Correct: B)
Explanation: Mass balancing places counterweights ahead of the control surface hinge line, moving the center of gravity of the surface forward. This prevents flutter — a destructive, self-exciting oscillation that occurs when the inertia of an unbalanced control surface couples with aerodynamic forces at high speed. Option A (aerodynamic balance) reduces control forces but does not prevent flutter. Option C (spring tabs) assist control deflection at high speed. Option D (trim tabs) set zero-force equilibrium points but do not address flutter.
Correct: C)
Explanation: Best glide speed occurs at the minimum total drag point, where induced drag equals parasite drag. Below this speed, induced drag dominates (high angle of attack, strong vortices); above it, parasite drag dominates (friction and form drag increase with speed squared). At the crossover point, the sum is minimized, giving the best lift-to-drag ratio. Option A describes slow flight. Option B describes high-speed flight. Option D ignores induced drag, which is always present when lift is generated.
Correct: B)
Explanation: Adding water ballast increases the aircraft weight, which shifts the performance polar toward higher speeds — each point on the curve moves to a faster speed while maintaining approximately the same sink rate. The best L/D ratio remains unchanged, but it occurs at a higher airspeed. This is beneficial in strong conditions where faster inter-thermal speeds are needed. Option A overstates the improvement — the L/D does not increase. Option C ignores the weight-speed relationship. Option D incorrectly suggests degraded performance at all speeds.
Correct: C)
Explanation: A stall is the aerodynamic condition where the wing exceeds its critical angle of attack and loses lift. A spin develops when one wing stalls more deeply than the other (asymmetric stall), creating a rolling and yawing moment that drives the aircraft into autorotation around the vertical axis while descending. Option A is incorrect — they are related but distinct phenomena. Option B reverses the speed relationship — stalls occur at low speed. Option D is wrong because spins can and do occur in unpowered gliders.
Correct: B)
Explanation: In a steady straight glide, three forces act on the glider: lift (perpendicular to the flight path), drag (opposing the flight path), and weight (acting vertically downward). There is no thrust in a glider — the component of weight along the flight path replaces thrust by providing the energy to overcome drag. Option A includes thrust, which does not exist in a glider. Option C omits drag, which is always present. Option D omits weight, the fundamental driving force of gliding flight.
Correct: B)
Explanation: In ground effect (within approximately one wingspan of the surface), the ground restricts the development of wingtip vortices, reducing induced downwash. This effectively increases the wing's angle of attack and lift while reducing induced drag. The glider floats longer during the landing flare because of this beneficial aerodynamic cushion. Option A incorrectly states drag increases. Option C wrongly identifies parasite drag as affected. Option D ignores a well-documented and pilot-noticeable phenomenon.
Correct: B)
Explanation: VNE is the absolute maximum airspeed the aircraft may reach under any circumstances. Exceeding VNE risks structural failure due to excessive aerodynamic loads, control surface flutter, or aeroelastic divergence. It is marked with a red line on the airspeed indicator. Option A describes VFE (maximum flap extension speed). Option C describes a speed calculated from the polar, not VNE. Option D has no relation to VNE — maximum climb occurs at much lower speeds.
Correct: B)
Explanation: Wing sweep contributes to lateral (roll) stability in a manner similar to dihedral. When the aircraft sideslips, the forward (leading) wing effectively presents a higher aspect ratio to the airflow and generates more lift than the trailing wing, producing a restoring roll moment. This "effective dihedral" effect from sweep is why some swept-wing designs use less geometric dihedral. Option A states the opposite. Option C ignores a well-established aerodynamic relationship. Option D confuses lateral with directional stability.
Correct: C)
Explanation: Aspect ratio (AR) is defined as the wingspan squared divided by the wing area (AR = b^2/S), or equivalently, the wingspan divided by the mean aerodynamic chord (AR = b/c_mean). High aspect ratio wings (long and narrow, like on gliders) have lower induced drag. Option A defines the thickness-to-chord ratio. Option B is not a standard aerodynamic parameter. Option D inverts the correct ratio — that would give the reciprocal of aspect ratio.
Correct: B)
Explanation: In a coordinated level turn, the load factor n = 1/cos(bank). At 45° bank: n = 1/cos(45°) = 1/0.707 = 1.414. The stall speed increases by the square root of the load factor: Vsturn = Vs1g x sqrt(1.414) = Vs_1g x 1.189, an increase of approximately 19%. Option A incorrectly states a decrease. Option C ignores the load factor effect on stall speed. Option D would require a 4g maneuver (about 75° bank).
