Source: exam.quizvds.it (EASA ECQB-SPL) | 95 questions
Correct: D)
Explanation: In steady (stationary) gliding flight, there is no thrust, so only two forces act: gravity (weight) and the total aerodynamic force (the vector sum of lift and drag). For the glider to be in equilibrium, these two must be equal and opposite — meaning the resultant air force exactly compensates gravity. Lift and drag are merely components of this single aerodynamic resultant; neither lift alone nor drag alone balances weight.
Correct: C)
Explanation: Extending flaps increases wing camber, which raises the maximum lift coefficient (CLmax). From the stall speed formula Vs = sqrt(2W / (rho * S * CLmax)), a higher CL_max directly lowers the minimum flying speed Vs. This allows the aircraft to fly slower without stalling, which is why flaps are used during approach and landing. The maximum permissible speed typically decreases with flaps extended (not increases), because flap structures are not designed for high dynamic pressure.
Correct: B)
Explanation: The lateral axis is the pitch axis (nose up/down). The horizontal stabilizer provides longitudinal (pitch) stability: it generates a restoring moment whenever the nose pitches up or down from trim, because its lift force changes with AoA at the tail. Ailerons control roll (longitudinal axis), the vertical rudder controls yaw (vertical axis), and flaps are high-lift devices, not stability surfaces.
Correct: D)
Explanation: The center of pressure (CP) is the single point on an aerofoil through which the resultant of all distributed aerodynamic pressure forces acts. It is analogous to the center of gravity for weight distribution. The CP moves with angle of attack — generally forward as AoA increases toward the critical angle. The center of gravity is where weight acts, not aerodynamic forces; the transition point is where the boundary layer changes from laminar to turbulent.
Correct: D)
Explanation: Point 4 on the aerofoil diagram (PFA-009) represents the separation point, where the boundary layer detaches from the upper wing surface and turbulent wake forms behind it. This is not the transition point (where laminar flow becomes turbulent), the stagnation point (where airflow splits at the leading edge), or the center of pressure (the resultant aerodynamic force application point).
Correct: B)
Explanation: Point 1 on the aerofoil diagram (PFA-009) is the stagnation point — located at the leading edge where incoming airflow splits, with one stream going over the upper surface and one under the lower surface; velocity here is zero and pressure is at its maximum. The transition point is where laminar flow transitions to turbulent flow, the separation point is where flow detaches from the surface, and the center of pressure is an abstract force application point.
Correct: D)
Explanation: The stagnation point is precisely the dividing location where incoming streamlines bifurcate — the streamline that arrives at the stagnation point splits, with air flowing around the upper and lower surfaces separately. At this point, kinetic energy is fully converted to pressure (V = 0, p = p_total). Boundary layer transition (C) occurs further aft on the upper surface; separation (A) is further aft still; aerodynamic forces are considered to act at the center of pressure, not the stagnation point.
Correct: A)
Explanation: CL increases approximately linearly with AoA up to the critical angle (typically 15–18° for most aerofoils). Beyond this critical AoA, the adverse pressure gradient on the upper surface causes the boundary layer to separate, destroying the smooth flow and causing a sudden drop in lift (stall) accompanied by a large increase in drag. Lift does not increase exponentially (D), and reducing AoA generally reduces both lift and drag (not increases drag as C suggests).
Correct: A)
Explanation: As angle of attack increases, the relative airflow meets the wing at a steeper upward angle. The streamline that arrives exactly at the stagnation point shifts downward (toward the lower surface of the leading edge), because more airflow is now directed over the upper surface. Simultaneously, the centre of pressure moves forward (not up or down — it moves chordwise), and the suction on the upper surface increases as flow accelerates more strongly over the curved upper side.
Correct: A)
Explanation: High pressure below the wing and low pressure above create a tendency for air to flow around the wingtip from the high-pressure lower surface to the low-pressure upper surface. This spanwise flow wraps around the wingtip, creating trailing vortices (wingtip vortices). These vortices are the physical mechanism of induced drag — they impart a downward component (downwash) to the oncoming flow, effectively reducing the local angle of attack and tilting the lift vector rearward, creating an induced drag component.
Correct: B)
Explanation: Induced drag is proportional to CL^2 / (pi * AR * e), where AR is aspect ratio and e is Oswald efficiency factor. A small aspect ratio (short, stubby wing) produces high induced drag for a given lift coefficient because the wingtip vortices are strong relative to the span. Conversely, high aspect ratio (long, slender) wings minimise induced drag — hence gliders use very high AR wings. Low CL (option C) would reduce induced drag, not increase it.
