Correct: B)
Explanation: The centre of gravity (CG) is determined by the distribution of mass within the aircraft, so only physically moving mass — such as shifting ballast, passengers, or baggage — changes it. Option A is wrong because changing angle of attack alters aerodynamic forces, not mass distribution. Option C is incorrect because the angle of incidence is a fixed structural dimension. Option D is wrong because the aerodynamic centre is a property of the wing shape, not of the aircraft's mass distribution.
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- A) Plain Flap
- B) Split Flap
- C) Slotted Flap
- D) Fowler
Correct: D)
Explanation: A Fowler flap moves rearward and downward, simultaneously increasing both wing area and camber, making it the most effective type of trailing-edge flap. The diagram shows this characteristic rearward extension. A plain flap (A) simply hinges downward without moving aft. A split flap (B) deflects only the lower surface panel. A slotted flap (C) opens a gap but does not significantly increase wing area like the Fowler design.
Correct: C)
Explanation: The aerodynamic centre is the point on the aerofoil through which the resultant of all aerodynamic pressure forces (lift and drag combined) is considered to act, and about which the pitching moment coefficient remains approximately constant with changes in angle of attack, located near the quarter-chord point. Option A is wrong because the centre of gravity is where weight acts, not aerodynamic forces. Option B is incorrect because the stagnation point is where airflow velocity is zero at the leading edge. Option D is not a standard aerodynamic term.
Correct: D)
Explanation: In the ICAO standard atmosphere, air density decreases approximately exponentially with altitude and reaches half its sea-level value at roughly 6,600 m (about 21,600 ft). Option A (2,000 ft) is far too low — density barely changes at that altitude. Option B (20,000 m) is in the stratosphere, where density is far below half. Option C (2,000 m) is also too low — density there is still about 80% of the sea-level value.
Correct: B)
Explanation: The ASI measures dynamic pressure, which is the difference between total (pitot) pressure and static pressure: q = ptotal - pstatic = 0.5 × rho × V². This differential measurement directly indicates airspeed. Option A is nonsensical — a weathervane measures wind direction, not pressure. Option C is wrong because measuring only total pressure without subtracting static pressure gives no speed information. Option D is also incorrect because static pressure alone tells you only about altitude, not airspeed.
Correct: D)
Explanation: Roll (lateral) stability — the tendency to return to wings-level after a disturbance — is primarily provided by wing dihedral and wing sweep, both of which create restoring roll moments when the aircraft sideslips after a bank disturbance. Option A is wrong because leading-edge slats are high-lift devices that delay stall, not stability features. Option B describes pitch motion, not roll stability. Option C is incorrect because the horizontal stabiliser provides pitch (longitudinal) stability, not roll stability.
Correct: C)
Explanation: The permitted speed range for flap operation varies between aircraft types and is always specified in the Aircraft Flight Manual (AFM), typically also indicated on the ASI as a white arc. Option A is dangerously wrong — flaps have structural speed limits. Option B is incorrect because the upper flap speed (VFE) is typically different from the manoeuvring speed (VA). Option D is wrong because the red radial line is VNE (never-exceed speed), which has nothing to do with the lower flap speed limit.
Correct: C)
Explanation: Geometric twist (washout) is a physical twist built into the wing so that the angle of incidence progressively decreases from root to tip. This ensures the root stalls first, preserving aileron effectiveness near the tips. Option A (aspect ratio) is the span-to-chord ratio. Option B (aerodynamic twist) achieves a similar stall progression by using different aerofoil profiles along the span rather than physical twist. Option D (interference compensation) is not a standard aerodynamic term for wing twist.
Correct: D)
Explanation: Atmospheric pressure follows an approximately exponential decay with altitude, as described by the barometric formula. Each equal altitude increment reduces pressure by the same percentage, not the same absolute amount. Option A is wrong because the relationship is exponential, not linear. Option B is obviously false — pressure clearly drops with altitude. Option C is incorrect because pressure continues to decrease in the stratosphere; it is temperature, not pressure, that stabilises or increases in the stratosphere.
Correct: B)
Explanation: The continuity equation for incompressible flow states A1 × V1 = A2 × V2 (area times velocity is constant). If the cross-section increases, velocity must decrease proportionally to maintain the same mass flow rate. Option A is wrong because velocity does change with cross-section. Option C reverses the relationship — velocity decreases, not increases, with a larger cross-section. Option D also reverses it — velocity increases through a smaller section, not decreases.
Correct: B)
Explanation: Point 4 on the boundary layer diagram (PFA-009) marks the separation point, where the boundary layer detaches from the upper wing surface due to an adverse pressure gradient, forming a turbulent wake behind it. Option A is wrong because the stagnation point is at the leading edge (point 1). Option C is incorrect because the centre of pressure is a theoretical force application point, not a boundary layer feature. Option D is wrong because the transition point (laminar to turbulent) occurs further forward on the surface.
Correct: C)
Explanation: Point 1 on the boundary layer diagram (PFA-009) is the stagnation point at the leading edge, where the incoming airflow divides into upper and lower streams, velocity is zero, and static pressure reaches its maximum. Option A is wrong because the transition point occurs further aft where laminar flow becomes turbulent. Option B is incorrect because the centre of pressure is a resultant force point, not a physical flow location on the leading edge.
