Correct: D)
Explanation: In a steady glide at the same mass, lift must equal weight regardless of the aerofoil thickness, so lift remains the same. However, a thicker aerofoil generates greater form (pressure) drag due to its larger cross-section and more severe adverse pressure gradients. Options A and C are wrong because a thicker profile produces more, not less, drag. Option B is incorrect because lift does not decrease — it is fixed by the weight requirement in steady flight.
Correct: D)
Explanation: A profile polar (Lilienthal polar) plots the lift coefficient (cA or CL) against the drag coefficient (cD or CD) at various angles of attack, showing how aerodynamic efficiency changes across the operating range. Option A describes only a CL-vs-alpha curve, not a polar. Option B relates to the speed polar of a glider, not a profile polar. Option C is imprecise — the polar shows the CL-CD relationship directly, not a simple ratio.
Correct: C)
Explanation: Any body in a moving airflow always experiences drag due to viscous friction and pressure forces opposing the motion — this is unavoidable in a real fluid. Lift, however, requires specific aerodynamic shaping or orientation. Option A is wrong because drag varies with the square of velocity, not constant. Option B is physically impossible — drag-free lift does not exist. Option D is incorrect because an arbitrarily shaped body is not guaranteed to produce lift; only specifically shaped or oriented bodies generate lift.
Correct: C)
Explanation: In the aerofoil diagram PFA-010, number 3 represents the camber line (mean camber line), which is the curved line equidistant between the upper and lower surfaces of the aerofoil. Options A and B both refer to the straight reference line from leading to trailing edge, which is a different feature. Option D (thickness) is the perpendicular distance between the upper and lower surfaces, not a line on the diagram.
Correct: C)
Explanation: Differential aileron deflection reduces adverse yaw by deflecting the down-going aileron less than the up-going aileron, thereby reducing the extra induced drag on the descending wing that causes the nose to yaw opposite to the intended turn. Option A is wrong because wing dihedral provides roll stability, not yaw compensation. Option B would actually worsen adverse yaw because full deflection maximises the drag asymmetry. Option D is not a valid answer — it merely repeats the question.
Correct: D)
Explanation: Wing loading is defined as total aircraft weight divided by wing reference area, expressed in units such as N/m² or kg/m². It determines stall speed, gust sensitivity, and overall handling characteristics. Option A (drag per weight) describes a drag-to-weight ratio. Option B is the inverse of wing loading. Option C (drag per wing area) is not a standard aeronautical parameter.
Correct: D)
Explanation: Point 5 on the polar diagram (PFA-008) corresponds to slow flight — a high angle of attack, low speed condition on the positive portion of the polar before reaching the stall point. Option A (best gliding angle) corresponds to the tangent from the origin touching the polar. Option B (inverted flight) would appear on the negative CL side. Option C (stall) is at the CL_max point, which is the very top of the polar, beyond slow flight.
Correct: C)
Explanation: Airbrakes (spoilers/dive brakes) serve to steepen the glide path by significantly increasing drag while simultaneously disrupting upper-surface airflow, which reduces lift. Option A is wrong because lift decreases with airbrakes deployed. Option B is incorrect because drag increases, not decreases. Option D reverses both effects — airbrakes increase drag and decrease lift.
Correct: D)
Explanation: Glide ratio (L/D) is maximised by minimising total drag while flying at the optimal speed. Cleaning surfaces reduces skin friction, taping gaps prevents leakage drag, retractable gear eliminates a major source of parasite drag, and maintaining best-glide speed keeps the aircraft at peak L/D. Option A is suboptimal because a forward CG increases trim drag. Option B is wrong because higher mass does not improve the L/D ratio itself. Option C omits important drag-reduction measures like taping gaps and surface cleaning.
Correct: B)
Explanation: In a spin, the inner (lower) wing is deeply stalled while the outer wing may still be producing some lift, creating autorotation at a near-constant, relatively low airspeed. In a spiral dive, neither wing is stalled, and the aircraft descends in a tightening bank with rapidly increasing airspeed. Option A incorrectly identifies the outer wing as stalled. Options C and D incorrectly assign speed characteristics — in a spin, speed is roughly constant; in a spiral dive, speed increases rapidly.
Correct: C)
Explanation: The longitudinal (fore-aft) position of the CG directly determines pitch stability, which is stability around the lateral axis. The CG must be forward of the neutral point for positive pitch stability; the further forward, the more statically stable but the heavier the elevator forces. Option A is wrong because the longitudinal axis governs roll stability, influenced by dihedral. Option B is not a standard axis. Option D is wrong because the vertical axis governs directional stability, influenced by the vertical tail.
Correct: C)
Explanation: The vertical tail fin acts as a weathervane, producing a restoring yawing moment whenever the aircraft sideslips, thereby providing directional (yaw) stability around the vertical axis. A larger fin provides greater stability. Option A (wing dihedral) provides lateral (roll) stability. Option B (elevator) contributes to pitch stability. Option D (differential aileron deflection) reduces adverse yaw but is not a stability feature.
