=== EXISTING QUESTIONS (from SPL Exam Questions EN) ===
Source: QuizVDS.it (EASA ECQB-SPL) | 50 questions Free practice: https://quizvds.it/en-en/quiz/spl-en
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q1) - A) The sum of air forces acts along the direction of air flow - B) The sum the air forces acts along with the lift force - C) The lift force compensates the drag force - D) The sum of air forces compensates the gravity force 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q2) - A) Maximum permissable speed increases - B) Minimum speed increases - C) Minimum speed decreases - D) C.G. position moves forward 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q3) - A) Deflect all rudders opposite to lower wing - B) Rudder opposite lower wing, releasing elevator to build up speed - C) Pushing the elevator to build up speed to re-attach airflow on wings - D) Pulling the elevator to bring the plane back to normal attitude 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q4) - A) Wing flaps. - B) Horizontal stabilizer - C) Airlerons. - D) Vertical rudder 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q5) - A) Reduced drag with increased control forces. - B) An increased lift-to-drag ratio and a better glide angle. - C) Too high total pressure resulting in an unusable airspeed indicator. - D) Flutter and mechanically damaging the wings. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q6) - A) Position beyond the front C.G. limit - B) Position too far aside permissable C.G. limits. - C) Position far back within permissable C.G. limits - D) Position beyond the rear C.G. limit 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q7) - A) In all directions. - B) Only in flow direction. - C) Only in the direction of the total pressure. - D) Only vertical to the flow direction. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q8) - A) Total pressure = dynamic pressure - static pressure. - B) Total pressure = dynamic pressure + static pressure. - C) Static pressure = total pressure + dynamic pressure - D) Dynamic pressure = total pressure + static pressure. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q9) - A) Drag and lift. - B) Drag. - C) Lift without drag. - D) Constant drag at any speed. Correct: B)
Explanation: Any body immersed in a flow always produces drag, because skin friction (viscosity) and pressure drag are unavoidable for any real shape. Lift, however, requires an asymmetry — either in geometry (camber, angle of attack) or circulation. A symmetric body at zero angle of attack produces no lift but always produces drag. Therefore, drag is the universal result for any shape, while lift is only produced under specific geometric conditions.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q10) - A) Center of gravity. - B) Lift point. - C) Transition point. - D) Center of pressure. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q11) - A) Only the resulting total drag. - B) Gravity forces of the profile. - C) All aerodynamic forces of the profile. - D) Gravity and aerodynamic forces. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q12)
Explanation: The chord line is a straight reference line connecting the leading edge to the trailing edge of an aerofoil. It is the baseline from which the angle of attack is measured (the angle between the chord line and the undisturbed freestream direction). In standard aerofoil diagrams, the chord line (item 2) is typically the straight baseline of the cross-section, while the mean camber line curves above it and the thickness is measured perpendicular to the chord.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q13)
Explanation: The mean camber line (also called the mean line) is the locus of points equidistant between the upper and lower surfaces of the aerofoil, measured perpendicular to the chord line. It describes the aerofoil's curvature or camber — a cambered (curved) aerofoil generates lift even at zero angle of attack because the asymmetry in curvature accelerates flow more over the upper surface. Maximum camber and its location are key parameters defining aerofoil character.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q14) - A) The chord line and the longitudinal axis of an aeroplane. - B) The chord line and the oncoming airflow. - C) The wing and the fuselage of an aeroplane - D) The undisturbed airflow and the longitudinal axis of an aeroplane. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q15) - A) Trapezium shape. - B) Tapering. - C) Aspect ratio. - D) Wing sweep. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q16)
Explanation: The transition point is where the boundary layer changes character from laminar to turbulent flow. Laminar flow (near the leading edge) has lower friction drag but is fragile and prone to separation. The turbulent boundary layer that follows is thicker and has higher friction drag but resists separation better. The position of the transition point depends on Reynolds number, surface roughness, and pressure gradient — aerofoil designers try to delay transition as far back as possible to minimise skin friction.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q17)