Correct: C)
Explanation: The figure shows wing dihedral — the upward V-angle of the wings relative to the horizontal plane — which provides lateral (roll) stability. When one wing drops in a sideslip, the lower wing experiences a higher effective angle of attack, generating more lift and producing a restoring roll moment. Option A is wrong because directional stability comes from the vertical tail, not dihedral. Option B incorrectly identifies the axis — dihedral affects roll (lateral), not pitch (longitudinal) stability. Option D describes an aileron design feature unrelated to the figure.
Correct: C)
Explanation: Despite its potentially confusing name, longitudinal stability refers to pitch stability, which is rotation around the lateral axis (the axis running from wingtip to wingtip). It describes the aircraft's tendency to return to a trimmed pitch attitude. Option A is wrong because the vertical axis governs yaw (directional stability). Option B is incorrect because the longitudinal axis governs roll (lateral stability). Option D is not a recognised stability axis in standard aeronautical terminology.
Correct: B)
Explanation: Yawing is the rotation of the aircraft around the vertical (normal) axis, causing the nose to swing left or right. It is controlled primarily by the rudder. Option A (pitching) is rotation around the lateral axis. Option C (rolling) is rotation around the longitudinal axis. Option D (slipping) describes a flight condition with a sideways airflow component, not a specific rotational axis.
Correct: D)
Explanation: Pitching is the rotation of the aircraft around the lateral axis (wingtip to wingtip), resulting in nose-up or nose-down movement, controlled by the elevator. Option A (stalling) is an aerodynamic phenomenon of flow separation, not a rotational term. Option B (rolling) is rotation around the longitudinal axis. Option C (yawing) is rotation around the vertical axis.
Correct: B)
Explanation: The elevator controls pitch, which is rotation around the lateral axis (running from wingtip to wingtip). By deflecting the elevator, the pilot changes the aerodynamic force on the tail, creating a pitching moment that raises or lowers the nose. Option A is wrong because the longitudinal axis governs roll, controlled by ailerons. Option C is not a standard aeronautical axis. Option D is wrong because the vertical axis governs yaw, controlled by the rudder.
Correct: C)
Explanation: The centre of gravity position is determined solely by how mass is distributed within the aircraft — only correct loading of occupants, baggage, and ballast within approved limits ensures a safe CG. Option A is wrong because CG must be verified on the ground before flight using weight and balance calculations. Option B is incorrect because aileron trim tabs adjust roll forces, not mass distribution. Option D is also wrong because trim tabs change aerodynamic balance forces, they cannot physically move the CG.
Correct: D)
Explanation: Differential aileron deflection means the down-going aileron deflects less than the up-going aileron, which reduces the extra induced drag on the descending wing and thus minimises adverse yaw — the unwanted yawing opposite to the intended roll direction. Option A is wrong because the purpose is drag reduction, not increasing the drag-to-lift ratio. Option B is incorrect because total lift does change somewhat during aileron deflection. Option C states the opposite of the actual effect — differential ailerons decrease adverse yaw, not increase it.
Correct: B)
Explanation: An aerodynamic rudder balance (such as a horn balance or set-back hinge) positions part of the control surface ahead of the hinge line, so that aerodynamic pressure partially assists the pilot's input, reducing the force needed to deflect the control. Option A is incorrect because the purpose is force reduction, not improved effectiveness. Option C is wrong because stall delay is achieved by devices like slats or vortex generators, not control surface balancing. Option D makes no sense — aerodynamic balance does not reduce the size of control surfaces.
Correct: C)
Explanation: Static (mass) balancing places counterweights ahead of the hinge line to move the control surface's centre of mass to or forward of the hinge. This prevents flutter — a dangerous self-exciting aeroelastic oscillation that can destroy the control surface and airframe at speed. Option A is wrong because limiting stick forces is the role of aerodynamic balance, not mass balance. Option B is the opposite of any balancing goal. Option D is incorrect because force-free trimming is achieved by trim tabs, not mass balance.
Correct: C)
Explanation: An upward-deflected trim tab generates a downward aerodynamic force on the trailing edge of the elevator, which pushes the elevator's leading edge upward, creating a nose-down pitching moment. The trim indicator therefore shows a nose-down position. Option A is irrelevant — lateral trim concerns roll, not pitch. Option B would require the tab to be neutral. Option D is the opposite — a nose-up indication would require the trim tab to deflect downward.
Correct: D)
Explanation: Point 1 on the polar diagram (PFA-008) lies in the region of negative lift coefficient, representing inverted flight where the aircraft flies upside down and the wing produces downward lift relative to its normal orientation. Options A, B, and C all correspond to positive (upright) portions of the polar curve — slow flight is near maximum CL, stall is at CL_max, and best gliding angle is at the tangent point from the origin.
Correct: B)
Explanation: In a coordinated banked turn, the lift vector must support both the weight and provide centripetal force, so the load factor n = 1/cos(bank angle) is always greater than 1. The stall speed increases by the factor sqrt(n), because more lift is needed and thus a higher speed is required to avoid the stall. Options A and C are wrong because n is always above 1 in a level turn. Option D incorrectly states that Vs decreases — higher load factor always raises stall speed.
Correct: D)
Explanation: The pressure difference between the lower (high pressure) and upper (low pressure) wing surfaces causes air to flow around the wingtips, forming trailing vortices. These vortices create downwash that tilts the lift vector rearward, producing induced drag. Option A is wrong because wingtip vortices cause induced drag, not profile drag. Option B is incorrect because vortices create turbulent, not laminar, flow. Option C is false because vortices actually reduce effective lift by reducing the local angle of attack.
