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Preparation > civilian : When the air is passing through a shock wave the static temperature will ?

Question 213-1 : Increase decrease stay constant decrease and beyond a certain mach number start increasing again

. /com en/normal and oblic shock wave jpg. exemple 313 increase.increase.

When the air is passing through a shock wave the density will ?

Question 213-2 : Increase decrease stay constant decrease and beyond a certain mach number start increasing again

. /com en/normal and oblic shock wave jpg. exemple 317 increase.increase.

When air has passed through a shock wave the local speed of sound is ?

Question 213-3 : Increased not affected decreased decreased and beyond a certain mach number start increasing again

. /com en/normal and oblic shock wave jpg. exemple 321 increased.increased.

If the mach number of an aeroplane in supersonic flight is increased the mach ?

Question 213-4 : Decrease increase stay constant decrease and beyond a certain mach number start increasing again

. /com en/com080 602 jpg.. /com en/com080 308 jpg.the higher the mach number is the narrower the cone angle will be exemple 325 decrease.decrease.

The loss of total pressure in a shock wave is due to the fact that ?

Question 213-5 : Kinetic energy in the flow is converted into heat energy the speed reduction is too high the static pressure decrease is comparatively high the friction in the boundary layer is higher

exemple 329 kinetic energy in the flow is converted into heat energy.kinetic energy in the flow is converted into heat energy.

When the air is passing through an expansion wave the local speed of sound will ?

Question 213-6 : Decrease increase stay constant decrease and beyond a certain mach number start increasing again

.the effect on pressure temperature density and velocity is the opposite in expansion waves to oblique/normal 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 corner .airflowing through an expansion fan goes through the following changes.1 the airsteam accelerates and the air behind the shock wave has higher supersonic velocity.2 the airflow direction follows the surface contour.3 the static pressure behind the expansion wave decreases.4 the density behind the expansion wave decreases.5 there is no loss of energy. /com en/com080 369 jpg.. oblique/normal wave. /com en/normal and oblic shock wave jpg. exemple 333 decrease.decrease.

When the air is passing through an expansion wave the mach number will ?

Question 213-7 : Increase decrease stay constant decrease and beyond a certain mach number start increasing again

.the effect on pressure temperature density and velocity is the opposite in expansion waves to oblique/normal 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 corner .airflowing through an expansion fan goes through the following changes.1 the airsteam accelerates and the air behind the shock wave has higher supersonic velocity.2 the airflow direction follows the surface contour.3 the static pressure behind the expansion wave decreases.4 the density behind the expansion wave decreases.5 there is no loss of energy. /com en/com080 369 jpg.. oblique/normal wave. /com en/normal and oblic shock wave jpg. exemple 337 increase.increase.

When the air is passing through an expansion wave the static temperature will ?

Question 213-8 : Decrease increase stay constant decrease and beyond a certain mach number start increasing again

.the effect on pressure temperature density and velocity is the opposite in expansion waves to oblique/normal 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 corner .airflowing through an expansion fan goes through the following changes.1 the airsteam accelerates and the air behind the shock wave has higher supersonic velocity.2 the airflow direction follows the surface contour.3 the static pressure behind the expansion wave decreases.4 the density behind the expansion wave decreases.5 there is no loss of energy. /com en/com080 369 jpg.. oblique/normal wave. /com en/normal and oblic shock wave jpg. exemple 341 decrease.decrease.

Compared with an oblique shock wave at the same mach number a normal shock wave ?

Question 213-9 : Higher compression higher expansion smaller compression smaller expansion

.normal at 90° perpendicular to the shock medium's flow direction .oblique at an angle to the direction of flow.a normal shock wave has a higher loss in total pressure and a higher compression exemple 345 higher compression.higher compression.

Compared with an oblique shock wave at the same mach number a normal shock wave ?

Question 213-10 : Higher loss in total pressure higher total pressure higher total temperature lower static temperature

.normal at 90° perpendicular to the shock medium's flow direction .oblique at an angle to the direction of flow.a normal shock wave has a higher loss in total pressure and a higher compression exemple 349 higher loss in total pressure.higher loss in total pressure.

To increase the critical mach number a conventional aerofoil should ?

Question 213-11 : Have a low thickness to chord ratio have a large camber be used with a high angle of attack have a large leading edge radius

exemple 353 have a low thickness to chord ratio.have a low thickness to chord ratio.

The critical mach number can be increased by ?

Question 213-12 : Sweepback of the wings positive dihedral of the wings a t tail an increase in wing aspect ratio

exemple 357 sweepback of the wings.sweepback of the wings.

What is the influence of decreasing aeroplane weight on mcrit at constant ias ?