Explanation: The separation point is where the boundary layer detaches from the aerofoil surface. Beyond this point, the smooth attached flow breaks down into a turbulent, reversed-flow wake. As angle of attack increases, the adverse pressure gradient on the upper surface intensifies, and the separation point moves progressively forward toward the leading edge. When separation reaches the leading edge, the wing is fully stalled — CL drops abruptly and CD rises sharply.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q18)
Explanation: The stagnation point is the location on the aerofoil's leading edge region where the oncoming airflow divides — some going over the upper surface, some beneath. At this point, the local flow velocity is zero and static pressure reaches its maximum (equal to total pressure, since dynamic pressure is zero). With increasing angle of attack, the stagnation point moves slightly downward on the leading edge, as more flow is directed over the upper surface to generate greater lift.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q19) - A) The boundary layer starts separating on the upper surface of the profile - B) All aerodynamic forces can be considered as attacking at this single point - C) The laminar boundary layer changes into a turbulent boundary layer - D) Streamlines are divided into airflow above and below the profile 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q20) - A) Low pressure is created above, higher pressure below the profile - B) Pressure above remains unchanged, higher pressure is created below the profile - C) High pressure is created above, lower pressure below the profile - D) Pressure below remains unchanged, lower pressure is created above the profile 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q21) - A) It moves to the wing tips - B) It moves forward until reaching the critical angle of attack - C) It moves forward until reaching the critical angle of attack - D) It moves forward first, then backward 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q22) - A) Increasing the angle of attack too far may result in a loss of lift and an airflow separation - B) Increasing the angle of attack results in less lift being generated by the aerofoil - C) Decreasing the angle of attack results in more drag being generated by the aerofoil - D) Too large angles of attack can lead to an exponential increase in lift 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).
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q23) - A) The stagnation point moves down - B) The center of pressure moves down - C) The center of pressure moves up - D) The stagnation point moves up 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q24) - A) The center of pressure moves aft - B) The center of pressure moves forward - C) The stagnation point moves down - D) The stagnation point remains constant 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q25)
Explanation: The angle of attack (alpha, α) is the angle between the chord line and the direction of the oncoming airflow (relative wind). In the figure, the direction of airflow (DoF) vector and the chord line form angle alpha — this is the fundamental angle that determines the lift coefficient and stall behaviour. The angle of incidence is a fixed structural angle between the chord line and the aircraft's longitudinal axis (set during manufacturing), and does not change in flight.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q26) - A) Arrow shape. - B) V-form - C) Geometric washout. - D) Aerodynamic washout. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q27) - A) With the washout the form drag reduces at high speeds - B) Greater hardness because the wing can withstand more torsion forces - C) At high angles of attack the effectiveness of the aileron is retained as long as possible - D) Structurally the wing is made more rigid against rotation 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q28) - A) Increasing the angle of attack results in decreasing lift - B) The angle of attack cannot be negative - C) A too large angle of attack may result in a loss of lift - D) The angle of attack is constant throughout the flight 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q29) - A) It decreases by a factor of 2 - B) It increases by a factor of 2 - C) It decreases by a factor of 4 - D) It increases by a factor of 4 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q30) - A) Is proportional to the lift coefficient - B) Increases with increasing airspeed. - C) May range from zero to an infinite positive value - D) Cannot be lower than a non-negative, minimal value. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q31) - A) Wing tips. - B) Leading edge. - C) Trailing edge. - D) Wing roots 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q32) - A) Large aspect ratio - B) Small aspect ratio - C) Low lift coefficients - D) Tapered wings 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q33) - A) The front part of the fuselage. - B) The outer part of the ailerons. - C) The lower part of the gear. - D) The wing tips. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q34) - A) At the ailerons - B) At the the gear - C) At the wing root - D) Near the wing tips 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q35) - A) Parasite drag - B) Main resistance. - C) Induced drag. - D) Total drag. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q36) - A) Parasite drag decreases and induced drag increases - B) Induced drag decreases and parasite drag increases - C) Parasite drag decreases and induced drag decreases - D) Induced drag increases and parasite drag increases 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q37) - A) Rectangular shape - B) Trapezoidal shape - C) Elliptical shape - D) Double trapezoidal shape 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q38) - A) The induced drag will slightly decrease - B) The induced drag will collapse - C) The induced drag will increase - D) The induced drag will remain constant 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q39) - A) Induced drag decreases with increasing airspeed - B) Induced drag has a minimum at a certain speed and increases at higher as well as lower speeds - C) Induced drag has a maximum at a certain speed and decreases at higher as well as lower speeds - D) Induced drag increases with increasing airspeed 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q40) - A) Interference drag and parasite drag - B) Induced drag and parasite drag - C) Induced drag, form drag, skin-friction drag - D) Form drag, skin-friction drag, interference drag 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q41) - A) Lift decreases and drag increases - B) Lift and drag increase - C) Lift increases and drag decreases - D) Lift and drag decrease 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q42) - A) Increase the angle of attack and increase the speed. - B) Decrease the angle of attack and increase the speed. - C) Increase the angle of attack and reduce the speed. - D) Increase the bank angle and reduce the speed. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q43) - A) Decreases and drag increases. - B) Increases and drag increases. - C) Decreases and drag decreases - D) Increases and drag decreases. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q44) - A) Decreases with forward center of gravity position. - B) Changes with increasing weight. - C) Is independent of the weight. - D) Increases with backward center of gravity position. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q45) - A) Lower density - B) Decreasing weight - C) Lower altitude - D) Higher load factor 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q46) - A) During recovery the ailerons should be kept neutral - B) During the spin the speed constantly increases - C) During recovery the ailerons should be crossed - D) Only very old aeroplanes have a risk of spinning 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q47) - A) The stagnation point and the center of pressure. - B) The stagnation point and the transition point. - C) The transition point and the separation point. - D) The transition point and the center of pressure. 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q48) - A) Laminar boundary layer along the complete upper surface with non-separated airflow - B) Turbulent layer at the leading wing areas, laminar boundary layer at the trailing areas - C) Turbulent boundary layer along the complete upper surface with separated airflow - D) Laminar layer at the leading wing areas, turbulent boundary layer at the trailing areas 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q49) - A) The laminar boundary layer is thinner and provides more skin-friction drag - B) The turbulent boundary layer can follow the airfoil camber at higher angles of attack - C) The laminar boundary layer produces lift, the turbulent boundary layer produces drag - D) The turbulent boundary layer is thicker and provides less skin-friction drag 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^q50) - A) Wing dihedral - B) Vertical tail - C) Differential aileron deflection - D) Elevator 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.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_2) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: D)
Explanation: The standard gravitational acceleration at the Earth's surface is 9.81 m/s² (ISA value). This value is fundamental in aeronautics: it is used to calculate weight (W = m × g), load factor, and appears in all performance equations. 1013.25 hPa is the standard pressure at sea level, and 15°C/100 m is not a correct gradient (the standard lapse rate is 0.65°C/100 m).