Correct: A)
Explanation: Total drag = parasite drag + induced drag. Parasite drag encompasses all drag not associated with lift production: skin friction drag (viscous shear on surfaces), form/pressure drag (pressure difference between leading and trailing edges due to boundary layer separation), and interference drag (junction effects). Induced drag is separately caused by the lift generation process itself (wingtip vortices and downwash). Parasite drag increases with V^2, while induced drag decreases with V^2.
Correct: B)
Explanation: The standard aerodynamic breakdown of total drag is: Total drag = Induced drag + Parasite drag. Induced drag arises from lift generation (wingtip vortices). Parasite drag is the collective term for all non-lift-related drag: form/pressure drag, skin friction drag, and interference drag. Options C and D list sub-components of parasite drag but omit induced drag or incorrectly combine them. Option A omits induced drag, which is a major component especially at low speeds.
Correct: B)
Explanation: Stall recovery requires reducing angle of attack below the critical value so that airflow can re-attach to the upper surface and lift can be restored. The pilot must push forward on the elevator control to lower AoA, which also allows the aircraft to accelerate (or the pilot applies power if available). Increasing AoA (A, C) deepens the stall. Reducing speed (C, D) worsens the condition. Banking (D) increases the load factor, which raises the stall speed — exactly the wrong input.
Correct: D)
Explanation: The natural sequence of boundary layer development on an aerofoil runs from laminar (near the leading edge, where the flow is orderly and Reynolds number is low) to turbulent (further aft, after transition). The reverse sequence (turbulent first, then laminar) does not occur naturally. This forward laminar / aft turbulent arrangement is why designers place the maximum thickness of laminar-flow aerofoils further back — to extend the favourable pressure gradient that maintains laminar flow as far as possible before transition.
Correct: A)
Explanation: Wing dihedral — the upward V-angle of the wings relative to the horizontal — provides lateral (roll) stability. When one wing drops, the dihedral geometry increases the angle of attack and lift on the lower wing, producing a restoring roll moment. This is a geometric/structural feature, not related to differential aileron deflection or directional stability.
Correct: A)
Explanation: Longitudinal stability refers to the aircraft's tendency to maintain or return to its trimmed pitch attitude, which is rotation around the lateral axis (the axis running wingtip to wingtip). The propeller axis is not a standard stability axis; the longitudinal axis governs roll (lateral stability); the vertical axis governs yaw (directional stability).
Correct: C)
Explanation: Yawing is defined as rotation around the vertical (yaw) axis, producing a nose-left or nose-right movement. Pitching is rotation around the lateral axis, rolling is rotation around the longitudinal axis, and slipping is a lateral flight condition — not a rotational axis term.
Correct: B)
Explanation: Pitching is rotation around the lateral axis (wingtip to wingtip), causing the nose to move up or down. Yawing is rotation around the vertical axis, rolling is rotation around the longitudinal axis, and stalling is an aerodynamic phenomenon — not an axis of rotation.
Correct: D)
Explanation: The elevator controls pitch, which is rotation around the lateral axis. By deflecting the elevator up or down, the tailplane generates a pitching moment that raises or lowers the nose. The vertical axis governs yaw (rudder), the longitudinal axis governs roll (ailerons), and an 'elevator axis' is not a standard aeronautical term.
Correct: B)
Explanation: Only correct loading of the aircraft — placing occupants and baggage within the approved limits — can ensure the center of gravity (CG) remains within the certified forward and aft limits. Trim tabs adjust aerodynamic balance in flight but cannot physically move the CG; aileron trim tabs control roll, not pitch CG; and the CG must be verified before flight, not determined during it.
Correct: A)
Explanation: Differential aileron movement deflects the down-going aileron less than the up-going aileron, which reduces the additional induced drag on the descending wing. This reduces adverse yaw — the unwanted yaw opposite to the intended roll direction — making coordinated turns easier. It does not keep total lift constant during aileron deflection, and it decreases, not increases, the drag-to-lift ratio.
Correct: C)
Explanation: An aerodynamic rudder balance (also called a horn balance or set-back hinge) places part of the control surface ahead of the hinge line, so aerodynamic forces partly assist the pilot's input, thereby reducing the stick/pedal forces required. It does not reduce the size of the control surface, delay stall, or improve rudder effectiveness per se.
Correct: A)
Explanation: A static (mass) balance places counterweights ahead of the hinge line to bring the control surface's center of mass to or forward of the hinge line. This prevents control surface flutter, which is a potentially destructive resonant oscillation. It is not designed to enable trimming without force, increase stick forces, or limit stick forces.