Question 213-13 : Mcrit increases as a result of flying at a smaller angle of attack mcrit increases as a result of compressibility effects mcrit decreases mcrit decreases as a result of flying at a greater angle of attack

.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. in this example mcrit = 0 72.if the aerofoil is thicker the airflow will have to travel a larger distance in a same time mach 1 will be reached earlier mcrit the speed in front of the aerofoil is reduced.if you increase angle of attack the speed of the airflow over the wing is increased during lift generation the airflow is accelerated on the upper side of the wing mach 1 over the wing will be reached earlier .therefore if weight is reduced the angle of attack is reduced this increasing the mcrit speed limit exemple 361 mcrit increases as a result of flying at a smaller angle of attack.mcrit increases as a result of flying at a smaller angle of attack.

Assuming isa conditions which statement with respect to the climb is correct ?

Question 213-14 : At constant ias the mach number increases at constant mach number the ias increases at constant tas the mach number decreases at constant ias the tas decreases

.the mach number is the ratio of the aircraft true airspeed to the sonic velocity at the altitude considered..for those questions use the very simple 'ertm' diagram. /com en/com080 336 jpg..the eas/ias line is vertical because the question states climb at constant ias. ertm for e as/ r as rectified air speed or cas / t as/ m ach.ias corrected for instrumental and static error = cas .cas = 1/2 rho v².density will decrease during climb and since we want to maintain constant ias tas will increase.mach = tas / local speed of sound.local speed of sound varies only with temperature and the question states assuming isa conditions temperature decreases by 2° per 1000 ft thus if tas increases and lss decreases the mach number increases exemple 365 at constant ias the mach number increases.at constant ias the mach number increases.

Vortex generators mounted on the upper wing surface will ?

Question 213-15 : Decrease the shock wave induced separation decrease the interference drag of the trailing edge flaps decrease the stall speed by increasing spanwise flow on the wing increase the effectiveness of the spoiler due to increase in parasite drag

.many swept wings were found to suffer from separation at transonic speeds because shocks formed on the wing create an increasing pressure that slows the air suddenly and causes flow separation laminar airflow will separate from the airfoil stall easier than turbulent airflow vortex generators cause turbulent high energy little tornado airflow in the boundary layer .at low speed these vortices essentially 'sweep away' the boundary layer and 'excited' air close to the wing and the trailing control surfaces.vortex generators decrease shock wave induced flow separation by transfer energy from the free airflow into the boundary layer.the advantage of wing devices that create vortices is that a vortex adds energy to the airflow and increases its forward momentum this momentum encourages the airflow to remain attached to the surface of the wing at higher angles of attack than it would otherwise as a result the wing is able to continue generating lift in conditions where it would have stalled this behavior is particularly advantageous on high performance military aircraft that need to be extremely maneuverable at high angles of attack in combat the advantage for commercial airliners is increased safety since the plane is less likely to experience a wing stall during critical stages of flight like takeoff and landing. /com en/com080 162 jpg. exemple 369 decrease the shock wave induced separation.decrease the shock wave induced separation.

Tuck under will happen ?

Question 213-16 : Only above the critical mach number only at the critical mach number only below the critical mach number above or below the critical mach number depending on the angle of attack

/com en/com080 418 jpg. exemple 373 only above the critical mach number.only above the critical mach number.

High speed buffet is induced by ?

Question 213-17 : Boundary layer separation due to shock waves a shift of the centre of gravity boundary layer control expansion waves on the wing upper side

exemple 377 boundary layer separation due to shock waves.boundary layer separation due to shock waves.

If a symmetrical aerofoil is accelerated from subsonic to supersonic speed the ?

Question 213-18 : Aft to the mid chord aft to the trailing edge forward to the leading edge forward to the mid chord

exemple 381 aft to the mid chord.aft to the mid chord.

At what speed does the front of a shock wave move across the earth's surface ?

Question 213-19 : The ground speed of the aeroplane the speed of sound at ground level the speed of sound at flight level the true air speed of the aeroplane

. /com en/com080 352 jpg.the front of a shock wave move across the earth's surface at the ground speed of the aeroplane exemple 385 the ground speed of the aeroplane.the ground speed of the aeroplane.

A machtrimmer ?

Question 213-20 : Corrects insufficient stick force stability at high mach numbers increases the stick force per g at high mach numbers is necessary for compensation of the autopilot at high mach numbers has no effect on the shape of the elevator position versus speed ias curve for a fully hydraulic controlled aeroplane

.as soon as mcrit is exceeded shockwave formation on the top of the wing moves the centre of pressure cp rearwards this generates the nose down pitching moment known as mach tuck...by design all aeroplanes must require an increasing push force from the pilot with increasing speed but the illustration shows the effect of the cp moving rearwards is to decrease the basic stick force at speeds above mcrit this is unacceptable and would eventually require an increasing pull force with increasing speed...to maintain the required stick force gradient a mach trim system is fitted the mach trim system input gives a resultant stick force to maintain the required stick force gradient...because the mach trim system maintains the required stick force gradient the 'tempting' answer of 'increases the stick force per g at high mach numbers' is clearly incorrect exemple 389 corrects insufficient stick force stability at high mach numbers.corrects insufficient stick force stability at high mach numbers.

