Question 263-1 : In the event of failure of the mach trimmer ? [ Theoretical lift off ]

Question 263-2 : In the transonic range the aeroplane characteristics are strongly determined by the ?

Mach number.

Transonic flight regime between sonic and supersonic speeds only part of the airflow over the wing is above the speed of soundthe mach number is the speed used in transonic range

Question 263-3 : 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 chrism supersonic flight is no longer part of the learning objectives i believelearning 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

Question 263-4 : What is the relation between the mach angle mu and the corresponding mach number ?

Sin mu = 1m.

com encom080 602jpg

Question 263-5 : Which type of buffet will occur if a jet aeroplane slowly accelerates in level flight from its cruise speed in still air at high altitude ?

Mach buffet.

Question 263-6 : Which speeds are used and in which sequence if an emergency descent is carried out from the normal cruise altitude of a large jet transport aeroplane ?

Mmo vmo.

Vmommo is defined as the maximum operating limit speed vmo is expressed in knots calibrated airspeed kcas while mmo is expressed in mach number the vmo limit is usually associated with operations at lower altitudes and deals with structural loads and flutter the mmo limit is associated with operations at higher altitudes and is usually more concerned with compressibility effects and flutter at lower altitudes structural loads and flutter are of concern at higher altitudes compressibility effects and flutter are of concernin descent and at low altitude vmoin climb and at high altitude mmoat first at high altitude mmo must be taken in consideration and after passing the 'crossosver altitude' the altitude at which a specified cas and mach value represent the same tas value vmo must be used

Question 263-7 : Aileron flutter can be caused by ?

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

Question 263-8 : Regarding the transonic speed range ?

Both subsonic and supersonic speeds exist in the flow around the aeroplane.

Subsonic range is from 0 and ends at mcrittransonic range starts at mcrit up to mach 13supersonic range is from mach 13 to approximately mach 5above mach 5 the hypersonic speed range

Question 263-9 : The subsonic speed range ?

Ends at mcrit.

Subsonic range is from 0 and ends at mcrittransonic range starts at mcrit up to mach 13supersonic range is from mach 13 to approximately mach 5above mach 5 the hypersonic speed range

Question 263-10 : Which of these statements about the supersonic speed range is correct ?

The airflow everywhere around the aeroplane is supersonic.

Subsonic range is from 0 and ends at mcrittransonic range starts at mcrit up to mach 13supersonic range is from mach 13 airflow everywhere around the aeroplane is supersonic to approximately mach 5above mach 5 the hypersonic speed range

Question 263-11 : Which of these statements about an oblique shock wave are correct or incorrect i the static temperature in front of an oblique shock wave is lower than behind it ii the static pressure in front of an oblique shock wave is lower than behind it ?

I is correct ii is correct.

Question 263-12 : Which of these statements about an oblique shock wave are correct or incorrect i the density in front of an oblique shock wave is lower than behind it ii the total pressure in front of an oblique shock wave is higher than behind it ?

I is correct ii is correct.

Question 263-13 : Which of these statements about an oblique shock wave are correct or incorrect i the density behind an oblique shock wave is higher than in front of itii the local speed of sound behind an oblique shock wave is higher than in front of it ?

I is correct ii is correct.

com ennormal and oblic shock wavejpgair is warmer behind the shock wave thus local speed of sound is higher lss is directly proportional to air temperature

Question 263-14 : Which of these statements about 'tuck under' are correct or incorrect i a contributing factor to 'tuck under' is a forward movement of the centre of pressure of the wingii a contributing factor to 'tuck under' is an increase in the downwash angle at the location of the horizontal stabiliser ?

I is incorrect ii is incorrect.

'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 encom080 418jpg'tuck under' is caused by a reduction in the downwash angle at the location of the horizontal stabiliser

Question 263-15 : Which of these statements about an oblique shock wave are correct or incorrect i the local speed of sound in front of an oblique shock wave is lower than behind itii the mach number in front of an oblique shock wave is higher than behind it ?

I is correct ii is correct.

obliquenormal wave com ennormal and oblic shock wavejpg

Question 263-16 : The speed range from approximately m=13 to approximately m=5 is called the ?

Supersonic range.

Subsonic range is from 0 and ends at mcrittransonic range starts at mcrit up to mach 13supersonic range is from mach 13 to approximately mach 5above mach 5 the hypersonic speed range

Question 263-17 : What is the highest speed possible without supersonic flow over the wing ?

Critical mach number.

