Principles of Flight

125 questions

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Atmosphere and Physical Fundamentals

Q1: In the ICAO standard atmosphere, at what rate does temperature decrease with altitude in the troposphere? ^q1

• A) 2°C per 100 ft
• B) 0.65°C per 1000 ft
• C) 0.65°C per 100 m
• D) 2°C per 100 m

Correct: C)

Explanation: In the ICAO standard atmosphere (ISA), temperature drops by 0.65°C for every 100 m of altitude gain in the troposphere (equivalently 6.5°C/1000 m or 2°C/1000 ft). Option B (0.65°C/1000 ft) uses the wrong unit — that lapse rate would be far too small. Option D (2°C/100 m) is ten times too large.

Q2: What are the standard sea-level values of temperature and atmospheric pressure in the ICAO standard atmosphere? ^q2

• A) 15°C and 1013.25 hPa
• B) 15°F and 29.92 Hg
• C) 59°C and 29.92 hPa
• D) 15°C and 1013.25 Hg

Correct: A)

Explanation: The ICAO standard atmosphere defines sea-level conditions as 15°C and 1013.25 hPa (millibars). In imperial units this equals 59°F and 29.92 inHg — but the question asks for metric values. 29.92 hPa would be absurdly low, and 59°C is not a valid standard temperature.

Q3: At roughly what altitude is atmospheric pressure half its sea-level value? ^q3

• A) 6,600 ft
• B) 5,500 ft
• C) 6,600 m
• D) 5,500 m

Correct: D)

Explanation: Atmospheric pressure falls approximately exponentially with altitude. In the standard atmosphere, it reaches about half the sea-level value (~506 hPa) near 5,500 m (approximately 18,000 ft). This figure is important for oxygen physiology and density-altitude calculations.

Q4: How does barometric pressure change with increasing altitude? ^q4

• A) It falls linearly
• B) It remains constant throughout
• C) It decreases exponentially
• D) It falls in the troposphere then rises in the stratosphere

Correct: C)

Explanation: The barometric formula shows that pressure decreases exponentially (not linearly) with altitude. The rate of decrease slows as altitude increases because the air above becomes less dense. Pressure continues to fall in the stratosphere — it never increases.

Q5: At approximately what altitude is air density half its sea-level value? ^q5

• A) 2,000 ft
• B) 20,000 m
• C) 2,000 m
• D) 6,600 m

Correct: D)

Explanation: Air density is roughly half the sea-level value at about 6,600 m (around 22,000 ft). This is higher than the altitude where pressure halves because temperature also decreases with altitude, partially compensating the density change.

Q6: Density altitude always corresponds to... ^q6

• A) the altitude at which atmospheric pressure and temperature match those of the standard atmosphere
• B) true indicated altitude corrected for instrument error
• C) pressure altitude corrected for the temperature deviation from standard temperature
• D) altimeter altitude set to QNH, corrected for temperature deviation

Correct: C)

Explanation: Density altitude is determined by taking pressure altitude (altimeter set to 1013.25 hPa) and adjusting it for the difference between actual temperature and ISA temperature. Warmer-than-standard air gives a density altitude above pressure altitude, degrading aircraft performance.

Q7: What is the mean value of gravitational acceleration at the Earth's surface? ^q7

• A) 1013.25 hPa
• B) 100 m/s²
• C) 15°C/100 m
• D) 9.81 m/s²

Correct: D)

Explanation: Standard gravitational acceleration at Earth's surface is 9.81 m/s², the ISA reference value used in all aeronautical weight and load-factor calculations. The other options represent standard sea-level pressure, a temperature lapse rate, and an unrealistically large acceleration value, respectively.

Q8: In which units is pressure expressed? ^q8

• A) bar, Pa, m/s²
• B) bar, psi, α
• C) Pa, psi, g
• D) bar, psi, Pa

Correct: D)

Explanation: Bar, psi (pounds per square inch), and Pascal (Pa) are all valid units of pressure. The symbol g denotes acceleration, α typically denotes an angle, and m/s² is the unit of acceleration — none of these are pressure units.

Bernoulli's Principle, Continuity, and Pressure

Q9: Static pressure in a gas acts... ^q9

• A) only perpendicular to the flow direction
• B) only along the direction of total pressure
• C) in all directions equally
• D) only in the direction of flow

Correct: C)

Explanation: Static pressure is a scalar quantity arising from random molecular motion. Because molecules collide in every direction with equal vigour, static pressure acts omnidirectionally — it pushes equally on all surfaces regardless of orientation. Dynamic pressure, by contrast, is directional and associated with the bulk velocity of the flow.

Q10: What does Bernoulli's equation for frictionless, incompressible flow state? ^q10

• A) Dynamic pressure equals total pressure plus static pressure
• B) Static pressure equals total pressure plus dynamic pressure
• C) Total pressure equals dynamic pressure minus static pressure
• D) Total pressure equals static pressure plus dynamic pressure

Correct: D)

Explanation: Bernoulli's theorem states that along a streamline in ideal, incompressible flow, total pressure is conserved: ptotal = pstatic + ½ρV². Where air accelerates over the upper wing surface, static pressure drops (dynamic pressure rises) while total pressure stays constant — this pressure difference produces lift.