Whilst flying at a constant ias and at n = 1 as the aeroplane mass decreases ?

Question 213-21 : Increases remains constant is independent of the angle of attack decreases

At a lower mass at the same speed you have to reduce your angle of attack to maintain the value of lift at a reduced angle of attack the air is less accelerated over the upper wing surface . .the critical mach number of an aeroplane is the highest speed possible without supersonic flow over the wing consequently as the aeroplane mass decreases the value of mcrit increases exemple 393 increases.increases.

Which statement is correct about an expansion wave in a supersonic flow .1 the ?

Question 213-22 : 1 and 2 are correct 1 is correct and 2 is incorrect 1 is incorrect and 2 is correct 1 and 2 are incorrect

.the effect on pressure temperature density and velocity is the opposite in expansion waves to oblique/normal 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 corner .airflowing through an expansion fan goes through the following changes.1 the airsteam accelerates and the air behind the shock wave has higher supersonic velocity.2 the airflow direction follows the surface contour.3 the static pressure behind the expansion wave decreases.4 the density behind the expansion wave decreases.5 there is no loss of energy. /com en/com080 369 jpg. exemple 397 1 and 2 are correct.1 and 2 are correct.

How will the density and static temperature change in a supersonic flow from a ?

Question 213-23 : Density will increase static temperature will increase density will increase static temperature will decrease density will decrease static temperature will increase density will decrease static temperature will decrease

exemple 401 density will increase, static temperature will increase.density will increase, static temperature will increase.

In order to provide an adequate 'buffet boundary' at the commencement of the ?

Question 213-24 : Increased to 191 knots drag will increase and air distance per kg of fuel will decrease increased to 191 knots drag will decrease and air distance per kg of fuel will increase increased to 202 knots but since the same angle of attack is used drag and range will remain the same unaffected as vs always occurs at the same angle of attack

.value of 1 3vs at 135000 kg = 180 x sqrt 135000 / 120000..value of 1 3vs at 135000 kg = 180 x 1 0607...value of 1 3vs at 135000 kg = 190 926 kt.'sqrt' means 'square root' exemple 405 increased to 191 knots, drag will increase and air distance per kg of fuel will decrease.increased to 191 knots, drag will increase and air distance per kg of fuel will decrease.

The speed range between high and low speed buffet ?

Question 213-25 : Increases during a descent at a constant ias increases during climb decreases during a descent at a constant mach number is always positive at mach numbers below mmo

Mach buffet boundaries .mach buffet is a function of the speed of the airflow over the wing not necessarily the speed of the aircraft any time that too great a lift demand is made on the wing whether from too fast an airspeed or from too high an aoa near the mmo the 'high speed' buffet occurs there are also occasions when the buffet can be experienced at much lower speeds known as the 'low speed mach buffet' .an aircraft flown at a speed too slow for its weight and altitude necessitating a high aoa is the most likely situation to cause a low speed mach buffet this very high aoa has the effect of increasing airflow velocity over the upper surface of the wing until the same effects of the shock waves and buffet occur as in the high speed buffet situation the aoa of the wing has the greatest effect on inducing the mach buffet at either the high speed or low speed boundaries for the aircraft.if the ias remains constant during a descent the mach number will also steadily reduce this is because tas reduces and the local speed of sound increases low speed buffet will therefore occur at a lower mach number the speed range between high and low speed buffet will increase exemple 409 increases during a descent at a constant ias.increases during a descent at a constant ias.

'tuck under' is caused by i movement of the centre of pressure of the wing and ?

Question 213-26 : I aft ii decreasing i forward ii decreasing i aft ii increasing i forward ii increasing

/com en/com080 418 jpg. exemple 413 (i) aft (ii) decreasing.(i) aft (ii) decreasing.

What is the significance of the maximum allowed cruising altitude based on the ?

Question 213-27 : A manoeuvre with a load factor of 1 3 will cause buffet onset a manoeuvre with a load factor of 1 3 will cause mcrit to be exceeded a manoeuvre with a load factor of 1 3 will cause a mach number at which accelerated low speed stall occurs exceeding a load factor of 1 3 will cause permanent deformation of this aeroplane

.in order to maintain a minimum margin against buffeting and ensure good aircraft maneuverability it is necessary to determine an acceptable load factor limit below which buffeting shall never occur this load factor limit is generally fixed to 1 3 this value is an operating limitation but not a regulatory one the corresponding altitude is called the '1 3g buffet limited altitude' or 'buffet ceiling' exemple 417 a manoeuvre with a load factor of 1.3 will cause buffet onset.a manoeuvre with a load factor of 1.3 will cause buffet onset.

