Correct: B)
Explanation: In steady (unaccelerated) gliding flight, only two forces act on the aircraft: weight (gravity) and the total aerodynamic resultant (the vector sum of lift and drag). For equilibrium, these two forces must be equal in magnitude and opposite in direction, meaning the resultant aerodynamic force exactly counterbalances gravity. Option A is incorrect because the aerodynamic resultant is tilted backward from the flight path, not aligned with the airflow. Option C wrongly states lift alone compensates drag — lift and drag are perpendicular components that together form the resultant. Option D confuses the resultant with the lift vector alone.
Correct: B)
Explanation: Extending flaps increases wing camber, which raises the maximum lift coefficient (CLmax). From the stall speed formula Vs = sqrt(2W / (rho x S x CLmax)), increasing CL_max directly reduces the minimum flying speed. This is why flaps are deployed during approach and landing — they allow safe flight at lower speeds. Option A confuses a CG effect with a flap effect. Option C is wrong because maximum permissible speed actually decreases with flaps extended due to structural limitations. Option D states the opposite of the true effect.
Correct: A)
Explanation: When one wing stalls and the nose drops, the immediate action is to push the elevator forward to reduce the angle of attack below the critical value, allowing airflow to reattach to the wings and restore normal flight. This is the fundamental stall recovery technique. Option B (rudder only) does not reduce the angle of attack. Option C (pulling back) deepens the stall and using ailerons near the stall can trigger a spin. Option D (full opposite rudder) is a spin recovery technique, but the priority here is preventing the spin from developing by unstalling the wing.
Correct: B)
Explanation: Extending the landing gear adds parasite drag, which shifts the entire drag polar to the right on a cL versus cD diagram. At every angle of attack, the same lift is produced but with additional drag from the gear. This worsens the lift-to-drag ratio at all operating points. Option A states the opposite effect. Option C incorrectly claims the gear affects CL_max, which depends on the wing, not the gear. Option D incorrectly states lift is reduced — the gear adds drag but does not change the wing's lift characteristics.
Correct: A)
Explanation: In a banked turn, the lift vector tilts with the wing, so its vertical component is reduced (it no longer fully supports the aircraft's weight without additional lift input) while the horizontal component of the tilted lift vector provides the centripetal force needed for the curved flight path. Option B is misleading — the pilot must increase total lift in a turn, not decrease it. Option C is physically impossible. Option D is wrong because weight does not change; the apparent load factor increases but actual gravitational weight remains constant.
Correct: B)
Explanation: In steady gliding flight, the tangent of the glide angle (gamma) equals the ratio of drag to lift: tan(gamma) = D/L = 1/(L/D). A higher L/D ratio means a smaller glide angle and a flatter glide path, allowing greater distance per altitude lost. Option A incorrectly equates angle to ratio without a trigonometric function. Option C wrongly claims independence. Option D uses the wrong trigonometric function. Understanding this relationship is essential for cross-country glider performance calculations.
Correct: C)
Explanation: Induced drag is inversely proportional to aspect ratio: Di = L^2 / (q x pi x e x b^2), where b is wingspan. A higher aspect ratio (longer, narrower wing) produces weaker wingtip vortices and less downwash, reducing induced drag. This is why gliders have very high aspect ratio wings — to minimize induced drag and maximize glide performance. Options A and D incorrectly state induced drag increases. Option B incorrectly claims no relationship exists.
Correct: B)
Explanation: Maximum lift occurs at the critical (stall) angle of attack, which for most conventional aerofoils is approximately 15-18 degrees. Beyond this angle, airflow separates from the upper surface and lift decreases dramatically (stall). Option A (0°) produces relatively little lift for a cambered aerofoil. Option C (45°) and option D (90°) are well beyond the stall angle, where the wing produces minimal lift and massive drag.
Correct: B)
Explanation: Wing washout reduces the angle of incidence from root to tip, ensuring the root section reaches its critical angle of attack (and stalls) before the tip. This preserves aileron control during the initial phase of a stall, giving the pilot roll authority for recovery. Option A has no direct relationship to maximum speed. Option C does not reduce parasite drag. Option D is the opposite of the intent — washout reduces, not increases, the tip's angle of incidence to delay tip stall.
Correct: B)
Explanation: Parasite drag consists of skin friction (air molecules dragging against surfaces) and form drag (pressure drag caused by the aircraft's shape disrupting airflow). It exists regardless of whether lift is being produced. Option A describes induced drag, which is caused by lift generation. Option C (wingtip vortices) is the mechanism of induced drag, not parasite drag. Option D (weight) affects the amount of lift required but does not directly cause parasite drag.