Q11: The continuity equation states that the same air mass passes through different cross-sections in a given time. This means that... ^q11

• A) flow velocity rises when the cross-section shrinks
• B) flow velocity drops when the cross-section shrinks
• C) flow velocity rises when the cross-section grows
• D) flow velocity stays constant regardless of cross-section

Correct: A)

Explanation: For incompressible flow, the continuity equation requires A₁V₁ = A₂V₂. If the cross-sectional area decreases, velocity must increase proportionally to maintain the same mass flow rate. Combined with Bernoulli's principle, this explains why air accelerates over the curved upper surface of an aerofoil, creating a low-pressure region that generates lift.

Q12: What does the airspeed indicator (ASI) actually measure? ^q12

• A) Total pressure inside an aneroid capsule
• B) The difference between total pressure and static pressure
• C) Static pressure around an aneroid capsule
• D) A weathervane effect where pressure decreases

Correct: B)

Explanation: The ASI works by measuring the difference between total (pitot) pressure and static pressure — this difference equals dynamic pressure, q = ½ρV². Dynamic pressure is directly related to indicated airspeed.

Q13: True Airspeed (TAS) is obtained from the ASI reading by applying which corrections? ^q13

• A) No corrections at all
• B) Position and instrument errors only
• C) An adjustment for atmospheric density only
• D) Both position/instrument error correction and density correction

Correct: D)

Explanation: TAS is obtained from IAS by first correcting for position and instrument errors (yielding CAS), then correcting for the difference between actual air density and standard sea-level density. At high altitude, TAS is significantly greater than IAS because the air is thinner.

Q14: True Airspeed (TAS) represents the speed of... ^q14

• A) the aircraft relative to the ground
• B) the aircraft relative to the surrounding air mass
• C) the reading shown directly on the ASI
• D) the aircraft relative to the air, corrected for wind and atmospheric pressure

Correct: B)

Explanation: TAS is the aircraft's speed relative to the surrounding air mass — the actual speed through the air once all instrument and density corrections have been applied. Groundspeed includes wind effects; the raw ASI reading is IAS.

Q15: The aerodynamic resultant (lift and drag) depends on air density. When density decreases... ^q15

• A) drag rises while lift falls
• B) both lift and drag increase
• C) drag falls while lift rises
• D) both lift and drag decrease

Correct: D)

Explanation: Both lift and drag are proportional to dynamic pressure q = ½ρV². When air density ρ decreases (at altitude or in heat), q falls for a given airspeed, reducing both lift and drag proportionally.

Aerofoil Geometry

Q16: What does number 2 in the aerofoil diagram represent? See figure (PFA-010) ^q16

• A) Angle of attack
• B) Profile thickness
• C) Chord line
• D) Camber line

Correct: C)

Explanation: The chord line is the straight reference line connecting the leading edge to the trailing edge of an aerofoil. It serves as the baseline from which angle of attack is measured. Profile thickness is the distance between upper and lower surfaces; the camber line curves above the chord.

Q17: What does number 3 in the aerofoil diagram represent? See figure (PFA-010) ^q17

• A) Chord line
• B) Camber line
• C) Thickness
• D) Chord

Correct: B)

Explanation: The mean camber line is the locus of points equidistant between the upper and lower surfaces. It defines the aerofoil's curvature — a cambered wing generates lift even at zero angle of attack because the asymmetric curvature accelerates flow more over the upper surface.

Q18: In the figure shown, the chord of the aerofoil is represented by which letter? ^q18

• A) M
• B) H
• C) K
• D) A

Correct: B)

Explanation: The chord is the straight line from leading edge to trailing edge. In this aerofoil figure, line H represents that reference line.

Q19: In the figure shown, which letter designates the mean camber line? ^q19

• A) H
• B) G + J
• C) B
• D) A

Correct: C)

Explanation: The mean camber line runs equidistant between the upper and lower surfaces of the aerofoil. In this figure it is designated by letter B.

Q20: The angle of attack is defined as the angle between... ^q20

• A) the chord line and the direction of the oncoming airflow
• B) the undisturbed airflow and the aircraft's longitudinal axis
• C) the wing and the fuselage
• D) the chord line and the aircraft's longitudinal axis

Correct: A)

Explanation: Angle of attack (α) is the angle between the aerofoil's chord line and the relative wind direction. It is the primary variable determining the lift coefficient. It must not be confused with pitch attitude or the rigging angle (chord relative to fuselage axis).

Q21: The angle α shown between the chord line and the airflow direction in the figure is called... See figure (PFA-003) ^q21

• A) Angle of incidence
• B) Angle of inclination
• C) Angle of attack
• D) Lift angle

Correct: C)

Explanation: The angle of attack (α) is the angle between the chord line and the oncoming airflow vector. The angle of incidence is a fixed structural angle between the chord line and the fuselage axis, set during manufacture and unchanging in flight.

