DGCA Technical General: High-Speed Flight Questions
151 exam-style High-Speed Flight questions for the DGCA Technical Generalpaper (CPL & ATPL). The first 12 are free below with answers and explanations — sign up free to practise all of them with progress tracking.
- Q1
When an aircraft is flying at supersonic speed, in what area will the pressure disturbances caused by its motion be felt?
- AWithin the mach cone.
- BIn front of the normal shock wave.
- CIn front of the oblique shock wave.
- DIn front of the mach cone.
Show answer
Correct answer: A. Within the mach cone.
This Explanation is Coming Soon
- Q2
What happens to the location of the centre of pressure as an aerofoil accelerates to M CRIT?
- AIt 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.
- BIt moves towards the mid chord position due to the effects of the upper surface shock wave.
- CIt 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.
- DIt remains stationary due to the balancing effects of changing pitch angle and shock wave formation.
Show answer
Correct answer: C. 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.
This Explanation is Coming Soon
- Q3
What happens to the location of the centre of pressure as an aerofoil accelerates from just below MCRITto supersonic speed?
- AIt moves forward as the second shock wave forms on the lower surface of the wing.
- BIt 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.
- CIt moves rapidly backwards as pitch angle is reduced to maintain a constant lift force with increasing airspeed.
- DIt remains stationary due to the balancing effects of shock waves at the leading and trailing edges.
Show answer
Correct answer: B. 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.
This Explanation is Coming Soon
- Q4
Swept back and Delta wings are:
- AVery efficient at high supped but corresponding inefficient at low speeds
- BFairly inefficient at high speed but very efficient at low speed
- CNeither efficient at low or high speed
Show answer
Correct answer: A. Very efficient at high supped but corresponding inefficient at low speeds
Sweepback and delta planforms delay the compressibility drag rise, making them very efficient at high speed, but their poor lift production at low speed forces high angles of attack and high take-off and approach speeds.
- Q5
What happens to the pressure distribution above the upper surface of the wing as an aircraft accelerates through the transonic speed range?
- AIt 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.
- BIt retains its smooth shape, the pressure drop intensifying and moving forward before collapsing as the first shock wave forms.
- CIt retains its smooth shape, the pressure drop intensifying and moving forward before becoming irregular as the first shock wave forms.
- DIt retains its smooth shape, the pressure drop intensifying and moving forward before moving rapidly aft as the first shock wave forms.
Show answer
Correct answer: C. It retains its smooth shape, the pressure drop intensifying and moving forward before becoming irregular as the first shock wave forms.
This Explanation is Coming Soon
- Q6
503.MACH TRIM and TUCK UNDER are associated with:
- A Flying at low speed and high grass weight
- BFlying at supersonic speed
- CFlying at higher subsonic speeds
Show answer
Correct answer: C. Flying at higher subsonic speeds
Tuck under is the nose-down pitching tendency that appears at high subsonic Mach numbers as shockwaves move the centre of pressure rearward and alter the downwash at the tail; the Mach trim system operates in this speed regime to counter it automatically.
- Q7
What causes the centre of pressure of a wing to move aft, as an aircraft accelerates through the transonic speed range?
- AThe 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.
- BThe 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.
- CAs 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.
- DThe 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.
Show answer
Correct answer: C. 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.
This Explanation is Coming Soon
- Q8
Shock stall is caused is due to:
- AAbrupt movement of the control column
- BSudden increase in lift
- CBoundary layer separation aft of the shockwave causing sudden loss of lift
Show answer
Correct answer: C. Boundary layer separation aft of the shockwave causing sudden loss of lift
At high Mach numbers the shockwave forming on the wing causes the boundary layer behind it to separate, and the resulting sudden loss of lift with buffet is the shock stall; it is a compressibility effect, not the result of control mishandling.
- Q9
Why do shock waves form above and below wings as they accelerate through the transonic speed range?
- AAirflow at supersonic or sonic speeds always produces shock waves
- BThe shock waves form because acceleration due to the curvature of the wing surfaces, causes airspeed to exceed the local speed of sound.
- CThe 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.
- DThe 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.
Show answer
Correct answer: C. 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.
This Explanation is Coming Soon
- Q10
At what speed does the shock wave produced by an aircraft pass over the ground?
- ABecause pressure waves cannot move faster than the local speed of sound, the shock waves move over the ground at Mach 1
- BBecause 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.
- CBecause 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.
- DBecause the mach cone angle is constant for a given mach number, the shock wave passes over the ground at the aircraft's ground speed.
Show answer
Correct answer: D. 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.
This Explanation is Coming Soon
- Q11
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?
- AA normal shock wave reducing flow to subsonic in a single stage.
- BA 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.
- CA series of normal shock waves, each resulting in a small proportion of the required deceleration.
- DA single oblique shock wave, taking flow from supersonic to subsonic.
Show answer
Correct answer: B. 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.
This Explanation is Coming Soon
- Q12
Which of the following best describes the area rule principle?
- ABy carefully contouring the fuselage of the aircraft, accelerations around it are maximised, resulting in minimum drag.
- BBy carefully contouring the fuselage of the aircraft to minimise rates of change of cross sectional area, accelerations around it are reduced, minimising drag.
- CBy carefully contouring the fuselage of the aircraft, accelerations around it are prevented, resulting in minimum drag.
- DBy carefully contouring the wings of the aircraft, accelerations around it are minimised resulting in minimum drag.
Show answer
Correct answer: B. By carefully contouring the fuselage of the aircraft to minimise rates of change of cross sectional area, accelerations around it are reduced, minimising drag.
This Explanation is Coming Soon
139 more High-Speed Flight questions in the full bank
Create a free account to practise every High-Speed Flight question with instant scoring, chapter tests, previous DGCA papers and full-length mock exams.
Start practising free