Correct: C)
Explanation: In steady (stationary) gliding flight, there is no thrust, so only two forces act: gravity (weight) and the total aerodynamic force (the vector sum of lift and drag). For the glider to be in equilibrium, these two must be equal and opposite — meaning the resultant air force exactly compensates gravity. Lift and drag are merely components of this single aerodynamic resultant; neither lift alone nor drag alone balances weight.
Correct: C)
Explanation: Extending flaps increases wing camber, which raises the maximum lift coefficient (CLmax). From the stall speed formula Vs = sqrt(2W / (rho * S * CLmax)), a higher CL_max directly lowers the minimum flying speed Vs. This allows the aircraft to fly slower without stalling, which is why flaps are used during approach and landing. The maximum permissible speed typically decreases with flaps extended (not increases), because flap structures are not designed for high dynamic pressure.
Correct: D)
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 (A) would increase AoA and deepen the stall; pushing alone (C) without rudder does not stop the yaw.
Correct: D)
Explanation: The lateral axis is the pitch axis (nose up/down). The horizontal stabilizer provides longitudinal (pitch) stability: it generates a restoring moment whenever the nose pitches up or down from trim, because its lift force changes with AoA at the tail. Ailerons control roll (longitudinal axis), the vertical rudder controls yaw (vertical axis), and flaps are high-lift devices, not stability surfaces.
Correct: A)
Explanation: Exceeding VNE risks aeroelastic flutter — a self-reinforcing oscillation of the control surfaces or wings that can destroy the structure within seconds. Flutter onset speed is close to VNE. Structural failure of spars, attachments, or control surfaces may follow. The other options describe effects that do not occur at excessive speed: glide angle does not improve, drag does not decrease, and the ASI is designed to function at all normal and abnormal speeds.
Correct: B)
Explanation: A rearward CG reduces the restoring moment arm between the CG and the horizontal stabiliser, diminishing longitudinal (pitch) stability. In extreme cases the aircraft can become unstable in pitch — the pilot may be unable to prevent a nose-up divergence, especially during winch launch or in turbulence. The forward CG limit ensures adequate pitch stability; the aft limit ensures adequate controllability. A rearward CG does not increase stall speed or roll effectiveness, and it makes the aircraft less, not more, stable.
Correct: D)
Explanation: The vertical tail fin (fin + rudder) provides yaw stability and yaw control. The fixed fin acts as a weathervane that generates a restoring yaw moment if the aircraft sideslips. The movable rudder allows the pilot to command deliberate yaw inputs for coordination, crosswind correction, or spin recovery. The horizontal stabiliser handles pitch; wing dihedral handles roll stability; the vertical tail does not generate lift in the conventional sense.
Correct: C)
Explanation: In a level coordinated turn, the load factor n = 1/cos(bank angle). At 60° bank, n = 1/cos(60°) = 1/0.5 = 2.0. This means the effective weight the wings must support doubles. Stall speed increases by a factor of √n = √2 ≈ 1.41, i.e. a 41% increase. This is why steep turns at low altitude are dangerous for gliders — the stall margin shrinks dramatically.
Correct: C)
Explanation: Induced drag is inversely proportional to aspect ratio (AR): D_induced ∝ CL² / (π × AR × e). A longer, narrower wing (high AR) produces the same lift with weaker wingtip vortices and therefore less induced drag. This is why gliders have very high aspect ratios — it is the primary design feature that maximises the lift-to-drag ratio and glide performance.
Correct: A)
Explanation: A downward-deflected trim tab produces an upward aerodynamic force on the trailing edge of the elevator, pushing the elevator's trailing edge up and its leading edge down — this effectively deflects the elevator downward, creating a nose-up pitching moment. Trim tabs work by aerodynamic force to relieve the pilot of sustained stick forces; their deflection is opposite to the desired elevator deflection.
Correct: B)
Explanation: The glider's speed polar plots the vertical sink rate (Vz, typically in m/s) against the horizontal airspeed (Vh). It is the fundamental performance diagram for a glider: it reveals the minimum sink speed (the lowest point on the curve), the best glide speed (given by the tangent from the origin), and inter-thermal cruise speeds (McCready tangents). All cross-country speed-to-fly decisions are based on this curve.
Correct: C)
Explanation: In level flight, lift must equal weight (L = W). Since L = CL × 0.5 × ρ × V² × S, when speed V increases the lift coefficient CL must decrease to keep lift constant. A lower CL corresponds to a lower angle of attack. Therefore, faster flight requires a smaller angle of attack, and slower flight (toward the stall) requires a progressively larger angle of attack.
Correct: C)
Explanation: Wing fences are thin vertical plates on the upper surface of a swept or tapered wing that prevent the boundary layer from flowing spanwise (outward toward the tips). Without fences, the boundary layer migrates outward due to the pressure gradient, thickening at the tips and promoting tip stall. Fences confine the boundary layer to its local region, improving tip stall characteristics and aileron effectiveness at high angles of attack.