Q22: The angle between the aerofoil chord line and the aircraft's longitudinal axis is called... ^q22

• A) the sweep angle
• B) the angle of attack
• C) the dihedral angle
• D) the rigging angle (angle of incidence)

Correct: D)

Explanation: The rigging angle (or angle of incidence) is the fixed angle defined at construction between the chord line and the fuselage longitudinal axis. Unlike the angle of attack, it does not change in flight. The manufacturer chooses it so the wing produces the required lift during cruise at an efficient fuselage attitude.

Q23: What is the ratio of wingspan to mean chord length called? ^q23

• A) Wing sweep
• B) Tapering
• C) Aspect ratio
• D) Trapezium shape

Correct: C)

Explanation: Aspect ratio (AR) = wingspan / mean chord = b²/S. High-aspect-ratio wings (long and narrow, typical of gliders at AR 20–40) produce less induced drag because wingtip vortices are proportionally weaker relative to the span.

Q24: What does "wing loading" describe? ^q24

• A) Drag per wing area
• B) Wing area per weight
• C) Weight per wing area
• D) Drag per weight

Correct: C)

Explanation: Wing loading is the aircraft's weight divided by its wing reference area, expressed in N/m² or kg/m². Higher wing loading means the wing must work harder to generate lift, resulting in higher stall speeds but better turbulence penetration.

Aerodynamic Forces and Lift

Q25: When surrounded by airflow (v > 0), any arbitrarily shaped body produces... ^q25

• A) Lift without drag
• B) Constant drag regardless of speed
• C) Both drag and lift
• D) Drag

Correct: D)

Explanation: Any body immersed in a flow always experiences drag from skin friction and pressure forces. Lift, however, requires specific geometry (camber, angle of attack) or circulation. A symmetric body at zero angle of attack produces drag but no lift. Drag also varies with the square of velocity, so it is not constant.

Q26: The single point through which all aerodynamic forces on a wing are considered to act is called the... ^q26

• A) Centre of gravity
• B) Transition point
• C) Centre of pressure
• D) Lift point

Correct: C)

Explanation: The centre of pressure (CP) is the theoretical point on the aerofoil through which the resultant of all distributed aerodynamic pressure forces acts. It shifts with angle of attack — generally moving forward as AoA increases toward the critical angle.

Q27: The centre of pressure is the theoretical point of origin of... ^q27

• A) gravity forces acting on the profile
• B) only the resulting total drag
• C) all aerodynamic forces acting on the profile
• D) both gravity and aerodynamic forces

Correct: C)

Explanation: The centre of pressure is defined as the point through which the entire resultant aerodynamic force — including both lift and drag — is considered to act. Gravity acts through the centre of gravity, a completely separate point.

Q28: The aerodynamic centre of a wing profile in an airflow is the point where... ^q28

• A) the weight acts
• B) the resultant of all aerodynamic pressure forces is applied
• C) the airflow meets the leading edge
• D) tyre pressure acts on the runway

Correct: B)

Explanation: The aerodynamic centre is the point where the resultant of all aerodynamic forces on a profile is applied. For an isolated aerofoil it lies near the quarter-chord point. It is distinct from the centre of gravity.

Q29: What point on a wing has the property that the pitching moment about the lateral axis does not change when the angle of attack varies? ^q29

• A) Centre of gravity
• B) Centre of symmetry
• C) Aerodynamic centre
• D) Neutral point

Correct: D)

Explanation: The neutral point (for the complete aircraft) is where the pitching moment coefficient remains constant regardless of AoA changes. For a stable aircraft, the CG must be forward of the neutral point — the distance between them defines the static stability margin.

Q30: When a lift-generating wing operates at a positive angle of attack, what pressure pattern is observed? ^q30

• A) Pressure above stays unchanged; higher pressure forms below
• B) Higher pressure above, lower pressure below
• C) Lower pressure above, higher pressure below
• D) Pressure below stays unchanged; lower pressure forms above

Correct: C)

Explanation: Lift arises from a pressure differential: flow accelerates over the curved upper surface, reducing static pressure (Bernoulli's principle), while flow decelerates on the lower surface, increasing static pressure.

Q31: How does the centre of pressure move on a cambered profile as angle of attack increases? ^q31

• A) It shifts toward the wingtips
• B) It moves forward first, then backward
• C) It shifts rearward continuously
• D) It shifts forward until the critical angle of attack is reached

Correct: D)

Explanation: As AoA increases, the suction peak on the upper surface intensifies and migrates toward the leading edge, pulling the centre of pressure forward. This continues until the critical (stall) angle. Beyond the stall, the suction peak collapses and the CP moves abruptly rearward.

Q32: Which statement about lift and angle of attack is correct? ^q32

• A) Reducing the angle of attack causes more drag
• B) An excessively large angle of attack causes a loss of lift and flow separation
• C) Raising the angle of attack always generates less lift
• D) Very large angles of attack lead to an exponential lift increase

Correct: B)

Explanation: CL increases roughly linearly with AoA up to the critical angle (typically 15–18°). Beyond this, boundary-layer separation destroys the smooth flow and causes a sudden lift drop (stall) with a large drag increase.

Q33: As angle of attack increases, what happens to the stagnation point on the aerofoil? ^q33

• A) It shifts upward
• B) The centre of pressure shifts upward
• C) It shifts downward
• D) The centre of pressure shifts downward

Correct: C)

Explanation: As AoA rises, the relative wind meets the wing at a steeper angle. The stagnation point shifts downward toward the lower surface of the leading edge, as more airflow is directed over the upper surface.