Correct: C)
Explanation: Parasite drag is proportional to dynamic pressure (q = 1/2 x rho x V^2), so it increases with the square of airspeed. Doubling the speed quadruples the parasite drag. This is why gliders have very clean, streamlined designs — even small improvements in surface finish dramatically reduce drag at cruise speeds. Option A states the opposite. Option B ignores the fundamental aerodynamic relationship. Option D underestimates the rate of increase — the square relationship, not linear, is correct.
Correct: B)
Explanation: Parasite drag (consisting of friction drag and form drag) is present whenever the aircraft moves through the air, regardless of whether any lift is being produced. It depends on speed, shape, and surface roughness — not on lift. Options A, C, and D all describe drag components that are directly related to lift production: induced drag is caused by wingtip vortices generated by the pressure differential that creates lift.
Correct: C)
Explanation: Total drag is the sum of induced drag (which decreases with speed) and parasite drag (which increases with the square of speed). The minimum total drag occurs at the speed where these two components are equal — this is also the speed for best lift-to-drag ratio and best glide angle. Option A (VNE) is far above minimum drag speed. Option B (stall speed) has maximum induced drag. Option D (max CL speed) is at or near stall, where induced drag dominates.
Correct: C)
Explanation: From the stall speed formula Vs = sqrt(2W / (rho x S x CLmax)), increasing weight (W) directly increases the stall speed. The wing must produce more lift to support the heavier aircraft, requiring either higher speed or higher angle of attack — but since CLmax is fixed by the aerofoil shape, the only option is higher speed. Option A states the opposite. Option B ignores the weight-speed relationship. Option D incorrectly limits the effect to turns only.
Correct: C)
Explanation: The load factor in a level coordinated turn is n = 1/cos(bank angle). At 60° bank: n = 1/cos(60°) = 1/0.5 = 2.0. This means the wing must produce twice the lift compared to straight-and-level flight, and the stall speed increases by the square root of 2 (about 41%). Option A (1.0) is the load factor in straight flight. Option B (1.41) corresponds to a 45° bank turn. Option D (3.0) would require a bank angle of approximately 70°.
Correct: A)
Explanation: On a conventional cambered aerofoil, as the angle of attack increases from zero toward the stall, the center of pressure moves forward along the chord. This is because the lift distribution shifts toward the leading edge as the angle of attack increases. The aerodynamic center (option B) is where the pitching moment coefficient remains constant — it is not the same as the center of pressure. Option C is the opposite of what occurs. Option D does not describe normal aerodynamic behavior.
Correct: B)
Explanation: A trim tab on the elevator allows the pilot to set a desired pitch attitude by adjusting the aerodynamic balance of the elevator so that no continuous stick force is needed to maintain the trim speed. This reduces pilot fatigue during extended flights. Option A is unrelated to trim function. Option C describes flap effects, not trim effects. Option D is incorrect — trim tabs adjust control forces, not the wing's stalling characteristics.
Correct: B)
Explanation: When the boundary layer transitions from laminar to turbulent flow, the random mixing of air particles increases skin friction drag and causes the boundary layer to thicken considerably. However, the turbulent boundary layer is more energetic near the surface and therefore more resistant to adverse pressure gradients, delaying flow separation. Option A states the opposite — turbulent flow has more friction. Option C is wrong — turbulent layers are thicker. Option D is incorrect — velocity at the surface itself remains zero (no-slip condition).
Correct: A)
Explanation: Bernoulli's principle states that in a steady, incompressible flow, an increase in fluid velocity corresponds to a decrease in pressure. Applied to a wing, the curved upper surface accelerates the airflow, creating lower pressure above the wing compared to below it. This pressure difference generates the net upward force called lift. Option B describes a simplistic and incomplete explanation. Option C reverses the pressure distribution. Option D describes Newton's third law reaction but states the deflection direction wrong — air is deflected downward, not upward.
Correct: B)
Explanation: Increasing wing camber (through positive flap deflection) shifts the entire lift curve upward, meaning the wing produces a higher lift coefficient at every angle of attack. This also lowers the zero-lift angle of attack. The maximum CL_max increases, reducing stall speed. Option A (rightward shift) would imply more drag without more lift, which is not the primary effect. Option C (flatter curve) would mean less lift per degree of angle change, which is incorrect. Option D ignores the well-established camber-lift relationship.