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_15) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: A)
Explanation: The permitted flap position during a sideslip is always specified in the aircraft flight manual (AFM/POH). Some gliders prohibit extended flaps in a sideslip because the combination of flaps and deflected rudder can create dangerous aerodynamic couples or exceed structural limits. Others permit certain configurations. The only correct answer is therefore to consult the AFM.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_19) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: A)
Explanation: Dynamic stability describes the behaviour of an aircraft over time after a disturbance. A dynamically stable aircraft returns automatically to its original equilibrium (trim) after being disturbed — the oscillations progressively damp out. Answer B describes so-called "neutral or convergent stability towards a new equilibrium", which is different. Static stability (the immediate tendency to return) is a necessary but not sufficient condition for dynamic stability.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_20) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: A)
Explanation: The manoeuvring speed VA (or turbulence penetration speed) is the maximum speed at which full control surface deflections or severe wind gusts will not cause the structural limit load to be exceeded. Below VA, the wing will stall before the structural limit load is reached, thereby protecting the structure. In severe turbulence, speed must be reduced below V_A to avoid structural damage from gust dynamic loads.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_1) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: D)
Explanation: In the ICAO standard atmosphere (ISA), temperature decreases by 0.65°C for every 100 m of altitude in the troposphere (or equivalently, 2°C per 1000 ft, or 6.5°C/1000 m). Answer B (0.65°C/1000 ft) is incorrect because the unit is wrong — this would be far too small a lapse rate. Answer D is the only correct one: 0.65°C per 100 m of altitude.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_3) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: C)
Explanation: Atmospheric pressure decreases with altitude in an approximately exponential manner. In the ICAO standard atmosphere, pressure is approximately half the sea-level pressure (1013.25 hPa → ~506 hPa) at an altitude of approximately 5,500 m (18,000 ft). This value is important for high-altitude physiology (oxygen requirements) and for density altitude performance calculations.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_4) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: C)
Explanation: Density altitude is the altitude at which the aircraft would be in the ISA standard atmosphere if the air density were the same as in actual conditions. It is calculated from pressure altitude (altimeter set to 1013.25 hPa) corrected for the temperature deviation from ISA. A temperature higher than ISA gives a density altitude higher than pressure altitude, reducing aircraft performance. Answer D describes pressure altitude, not density altitude.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_5) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: A)
Explanation: The continuity equation states that for an incompressible fluid, the volumetric flow rate Q = S × V is constant along a streamtube. If the cross-section S decreases, the velocity V must increase proportionally to keep Q constant. This principle, combined with Bernoulli's theorem, explains why air accelerates over the curved upper surface of an aerofoil, creating a low-pressure region that generates lift.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_6) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: A)
Explanation: Both lift and drag are proportional to the dynamic pressure q = 0.5 × ρ × V². When air density ρ decreases (at altitude or in high temperatures), q decreases for a given speed, which reduces both lift and drag. This is why aircraft performance deteriorates at high altitude or in great heat: the aircraft must fly faster (higher TAS) to generate the same lift, while the total aerodynamic resistance decreases for a constant indicated airspeed.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_11) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: D)
Explanation: The neutral point (also called the aerodynamic centre at wing level, but "neutral point" for the complete aircraft) is the point about which the pitching moment remains constant regardless of changes in angle of attack. For a stable aircraft, the centre of gravity must be forward of the neutral point — the CG-to-neutral point distance constitutes the static stability margin. Note: for an isolated aerofoil, this point corresponds to the aerodynamic centre (at approximately 25% of the chord); for the complete aircraft, the neutral point accounts for the contribution of the horizontal stabiliser.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_9) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: D)
Explanation: The rigging angle (or angle of incidence) is the fixed angle, defined at construction, between the aerofoil chord line and the longitudinal axis of the fuselage. It does not vary in flight. It should not be confused with the angle of attack, which is the angle between the chord line and the direction of the relative wind (and which varies in flight according to attitude and speed). The rigging angle is chosen by the manufacturer so that the wing generates the necessary lift in cruise at an aerodynamically favourable fuselage attitude.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_17) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: C)