Q34: As angle of attack decreases, how does the centre of pressure move? ^q34

• A) It shifts forward
• B) The stagnation point shifts downward
• C) The stagnation point stays fixed
• D) It shifts rearward

Correct: D)

Explanation: When AoA decreases, the aerodynamic loading on the forward upper surface diminishes, shifting the resultant force rearward — the centre of pressure moves aft toward the trailing edge.

Q35: Which statement about the angle of attack is correct? ^q35

• A) The angle of attack remains constant throughout flight
• B) An excessively large angle of attack can cause a loss of lift
• C) Raising the angle of attack always decreases lift
• D) The angle of attack can never be negative

Correct: B)

Explanation: AoA can be negative, changes continuously in flight, and increasing it raises lift up to a point. Beyond the critical angle (~15°), flow separation destroys lift.

Q36: At steady glide with the same mass, how does using a thicker aerofoil compare to a thinner one? ^q36

• A) Less drag, less lift
• B) Less drag, same lift
• C) More drag, less lift
• D) More drag, same lift

Correct: D)

Explanation: At the same mass in steady glide, lift must equal weight regardless of aerofoil thickness — so lift stays the same. However, a thicker aerofoil generates more form (pressure) drag due to its larger cross-section.

Q37: What does a profile polar diagram show? ^q37

• A) The relationship between cL and cD at different angles of attack
• B) The ratio of minimum sink rate to best glide
• C) The lift coefficient cL at various angles of attack only
• D) The ratio between total lift and total drag as a function of angle of attack

Correct: A)

Explanation: A profile polar (Lilienthal polar) plots the lift coefficient cL against the drag coefficient cD for a wing profile across a range of angles of attack. It directly reveals the aerodynamic efficiency of the aerofoil.

Q38: In straight and level flight at constant power, the wing's angle of attack is... ^q38

• A) greater than in a climb
• B) greater than at take-off
• C) smaller than in a descent
• D) smaller than in a climb

Correct: D)

Explanation: 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 produce sufficient lift. The level-flight AoA is therefore smaller than the climbing AoA.

Q39: What flight state does point 1 on the lift polar indicate? See figure (PFA-008) ^q39

• A) Best gliding angle
• B) Slow flight
• C) Inverted flight
• D) Stall

Correct: C)

Explanation: Point 1 on the PFA-008 polar represents inverted flight, where the lift coefficient is negative. Slow flight, stall, and best glide all correspond to the positive (upright) portion of the curve.

Q40: What flight state does point 5 on the lift polar indicate? See figure (PFA-008) ^q40

• A) Best gliding angle
• B) Inverted flight
• C) Stall
• D) Slow flight

Correct: D)

Explanation: Point 5 on the PFA-008 polar corresponds to slow flight — a low-speed, high-AoA condition on the positive portion of the polar, before stall onset.

Drag Types

Q41: If airflow speed doubles while all other parameters remain constant, how does parasite drag change? ^q41

• A) It halves
• B) It doubles
• C) It drops by a factor of 4
• D) It quadruples

Correct: D)

Explanation: Parasite drag is proportional to V². Doubling V quadruples dynamic pressure (2² = 4), so parasite drag increases by a factor of four.

Q42: What can be said about the drag coefficient? ^q42

• A) It increases with increasing airspeed
• B) It is proportional to the lift coefficient
• C) It has a non-negative minimum value that cannot be zero
• D) It can range from zero to infinity

Correct: C)

Explanation: Every aerofoil has a minimum drag coefficient (CD_min) that is always greater than zero, because skin friction and form drag exist even at the optimum angle of attack.

Q43: On a finite wing, pressure equalisation between upper and lower surfaces occurs at the... ^q43

• A) Trailing edge
• B) Wing roots
• C) Leading edge
• D) Wingtips

Correct: D)

Explanation: The pressure difference between the lower (high) and upper (low) surfaces drives air around the wingtips from below to above, creating trailing vortices — the physical mechanism of induced drag.

Q44: Wing-tip vortices arise from pressure equalisation flowing from... ^q44

• A) the upper surface to the lower surface at the wingtip
• B) the lower surface to the upper surface at the wingtip
• C) the upper surface to the lower surface along the entire trailing edge
• D) the lower surface to the upper surface along the entire trailing edge

Correct: B)

Explanation: High pressure beneath the wing and low pressure above drive air from the lower surface around the wingtip to the upper surface. This rolling motion generates the trailing vortices responsible for induced drag.

Q45: The pressure equalisation between upper and lower wing surfaces produces... ^q45

• A) Profile drag through wingtip vortices
• B) Laminar flow through wingtip vortices
• C) Induced drag through wingtip vortices
• D) Additional lift through wingtip vortices

Correct: C)

Explanation: The pressure differential drives air around the wingtips, forming trailing vortices. These vortices tilt the local airflow downward (downwash), reducing the effective angle of attack and tilting the lift vector rearward, creating induced drag.