Correct: C)
Explanation: The best glide ratio (maximum L/D) occurs at the speed where total drag is minimum. At this point, induced drag exactly equals parasite drag — any faster increases parasite drag more than induced drag decreases, and any slower increases induced drag more than parasite drag decreases. For a glider, this speed gives the flattest glide angle and the greatest distance per unit of altitude lost in still air.
Correct: C)
Explanation: Wing dihedral — the upward V-angle of the wings — is the primary design feature providing lateral (roll) stability. When a gust or disturbance causes one wing to drop, the dihedral geometry increases the angle of attack on the lower wing, generating more lift and creating a restoring roll moment toward wings-level. The vertical fin provides directional stability; the horizontal stabiliser provides pitch stability; and elevator trim sets a pitch reference, not a roll reference.
Correct: C)
Explanation: IAS is based on dynamic pressure (q = 0.5 × ρ × V²). At higher altitude, air density ρ is lower, so a given IAS corresponds to a higher TAS. The relationship is TAS = IAS × √(ρ₀/ρ), where ρ₀ is sea-level density. For glider pilots, this means that at altitude, the ground speed for the same indicated approach speed is higher, and the landing roll will be longer.
Correct: B)
Explanation: Load factor (n) is defined as the ratio of the lift generated by the wings to the aircraft's weight: n = L/W. In straight and level flight, n = 1. In a turn, n > 1 because extra lift is needed for the centripetal force. In a vertical pullup, n can exceed the design limits. The structural design of the glider is rated for specific load factor limits (typically +5.3g / -2.65g for utility category).
Correct: C)
Explanation: The best L/D ratio is determined by the aerodynamic shape of the aircraft and is independent of weight. Increasing weight shifts the speed polar downward and to the right — the best glide speed increases (must fly faster) but the maximum L/D ratio stays the same. This is why adding water ballast in gliders improves inter-thermal cruise speed without changing the glide angle — only the speed at which that angle is achieved changes.
Correct: C)
Explanation: The minimum sink rate speed is the speed at the lowest point of the speed polar. Any speed change — faster or slower — from this point increases the sink rate. Accelerating beyond minimum sink speed increases parasite drag faster than induced drag decreases, resulting in a higher total drag and therefore a greater rate of descent. This is the trade-off in cross-country flying: flying faster covers more ground but at the cost of increased sink rate.
Correct: C)
Explanation: Airbrakes (spoilers) disrupt the smooth airflow over the wing surface, reducing the pressure differential and therefore reducing lift. Simultaneously, the raised spoiler panels create a large increase in drag. This combined effect steepens the glide path dramatically, which is precisely their purpose — to allow the pilot to control the approach angle and land precisely. Without airbrakes, gliders would float long distances due to their excellent L/D ratio.
Correct: C)
Explanation: Induced drag is proportional to CL², and CL is highest in slow flight at high angle of attack (where the wing must generate maximum lift per unit of dynamic pressure). In a dive or at high speed, CL is low and induced drag is minimal — parasite drag dominates instead. At best glide speed, induced drag equals parasite drag but is not at its maximum. The slow-flight regime is where induced drag dominates total drag.
Correct: A)
Explanation: The elevator trim tab allows the pilot to reduce or eliminate the stick force needed to hold a given pitch attitude in steady flight. By deflecting the trim tab, an aerodynamic force is applied to the elevator that counters the natural hinge moment, allowing hands-off or reduced-force flight at the trimmed speed. This reduces pilot fatigue on long flights and allows the pilot to concentrate on navigation and thermal exploitation.
Correct: C)
Explanation: In a turn, the load factor n = 1/cos(bank angle) exceeds 1, meaning the wings must generate more lift than in straight flight. The stall speed increases by the factor √n. At 45° bank, stall speed increases by 19%; at 60° bank by 41%. This is a critical safety consideration when thermalling near the ground — the steeper the bank, the closer the pilot is to the elevated stall speed.
Correct: C)
Explanation: The centre of pressure (CP) is the point on the chord line where the resultant aerodynamic force (sum of all pressure and friction forces) can be considered to act. Unlike the aerodynamic centre, the CP moves with changing angle of attack — it moves forward as AoA increases and rearward as AoA decreases. This movement is one reason why the CG position must remain within limits: if the CP moves too far from the CG, pitch control may be compromised.
Correct: D)
Explanation: Parasite drag is proportional to V² (dynamic pressure). The faster the aircraft flies, the greater the parasite drag. At VNE — the maximum speed — parasite drag reaches its peak within the normal flight envelope. At slow speeds near the stall, parasite drag is minimal while induced drag dominates. Parasite drag includes form drag, skin friction drag, and interference drag — all of which grow with the square of the airspeed.