Correct: B)
Explanation: When the elevator trim tab is deflected upward, it generates a downward aerodynamic force on the trailing edge of the elevator, pushing the elevator leading edge up — this produces a nose-down pitching moment. The indicator therefore shows a nose-down (forward) position. Upward trim tab deflection does not result in a neutral, nose-up, or lateral trim indication.
Correct: A)
Explanation: Point 1 in figure PFA-008 represents inverted flight, where the lift polar shows a negative lift coefficient with the aircraft flying upside down. Slow flight, stall, and best gliding angle all correspond to positive (upright) portions of the polar curve, not the inverted segment.
Correct: C)
Explanation: In a coordinated (banked) turn, the lift vector must support both the vertical component (equal to weight) and provide the centripetal force for the turn, so total lift — and hence load factor n — exceeds 1. The higher effective weight means the wing must produce more lift to avoid descending, raising the stall speed Vs above its straight-and-level value. Options with n less than 1 or Vs decreasing are incorrect.
Correct: A)
Explanation: The higher pressure beneath the wing and lower pressure above create a pressure differential. At the wingtips, air flows from the high-pressure lower surface around to the low-pressure upper surface, forming trailing vortices. These vortices tilt the local airflow downward (downwash), effectively reducing the angle of attack and creating induced drag — not laminar flow, profile drag, or additional lift.
Correct: A)
Explanation: At the same mass and in steady glide, lift equals weight regardless of airfoil thickness, so lift remains the same. However, a thicker airfoil has greater form (pressure) drag due to its larger frontal area and more adverse pressure gradients, resulting in more drag with the same lift.
Correct: C)
Explanation: A profile polar (Lilienthal polar) plots the lift coefficient (cA) against the drag coefficient (cD) for a wing profile at various angles of attack. It directly shows the relationship between cA and cD across the operating range. It is not a polar of minimum sink versus best glide, nor does it show total aircraft lift or drag independently.
Correct: B)
Explanation: An incipient spin begins when one wing stalls before the other — the stalled wing drops, creating a yawing and rolling moment. The correct response is to apply rudder opposite the direction of yaw/lower wing to stop the rotation, and simultaneously release elevator back-pressure (or push forward) to reduce the angle of attack below the critical value, allowing airflow to re-attach and lift to be restored. Pulling the elevator (D) would increase AoA and deepen the stall; pushing alone (C) without rudder does not stop the yaw.
Correct: D)
Explanation: VNE is the red-line speed above which structural or aeroelastic failure becomes possible. At excessive speeds, dynamic pressure (q = 0.5 * rho * V^2) rises dramatically, and control surfaces and wing structures may enter flutter — a self-reinforcing oscillation where aerodynamic forces and structural elasticity feed each other, potentially causing rapid structural disintegration. The airspeed indicator remains usable at high speeds; glide ratio does not improve beyond the best-glide speed.
Correct: B)
Explanation: Any body immersed in a moving fluid (v > 0) will produce drag due to pressure and friction forces opposing the flow. Only specially shaped (lifting) bodies oriented appropriately produce lift; an arbitrarily shaped body has no guaranteed lift but always produces drag. Drag is also not constant — it increases with the square of velocity.
Correct: A)
Explanation: In an aerofoil diagram (PFA-010), line 3 represents the camber line (mean camber line), which is the locus of points midway between the upper and lower surfaces. The chord is the straight line from leading to trailing edge, the chord line is the same geometric reference, and thickness is the vertical distance between upper and lower surfaces at any chordwise station.
Correct: B)
Explanation: As angle of attack increases, the suction peak on the upper surface intensifies and moves toward the leading edge, causing the center of pressure to migrate forward. This continues until the critical (stall) angle of attack is reached. Beyond the stall, the suction peak collapses as flow separates, and the center of pressure moves abruptly rearward. The forward movement of the CP with increasing AoA is important for stability analysis and contributes to the pitching moment characteristics of the aerofoil.
Correct: A)
Explanation: As angle of attack decreases, the aerodynamic loading on the forward portion of the upper surface diminishes, shifting the resultant pressure force rearward — so the center of pressure moves aft (toward the trailing edge). The stagnation point also moves upward (not down) as less flow is forced over the upper surface. Understanding CP movement is important because it affects the pitching moment balance of the aircraft throughout the flight envelope.
Correct: C)
Explanation: AoA can be negative (when the chord line points downward relative to the freestream, some aerofoils still generate positive lift due to camber, but very negative AoA produces negative lift). AoA continuously changes in flight as the pilot adjusts pitch and as airspeed changes. Within the normal range, increasing AoA increases lift — but beyond the critical angle (typically ~15°), flow separation destroys lift. Option C correctly identifies this upper limit of AoA beyond which lift collapses.