Q46: Which wing characteristic tends to produce large induced drag? ^q46

• A) Tapered planform
• B) Low lift coefficient
• C) High aspect ratio
• D) Low aspect ratio

Correct: D)

Explanation: Induced drag is proportional to CL²/(π·AR·e). A low aspect ratio (short, stubby wing) produces high induced drag for a given lift coefficient because the wingtip vortices are strong relative to the span.

Q47: Which part of an aircraft primarily influences induced drag generation? ^q47

• A) The forward fuselage
• B) The landing gear
• C) The outer ailerons
• D) The wingtips

Correct: D)

Explanation: Induced drag originates from pressure differences at the wingtips creating concentrated trailing vortices. Winglets and elliptical planforms specifically target wingtip effects to reduce vortex strength.

Q48: What does induced drag of a wing depend on? ^q48

• A) Pressure equalisation from the upper surface toward the lower surface
• B) Pressure equalisation from the lower surface toward the upper surface
• C) The angle at the wing-fuselage junction
• D) Speed alone

Correct: B)

Explanation: Induced drag comes from pressure equalisation from the lower surface (high pressure) to the upper surface (low pressure) at the wingtip. This creates tip vortices and thus induced drag.

Q49: Where does interference drag originate? ^q49

• A) Near the wingtips
• B) At the ailerons
• C) At the wing root
• D) At the landing gear

Correct: C)

Explanation: Interference drag arises where two surfaces meet and their boundary layers interact. The wing-fuselage junction (wing root) is the classic location. Fairings and fillets are used to smooth this junction.

Q50: Pressure drag, interference drag, and friction drag are collectively known as... ^q50

• A) Induced drag
• B) Total drag
• C) Parasite drag
• D) Main resistance

Correct: C)

Explanation: Total drag = parasite drag + induced drag. Parasite drag encompasses all drag not related to lift production: skin friction, form (pressure) drag, and interference drag.

Q51: Which drag types make up total drag? ^q51

• A) Interference drag and parasite drag
• B) Form drag, skin-friction drag, and interference drag
• C) Induced drag and parasite drag
• D) Induced drag, form drag, and skin-friction drag

Correct: C)

Explanation: Total drag is the sum of induced drag (from lift production) and parasite drag (from friction, form, and interference effects). Options B and D list sub-components of parasite drag but miss the top-level breakdown.

Q52: During level flight at increasing airspeed, how do induced drag and parasite drag change? ^q52

• A) Both increase
• B) Parasite drag falls while induced drag rises
• C) Both decrease
• D) Induced drag falls while parasite drag rises

Correct: D)

Explanation: In level flight, CL must decrease as speed increases, so induced drag (∝ CL²) decreases. Meanwhile, parasite drag (∝ V²) rises. The crossover — where induced equals parasite drag — gives the speed of minimum total drag and best L/D.

Q53: Which statement about induced drag in level cruise is correct? ^q53

• A) It rises with increasing airspeed
• B) It has a minimum at a certain speed, then rises at both higher and lower speeds
• C) It falls continuously with increasing airspeed
• D) It has a maximum at a certain speed, then falls at both higher and lower speeds

Correct: C)

Explanation: Induced drag decreases monotonically with increasing speed in level flight (D_induced ∝ 1/V²). There is no minimum or maximum — it simply falls as speed increases. Total drag (not induced drag alone) has the U-shaped curve.

Q54: When airspeed decreases in level cruise, what happens to induced drag? ^q54

• A) It drops slightly
• B) It stays constant
• C) It increases
• D) It collapses

Correct: C)

Explanation: Slowing down in level flight requires a higher AoA and higher CL to maintain lift. Since induced drag is proportional to CL², it grows as speed falls.

Q55: Induced drag increases with... ^q55

• A) decreasing angle of attack
• B) increasing airspeed
• C) increasing angle of attack
• D) increasing parasite drag

Correct: C)

Explanation: Induced drag is proportional to CL², and CL rises with angle of attack. Therefore induced drag grows as AoA increases.

Q56: Which listed wing planform produces the least induced drag? ^q56

• A) Rectangular
• B) Double trapezoidal
• C) Trapezoidal
• D) Elliptical

Correct: D)

Explanation: The elliptical planform produces a perfectly elliptical spanwise lift distribution — the theoretical optimum for minimum induced drag at a given span and total lift.

Q57: The form drag (profile drag) of a body is primarily influenced by... ^q57

• A) its internal temperature
• B) its mass
• C) the formation of vortices and wake turbulence
• D) its density

Correct: C)

Explanation: Form drag results from the pressure difference between front and rear of a body, caused by boundary-layer separation and vortex formation in the wake. Streamlining reduces form drag by keeping flow attached longer.

Q58: The aerodynamic drag of a flat disc in an airflow depends notably on... ^q58

• A) the surface area perpendicular to the airflow
• B) the disc's density
• C) the tensile strength of its material
• D) its weight

Correct: A)

Explanation: Drag on a flat disc is predominantly pressure drag: D = CD × ½ρV² × S. It depends on the frontal area S exposed to the flow. The disc's material properties, density, and weight do not affect aerodynamic drag.