When the mach number is slowly increased in straight and level flight the first ?

Question 213-28 : On the upper surface at the wing root on the lower surface of the wing somewhere on the fin somewhere on the horizontal tail

exemple 421 on the upper surface at the wing root.on the upper surface at the wing root.

A transonic mach number is a mach number ?

Question 213-29 : At which both subsonic and supersonic local speeds occur between the buffet onset mach number and the mach number corresponding to total supersonic flow at which only supersonic local speeds occur in the range between mcrit and mmo

exemple 425 at which both subsonic and supersonic local speeds occur.at which both subsonic and supersonic local speeds occur.

During a climb at a constant ias the mach number will ?

Question 213-30 : Increase decrease initially and increase subsequently remain constant increase initially and remain constant subsequently

As the mach number increases in straight and level flight a shock wave on the ?

Question 213-31 : Move towards the trailing edge move towards the leading edge not move disappear

exemple 433 move towards the trailing edge.move towards the trailing edge.

During which type of stall does the angle of attack have the smallest value ?

Question 213-32 : Shock stall accelerated stall low speed stall deep stall

.a shock stall is a stall caused by the airflow over an aircraft's wings being disturbed by shock waves when flying at or near to the aircraft's critical mach number.shock stall is the separation of the boundary layer behind the shock wave. bcg160 .i would like to request a brief explanation or definition about accelerated stall thanks..an accelerated stall is caused by abrupt or excessive control movement an accelerated stall can occur during a sudden change in the flight path during manoeuvres such as steep turns or a rapid recovery from a dive it is called an 'accelerated stall' because it occurs at a load factor greater than 1g an accelerated stall is usually more violent than a low speed stall 'normal' stall at 1g and is often unexpected because of the relatively high airspeed exemple 437 shock stall.shock stall.

A normal shock wave is a discontinuity plane ?

Question 213-33 : That is always normal to the local flow across which the temperature drops suddenly across which the pressure drops suddenly that is always normal to the surface

An aeroplane is flying through the transonic range whilst maintaining straight ?

Question 213-34 : A pitch up input of the stabiliser a stability augmentation system to improve dynamic stability much more thrust from the engines a higher ias to compensate the nose down effect

.as the mach number inscreases 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

If the mach number is 0 8 and the tas is 400 kt what is the speed of sound ?

Question 213-35 : 500 kt 320 kt 480 kt 600 kt

Jamacof .mach no formula .mach no = tas / lss....mach no is mach number..tas is true airspeed expressed in knots..lss is local speed of sound expressed in knots....so in this question...0 8 = 400/lss..0 8 lss = 400..lss = 400 0 8..lss = 500 kt exemple 449 500 kt.500 kt.

In supersonic flight all disturbances produced by an aeroplane are ?

Question 213-36 : Within a conical zone dependent on the mach number outside a conical zone dependent on the mach number in front of the aeroplane very weak and negligible

exemple 453 within a conical zone, dependent on the mach number.within a conical zone, dependent on the mach number.

Mach buffet occurs ?

Question 213-37 : At the mach number at which shock wave induced boundary layer separation occurs when the mach number has increased to mcrit directly after exceeding mcrit when the stall angle of attack is exceeded

In the event of failure of the mach trimmer ?

Question 213-38 : The mach number must be limited the centre of gravity must be moved aft the speed must be kept constant the aeroplane mass must be limited

exemple 461 the mach number must be limited.the mach number must be limited.

In the transonic range the aeroplane characteristics are strongly determined by ?

Question 213-39 : Mach number tas ias cas

.transonic flight regime between sonic and supersonic speeds only part of the airflow over the wing is above the speed of sound .the mach number is the speed used in transonic range exemple 465 mach number.mach number.

Which statement is correct about an expansion wave in supersonic flow .1 the ?

Question 213-40 : 1 is correct and 2 is incorrect 1 and 2 are correct 1 is incorrect and 2 is correct 1 and 2 are incorrect

.the effect on pressure temperature density and velocity is the opposite in expansion waves to oblique/normal shock waves. chrism .supersonic flight is no longer part of the learning objectives i believe..learning objectives 081 02 01 05 subdivision of aerodynamic flow . list the subdivision of aerodynamic flow . subsonic flow . transonic flow . supersonic flow . describe the characteristics of the flow regimes listed above

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