Correct: D)
Explanation: Parasite drag follows the formula Dparasite = CDp * 0.5 * rho * V^2 * S. Since dynamic pressure q = 0.5 * rho * V^2 is proportional to V^2, doubling the speed (V × 2) quadruples dynamic pressure (2^2 = 4), and thus quadruples parasite drag. This square-law relationship is fundamental: halving your speed reduces parasite drag by a factor of four, while doubling speed costs four times as much drag — which is why high-speed flight is energetically expensive.
Correct: D)
Explanation: Every aerofoil has a minimum drag coefficient (CDmin) greater than zero, because skin friction and form drag exist even at the optimal low-drag AoA. The drag coefficient cannot reach zero for a real body in viscous flow — there is always some irreducible friction drag. It can increase without bound as AoA increases (especially post-stall), but has a finite positive minimum. The drag polar (CD vs CL curve) shows CDmin as the lowest point of the parabolic curve.
Correct: D)
Explanation: Induced drag originates from the pressure difference between the upper and lower wing surfaces causing spanwise flow that rolls up into concentrated vortices at the wingtips. The strength of these vortices — and thus the induced drag — is directly related to what happens at the wingtips. This is why winglets, raked wingtips, and elliptical planforms are used to reduce wingtip vortex strength. The fuselage, ailerons, and landing gear primarily generate parasite drag, not induced drag.
Correct: C)
Explanation: Interference drag occurs where two surfaces meet and their boundary layers interact, creating turbulence and additional drag beyond what each surface would produce in isolation. The wing-fuselage junction (wing root) is the classic location: the boundary layers from the fuselage and wing interfere, creating complex flow that increases total drag. Fairings and fillets are used at wing roots to smooth this junction and reduce interference drag. The landing gear generates form drag, not interference drag specifically.
Correct: C)
Explanation: The elliptical wing planform produces the minimum possible induced drag for a given span and total lift. This is because it creates a perfectly elliptical spanwise lift distribution, which results in a uniform downwash across the span — the theoretical optimum. An elliptical distribution means no "wasteful" concentration of lift near the root or sudden drops near the tips. The Spitfire used an elliptical wing for this reason. Tapered (trapezoidal) wings approximate this and are easier to manufacture; rectangular wings have higher induced drag.
Correct: B)
Explanation: Adverse yaw is the tendency of the nose to yaw away from the intended turn direction when ailerons are applied. Differential aileron deflection (the down aileron moves less than the up aileron) reduces the extra drag on the descending wing, thereby reducing the adverse yaw moment. Wing dihedral addresses roll stability, not yaw; full aileron deflection would worsen adverse yaw.
Correct: C)
Explanation: Wing loading is defined as the aircraft's weight (mass times gravity) divided by the wing reference area, expressed in N/m² or kg/m². It is not wing area per weight (that would be the inverse), nor is it related to drag.
Correct: A)
Explanation: Point 5 in figure PFA-008 corresponds to slow flight — a low speed, high angle-of-attack condition on the positive portion of the polar, before stall onset. Inverted flight would appear on the negative lift side, stall at the maximum cA point, and best gliding angle at the cA/cD maximum point.
Correct: B)
Explanation: Extending airbrakes (spoilers/dive brakes) significantly increases profile drag, which is their primary purpose for steepening the glide path. They also partially disrupt upper-surface lift, reducing the total lift generated. The other combinations (less drag, more lift, etc.) are aerodynamically incorrect for airbrake deployment.
Correct: C)
Explanation: Glide ratio (L/D) is maximized by minimizing drag and maintaining the optimum speed. Cleaning the aircraft and taping gaps reduces surface roughness and leakage drag; maintaining the correct (best-glide) speed keeps the aircraft at peak L/D; a retractable undercarriage removes a major source of parasite drag. Higher mass shifts the polar but does not change the maximum L/D ratio itself. A forward CG can actually increase trim drag.
Correct: B)
Explanation: In a spin, one wing is stalled (typically the inner wing) while the other continues to fly, so the aircraft autorotates and descends at near-constant airspeed. In a spiral dive, both wings are flying (neither is stalled), and the aircraft enters an ever-steepening banked dive with rapidly increasing airspeed. Confusing the two is dangerous — recovery techniques differ fundamentally.
