HIGH SPEED FLIGHT – Air – DGCA Question Bank For Politics

#1. When an aircraft is flying at supersonic speed, in what area will the pressure disturbances caused by its motion be felt?

Within the mach cone.

In front of the normal shock wave.

In front of the oblique shock wave.

In front of the mach cone.

#2. What happens to the location of the centre of pressure as an aerofoil accelerates to M CRIT?

It moves backwards as pitch is reduced to maintain constant lift then moves forward as the first shock wave forms on the upper surface of the wing.

It moves towards the mid chord position due to the effects of the upper surface shock wave.

It moves slowly backwards as pitch angle is reduced to maintain a constant lift force with increasing airspeed, then forwards as the first shock waves form.

It remains stationary due to the balancing effects of changing pitch angle and shock wave formation.

#3. What happens to the location of the centre of pressure as an aerofoil accelerates from just below MCRITto supersonic speed?

It moves forward as the second shock wave forms on the lower surface of the wing.

It moves forward as the initial shock waves form, then moves aft towards the mid chord position as the shock waves on the upper and lower surfaces move towards the trailing edge.

It moves rapidly backwards as pitch angle is reduced to maintain a constant lift force with increasing airspeed.

It remains stationary due to the balancing effects of shock waves at the leading and trailing edges.

#4. What happens to the pressure distribution above the upper surface of the wing as an aircraft accelerates through the transonic speed range?

It retains its smooth shape, but the pressure drop intensifies and its peak moves forward as airflow over the front of the wing accelerates to supersonic speed.

It retains its smooth shape, the pressure drop intensifying and moving forward before collapsing as the first shock wave forms.

It retains its smooth shape, the pressure drop intensifying and moving forward before becoming irregular as the first shock wave forms.

It retains its smooth shape, the pressure drop intensifying and moving forward before moving rapidly aft as the first shock wave forms.

#5. What causes the centre of pressure of a wing to move aft, as an aircraft accelerates through the transonic speed range?

The shock wave on the upper surface causes an abrupt deceleration of airflow to subsonic speed. This produces an instantaneous decrease in pressure over the aft section of the wing.

The shock wave on the upper surface causes an abrupt deceleration of airflow to subsonic speed, resulting in an instantaneous increase in pressure over the aft section of the wing.

As speed increases the upper shock wave moves towards the trailing edge. The curvature of the wing upstream of the shock wave forms a series of expansion corners, causing the airflow to accelerate to higher supersonic speeds. This reduces the pressure over the aft section of the wing ahead of the shock wave.

The shock wave on the lower surface causes an abrupt pressure drop under the aft section of the wing, causing the effective lifting force to move aft.

#6. Why do shock waves form above and below wings as they accelerate through the transonic speed range?

Airflow at supersonic or sonic speeds always produces shock waves

The shock waves form because acceleration due to the curvature of the wing surfaces, causes airspeed to exceed the local speed of sound.

The adverse pressure gradients above and below the wings move forward with it in the form of pressure waves. These pressure waves pile up at the point where airspeed equals the local speed of sound. This piling up of the pressure gradient forms an instantaneous pressure increase or shock wave.

The adverse pressure gradients above and below the wing move forward with it in the form of pressure waves. These pressure waves pile up at the point where airspeed changes from sonic to supersonic, forming an instantaneous pressure increase or shock wave.

#7. At what speed does the shock wave produced by an aircraft pass over the ground?

Because pressure waves cannot move faster than the local speed of sound, the shock waves move over the ground at Mach 1

Because the shock wave loses energy as it moves away from the aircraft, it moves over the ground at less than the local speed of sound.

Because the speed of sound is lower at high altitude, the shock wave moves over the ground at less than the true airspeed of the aircraft.

Because the mach cone angle is constant for a given mach number, the shock wave passes over the ground at the aircraft's ground speed.

#8. If airflow is to be decelerated from high supersonic to subsonic level, what form of shock wave or shock waves will produce the lowest energy loss?

A normal shock wave reducing flow to subsonic in a single stage.

A series of oblique shock waves, each causing flow to change from supersonic to a lower supersonic level, followed by a normal shock wave, taking flow from sonic to subsonic.

