased it creates a pitching moment .to counteract you must push the stick or control column forward the elevator is deflected downward the tail will be pushed upward . 885. exemple 453 The elevator must be deflected downward.The elevator must be deflected downward.

During landing of a low winged jet aeroplane the greatest elevator up ?

Question 233-32 : Fully down and the cg is fully forward up and the cg is fully forward fully down and the cg is fully aft up and the cg is fully aft

Img681.

Rotation about the lateral axis is called ?

Question 233-33 : Pitching rolling yawing slipping

Rotation about the lateral axis is called pitching . 686 exemple 461 Pitching.Pitching.

Rolling is the rotation of the aeroplane about the ?

Question 233-34 : Longitudinal axis vertical axis lateral axis wing axis

.rolling is the rotation of the aeroplane about the longitudinal axis . 684 exemple 465 Longitudinal axis.Longitudinal axis.

An aeroplane has static directional stability in a side slip to the right ?

Question 233-35 : Nose of the aeroplane tends to move to the right right wing tends to go down nose of the aeroplane will remain in the same direction nose of the aeroplane tends to move to the left

.a side slip to the right is the slip of the tail to the right the nose goes left .if an aeroplane has static directional stability the intial tendency is to come back in the flight pattern of the aircraft through the air . /com en/com080 74 jpg.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

The cg of an aeroplane is in a fixed position forward of the neutral point ?

Question 233-36 : Stick force stability is not affected by trim maintaining a steady speed above the trim speed requires a pull force aeroplane nose up trim decreases the stick force stability an increase of 10 kt from the trimmed position at low speed has more effect on the stick force than an increase of 10 kt from the trimmed position at high speed

.stick force gradient stick force stability is one measure of longitudinal stability if the stability does not change then neither does the stick force gradient changing the trim setting changes the total stick force and the 'in trim' point but not the gradient stick force stability is not affected by trim .it can be seen from this figure . /com en/com080 75 jpg.the slope of the curve is much smaller at low speed than at high speed indicating that answer 'an increase of 10 kt from the trimmed position at low speed has more effect on the stick force than an increase of 10 kt from the trimmed position at high speed' is incorrect .an increase in speed must generate a pull force .answer 'aeroplane nose up trim decreases the stick force stability' is incorrect because aeroplane nose up trim decreases stick force stability exemple 473 Stick force stability is not affected by trim.Stick force stability is not affected by trim.

The 1 stick force stability and the 2 manoeuvre stability are positively ?

Question 233-37 : 1 forward cg movement 2 forward cg movement 1 forward cg movement 2 trimming the aeroplane nose up 1 aft cg movement 2 aft cg movement 1 trimming the aeroplane nose up 2 trimming the aeroplane nose up

.positive is more stick force and more manoeuvre stability .negative is less stick force and less manoeuvre stability .cs 25 requires a minimum stick force stability of 1 lb per 6 kt change in speed .if you move the cg too far back towards the neutral point then it gets lighter on the stick and you will not satisfy the regulation so if the cg is forward your aircraft is more stable and a change in pitch requires a positive 'force' on the stick or on the control column exemple 477 (1) forward cg movement (2) forward cg movement.(1) forward cg movement (2) forward cg movement.

The value of the manoeuvre stability of an aeroplane is 150 n/g the stick force ?

Question 233-38 : 225 n 375 n 450 n 150 n

.the question states steady level flight so we are at 1g ..we only require +1 5g to reach a load factor of 2 5g..1 5 x 150 n/g = 225 n exemple 481 225 n.225 n.

For a normal stable aeroplane the centre of gravity is located ?

Question 233-39 : With a sufficient minimum margin ahead of the neutral point of the aeroplane aft of the neutral point of the aeroplane at the neutral point of the aeroplane between the aft limit and the neutral point of the aeroplane

exemple 485 With a sufficient minimum margin ahead of the neutral point of the aeroplane.With a sufficient minimum margin ahead of the neutral point of the aeroplane.

The maximum aft position of the centre of gravity is amongst others limited by ?

Question 233-40 : Required minimum value of the stick force per g maximum longitudinal stability of the aeroplane maximum elevator deflection inability to achieve maximum rotation rate during take off

.the magnitude of the stick force required to pitch for an aircraft with manual controls is determined by the distance the cg is forward of the neutral point .when the centre of gravity moves forward the stick force per g increases but you need a minimum value of the stick force per g and if the position of the centre of gravity is too aft a small input from the tail will generate a large unstable wing moment and you will get a rapid attitude change with little tailplane deflection moving the cg aft reduces longitudinal static stability and hence the degree of stick force the maximum aft position of the centre of gravity is amongst others limited by the required minimum value of the stick force per g exemple 489 Required minimum value of the stick force per g.Required minimum value of the stick force per g.

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