Explanation: The transition point is precisely the location on the aerofoil where the boundary layer changes from a laminar regime (ordered flow, in parallel layers) to a turbulent regime (disordered flow, with transverse mixing). This transition is irreversible in the direction of flow: the change is from laminar to turbulent, never the reverse. The position of the transition point depends on the Reynolds number, the pressure gradient, and surface roughness — a favourable pressure gradient (acceleration) maintains laminar flow, while an adverse gradient (deceleration) triggers transition.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_10) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: B)
Explanation: Wing twist (geometric or aerodynamic) varies the angle of incidence or aerodynamic characteristics along the span, so that the stall does not occur simultaneously across the entire wing. The root (higher angle of incidence) reaches the critical angle first and stalls progressively, while the outer sections remain attached. This progressive (rather than simultaneous) flow separation improves stall safety and maintains roll control via the ailerons. The effect on adverse yaw (A) is indirect and marginal.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_14) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: C)
Explanation: Form drag (pressure drag) is caused by the pressure difference between the front and rear of a body, due to boundary layer separation and the formation of vortices in the wake. The more intense the vortex formation (unStreamlined body, blunt trailing edge), the higher the form drag. This is why streamlined aerofoils have much lower form drag than a flat plate or sphere — their progressively converging shape allows the flow to remain attached longer, reducing the turbulent wake.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_12) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: B)
Explanation: The drag of a flat disc (non-streamlined body) is pressure drag: it depends primarily on the frontal surface area S exposed perpendicularly to the airflow, and on the dynamic pressure q = 0.5 × ρ × V². The formula is D = CD × q × S. The material strength, the disc's own density, or its weight do not influence aerodynamic drag — this is purely a function of shape, projected area, and flow conditions.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_16) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Speed Polar:
] A = tangent from the origin → best glide speed (best L/D ratio, best glide) B = tangent from a point shifted to the right on the V axis → best glide with headwind C = tangent from a point above the origin on the W axis (McCready) → optimal inter-thermal speed; touches the polar at the point of minimum sink rate D = horizontal line at the level of minimum sink rate → indicates the minimum sink speed (Vmin sink)
Correct: C)
Explanation: On the speed polar (curve showing the sink rate W as a function of horizontal speed V), the point of minimum sink rate corresponds to the lowest point of the curve (the smallest value of W in absolute terms). The tangent at this point is a horizontal tangent — this is tangent (C) on the diagram. This point corresponds to the minimum sink speed, used to maximise flight time or to exploit thermals. The tangent drawn from the origin to the polar (tangent B) gives the speed for the best L/D ratio (best glide ratio).
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_13) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: A)
Explanation: Induced drag is proportional to CL²: Dinduced = CL² / (π × AR × e) × q × S. By increasing the angle of attack, CL increases, and therefore CL² increases, causing induced drag to grow. In level flight at constant speed, an increase in angle of attack corresponds to a lower speed, which further increases induced drag (Dinduced ∝ 1/V²). By increasing speed (C), CL decreases in level flight and induced drag decreases. Parasite drag (D) varies independently of induced drag.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_18) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: C)
Explanation: In a horizontal turn at bank angle φ, the load factor is n = 1/cos(φ). At 45° of bank, n = 1/cos(45°) = 1/0.707 ≈ 1.41. The stall speed in the turn is Vs_turn = Vs × √n = Vs × √1.41 ≈ Vs × 1.19. Therefore the minimum speed increases by approximately 19% compared to straight-and-level flight. This increase in stall speed during turns is a fundamental safety concept — tight turns at low altitude (such as on final approach) are particularly dangerous because the margin above the stall is reduced.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_8) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: D)
Explanation: Adverse yaw is caused by the asymmetry of drag between the two ailerons during turn entry. The aileron that rises (on the high-wing side) increases the local angle of attack, generating more lift but also more induced drag. This additional drag on the rising side creates a yawing moment towards the rising side — i.e. in the opposite direction to the turn (hence "adverse yaw"). Differential ailerons and spoiler-airbrakes are technical solutions to mitigate this effect.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_80_7) Source: BAZL/OFAC Serie 1 - Branches Spécifiques