A series of normal shock waves, each resulting in a small proportion of the required deceleration.

A single oblique shock wave, taking flow from supersonic to subsonic.

#9. Which of the following best describes the area rule principle?

By carefully contouring the fuselage of the aircraft, accelerations around it are maximised, resulting in minimum drag.

By carefully contouring the fuselage of the aircraft to minimise rates of change of cross sectional area, accelerations around it are reduced, minimising drag.

By carefully contouring the fuselage of the aircraft, accelerations around it are prevented, resulting in minimum drag.

By carefully contouring the wings of the aircraft, accelerations around it are minimised resulting in minimum drag.

#10. High-speed tuck under occurs in the ................. speed range, causing the aircraft to pitch down. It is caused by .... movement of the ............ as the shock waves above and below the wings move ....... Changes in airflow over the ............ also contribute to tlre problem. It is counteracted by the ................. system

Transonic, fwd, centre of pressure, fwd, tailplane, mach trim.

Subsonic, fwd, . centre of gravity, aft, fin, auto-stab.

Transonic, aft, centre of pressure, aft, tailplane, mach trim.

Supersonic, aft, centre of gravity, aft, elevons, autopilot.

#11. Static pressure is ......... proportional to volume and directly proportional to ....... so volume increases and density ............ with the square of velocity. As velocity increases static pressure and temperature are converted into ........ energy, which increases with the square of velocity. A given increase in velocity therefore has a greater effect on density at ..... speed than at ..... speed. It is therefore possible to make calculations based on the assumption that air is ............. a t low speeds but not at high speeds.

Directly, density, increases, kinetic, high, low, incompressible

Inversely, density, decreases, kinetic, high, low, incompressible

Directly, temperature, decreases, kinetic, high, low, incompressible

Inversely, density, decreases, kinetic, high, low, compressible

#12. What happens to the static pressure, velocity, density and temperature of supersonic airflow as it passes through an expansion corner?

Decrease, decrease, increase, increase.

Increase, increase, decrease, decrease.

Increase, decrease, increase, increase.

Decrease, increase, decrease, decrease.

#13. What happens to the static pressure, velocity, density and temperature of supersonic airflow as it passes through a compression corner?

Decrease, decrease, increase, increase.

Increase, increase, decrease, decrease.

Increase, decrease, increase, increase.

Decrease, increase, decrease, decrease.

#14. Which of the following statements is true?

A shock wave will form when supersonic airflow passes through an expansion corner.

A shock wave will form when supersonic airflow passes through a compression corner.

A shock wave might form when supersonic airflow passes through an expansion corner.

A shock wave might form when supersonic airflow passes through a compression corner.

#15. Select the correct words to complete the following statement. As an aircraft accelerates from C Lthe c~entr~e of p~ressu re of its wings ............................................... At MC~ ltThe centre of pressure .......... 1. Moves forward as flow over the leading edge area is increased. 2. Moves aft as pitch is reduced to maintain constant lift. 3. Moves forward as the shock waves increases pressure over the aft area. 4. Moves aft as flow accelerates into the slnock wave.

1, 3.

2, 4.

2, 3.

1, 4.

#16. As an aircraft continues to accelerate from MCRiTto mach 1, the shock waves move to the trailing edge causing the upper surface of the wings to ........................................... At supersonic speeds the highest velocity and hence lowest static pressure over the wing occur .................................................... 1. At the trailing edge and the centre of pressure is at about the mid chord point. 2. At the trailing edge and the centre of pressure is immediately in front of the shock wave. 3. Act as a series of compression corners. 4. Act as a series of expansion corners.

3, 2.

4, 1.

2, 4.

3, 1.

#17. At what speed do the shock waves produced by a supersonic aircraft appear to move ever the ground?

At the local speed of sound.

At the speed of sound local to the altitude at which the aircraft is flying.

At the speed at which the aircraft moves over the ground.

At the TAS of the aircraft.

#18. What does the mach trim system do?

Adjusts the longitudinal trim of the aircraft.

Adjusts the elevator trim tabs or servo tabs.

Moves C of G aft by pumping fuel into aft trim tanks.