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 encom080 152jpg

Question 263-18 : When the speed over an aerofoil section increases from subsonic to supersonic its aerodynamic centre ?

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

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 itin the transonic region the formation of shock waves on the wing surface and the resulting separated flow causes movement of the wing aerodynamic centerthe 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

Question 263-19 : What is the value of the mach number if the mach angle equals 45° ?

14.

The formula is mach angle = sin^ 1 x 1machnumber 45° = sin^ 1 x 1m sin 45° = 1mm = 141

Question 263-20 : If the mach number is 08 and the tas is 480 kt what is the speed of sound ?

600 kt.

Jamacof m = tas lss08 = 480 lsslss = 600

Question 263-21 : One advantage of a supercritical wing aerofoil over a conventional one is ?

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

Question 263-22 : The sonic boom of an aeroplane flying at supersonic speed is created by ?

Shock waves around the aeroplane.

Question 263-23 : A supercritical wing ?

Will develop no noticeable shock waves when flying 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 encom080 969jpgsupercritical 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 wingjust above mcrit a supercritical wing will develop no noticeable shock waves

Question 263-24 : The aft movement of the centre of pressure during the acceleration through the transonic flight regime will ?

Increase in static longitudinal stability.

Transonic flight regime between sonic and supersonic speeds only part of the airflow over the wing is above the speed of soundthe aft movement of the centre of pressure during the acceleration through the transonic flight regime will increase the static longitudinal stabilityas the mach number increases in the transonic range the centre of pressure will move afta corrective pitch up input on the stabiliser is required 685to 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 gravitytransonic range starts at mcrit up to mach 13the 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 686an aeroplane exhibits static longitudinal stability if when the angle of attack changes the change in total aeroplane lift acts aft of the centre of gravitynotice 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

Question 263-25 : What is the effect of aeroplane mass on shock wave intensity at constant mach number ?

Increasing mass increases 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

Question 263-26 : The position of the centre of pressure on an aerofoil of an aeroplane cruising at supersonic speed when compared with that at subsonic speed is ?

Further aft.

Question 263-27 : Which of these statements about an oblique shock wave are correct or incorrect i the density in front of an oblique shock wave is higher than behind itii the total pressure in front of an oblique shock wave is higher than behind it ?

I is incorrect ii is correct.

com ennormal and oblic shock wavejpgbehind 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 fallentotal pressure in front of an oblique shock wave is higher than behind it

Question 263-28 : Assuming isa conditions and a descent below the tropopause at constant mach number and aeroplane mass the ?

Lift coefficient decreases.

descent at constant mach number means the tas will increaseif 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 = 12 rho s v² cl thus the lift coefficient cl will be decreased

Question 263-29 : Which statement with respect to the speed of sound is correct ?

Question 263-30 : For most jet transport aeroplanes the maximum operating limit speed vmo ?

Is replaced by mmo at higher altitudes.

Question 263-31 : Behind a normal shock wave on an aerofoil section the local mach number is ?

Less than 1.

Img com ennormal and oblic shock wavejpg

Question 263-32 : When shock stall occurs lift will decrease because ?

Flow separation occurs behind the shock wave.

Question 263-33 : If ias remains constant the effect of decreasing aeroplane mass is that mcrit ?

Increases.

Question 263-34 : Which of these statements on shock stall is correct ?

Shock stall is a stall due to flow separation caused by a shock wave.

Question 263-35 : Which of these statements about the transonic speed range is correct ?

The transonic speed range starts at mcrit and extends to mach numbers above m = 1.

Question 263-36 : When an aeroplane with the centre of gravity forward of the centre of pressure of the combined wing fuselage is in straight and level flight the vertical load on the tailplane will be ?

Downwards.

com encom080 65jpg

Question 263-37 : On a jet aeroplane engines mounted below the low wing the thrust is suddenly increased which of these statements is correct about the elevator deflection required to maintain zero pitching moment ?

The elevator must be deflected downward.

com encom080 526jpgthrust line is below the center of gravity if thrust is suddenly increased it creates a pitching momentto counteract you must push the stick or control column forward the elevator is deflected downward the tail will be pushed upward 2775

Question 263-38 : During landing of a low winged jet aeroplane the greatest elevator up deflection is normally required when the flaps are ?

Question 263-39 : Rotation about the lateral axis is called ?

Pitching.

Rotation about the lateral axis is called pitching 686

Question 263-40 : Rolling is the rotation of the aeroplane about the ?

Longitudinal axis.

Rolling is the rotation of the aeroplane about the longitudinal axis 2389