Correct: D)
Explanation: In a climb at the same engine power, the aircraft flies slower because more energy goes into gaining altitude, requiring a higher angle of attack to maintain sufficient lift. Therefore, the level-flight angle of attack is smaller than in a climb. Option A reverses the relationship. Option B compares to take-off, which is not directly related to the question. Option C is incorrect because in a descent the aircraft accelerates, typically reducing AoA below the level-flight value.
Correct: A)
Explanation: The horizontal tail (stabiliser and elevator) provides longitudinal (pitch) stability, which is stability around the lateral axis. It generates restoring moments when the aircraft's pitch attitude is disturbed. Option B is wrong because turns around the vertical axis are initiated by the rudder. Option C is incorrect because vertical axis stability comes from the vertical tail. Option D is wrong because longitudinal axis (roll) stability is provided by wing dihedral and sweep.
Correct: D)
Explanation: When the rudder is deflected to the left, it produces a sideways aerodynamic force on the tail that pushes the tail to the right, yawing the nose to the left around the vertical axis. Options A and C are wrong because pitching is a nose-up/nose-down motion controlled by the elevator, not the rudder. Option B reverses the yaw direction — left rudder produces left yaw.
Correct: C)
Explanation: Differential aileron deflection gives the down-going aileron less deflection than the up-going aileron, reducing the drag asymmetry between the two wings during a roll input and thereby minimising adverse yaw. Option A is wrong because descent rate is controlled by airbrakes or speed, not aileron geometry. Option B is incorrect because stall prevention at low AoA is not an issue. Option D is wrong because wake turbulence is caused by wingtip vortices, not aileron design.
Correct: C)
Explanation: In a banked turn at constant altitude, the tilted lift vector must be large enough that its vertical component still equals weight while its horizontal component provides the centripetal force for the curved path. This means total lift must exceed the straight-and-level value, with the load factor n = 1/cos(bank angle). Option A is wrong because more, not less, lift is needed. Option B is imprecise — from the aircraft's reference frame it appears as centrifugal force, but the actual physics involves centripetal force. Option D does not fully describe the force balance requirement.
Correct: C)
Explanation: A retractable engine and propeller can be fully stowed inside the fuselage when not in use, completely eliminating the parasite drag from the powerplant and propeller during soaring flight. Options A, B, and D all involve fixed (non-retractable) installations that continuously produce drag even when the engine is shut down, because the propeller and engine cowling remain exposed to the airstream.
Correct: C)
Explanation: Adverse yaw occurs because the down-deflected aileron increases both lift and induced drag on its wing. This extra drag on the rising wing yaws the nose toward it — away from the intended direction of turn. Option A describes the opposite effect. Option B describes a secondary effect of rudder, not the primary adverse yaw phenomenon. Option D incorrectly attributes the extra drag to the up-deflected aileron, when in fact it is the down-deflected aileron that produces more drag.
Correct: A)
Explanation: When flying within approximately one wingspan of the ground, the ground surface restricts the full development of wingtip vortices, reducing downwash. This effectively increases the local angle of attack (more lift) and reduces induced drag simultaneously. Option B reverses both effects. Option C incorrectly states lift decreases. Option D incorrectly states induced drag increases. Pilots experience ground effect as a floating sensation during the landing flare.
Correct: D)
Explanation: The rudder controls yaw, which is rotation around the vertical axis, causing the nose to swing left or right. Option A is wrong because the longitudinal axis governs roll, controlled by ailerons. Option B is not a standard aeronautical axis designation. Option C is wrong because the lateral axis governs pitch, controlled by the elevator.
Correct: C)
Explanation: An upward gust suddenly increases the wing's angle of attack, temporarily generating lift in excess of the aircraft's weight. This additional lift translates into a load factor greater than 1, stressing the structure. Option A (forward CG) affects pitch stability and trim drag but does not directly cause load factor spikes. Option B (higher weight) means higher sustained loads but does not itself cause an increase in load factor n. Option D (lower density) reduces lift for a given speed, which would lower, not raise, the instantaneous load factor.
Correct: C)
Explanation: The McCready ring is always set to the expected climb rate in the next thermal (2 m/s in this case), and the recommended inter-thermal cruise speed is then read at the variometer needle position showing the current sink rate (3 m/s). Option A incorrectly sets the ring to the sink rate instead of the thermal strength. Option B sets the ring to zero, which would give a minimum-sink rather than optimal cruise speed. Option D erroneously adds the sink rate and climb rate together, which is not how McCready theory works.
Correct: C)
Explanation: During approach and landing, switching the camber flap from positive (increased camber, higher lift) to negative (reduced or reflexed camber) would cause a sudden and dramatic drop in lift close to the ground, potentially leading to a dangerous sink or ground contact. Option A is not universally correct — winch launch flap settings vary by type. Option B reverses the restriction. Option D is wrong because negative camber is a cruise setting, not appropriate for the high-lift-demand winch launch phase.
Correct: D)
Explanation: Point 3 on the boundary layer diagram (PFA-009) is the transition point, where the boundary layer changes from smooth laminar flow to turbulent flow. The position of this transition depends on Reynolds number, surface roughness, and pressure gradient. Option A (separation point) occurs further aft, where flow detaches entirely. Option B (centre of pressure) is not a boundary layer feature but a force application point. Option C (stagnation point) is at the leading edge, where flow velocity is zero.