Adjusts stabilator trim.

#19. What is the purpose of vortex generators in transonic flight?

To energies boundary layer, in order to prevent it spreading outward on swept wing aircraft.

To prevent the formation of shock waves on the upper surface of the wing.

To reduce the effects of shock induced boundary layer separation.

To slow down the boundary layer, to delay the formation of shock waves.

#20. What will be the effect on TAS, if an aircraft climbs at constant mach number to 50000 feet altitude in the international standard atmosphere?

TAS will increase.

TAS will decrease.

TAS will decrease then remain constant.

TAS will increase then remain constant.

#21. In what way will a mach trim system affect the stick force gradient for a powered flying control system, as an aircraft accelerates through the transonic speed range?

It will reduce .tick force gradient as speed increases, in order to enable the pilot to overcome the high control hinge moments experienced at high speeds.

It will ensure that the required negative stick force : speed gradient is maintained.

Mach trim systems are not required in fully powered flying control systems because the controls are irreversible.

It will adjust the stick force gradient to prevent high-speed pitch up.

#22. How do the velocity, static pressure, temperature and density of a supersonic air stream vary as it passes through a convergent duct?

Decrease, increase, increase, decrease.

Decrease, increase, increase, increase.

Increase, decrease, decrease, decrease.

Increase, decrease, increase, remains constant.

#23. How does an aircraft with sweptback wings behave in shock stall?

It pitches nose up.

It becomes more longitudinally stable.

It pitches nose down.

Shock stall does not affect sweptback wings.

#24. How quickly does the shock wave produced by an aircraft move over the ground?

Aircraft IAS.

Aircraft CAS.

Aircraft TAS

Aircraft ground speed.

#25. Where on an aerofoil does shock stall occur?

At the trailing edge.

At the leading edge.

Beneath the leading edge.

Behind the shock wave.

#26. What effect does a normal shock wave have on airflow passing through it?

Accelerates to supersonic.

Accelerates to sonic.

Decelerates to subsonic.

Density and temperature decrease.

#27. If velocity is to be decreased using a shock wave or shock waves, what is the most efficient method?

A single normal shock wave.

A single oblique shock wave.

A series of oblique shock waves.

Any of the above.

#28. If a series of shock waves is used to decelerate supersonic flow to subsonic speed, how would the shock waves vary?

Increasing half angle from the first to the last.

Decreasing half angle from the first to last.

Constant half angle from first to last.

They would all be normal.

#29. How can energy loss due to shock waves be minimised?

Fly below MCRIT.

Fly at mach 1.

Fly at mach 2.

Fly at high supersonic speeds.

#30. How does the shock wave angle vary with mach number?

Increases.

Decreases.

Remains constant.

Increases then decreases.

#31. Why does lift decrease when shock waves form on a wing at transonic speed?

The bow wave reduces free stream velocity.

The shock wave at the trailing edge reduces velocity over the upper surface.

The boundary layer separates behind the shock wave.

The boundary layer separates ahead of the shock wave.

#32. Why does drag increase at high transonic speeds?

High-speed friction.

Increased induced drag at the shockwave.

Increased parasite drag at the shockwave.

Separation behind the shockwave.

#33. What is the speed of the airflow immediately downstream of a normal shockwave?

Supersonic.

Subsonic.

Lower supersonic.

Transonic.

#34. \+'hat airspeed would produce the lowest wave drag?

Mach 1.

Subsonic.

Supersonic.

Transonic.

#35. What will be the speed of the local airflow immediately downstream of an oblique shockwave?

Subsonic

Transonic.

Lower supersonic than in front of the wave.

Higher supersonic than in front of the wave.

#36. What does the mach trim system do?

Move fuel aft.

Adjust the elevator trim tabs.

Adjust the variable incidence tailplane.

Adjust longitudinal trim.

#37. How can MCRIT be increased?

Sweep wings back.

Use high aspect ratio.

Use high thickness to chord ratio.

Use anhedral.

#38. What is MCRIT?

The highest free stream velocity at which a shock wave will form on the wings.

The minimum free stream velocity at which airflow first become sonic anywhere on an aircraft.

The minimum supersonic speed.