Correct: B)
Explanation: Angle of attack (AoA, alpha) is precisely defined as the angle between the aerofoil chord line and the direction of the undisturbed (relative) freestream airflow. It is the primary determinant of lift coefficient: CL increases with AoA until the critical (stall) angle. AoA must not be confused with pitch attitude (angle between longitudinal axis and horizon) — a glider descending nose-down can still have a positive AoA if the relative airflow comes from below the chord line.
Correct: C)
Explanation: Aspect ratio (AR) = wingspan (b) / mean chord (c) = b^2 / S, where S is wing area. High aspect ratio wings (long, narrow) produce less induced drag because the wingtip vortices are proportionally weaker relative to the total span. Gliders have very high aspect ratios (typically 20–40) for this reason — minimising induced drag is essential for maximum glide ratio. Low-aspect-ratio wings produce more induced drag but are structurally lighter and more agile.
Correct: B)
Explanation: The longitudinal position of the center of gravity directly determines the pitch stability, which is stability around the lateral axis. A CG forward of the neutral point provides positive (restoring) pitch stability; too far aft reduces or reverses it. Lateral stability is mainly influenced by wing dihedral, and directional stability by the vertical tail.
Correct: D)
Explanation: A large vertical tail fin acts as a weathervane, generating a restoring yawing moment whenever the aircraft sideslips, thereby providing directional (yaw) stability. Wing dihedral provides lateral (roll) stability; differential aileron deflection reduces adverse yaw; a large elevator contributes to pitch stability, not directional stability.
Correct: C)
Explanation: The critical (stall) angle of attack is a fixed aerodynamic property of the aerofoil shape — it is the AoA at which flow separation occurs regardless of airspeed, weight, or altitude. What changes with weight is the stall speed (Vs = sqrt(2W / (rho * S * CL_max))), not the stall AoA. A heavier aircraft must fly faster to generate the same lift, but it still stalls at the same critical AoA. C.G. position affects pitch stability and control effectiveness but does not change the aerofoil's critical angle.
Correct: D)
Explanation: In straight and level flight at constant engine power, the aircraft flies at a fixed speed and the wing operates at a specific angle of attack. In a climb at the same power, airspeed is lower (more energy goes into altitude gain), so the wing needs a higher angle of attack to generate sufficient lift. Therefore, the level-flight angle of attack is smaller than in a climb.
Correct: B)
Explanation: The horizontal tail (stabilizer and elevator) provides pitch stability — resistance to and recovery from pitch disturbances — which is stability around the lateral axis. It does not primarily provide lateral (roll) axis stability (that is the wing dihedral's role), nor does it initiate turns around the vertical axis or stabilize around the vertical axis.
Correct: B)
Explanation: The rudder deflects left, generating a leftward aerodynamic force on the tail, which yaws the nose to the left around the vertical axis. Pitching (nose up/down) is a movement around the lateral axis controlled by the elevator, not the rudder.
Correct: C)
Explanation: Differential aileron deflection reduces adverse yaw — the undesired nose movement opposite to the roll direction — by giving the down-going aileron less deflection, thereby reducing the extra induced drag on the descending wing. It is not used to reduce wake turbulence, prevent stalls, or increase the rate of descent.
Correct: B)
Explanation: In a banked turn, the lift vector is tilted sideways, so its vertical component is less than the total lift. To maintain altitude, the pilot must increase total lift above the straight-and-level value. The increased lift must balance both the weight (vertical component) and provide centripetal force (horizontal component). Load factor n = 1/cos(bank angle) and is always greater than 1 in a level turn.
Correct: B)
Explanation: A retractable (stowable) engine and propeller arrangement on a TMG allows the powerplant to be fully folded into the fuselage when not in use, eliminating all associated parasite drag and enabling pure glider performance. Fixed nose- or tail-mounted engines and fixed fuselage mounts all produce significant drag even when the engine is off.
Correct: D)
Explanation: Adverse yaw occurs because deflecting the ailerons asymmetrically changes the induced drag on each wing. The down-deflected aileron increases lift and — more importantly — also increases induced drag on that wing. This extra drag on the rising wing yaws the nose toward the descending wing, opposite to the intended direction of roll. Option C is incorrect because it states 'up-deflected aileron' causes more drag.
Correct: B)
Explanation: Close to the ground, the ground surface restricts the downward development of wing-tip vortices. This reduces the induced downwash angle, which effectively increases the local angle of attack and thus lift, while simultaneously reducing induced drag. At altitude, vortices develop freely, downwash is stronger, and induced drag is higher.
