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Module 8 Basic aerodynamics: 27 practice questions

Real EASA paper: Category A 24 Q / 30 min · B1.1 24 Q / 30 min · B1.2 24 Q / 30 min · B1.3 24 Q / 30 min · B2 24 Q / 30 min · B2L 24 Q / 30 min · B3 24 Q / 30 min. Three options, 75% to pass. Answer key on the last page. From part66exam.com · independent study aid, not an official exam or a past paper.

1. Ground effect becomes significant when the aircraft is within approximately:
1. A. Ten wingspans of the ground
2. B. One wingspan of the ground
3. C. The height of the landing gear only
2. According to the ISA, how does the speed of sound change with altitude up to the tropopause?
1. A. It decreases, because the temperature decreases
2. B. It increases, because the density decreases
3. C. It stays constant, because it depends only on pressure
3. What device is fitted to many swept-wing jet aircraft to counteract Dutch roll?
1. A. A yaw damper
2. B. A Mach trimmer
3. C. A stick shaker
4. For an aeroplane certified in the normal category (CS-23), the positive limit load factor is typically:
1. A. 6.0 g
2. B. 3.8 g
3. C. 2.5 g
5. Sweepback raises the critical Mach number because:
1. A. It increases the thickness/chord ratio of the wing section
2. B. It increases the aspect ratio of the wing for the same area
3. C. It reduces the velocity component normal to the leading edge
6. Drag is defined as the component of the total aerodynamic reaction that:
1. A. Acts perpendicular to the relative airflow direction
2. B. Acts parallel to the relative airflow, opposing motion
3. C. Acts along the chord line towards the trailing edge
7. Which combination of conditions gives the HIGHEST density altitude?
1. A. Low elevation, low temperature, low humidity
2. B. High elevation, low temperature, low humidity
3. C. High elevation, high temperature, high humidity
8. A 'Dutch roll' is a combined:
1. A. rolling and pitching oscillation
2. B. yawing oscillation with no roll
3. C. yawing and rolling oscillation
9. The best angle-of-climb speed (VX) is the speed that gives:
1. A. The greatest height gain in the shortest time
2. B. The lowest fuel consumption per kilometre
3. C. The greatest height gain in the shortest horizontal distance
10. Transonic flight is the speed range in which:
1. A. The airflow over the aircraft is partly subsonic and partly supersonic
2. B. All the airflow around the aircraft is supersonic, including the wake
3. C. All the airflow is subsonic and can be treated as incompressible
11. Increasing the camber of an aerofoil will generally:
1. A. Increase the lift coefficient at a given angle of attack
2. B. Reduce the lift coefficient at a given angle of attack
3. C. Increase the stalling angle of attack
12. At constant temperature, if the pressure of a mass of air is doubled, its density:
1. A. Halves
2. B. Doubles
3. C. Stays the same
13. A high-wing aeroplane has greater lateral stability than a similar low-wing aeroplane mainly because of:
1. A. The higher aspect ratio of a high-mounted wing
2. B. The keel (pendulum) effect of the weight below the wing
3. C. The more rearward centre of gravity of high-wing types
14. In a steady climb, which statement about the forces is correct?
1. A. Lift is greater than weight, as the aircraft is climbing
2. B. Thrust exceeds drag, as it also balances a component of weight
3. C. Thrust equals drag and lift equals weight, as in level flight
15. A supercritical aerofoil is designed to:
1. A. Increase the maximum lift coefficient for take-off and landing
2. B. Weaken and delay the shock, raising the drag-divergence Mach number
3. C. Produce stronger shocks to improve control at high Mach numbers
16. Compared with a laminar boundary layer, a turbulent boundary layer:
1. A. Has less skin-friction drag and separates more easily
2. B. Has more skin-friction drag but resists separation better
3. C. Has less skin-friction drag and resists separation better
17. Passive stability of an aircraft is stability provided by:
1. A. Flight control computers that move the controls automatically
2. B. Design features such as tailplane, fin, dihedral and CG position
3. C. The pilot making corrective control inputs during the flight
18. A split flap:
1. A. Moves rearward on tracks, increasing the wing area
2. B. Is hinged from the lower surface only, and adds much drag
3. C. Opens a slot between itself and the wing trailing edge
19. Two identical wings are flying at the same true airspeed and angle of attack. One is at sea level and one at a density altitude where the air density is half that at sea level. The lift at altitude is:
1. A. The same as at sea level
2. B. Half of that at sea level
3. C. A quarter of that at sea level
20. Boundary-layer control devices such as vortex generators and blown flaps belong to which group?
1. A. Trim devices
2. B. Primary flight controls
3. C. Lift-augmentation devices
21. The drag coefficient CD of a wing:
1. A. Decreases steadily as angle of attack increases
2. B. Is constant for all angles of attack below the stall
3. C. Increases with angle of attack, very rapidly near the stall
22. The absolute ceiling of an aircraft is the altitude at which:
1. A. The rate of climb is 100 ft/min
2. B. The maximum rate of climb is zero
3. C. The cabin pressure reaches its maximum differential
23. Stall strips fitted to the inboard leading edge of a wing are intended to:
1. A. Delay the stall of the root section to a higher angle
2. B. Reduce the drag of the wing in cruise flight
3. C. Make the root stall first, so the ailerons stay effective
24. An aerofoil with a thicker section and larger leading-edge radius will typically:
1. A. Stall more abruptly and at a lower angle of attack than a thin section
2. B. Stall more gently and at a higher angle of attack than a thin section
3. C. Have a higher critical Mach number than a thin, sharp-edged section
25. An aircraft has a lift/drag ratio of 12 and weighs 60 kN in level flight. The drag is:
1. A. 5 kN
2. B. 720 kN
3. C. 2.5 kN
26. Winglets reduce induced drag by:
1. A. Increasing the camber of the wing tip
2. B. Moving the centre of gravity forward
3. C. Weakening the wingtip vortex and reducing downwash
27. As the angle of attack increases towards the stall, the pressure on the upper surface of a wing:
1. A. Increases, and the lowest-pressure point moves aft
2. B. Decreases further, and the lowest-pressure point moves forward
3. C. Does not change; only the lower surface pressure changes