Correct: D)
Explanation: True airspeed (TAS) is obtained from indicated airspeed (IAS) by applying two successive corrections: first, position and instrument errors (yielding calibrated airspeed, CAS), then the density correction (accounting for the difference between actual air density and standard sea-level density). TAS is therefore the actual speed of the aircraft through the air mass. At high altitude, TAS is significantly higher than IAS because air density is lower.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_1) - A) unlimited - B) limited at the upper end by the maneuvering speed (Va) - C) limited at the lower end by the bottom of the green arc - D) indicated in the Flight Manual (AFM) and normally on the airspeed indicator (ASI) Correct: D)
Explanation: The slotted flap speed range is indicated in the Flight Manual (AFM) and normally on the airspeed indicator (white or light green arc). It varies by glider type.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_2) - A) the upper surface toward the lower surface at the wing tip - B) the lower surface toward the upper surface at the wing tip - C) the upper surface toward the lower surface along the entire trailing edge - D) the lower surface toward the upper surface along the entire trailing edge Correct: B)
Explanation: Wing tip vortices (induced vortices) come from pressure equalization from the lower surface (high pressure) to the upper surface (low pressure) at the wing tip. This phenomenon generates induced drag.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_3) - A) the longitudinal axis of the aircraft and the horizon - B) the longitudinal axis of the aircraft and the general airflow direction - C) the chord line and the general airflow direction - D) the horizon and the general airflow direction Correct: C)
Explanation: Angle of attack is the angle between the chord line and the general airflow direction (relative wind direction). It is not the angle with the horizon nor with the longitudinal axis.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_4) - A) 15 degrees F and 29.92 Hg - B) 59 degrees C and 29.92 hPa - C) 15 degrees C and 1013.25 Hg - D) 15 degrees C and 1013.25 hPa Correct: A)
Explanation: The pressure in ICAO standard atmosphere at sea level is 1013.25 hPa (millibars) = 29.92 inches of mercury (inHg). 29.92 hPa is incorrect.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_5)
] - A) the mass of air flows through a larger cross-section at a lower speed - B) the mass of air flows through a smaller cross-section at a lower speed - C) the mass of air flows through a larger cross-section at a higher speed - D) the speed of the air mass does not vary Correct: B)
Explanation: The mean camber line is the line equidistant between the lower and upper surfaces. In the figure, it is represented by line B.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_6) - A) to reduce speed and therefore centrifugal force - B) to prevent an outward sideslip in the turn - C) to slightly increase lift - D) to prevent slipping inward in the turn Correct: D)
Explanation: In a coordinated turn without altitude loss, back pressure is needed to increase lift and balance centrifugal force (load factor > 1). Lift must compensate for both gravity and centrifugal force.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_7) - A) 9 times - B) 6 times - C) 3 times - D) 1.5 times Correct: D)
Explanation: Stall occurs at a critical angle of attack (stall angle), regardless of airspeed. At this angle, airflow separation on the upper surface causes a sudden drop in lift.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_8) - A) the airfoil profile from root to wing tip - B) the angle of attack at the wing tip by means of the aileron - C) the angle of incidence of the same airfoil, from root to wing tip - D) the wing dihedral, from root to tip Correct: B)
Explanation: Airflow separation occurs at a determined angle of attack (critical angle), specific to each airfoil. It is not related to the nose attitude relative to the horizon.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_9) - A) 100 m/sec2 - B) 1013.25 hPa - C) 15° C/100 m - D) 9.81 m/sec2 Correct: D)
Explanation: Standard gravitational acceleration at Earth's surface is 9.81 m/s². This is the ISA value used in all performance calculations.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_10) - A) total pressure in an aneroid capsule - B) static pressure around an aneroid capsule - C) the difference between static pressure and total pressure - D) the weathervane effect, where pressure decreases Correct: C)
Explanation: Airspeed indicator reading is based on the difference between static pressure and total pressure (dynamic pressure). The ASI measures this difference via the Pitot tube and static port.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_11) - A) reduce air resistance - B) control the aircraft around its longitudinal axis - C) reduce the formation of wing tip vortices - D) stabilize the aircraft in flight Correct: D)
Explanation: The horizontal and vertical stabilizers serve primarily to stabilize the aircraft in flight (longitudinal and directional stability). Without them, the aircraft would be unstable.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_12) - A) occurs at the same speed as before extending the flaps - B) occurs at a lower speed - C) occurs at a higher speed - D) none of the answers is correct Correct: B)