Correct: A)
Explanation: Lift is generated by a pressure differential: lower pressure on the upper (suction) surface and higher pressure on the lower surface. On the upper surface, flow accelerates around the curved upper side — by Bernoulli's principle, higher velocity means lower static pressure. On the lower surface, flow is slowed and compressed, increasing static pressure. The net upward pressure force integrated over the entire surface constitutes lift: L = CL * 0.5 * rho * V^2 * S.
Correct: C)
Explanation: Geometric washout means the wing is physically twisted so that the angle of incidence (and thus the local angle of attack) decreases from root to tip. This ensures that the wing root reaches the critical stall angle before the wingtips, so the ailerons (located outboard) remain effective even as the inboard section stalls. This gives the pilot aileron control during the approach to stall, enabling better roll control and safer stall behaviour. Aerodynamic washout (D) achieves the same effect through changing aerofoil sections rather than physical twist.
Correct: A)
Explanation: This is the definitive stall characteristic: lift collapses because boundary layer separation destroys the pressure differential that generates it, while drag rises dramatically due to the large turbulent separated wake. The CL vs. AoA curve shows CL_max at the critical angle, then a steep drop — this is the stall. The CD vs. AoA curve rises steeply through and beyond the stall. This combination (less lift, more drag) is why the stall is critical — the aircraft loses lift while simultaneously experiencing high drag that would further reduce speed.
Correct: A)
Explanation: Spin recovery technique (PARE: Power off, Ailerons neutral, Rudder opposite to spin direction, Elevator forward) requires keeping ailerons neutral because using ailerons during a spin can worsen the rotation — applying aileron into the spin raises the inner wing's AoA (which may already be stalled) and can deepen the spin. Rudder opposite to spin direction stops the autorotation; forward elevator then reduces AoA to unstall both wings. Speed does not constantly increase in a spin — the aircraft reaches a stabilised spin with relatively constant speed and rotation rate.
Correct: A)
Explanation: Lateral (roll) stability — the tendency to return to wings-level after a roll disturbance — is primarily provided by wing dihedral (the upward angle of the wings from horizontal). When a gust rolls the aircraft, the lower wing descends and its angle of attack increases (it meets more airflow), generating more lift and creating a restoring moment back to level. The vertical tail provides directional (yaw) stability; ailerons are roll control surfaces (not stability), and the elevator controls pitch. High-wing aircraft achieve similar lateral stability through the pendulum effect of the fuselage hanging below the wings.
Correct: B)
Explanation: The rudder is the primary yaw control, rotating the aircraft around the vertical axis. Rudder deflection generates a sideways aerodynamic force on the fin/rudder assembly, which yaws the nose left or right. The lateral axis governs pitch (elevator), and the longitudinal axis governs roll (ailerons).
Correct: D)
Explanation: An upward gust suddenly increases the aircraft's angle of attack, momentarily generating more lift than needed for level flight — this additional lift acts as a load on the structure, increasing the load factor n above 1. Lower air density reduces lift (would decrease, not increase, load factor at the same speed); CG position and weight affect handling but not the instantaneous load factor from a gust.
Correct: C)
Explanation: The McCready ring is set to the expected climb rate in the next thermal (2 m/s), and the pilot reads the recommended inter-thermal cruise speed at the point on the variometer scale corresponding to the current sink rate (3 m/s). Setting the ring to the current sink rate (3 m/s) would be incorrect; the ring is always set to the anticipated thermal strength.
Correct: B)
Explanation: During approach and landing, changing the camber flap setting from positive (increased camber) to negative (reduced or reflexed camber) would dramatically reduce lift and could lead to an abrupt loss of lift very close to the ground — a potentially fatal situation. Positive camber should be maintained throughout the approach. Negative camber settings are typically used only for high-speed cruise.
Correct: D)
Explanation: Longitudinal (pitch) stability requires the centre of gravity to be ahead of the neutral point. When the C.G. moves aft beyond the rear limit, the static margin becomes negative: a pitch disturbance produces a moment that amplifies rather than corrects the disturbance, making the aircraft unstable and potentially uncontrollable. A forward C.G. (A) increases stability but requires more elevator force — it is uncomfortable but recoverable. Rearward C.G. beyond limits is the most dangerous condition because recovery from pitch divergence may be impossible.
Correct: A)
Explanation: Static pressure is a scalar thermodynamic quantity representing the random kinetic energy of gas molecules. Because molecular collisions occur in all directions equally, static pressure acts omnidirectionally — it presses equally on all surfaces of a container regardless of orientation. This contrasts with dynamic pressure (q = 0.5 * rho * V^2), which is directional and associated with the bulk flow velocity. Bernoulli's equation combines both: ptotal = pstatic + q.