Q59: At equal frontal area and equal airflow speed, the drag of a body depends on... ^q59

• A) the position of its centre of gravity
• B) its shape
• C) its weight
• D) its density

Correct: B)

Explanation: With frontal area and speed held constant, the remaining variable is the drag coefficient, which is entirely determined by the body's shape.

Q60: The drag of a body in an airflow depends notably on... ^q60

• 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 is given by F_D = CD × ½ρV² × A. Air density ρ appears directly in the formula. The body's own density, composition, and mass do not affect aerodynamic drag.

Q61: When the frontal area of a disc in an airflow is tripled, drag increases by a factor of... ^q61

• A) 9
• B) 1.5
• C) 6
• D) 3

Correct: D)

Explanation: Drag is directly proportional to the reference (frontal) area: D = CD × ½ρV² × S. Tripling S triples drag. The relationship is linear with area (unlike velocity, which is squared).

Boundary Layer

Q62: On an aerofoil, point 1 in the figure represents... See figure (PFA-009) ^q62

• A) The separation point
• B) The centre of pressure
• C) The stagnation point
• D) The transition point

Correct: C)

Explanation: The stagnation point is where oncoming airflow splits — some going over the upper surface, some beneath. Local velocity is zero and static pressure is at its maximum (equal to total pressure).

Q63: What occurs at the stagnation point? ^q63

• A) The boundary layer begins to separate on the upper surface
• B) All aerodynamic forces are considered to act at this point
• C) The laminar boundary layer transitions to turbulent
• D) Streamlines divide into flow above and below the profile

Correct: D)

Explanation: The stagnation point is where incoming streamlines bifurcate — the air splits to flow around both surfaces. At this point, kinetic energy is fully converted to pressure (V = 0).

Q64: On the aerofoil diagram, point 3 represents... See figure (PFA-009) ^q64

• A) The separation point
• B) The stagnation point
• C) The centre of pressure
• D) The transition point

Correct: D)

Explanation: The transition point is where the boundary layer changes from laminar to turbulent flow.

Q65: What does the transition point correspond to? ^q65

• A) The point at which CL_max is reached
• B) The change from a turbulent boundary layer to a laminar one
• C) The lateral roll of the aircraft
• D) The change from a laminar boundary layer to a turbulent one

Correct: D)

Explanation: The transition point is precisely where the boundary layer changes from a laminar regime (ordered flow) to a turbulent regime (disordered flow). This transition is irreversible in the direction of flow. Its position depends on Reynolds number, pressure gradient, and surface roughness.

Q66: On the aerofoil diagram, point 4 represents... See figure (PFA-009) ^q66

• A) The transition point
• B) The stagnation point
• C) The separation point
• D) The centre of pressure

Correct: C)

Explanation: The separation point is where the boundary layer detaches from the surface. Beyond it, smooth attached flow breaks down into a turbulent, reversed-flow wake. As AoA increases, the separation point moves forward.

Q67: The laminar boundary layer on an aerofoil extends between... ^q67

• A) the stagnation point and the centre of pressure
• B) the transition point and the separation point
• C) the transition point and the centre of pressure
• D) the stagnation point and the transition point

Correct: D)

Explanation: Boundary-layer development proceeds from the stagnation point through a laminar phase to the transition point (where it becomes turbulent). The laminar layer therefore occupies the region from stagnation point to transition point.

Q68: Which types of boundary layer are found on an aerofoil? ^q68

• A) Turbulent layer near the leading edge, laminar layer further aft
• B) Turbulent boundary layer over the entire upper surface with separated flow
• C) Laminar boundary layer over the entire upper surface without separation
• D) Laminar layer near the leading edge, turbulent layer further aft

Correct: D)

Explanation: The natural progression runs from laminar (near the leading edge, where Reynolds number is low) to turbulent (further aft, after transition). The reverse does not occur naturally.

Q69: How does a laminar boundary layer differ from a turbulent one? ^q69

• A) The laminar layer is thinner and creates more skin friction
• B) The turbulent layer remains attached against stronger adverse pressure gradients at higher angles of attack
• C) The turbulent layer is thicker and creates less skin friction
• D) The laminar layer produces lift while the turbulent layer produces drag

Correct: B)

Explanation: The turbulent boundary layer has more energetic mixing that allows it to resist flow separation against adverse pressure gradients better than the laminar layer. This is its critical advantage, even though it has higher friction drag.

Stall and Spin

Q70: As the stall condition is approached, how do lift and drag change? ^q70

• A) Both increase
• B) Both decrease
• C) Lift rises while drag falls
• D) Lift falls while drag rises

Correct: D)

Explanation: Near and beyond the critical AoA, flow separates from the upper surface. CL drops sharply while CD rises dramatically due to the large turbulent wake.

Q71: To recover from a stall, the pilot should... ^q71

• A) increase AoA and reduce speed
• B) decrease AoA and increase speed
• C) increase the bank angle and reduce speed
• D) increase AoA and increase speed

Correct: B)

Explanation: Stall recovery requires reducing the angle of attack below the critical value so airflow re-attaches. The pilot pushes forward on the elevator to lower AoA, allowing the aircraft to accelerate.