Explanation: When extending slotted flaps, airflow separation occurs at a lower speed, because flaps increase the maximum lift coefficient (CL max). Stall speed decreases.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_13) - A) the resultant of all pressure forces acting on the airfoil - B) the weight - C) the tire pressure on the runway - D) the airflow at the leading edge Correct: D)
Explanation: The aerodynamic center is the point of application of the resultant of aerodynamic forces on a profile. It is distinct from the center of pressure (which moves) and the center of gravity.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_14) - A) bar, psi, Pa - B) bar, psi, a(Alpha) - C) Pa, psi, g - D) bar, Pa, m/sec2 Correct: A)
Explanation: Pressures are expressed in bar, psi (pounds per square inch) and Pa (Pascal). g is an acceleration, not a pressure. Alpha (a) is not a pressure unit.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_15) - A) the aircraft relative to the ground - B) the aircraft relative to the air, corrected for wind component and atmospheric pressure - C) read on the airspeed indicator (ASI) - D) the aircraft relative to the surrounding air mass Correct: D)
Explanation: TAS (True Air Speed) is the aircraft's speed relative to the surrounding air mass. It is the actual speed through the air, corrected for atmospheric density.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_16) - A) the horizontal stabilizer - B) the fin (vertical stabilizer) - C) the wing dihedral - D) leading edge slats Correct: B)
Explanation: Yaw stability is provided by the fin (vertical stabilizer/rudder). Wing sweep contributes to roll stability, not yaw.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_17)
] - A) Fowler - B) Slotted Flap - C) Split Flap - D) Plain Flap Correct: B)
Explanation: The flap shown, extending from the wing with a slot, is a Slotted Flap. The slot channels air from the lower to upper surface, delaying separation.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_18) - A) during an abrupt pull-out after a dive - B) in calm air, in gliding flight, at the minimum authorized speed - C) in straight climbing flight at high speed, in atmospheric turbulence - D) in straight level cruise flight, in atmospheric turbulence Correct: A)
Explanation: The risk of stall/separation appears mainly during an abrupt pull-out after a dive, as the angle of attack increases very rapidly and can exceed the critical angle before the pilot can react.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_19) - A) the density of the body - B) the chemical composition of the body - C) the mass of the body - D) the density of the air Correct: D)
Explanation: Aerodynamic drag depends notably on air density (ρ), since F_D = Cd × 0.5 × ρ × v² × A. The body's own density, chemical composition, and mass do not directly affect aerodynamic drag.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_801_20)
] - A) A - B) H - C) M - D) K Correct: B)
Explanation: The chord line is the straight line connecting the leading edge to the trailing edge. In the figure, it is represented by H.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_1) - A) the longitudinal axis of the aircraft and the horizon - B) the longitudinal axis of the aircraft and the general airflow direction - C) the chord line and the general airflow direction - D) varies depending on the weight of the pilot Correct: C)
Explanation: Angle of attack is the angle between the chord line and the general airflow direction (relative wind). It is not related to the longitudinal axis or the horizon.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_2) - A) its shape - B) the position of its center of gravity - C) its weight - D) its density Correct: A)
Explanation: At equal frontal area and equal speed, aerodynamic drag depends on the body's shape (drag coefficient Cd). Shape determines aerodynamic efficiency.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_3) - A) pressure equalization from the upper surface toward the lower surface - B) pressure equalization from the lower surface toward the upper surface - C) the angle formed at the wing-fuselage junction - D) speed Correct: B)
Explanation: Induced drag comes from pressure equalization from lower surface (high pressure) to upper surface (low pressure) at the wing tip. This creates tip vortices and thus induced drag.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_4) - A) 1013.25 hPa - B) 29.92 hPa - C) 1012.35 hPa - D) depends on latitude Correct: A)
Explanation: ICAO standard pressure at sea level is 1013.25 hPa. (29.92 hPa would be absurd — that is 29.92 inches of mercury, the same pressure in inHg).
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_5)
] - A) G + J - B) A - C) H - D) B Correct: B)
Explanation: Mean camber is line B in the figure, equidistant between lower and upper surfaces.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_6) - A) to prevent an inward slip in the turn - B) to prevent an outward slip in the turn - C) to reduce speed and therefore centrifugal force - D) to increase lift and thereby balance centrifugal force Correct: D)
Explanation: In a coordinated turn without altitude loss, back pressure increases lift to balance centrifugal force (load factor > 1).