Correct: B)
Explanation: Bernoulli's theorem for an ideal (frictionless, incompressible) fluid along a streamline states that total pressure is conserved: ptotal = pstatic + 0.5 * rho * V^2. Total pressure is the sum of static pressure and dynamic pressure. Where air accelerates over the upper wing surface, static pressure decreases (dynamic pressure increases) while total pressure remains constant — this pressure difference generates lift. The airspeed indicator works on this principle by measuring the difference between total (pitot) and static pressure.
Correct: C)
Explanation: The center of pressure is defined as the single point through which the entire resultant aerodynamic force — which includes both lift (perpendicular to freestream) and drag (parallel to freestream) — is considered to act. It is not a physical feature of the wing but a mathematical convenience for analysis. Gravity acts through the center of gravity, which is a completely separate point determined by the aircraft's mass distribution.
Correct: D)
Explanation: Point 3 on the aerofoil diagram (PFA-009) represents the transition point — the location where the boundary layer changes from smooth laminar flow to turbulent flow. The stagnation point is at the leading edge (point 1), the separation point is further aft where flow detaches, and the center of pressure is the theoretical point of resultant lift application.
Correct: C)
Explanation: The primary aerodynamic benefit of washout is that the wingtip (where the ailerons are) has a lower angle of incidence than the root, so it reaches its critical stall angle later. When the pilot approaches stall speed and raises the nose to a high AoA, the inboard sections stall first while the outboard/aileron sections remain unstalled and continue to generate lift and respond to aileron inputs. This gives the pilot roll control authority during the stall approach, preventing inadvertent spin entry.
Correct: A)
Explanation: Induced drag decreases monotonically with increasing airspeed in level flight: D_induced = 2W^2 / (rho * V^2 * S^2 * pi * AR * e). As V increases, induced drag continuously falls — there is no minimum/maximum within the normal flight envelope. Parasite drag (not induced drag) has the U-shaped curve described in B/C. Total drag has a minimum at the speed where induced drag equals parasite drag; induced drag itself simply decreases with speed.
Correct: A)
Explanation: As the critical angle of attack is reached, flow begins to separate from the upper surface, starting at the trailing edge and progressing forward. Once past the critical AoA, the clean attached flow that generated lift breaks down — CL drops sharply. Simultaneously, the separated flow creates a large turbulent wake with very high pressure drag, so CD rises dramatically. The drag polar shows this clearly: the nose of the polar curves sharply as the stall condition is approached, with CL falling and CD rising.
Correct: B)
Explanation: From Vs = sqrt(2W / (rho * S * CLmax)): stall speed decreases when weight (W) decreases, since less lift is needed to maintain equilibrium. Lower density (A) increases true airspeed (TAS) stall speed but the IAS stall speed remains approximately constant (since IAS is based on dynamic pressure q = 0.5 * rho * VTAS^2, which equals 0.5 * rho0 * VIAS^2). Higher load factor (D) effectively increases apparent weight (n*W), raising stall speed. Lower altitude means higher density, which slightly lowers TAS stall speed but does not significantly change IAS stall speed.
Correct: B)
Explanation: The turbulent boundary layer, despite having higher skin friction drag than the laminar layer, has more energetic mixing that allows it to remain attached to the surface against an adverse pressure gradient at higher angles of attack. This is its critical advantage: it resists flow separation better. The laminar boundary layer is indeed thinner (A is partly correct about thickness) and has lower friction drag — but it separates more easily. This is why turbulators are sometimes used on gliders: deliberately triggering transition to turbulent flow to prevent laminar separation bubbles.
Correct: C)
Explanation: Number 2 in figure PFA-010 represents the chord line — the straight reference line drawn from the leading edge to the trailing edge of the aerofoil. The profile thickness is the perpendicular distance between upper and lower surfaces, and the angle of attack is the angle between the chord line and the relative airflow direction.
Correct: B)
Explanation: The angle of attack (alpha) is the angle between the chord line of the aerofoil and the relative direction of the oncoming airflow (free-stream velocity vector). It is not the lift angle, which is not a standard aeronautical term; the angle of incidence is the fixed geometric angle between the chord line and the aircraft's longitudinal axis.
Correct: B)
Explanation: When the right aileron deflects upward (reducing lift on the right wing) and the left aileron deflects downward (increasing lift on the left wing), the aircraft rolls to the right. Simultaneously, the down-deflected left aileron creates more induced drag on the left (rising) wing, yawing the nose to the left — this is adverse yaw. Rolling to the left or yawing to the right would be opposite to the aileron input described.