Correct: B)
Explanation: The vertical stabilizer (fin) acts as a weathervane, providing directional (yaw) stability. When the aircraft yaws, the fin generates a side force that creates a restoring yawing moment to return the aircraft to its original heading. Option A describes the function of the horizontal stabilizer. Option C describes the function of wing dihedral. Option D has no connection to the vertical stabilizer's purpose.
Correct: B)
Explanation: Negative (reflex) flap deflection reduces wing camber, which decreases the lift coefficient at any given angle of attack. This allows the glider to fly at higher speeds with reduced profile drag at low lift coefficients — ideal for inter-thermal cruise in strong conditions. Option A describes positive flap deployment. Option C is incorrect — at high speeds and low CL, reflex flaps reduce drag compared to neutral. Option D is wrong — reducing camber increases the stall speed because CL_max decreases.
Correct: B)
Explanation: Higher temperatures cause air to expand, reducing its density. At the same indicated airspeed, lower air density means less lift is generated and the true airspeed is higher. This effectively increases the takeoff distance and reduces climb performance. Option A reverses the temperature-density relationship. Option C ignores a fundamental gas law (PV = nRT). Option D reverses both relationships — lower temperature increases density, which would improve performance.
Correct: B)
Explanation: Maneuvering speed (VA) is the maximum speed at which the pilot may apply full, abrupt control deflection without exceeding the aircraft's design load limits. Above VA, a sudden full deflection could generate aerodynamic loads exceeding the structural design limits. Below VA, the aircraft will stall before the load limit is reached. Option A describes approach or reference speed. Option C describes stall speed plus margin. Option D describes best L/D speed.
Correct: C)
Explanation: In a steady glide (descending flight path), the lift vector is perpendicular to the flight path, which is inclined below the horizontal. Therefore, the vertical component of lift that supports the aircraft's weight is slightly less than the total lift, and the total lift itself is slightly less than the weight. The difference is compensated by the component of drag along the vertical. Option A would be true only in perfectly level flight. Option B is incorrect in a glide. Option D ignores the fundamental equilibrium condition.
Correct: C)
Explanation: As airspeed decreases below best glide speed, the wing must operate at a higher angle of attack to maintain lift equal to weight. Higher angle of attack means stronger wingtip vortices, more downwash, and therefore more induced drag. Induced drag is inversely proportional to the square of airspeed. Options A, B, and D all describe components of parasite drag, which decrease with reduced speed — they increase with speed, not decrease.
Correct: B)
Explanation: Spoilers (airbrakes) deploy from the wing's upper surface to disrupt airflow, dramatically increasing drag and reducing lift. This allows the pilot to steepen the approach angle for precise landing control. Without spoilers, gliders have very flat glide angles that make it difficult to land on short fields or clear obstacles. Option A is the opposite of their function. Option C describes ailerons, not spoilers. Option D is incorrect — spoilers increase, not decrease, the effective stall speed by reducing lift.
Correct: A)
Explanation: The Reynolds number (Re = rho x V x L / mu) relates the inertial forces to viscous forces in the flow. Higher Reynolds numbers (due to higher speed, larger chord, or denser air) promote earlier transition from laminar to turbulent boundary layer flow. This is why glider wings with laminar profiles are designed for specific Reynolds number ranges. Option B reverses the relationship — lower Re favors laminar flow. Option C ignores the fundamental role of Re in fluid dynamics. Option D overstates the effect — separation can still occur.
Correct: B)
Explanation: In still air, the glide angle depends solely on the lift-to-drag ratio (L/D): tan(glide angle) = 1/(L/D). A higher L/D gives a flatter (smaller) glide angle and greater range per unit of altitude. Weight (option A) affects the speed at which best L/D is achieved but not the angle itself. Wing area (option C) is a component of the aerodynamic equations but does not independently determine glide angle. Altitude (option D) has no effect on glide angle in still air.
Correct: B)
Explanation: When airbrakes are deployed, they disrupt the airflow over part of the wing, reducing the overall maximum lift coefficient (CLmax). Since stall speed is inversely proportional to the square root of CLmax, a lower CL_max results in a slightly higher stall speed. Option A states the opposite. Option C ignores the lift-reducing effect of airbrakes. Option D greatly exaggerates the effect — the increase is typically only a few percent.