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_7) - A) at the red radial line on the airspeed indicator (ASI) - B) following a reduction in engine power - C) only at an excessive nose-up angle relative to the horizon - D) at a critical angle of attack Correct: D)
Explanation: Stall occurs at a critical angle of attack, regardless of airspeed or nose attitude.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_8) - A) simultaneously - B) at a determined angle of attack - C) only for a given nose position relative to the horizon - D) only depending on aircraft altitude Correct: B)
Explanation: Airflow separation occurs at a determined angle of attack (critical stall angle), specific to the airfoil. It is not related to nose attitude relative to the horizon.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_9) - A) 100 m/sec2 - B) 1013.5 hPa - C) 15° C/100 m - D) 9.81 m/sec2 Correct: D)
Explanation: Standard gravitational acceleration is 9.81 m/s².
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_10) - A) without any correction - B) corrected for position and instrument errors - C) adjusted for atmospheric density - D) corrected for both B) and C) Correct: D)
Explanation: IAS reading is determined by the difference between static and total pressure (dynamic pressure = q = ½ρv²).
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_11) - A) modifying the angle of incidence - B) moving the load - C) modifying the angle of attack - D) modifying the position of the aerodynamic center Correct: B)
Explanation: Center of gravity shifts occur by moving the load (ballast, passenger, baggage). Modifying angle of attack or incidence does not move the CG.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_12)
] - A) Fowler - B) Slotted Flap - C) Split Flap - D) Plain Flap Correct: A)
Explanation: The flap shown (Fowler) moves rearward and downward, increasing both wing area and camber. It is the most effective flap type.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_13) - A) the center of symmetry - B) the stagnation point - C) the center of gravity - D) the aerodynamic center Correct: D)
Explanation: The aerodynamic center is the point of application of the resultant aerodynamic forces on a profile. It is generally located at the quarter-chord point.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_14) - A) 2,000 meters - B) 20,000 meters - C) 6,600 meters - D) 2,000 ft Correct: C)
Explanation: Air density is approximately half its sea-level value at approximately 6,600 m (approximately 18,000 ft).
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_15) - A) total pressure in an aneroid capsule - B) static pressure around an aneroid capsule - C) the difference between static pressure and total pressure - D) the weathervane effect where pressure decreases Correct: C)
Explanation: IAS is determined by the difference between static and total pressure (dynamic pressure).
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_16) - A) the action of the horizontal stabilizer - B) rotations around the lateral axis - C) wing sweep and dihedral - D) the use of leading edge slats Correct: C)
Explanation: Roll stability is influenced by wing sweep and dihedral. Dihedral creates a roll restoring moment, as does sweep.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_17) - A) is unlimited - B) is limited at the upper end by the maneuvering speed - C) is limited at the lower end by the red radial line on the airspeed indicator (ASI) - D) is indicated in the Flight Manual (AFM) Correct: D)
Explanation: The speed range for slotted flap use is indicated in the Flight Manual (AFM).
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_18) - A) aspect ratio - B) geometric twist (washout) - C) interference compensation - D) aerodynamic twist Correct: B)
Explanation: Geometric wing twist consists of a variation of the incidence angle of the same profile, from root (larger angle) to tip (smaller angle). This causes the root to stall first.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_19) - A) decreasing linearly as altitude increases - B) decreasing exponentially as altitude increases - C) decreasing in the troposphere and then increasing in the stratosphere - D) remaining constant Correct: B)
Explanation: Barometric pressure decreases exponentially with altitude (not linearly). This follows from the barometric law.
[FR](../SPL%20Exam%20Questions%20FR/80%20-%20Principes%20du%20vol.md#^bazl_802_20) - A) the mass of air flows through a larger cross-section at a lower speed - B) the mass of air flows through a smaller cross-section at a lower speed - C) the mass of air flows through a larger cross-section at a higher speed - D) the speed of the air mass does not vary Correct: A)
Explanation: Simplified continuity equation: for incompressible flow, the same air mass passes through any cross-section. If the section is larger, velocity is lower (A₁v₁ = A₂v₂).
=== NEW QUESTIONS (from QuizVDS, not yet in set) ===
Source: EASA ECQB-SPL (new questions not in existing set) | 52 questions
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: 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: 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: 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: 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: 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: 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: 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: 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: 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.