Correct: D)
Explanation: Water ballast must be kept above freezing level to prevent the water from freezing in the wings, which could jam ballast dump valves, shift the CG unpredictably, and damage wing structure. Water ballast increases wing loading and shifts the best-glide speed higher, but the best glide angle (L/D ratio) remains theoretically unchanged. CG shifts with water ballast are typically minor and managed within approved limits.
Correct: B)
Explanation: The boundary layer development follows a specific sequence: flow is divided at the stagnation point, a laminar boundary layer develops from the stagnation point rearward, then at the transition point the laminar layer converts to turbulent, and finally at the separation point the turbulent layer detaches from the surface. The laminar boundary layer therefore occupies the region from the stagnation point to the transition point. Laminar flow aerofoils are designed to push the transition point as far aft as possible to minimise friction drag.
Correct: B)
Explanation: In level flight, lift must equal weight, so CL decreases as speed increases (L = CL * 0.5 * rho * V^2 * S = W, thus CL = 2W / (rho * V^2 * S)). Induced drag ∝ CL^2 / V^2 ∝ 1/V^2 — it decreases with increasing speed. Parasite drag ∝ V^2 — it increases with speed. The speed where induced drag equals parasite drag is the speed of minimum total drag, which corresponds to the best lift-to-drag ratio and maximum glide range in a glider.
Correct: C)
Explanation: As speed decreases in level flight, the angle of attack must increase to maintain sufficient lift (since CL must increase to compensate for lower dynamic pressure). Higher CL means stronger wingtip vortices and greater induced drag: D_induced ∝ CL^2 ∝ 1/V^2. This is why slow flight is dominated by induced drag — at very low speeds near stall, induced drag is very high and is the main component of total drag, while parasite drag is relatively small.
Correct: A)
Explanation: Static stability means that when an aircraft is disturbed from its equilibrium by an external force (e.g., a gust), aerodynamic restoring forces automatically tend to return it toward the original position. An aircraft that moves further away from equilibrium has static instability; one that stays in the displaced position is neutrally stable; active rudder input is a pilot correction, not static stability.
Correct: B)
Explanation: Adding water ballast increases total aircraft weight, which requires flying faster to maintain the lift needed for level flight. The best-glide speed (minimum drag speed) therefore increases. However, the L/D ratio — and hence the best gliding angle — is a geometric property of the wing aerodynamics and remains unchanged for the same aircraft shape; water ballast does not change the aerodynamic efficiency, only the speed at which it is achieved.
Correct: D)
Explanation: An aerodynamic rudder balance (horn balance or inset hinge) extends part of the control surface ahead of the hinge line. The aerodynamic pressure on this forward portion creates a moment that partially counteracts the hinge moment, reducing the force the pilot must apply to deflect the control surface. The T-tail is a configuration choice affecting downwash; vortex generators delay stall; differential aileron reduces adverse yaw.
Correct: B)
Explanation: Any body placed in a moving airstream (v > 0) will experience drag, which is the component of the aerodynamic resultant force parallel to the free-stream direction. This is true regardless of shape. Only specially shaped lifting bodies produce lift; drag is not constant but varies with velocity squared; and lift without drag is physically impossible.
Correct: A)
Explanation: Longitudinal stability describes the aircraft's tendency to maintain or return to a trimmed pitch attitude — rotation around the lateral axis. The lateral axis runs from wingtip to wingtip. The propeller axis is not a stability axis; the longitudinal axis governs roll (lateral stability); the vertical axis governs yaw (directional stability).
Correct: C)
Explanation: Wing loading = aircraft weight / wing reference area (e.g., N/m² or kg/m²). A higher wing loading means the wing must work harder to generate sufficient lift, resulting in higher stall speeds and better penetration of turbulence. 'Wing area per weight' is the inverse (specific wing area); drag per weight is the drag-to-weight ratio; drag per wing area is not a standard performance metric.
Correct: D)
Explanation: Adverse yaw results from the asymmetric induced drag created by differential aileron deflection. When the pilot deflects the ailerons to roll, the down-going aileron on the rising wing creates more induced drag than the up-going aileron on the descending wing. This extra drag on the rising wing pulls the nose toward the descending wing — opposite to the intended roll direction. Option C incorrectly attributes adverse yaw to the up-deflected aileron.
Correct: B)
Explanation: In ground effect (within approximately one wingspan of the ground), the ground surface physically prevents the wing-tip vortices from fully forming and rolling downward. This reduces induced downwash, increasing the effective angle of attack and thus lift, while simultaneously reducing induced drag. Pilots experience this as a 'cushion' during flare. Options with decreased lift or increased induced drag are aerodynamically incorrect.