Correct: C)
Explanation: A forward CG position creates a stronger nose-down moment that requires more elevator deflection to maintain a given pitch attitude. Greater elevator deflection means larger aerodynamic forces on the tail, which translates to higher stick forces felt by the pilot. While this makes the aircraft more stable, it requires more effort to control. Option A states the opposite. Option B ignores the CG-control force relationship. Option D incorrectly limits the effect to the rudder.
Correct: B)
Explanation: A spiral dive develops when an aircraft enters a steep bank and the pilot fails to maintain back pressure or applies insufficient back elevator. The nose drops, speed increases, and the bank steepens in a self-reinforcing cycle. Both wings remain flying (unstalled), distinguishing it from a spin. Option A describes a symmetric stall, not a spiral dive. Option C describes an approach to stall, not spiral dive. Option D does not typically lead to a spiral dive directly.
Correct: B)
Explanation: A cambered aerofoil generates lift even at 0° angle of attack due to its curved shape. To produce zero lift, the angle of attack must be reduced to a small negative value (typically -2° to -4° for common aerofoils) where the pressure distribution above and below the wing exactly balances. Option A would be correct only for a symmetric aerofoil. Option C and D are far beyond the operating range.
Correct: B)
Explanation: Laminar flow aerofoils are designed to maintain laminar (smooth, low-friction) boundary layer flow over a larger portion of the wing chord at the design speed. This significantly reduces skin friction and profile drag compared to turbulent profiles, improving the glide ratio. Option A is not the primary advantage — laminar profiles may actually have lower CL_max. Option C is incorrect — laminar aerofoils can have sharper stall characteristics. Option D relates to structural design, not aerofoil shape.
Correct: A)
Explanation: The curved upper surface of the wing forces air to accelerate as it flows over the top. According to Bernoulli's principle, faster-moving air has lower static pressure. The lower surface has slower airflow and higher pressure. This pressure difference between the upper (low pressure) and lower (high pressure) surfaces generates the net upward force called lift. Option B reverses the velocity-pressure relationship. Option C introduces an irrelevant thermal effect. Option D describes atmospheric pressure, not the dynamic lift mechanism.
Correct: B)
Explanation: A phugoid is a long-period oscillation where the aircraft exchanges kinetic and potential energy — it alternately climbs (losing speed) and descends (gaining speed) while maintaining a nearly constant angle of attack. The period is typically 30-60 seconds and is usually lightly damped. Option A describes Dutch roll (a combined yaw-roll oscillation). Option C describes yaw oscillation. Option D describes a short-period pitch oscillation, which has rapid frequency and constant altitude.
Correct: B)
Explanation: Increasing wing loading (more weight per unit wing area) shifts the entire speed polar to higher speeds. The best L/D ratio remains theoretically unchanged because the aerodynamic efficiency of the wing shape does not change, but the speed at which best L/D occurs increases proportionally to the square root of the weight increase. Option A overstates the benefit. Option C is incorrect — minimum sink rate worsens with higher loading. Option D states the opposite — higher loading increases stall speed.
Correct: B)
Explanation: Winglets at the wingtips act as vertical fences that reduce the intensity of the wingtip vortices by preventing the high-pressure air below the wing from flowing around the tip to the low-pressure upper surface. Weaker vortices mean less induced downwash and therefore less induced drag, improving the glide ratio. Option A is an indirect benefit but not the primary purpose. Option C is not significantly affected by winglets. Option D is incorrect — winglets are aerodynamic devices, not structural components.
Correct: B)
Explanation: The horizontal tailplane provides longitudinal (pitch) stability by generating a restoring moment when the aircraft is disturbed from its trimmed attitude. If the nose pitches up, the tail sees a higher angle of attack and generates more downforce, pushing the nose back down — and vice versa. Option A is incorrect — the wing generates nearly all the lift; the tail typically generates a small downforce. Option C describes the vertical tail's function. Option D ignores the tailplane's critical stability role.
Correct: C)
Explanation: Extending airbrakes dramatically increases drag and slightly reduces lift, causing the lift-to-drag ratio to decrease substantially. A lower L/D means a steeper descent angle — exactly the intended purpose, as it allows the pilot to control the approach path and land precisely on target. Option A states the opposite. Option B ignores the large drag increase. Option D makes no aerodynamic sense — more drag cannot improve the glide ratio.