The speed at which wave drag is at a minimum.

#39. What effect does aircraft attitude have on MCRIT?

None.

Nose level attitudes increase it.

It decreases with nose up attitude.

It decreases wit11 roll.

#40. Which of the following is the best definition of mach number?

TAS/IAS

TAS/CAS.

TAS/LSS.

TAS/EAS.

#41. When does mach tuck under occur?

At any mach number depending on LSS.

At high fractional mach numbers.

At low fractional mach numbers.

Above mach 1 only.

#42. Which of the following affect the local speed of sound?

Dynamic pressure.

Temperature.

Density.

Velocity.

#43. Which of the following occurs in swept wing aircraft as speed increases above MCRIT?

Low speed buffet.

Pitch up and buffet.

Pitch down and buffet.

High-speed shimmy.

#44. Where on an aircraft would a normal shockwave form?

Wherever an adverse pressure gradient moving upstream meets sonic airflow.

Wherever an adverse pressure gradient moving upstream meets supersonic airflow.

At the trailing edge.

At the aerodynamic centre.

#45. Which of the following might be inadvertently exceeded when an aircraft descends at constant mach number?

VNE

VD

MMO

VMO

#46. How does airflow react when passing through a normal shockwave?

Accelerates to supersonic speed.

Decelerates to lower supersonic speed.

Pressure, temperature and density increase.

Pressure temperature increases, density decreases.

#47. How can shock induced separation be reduced?

Vortex generators.

Sweepback.

Anhedral.

High aspect ratio.

#48. What will be the shape of the pressure distribution over a wing at supersonic speeds?

Square

Rectangular

Triangular

Irregular

#49. What will be the shape of the pressure distribution over a wing in transonic flight?

Square

Rectangular

Triangular

Irregular

#50. Which of the following is caused by high-speed buffet?

Shock stall.

Shock separation.

Wave drag.

Vibration

#51. Why does lift decrease as MCRIT is exceeded?

Free stream separation.

Boundary layer separation.

Stagnation.

Shock waves.

#52. In what condition would outboard ailerons, inboard ailerons and roll spoilers be when cruising at M0.82?

Locked in neutral, active, active.

Locked in neutral, locked in neutral, active.

Active, active, locked in neutral.

Active, locked in neutral, active.

#53. What effect does mach trim have on stick forces?

Decreases stick forces to maintain manoeuvrability.

Decrease stick forces to prevent tuck under.

Increase stick forces to maintain negative gradient.

Increase stick forces to maintain positive gradient.

#54. What happens to air density as supersonic flow passes through an expansion wave?

Increases.

Decreases.

Unchanged.

Depends on speed.

#55. How do VMo and MMO compare when changing altitude?

The TAS at VMo and MMo are the same TAS at all altitudes.

The TAS at VMo is greater than that at MMO at all altitudes.

The TAS at VMo is less than that at MMO at all altitudes.

The TAS at VMo is greater than the TAS at MMO at high altitudes and less at low altitudes.

#56. What happens to the angle of the shock waves as speed increases?

Increases

Decreases

Constant

Collapses

#57. At what angle does the shock wave produced by a supersonic aircraft reflect from the ground?

Greater than before hitting it.

Less than before hitting it.

The same as before hitting it.

It does is not reflected from the ground.

#58. What is the minimum number of shock waves that an object flying at supersonic speed will produce?

None

1

2

3

#59. What will be the effect of airflow striking the front fuselage of an aircraft when sideslipping to the right in supersonic flight?

Destroy it.

Yaw to the left.

Yaw to the right.

Pitch down.

#60. How would the CL:a curves for an aircraft in subsonic and supersonic flight compare?

Identical

Subsonic is steeper.

Supersonic is steeper.

They cannot be compared.

#61. How does the CLMAX of an aerofoil at subsonic speed compare with that of the same aerofoil at supersonic speed.

Greater.

Smaller

Identical because CL depends only on shape and angle of attack.

They cannot be compared because of the great speed difference.

#62. What happens to CLMax as an aircraft approaches MCRIT?

Increases.

Decreases.

Constant

Decreases then increases.

#63. How does CL at MCRIT compare with that at mach 1?

Greater.