Q72: The critical angle of attack... ^q72

• A) increases when the CG moves aft
• B) decreases when the CG moves forward
• C) changes with increasing weight
• D) is independent of weight

Correct: D)

Explanation: The critical (stall) AoA is a fixed aerodynamic property of the aerofoil shape. What changes with weight is the stall speed — a heavier aircraft must fly faster but stalls at the same critical AoA.

Q73: What leads to a decreased stall speed (IAS)? ^q73

• A) Higher load factor
• B) Lower density
• C) Decreasing weight
• D) Lower altitude

Correct: C)

Explanation: From Vs = √(2W/(ρ·S·CL_max)): stall speed decreases when weight decreases. Higher load factor raises effective weight and thus stall speed.

Q74: A wing stall occurs... ^q74

• A) only when the nose is excessively high relative to the horizon
• B) at the red radial line on the ASI
• C) at a critical angle of attack
• D) following a reduction in engine power

Correct: C)

Explanation: Stall occurs when the wing exceeds its critical angle of attack, regardless of airspeed, nose attitude, or power setting.

Q75: Airflow separation on an aerofoil occurs at... ^q75

• A) any altitude regardless of other factors
• B) a specific angle of attack
• C) only a given nose position relative to the horizon
• D) a speed determined solely by aircraft altitude

Correct: B)

Explanation: Flow separation is triggered when a specific critical angle of attack is reached. It is not related to nose attitude relative to the horizon or altitude alone.

Q76: When is the risk of airflow separation on the wing greatest? ^q76

• A) In straight climbing flight at high speed in turbulence
• B) During an abrupt pull-out after a dive
• C) In calm air, gliding at minimum authorised speed
• D) In straight level cruise in turbulence

Correct: B)

Explanation: An abrupt pull-out after a dive rapidly increases the angle of attack, potentially exceeding the critical angle before the pilot can react. The high load factor combined with the sudden AoA increase creates the greatest stall risk.

Q77: When extending slotted flaps, airflow separation occurs at... ^q77

• A) a higher speed
• B) a lower speed
• C) the same speed as before extending
• D) none of these is correct

Correct: B)

Explanation: Slotted flaps increase CL_max, which lowers the stall speed. Separation therefore occurs at a lower speed than with flaps retracted.

Q78: After one wing stalls and the nose drops, how can a spin be prevented? ^q78

• A) Pull the elevator to bring the aircraft back to normal attitude
• B) Push the elevator to build speed and re-attach airflow on the wings
• C) Apply rudder opposite the lower wing while releasing elevator back-pressure to regain speed
• D) Deflect all controls opposite to the lower wing

Correct: C)

Explanation: An incipient spin begins when one wing stalls before the other. The correct response is opposite rudder to stop the yaw rotation, combined with releasing elevator back-pressure (reducing AoA) to un-stall the wings.

Q79: Which statement about a spin is correct? ^q79

• A) The speed constantly increases during the spin
• B) Only very old aircraft risk spinning
• C) Ailerons should be kept neutral during recovery
• D) Ailerons should be crossed during recovery

Correct: C)

Explanation: The standard spin recovery technique (PARE) requires ailerons neutral. Using ailerons during a spin can worsen the rotation. Speed does not constantly increase; the spin stabilises at roughly constant speed and rotation rate.

Q80: How does a spin differ from a spiral dive? ^q80

• A) Spin: inner wing stalled, speed increases rapidly; Spiral dive: both wings flying, speed constant
• B) Spin: outer wing stalled, speed constant; Spiral dive: both wings flying, speed increases rapidly
• C) Spin: inner wing stalled, speed roughly constant; Spiral dive: both wings flying, speed increases rapidly
• D) Spin: outer wing stalled, speed increases rapidly; Spiral dive: both wings flying, speed constant

Correct: C)

Explanation: In a spin, the inner wing is stalled while the outer continues to fly, producing autorotation at near-constant airspeed. In a spiral dive, neither wing is stalled and speed increases rapidly. Recovery techniques differ fundamentally.

Stability

Q81: Which CG position is most dangerous for longitudinal stability in a conventional glider? ^q81

• A) A position far back within the permissible CG limits
• B) A position beyond the forward CG limit
• C) A position beyond the rear CG limit
• D) A position off to one side of the permissible CG range

Correct: C)

Explanation: When the CG moves beyond the rear limit, the static margin becomes negative — pitch disturbances amplify rather than correct themselves, making the aircraft potentially uncontrollable.

Q82: The horizontal stabiliser provides stability around the... ^q82

• A) Vertical axis
• B) Longitudinal axis
• C) Lateral axis
• D) Rudder axis

Correct: C)

Explanation: The horizontal stabiliser provides pitch stability — stability around the lateral axis. It generates a restoring moment whenever the nose pitches up or down from trim.

Q83: The horizontal and vertical stabilisers serve primarily to... ^q83

• A) reduce wingtip vortex formation
• B) control the aircraft around the longitudinal axis
• C) stabilise the aircraft in flight
• D) reduce air resistance

Correct: C)

Explanation: The stabilisers exist primarily to provide longitudinal (pitch) and directional (yaw) stability. Without them, the aircraft would be uncontrollable.