Answer key

1. B — Ground effect is noticeable within a height of about one wingspan and becomes large at heights below about one tenth of the span, where induced drag can be reduced by nearly half.
2. A — The speed of sound a = √(γ·R·T) depends only on absolute temperature. In ISA it falls from about 340 m/s (661 kt) at sea level to about 295 m/s (573 kt) at the tropopause, then stays constant.
3. A — The yaw damper senses yaw rate and applies small rudder inputs automatically to damp the oscillation. It is an example of active (artificial) stability augmentation.
4. B — Typical limit load factors are: normal category +3.8 g / −1.52 g, utility +4.4 g / −1.76 g, aerobatic +6.0 g / −3.0 g. Large transports (CS-25) typically +2.5 g / −1.0 g.
5. C — With sweep angle Λ the effective Mach number normal to the leading edge is M × cos Λ. The aircraft can therefore fly faster before the flow over the wing reaches Mach 1.
6. B — Drag acts parallel to, and in the same direction as, the relative airflow; that is, it opposes the aircraft's motion through the air.
7. C — Density falls with lower pressure, higher temperature and higher humidity. All three together produce thin air (high density altitude), which reduces lift, thrust and engine power.
8. C — Dutch roll occurs when lateral stability is strong relative to directional stability; yaw dampers suppress it.
9. C — VX is flown at the speed of greatest excess thrust (thrust available minus drag). It is used for clearing obstacles after take-off.
10. A — The transonic range extends roughly from Mcrit (about 0.75–0.8) to about 1.2. It is the most difficult regime, with shock waves, separation, buffet and trim changes.
11. A — Camber increases the curvature of the flow and the pressure difference at a given angle of attack, raising CL and CLmax. This is how trailing-edge flaps work, although the stall then occurs at a lower angle of attack.
12. B — From the gas law ρ = p/(R·T), density is directly proportional to pressure at constant temperature and inversely proportional to absolute temperature at constant pressure.
13. B — With the CG below the wing, the weight produces a restoring moment in a sideslip. The wing-fuselage interference in a sideslip also adds a dihedral effect on high-wing designs.
14. B — In a steady climb at angle γ, the weight has a component W·sin γ acting rearward along the flight path. Thrust must equal drag + W·sin γ, while lift equals W·cos γ, which is slightly less than the weight.
15. B — A supercritical section has a flatter upper surface and more aft camber. The supersonic region is larger but ends in a weaker shock, raising the drag-divergence Mach number.
16. B — In a turbulent boundary layer the mixing brings high-energy air close to the surface. This raises skin friction but keeps the flow attached longer, which is why vortex generators deliberately energise the boundary layer.
17. B — Passive (inherent) stability comes from the aircraft's geometry and mass distribution, without any system acting. Active stability uses sensors, computers and actuators (for example yaw dampers or fly-by-wire) to provide or improve stability.
18. B — The split flap deflects only the lower surface of the trailing edge. It gives slightly more lift than a plain flap but much more drag, because of the turbulent wake behind it.
19. B — L = CL × ½ρV² × S. With CL, V and S unchanged, lift is directly proportional to density, so halving ρ halves the lift. To maintain lift at altitude the aircraft must fly faster (higher TAS) or at a higher angle of attack.
20. C — Lift augmentation includes flaps, slats, slots and boundary-layer control. They all delay separation or increase camber so that CLmax is raised and the aircraft can fly at lower speeds.
21. C — CD is a minimum at a small angle of attack and increases progressively with α as induced drag grows. Near and beyond the stall, separation makes it rise steeply.
22. B — At the absolute ceiling power available equals power required at only one speed, and no climb is possible. The service ceiling, where the maximum climb rate is 100 ft/min (0.5 m/s), is a more practical limit.
23. C — A stall strip is a small sharp-edged wedge that makes the flow separate at a lower angle of attack at that part of the wing. Placed inboard, it ensures a root-first stall and gives buffet warning.
24. B — A generous leading-edge radius lets the flow follow the surface at higher angles of attack, so the stall is more gradual. Thin sections are preferred for high-speed flight because they have a higher critical Mach number.
25. A — In level flight lift = weight = 60 kN. Drag = L/(L/D) = 60/12 = 5 kN, which is also the thrust required.
26. C — A winglet acts as an end plate and produces a small forward force component in the tip flow. The tip vortex is weakened, downwash is reduced and so is induced drag, which improves cruise efficiency.
27. B — With increasing angle of attack the airflow accelerates more over the leading edge, the suction peak increases and moves forward, which is why the centre of pressure moves forward until separation occurs.

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