Smaller.

Identical.

Much greater.

#64. What happens to the shock wave angle as supersonic speed is increased?

Increase.

Decrease.

Unchanged.

Increase then decrease.

#65. How can energy loss due to shock waves be prevented?

Fly below MCRIT.

Fly at MCRIT.

Fly at mach 1.

Fly at supersonic speeds.

#66. If air is to be compressed by passing it through a shock wave, what type of wave will result in lowest energy loss?

Normal.

Swept forward.

Slightly oblique.

Highly oblique.

#67. If shock waves are unavoidable, what flight speed will result in lowest energy loss?

MCRIT.

Mach 1.

High supersonic.

Low supersonic.

#68. How will an increase in weight affect MCRlT?

Increase.

Decrease.

Increase or decrease depending on speed.

None of the above.

#69. What affect will forward movement of C of G have on MCRIT?

Increase.

Decrease.

Increase or decrease depending on weight.

None of the above.

#70. What is minimum speed for high-speed buffet in a JAR certificated passenger aircraft?

MCRIT

VMO/MMO

VNE

VS

#71. What is the aerodynamic ceiling?

Maximum attainable altitude.

Altitude where it is just possible to pull 1.3g.

Altitude at which the margin between low and high speed buffet is zero.

Altitude where rate of climb is zero.

#72. At what speed does the over-speed warning operate in a JAR certificated passenger aircraft?

10 Kts above VMO.

MCRIT.

110% MCRIT.

M1.

#73. At what mach number does the over-speed warning operate in a JAR certificated passenger aircraft?

MCRIT

10 Kts above MMO.

110% MCRIT.

MI

#74. Where on a wing does laminar flow break down at, or slightly above MCRIT?

On the fin.

Behind the normal shock wave above the wing.

Behind the normal shock wave below the wing.

Ahead of the oblique shock wave above the wing.

#75. Over what part of a wing does velocity increase in supersonic flight?

None of it.

All of it except the leading edge.

Most of it.

Forward area only.

#76. Where above the surface of a wing is the velocity greatest in supersonic flight?

Just behind the shock wave at the trailing edge.

Just in'front of the shock wave at the trailing edge.

Just behind the shock wave at the 50% chord point.

Just ahead of the shock wave at the 50% chord point.

#77. Where above the wing is static pressure lowest in supersonic flight?

Just behind the shock wave at the trailing edge.

Just in front of the shock wave at the trailing edge.

Just behind the shock wave at the 50% chord point.

Just ahead of the shock wave at the 50% chord point.

#78. Where above the surface of a wing is the dynamic pressure greatest in supersonic flight?

Just behind the shock wave at the trailing edge.

Just in front of the shock wave at the trailing edge.

Just behind the shock wave at the 50% chord point.

Just ahead of the shock wave at the 50% chord point.

#79. What form of duct accelerates supersonic airflow?

Convergent

Divergent

Parallel

None

#80. What form of duct accelerates sonic airflow?

Convergent

Divergent

Parallel

None

#81. What form of duct increases static pressure of supersonic airflow?

Convergent

Divergent

Parallel

None

#82. What form of duct increases density of supersonic airflow?

Convergent

Divergent

Parallel

None

#83. What happens to CL as an aircraft accelerates from just below MCRIT to supersonic speeds?

Increases, decreases, increases, then,decreases again.

Decreases, increases, decreases, then increases again.

Remains constant.

Decreases then increases.

#84. What happens to CDa s an aircraft accelerates from just below MCRIT to supersonic speeds?

Increases, decreases, then decreases again.

Decreases, increases, then increases again.

Remains constant.

Increases then decreases.

#85. How does supersonic CL compare with subsonic CL?

Higher.

Lower.

The same.

Higher or lower depending on absolute temperature.

#86. How does supersonic CD compare with subsonic CD?

Higher.

Lower.

The same.

Higher or lower depending on absolute temperature.

#87. What does supersonic buffeting cause?

Pitch down.

Pitch up.

Acceleration.

Vibration.

#88. Why is lift dramatically reduced just above MCRIT?

High speed Buffet.

Shock waves.

Attached bow wave.

Boundary layer separation.