Correct: B)
Explanation: When ailerons are deflected, the down-going aileron on the rising wing increases both lift and induced drag on that wing. The extra induced drag on the rising wing pulls the nose toward the descending wing — opposite to the intended turn direction. This is adverse yaw. Option A is partially correct (the up-going aileron does reduce drag) but does not describe the cause of adverse yaw. Option C is incorrect — the rudder does not automatically deflect. Option D wrongly states equal drag increase on both wings.
Correct: B)
Explanation: Wing dihedral (upward V-angle from root to tip) provides lateral (roll) stability. When a disturbance causes one wing to drop, the sideslip that develops creates a higher angle of attack on the lower wing (due to the dihedral geometry), generating more lift and producing a restoring roll moment back toward wings-level flight. Option A has no connection to dihedral. Option C describes the effect of aspect ratio, not dihedral. Option D relates to the vertical tail, not wing dihedral.
Correct: D)
Explanation: Lift is always defined as perpendicular to the relative airflow and the wing surface, acting from the lower surface toward the upper surface of the wing — relative to the wing, not the ground. In inverted flight, this means lift acts toward the ground. Drag always acts opposite to the direction of flight regardless of orientation. The wing still produces aerodynamic forces according to the same principles. Options A and B partially describe the situation but use confusing reference frames. Option C incorrectly states drag reverses.
Correct: B)
Explanation: Moving the CG aft reduces the moment arm between the CG and the horizontal tailplane, decreasing the tail's restoring pitch moment. If the CG moves behind the neutral point, the aircraft becomes longitudinally unstable — any pitch disturbance will diverge rather than self-correct. This is extremely dangerous. Option A states the opposite. Option C ignores the fundamental CG-stability relationship. Option D confuses longitudinal stability (pitch) with lateral stability (roll), which is primarily affected by wing dihedral.
Correct: C)
Explanation: The aerodynamic centre is the special point on the chord (typically at about 25% chord from the leading edge) where the pitching moment coefficient remains approximately constant as the angle of attack changes. This makes it a useful reference point for stability analysis. The centre of pressure (option A) moves with angle of attack. The trailing edge (option B) and leading edge (option D) are geometric points with no particular moment-coefficient significance.
Correct: B)
Explanation: Stall speed increases with the square root of the load factor: Vsmaneuver = Vs1g x sqrt(n). At 2g: Vs2g = Vs1g x sqrt(2) = Vs1g x 1.414, an increase of approximately 41%. The higher load factor requires the wing to produce more lift, which at the same CLmax means a higher speed. Option A ignores the load factor effect. Option C overstates the increase — doubling would occur at 4g. Option D states the opposite.
Correct: B)
Explanation: Rain, ice, or any surface contamination disrupts the smooth laminar flow over the wing, causing premature transition to turbulent flow. This increases friction drag, raises the profile drag, and reduces the maximum achievable lift coefficient (CL_max), which increases stall speed and degrades glide performance. Option A states the opposite — contamination destroys laminar flow. Option C dangerously underestimates the effect. Option D is wrong because water droplets and ice roughen the surface.
Correct: C)
Explanation: The airspeed indicator measures dynamic pressure (q = 1/2 x rho x V^2), which is calibrated for sea-level air density. At altitude, where density (rho) is lower, the aircraft must fly at a higher true airspeed to produce the same dynamic pressure (same IAS reading). Therefore TAS exceeds IAS at altitude. Option A reverses the relationship. Option B ignores the density correction. Option D also reverses the relationship. The difference grows with altitude — at 6000 m, TAS can be roughly 40% higher than IAS.
Correct: B)
Explanation: Best glide ratio (also called maximum L/D ratio) represents the maximum horizontal distance the glider can cover for each unit of altitude lost in still air. It is achieved at the speed where total drag is minimized (where induced drag equals parasite drag). Option A describes thermal climb performance, not glide ratio. Option C describes minimum sink rate, which occurs at a lower speed than best glide and gives maximum endurance, not maximum range. Option D describes VNE, which is unrelated to glide ratio.
Correct: B)
Explanation: Deploying airbrakes adds significant parasite drag, shifting the polar curve to the right (higher drag at every lift coefficient). Additionally, airbrakes disrupt the airflow over the upper wing surface, slightly reducing the maximum achievable lift coefficient. This combination steepens the glide path, which is their intended purpose. Option A states the opposite. Option C is wrong because airbrakes have a major effect on the polar. Option D incorrectly claims more lift — airbrakes actually reduce lift while increasing drag.