Q84: "Longitudinal stability" refers to stability around which axis? ^q84

• A) Vertical axis
• B) Propeller axis
• C) Lateral axis
• D) Longitudinal axis

Correct: C)

Explanation: Longitudinal stability describes the aircraft's tendency to maintain or return to its trimmed pitch attitude — rotation around the lateral axis. Despite the potentially confusing name, "longitudinal" stability refers to pitch behaviour.

Q85: Stability around which axis is primarily influenced by the CG's longitudinal position? ^q85

• A) Vertical axis
• B) Longitudinal axis
• C) Gravity axis
• D) Lateral axis

Correct: D)

Explanation: The CG's fore-and-aft position directly determines pitch stability (around the lateral axis). A CG forward of the neutral point gives positive pitch stability; too far aft reduces or reverses it.

Q86: An aircraft has dynamic stability when... ^q86

• A) the permitted load factor allows at least 4 g positive and 2 g negative with flaps retracted
• B) pitch-axis rotation is automatically corrected by the ailerons
• C) it returns automatically to its original equilibrium after a disturbance
• D) it automatically stabilises at a new equilibrium after a disturbance

Correct: C)

Explanation: A dynamically stable aircraft returns to its original equilibrium after being disturbed — oscillations progressively damp out. Static stability (the immediate restoring tendency) is necessary but not sufficient for dynamic stability.

Q87: Which statement describes static stability? ^q87

• A) An aircraft disturbed by an external force drifts further from equilibrium
• B) An aircraft disturbed by an external force returns to its original position
• C) An aircraft disturbed by an external force holds the displaced position
• D) An aircraft can return to its original position only through pilot control input

Correct: B)

Explanation: Static stability means that when displaced from equilibrium, aerodynamic restoring forces automatically tend to push the aircraft back toward the original condition.

Q88: What structural feature provides lateral (roll) stability? ^q88

• A) Vertical tail
• B) Elevator
• C) Differential aileron deflection
• D) Wing dihedral

Correct: D)

Explanation: Wing dihedral (the upward V-angle of the wings) provides lateral stability. When a gust rolls the aircraft, the lower wing sees a higher effective AoA and produces more lift, creating a restoring moment.

Q89: The constructive feature shown in the figure provides... See figure (PFA-006) ^q89

• A) Directional stability through lift generation
• B) Differential aileron deflection
• C) Lateral stability through wing dihedral
• D) Longitudinal stability through wing dihedral

Correct: C)

Explanation: Wing dihedral — the upward V-angle of the wings — provides lateral (roll) stability by creating a restoring roll moment when one wing drops.

Q90: Good roll stability is influenced by... ^q90

• A) leading-edge slats
• B) rotation around the lateral axis
• C) wing sweep and dihedral
• D) the horizontal stabiliser

Correct: C)

Explanation: Roll stability is enhanced by both wing dihedral and wing sweep. Dihedral creates a roll restoring moment; sweep contributes because the advancing (lower) wing in a sideslip presents a higher effective AoA.

Q91: What structural feature provides directional (yaw) stability? ^q91

• A) Differential aileron deflection
• B) A large elevator
• C) Wing dihedral
• D) A large vertical tail fin

Correct: D)

Explanation: The vertical tail fin acts as a weathervane — when the aircraft sideslips, it generates a restoring yawing moment that re-aligns the nose with the airflow.

Q92: Yaw stability is provided by... ^q92

• A) leading-edge slats
• B) the horizontal stabiliser
• C) the fin (vertical stabiliser)
• D) wing dihedral

Correct: C)

Explanation: The fin (vertical stabiliser) provides directional (yaw) stability by creating a restoring moment when the aircraft sideslips.

Control Surfaces and Flight Axes

Q93: Rotation around the vertical axis is called... ^q93

• A) Pitching
• B) Slipping
• C) Rolling
• D) Yawing

Correct: D)

Explanation: Yawing is rotation around the vertical axis — nose left or right. Pitching is around the lateral axis; rolling around the longitudinal axis.

Q94: Rotation around the lateral axis is called... ^q94

• A) Stalling
• B) Yawing
• C) Rolling
• D) Pitching

Correct: D)

Explanation: Pitching is rotation around the lateral (wingtip-to-wingtip) axis, moving the nose up or down.

Q95: The elevator controls rotation around the... ^q95

• A) Vertical axis
• B) Elevator axis
• C) Lateral axis
• D) Longitudinal axis

Correct: C)

Explanation: The elevator controls pitch — rotation around the lateral axis. The rudder controls yaw (vertical axis); the ailerons control roll (longitudinal axis).

Q96: Rudder deflection causes the aircraft to rotate around the... ^q96

• A) Lateral axis
• B) Rudder axis
• C) Vertical axis
• D) Longitudinal axis

Correct: C)

Explanation: The rudder is the primary yaw control, rotating the aircraft around the vertical axis.

Q97: Deflecting the rudder to the left causes... ^q97

• A) the aircraft to pitch left
• B) the aircraft to yaw right
• C) the aircraft to pitch right
• D) the aircraft to yaw left

Correct: D)

Explanation: Left rudder deflection creates a leftward aerodynamic force on the tail, yawing the nose to the left around the vertical axis.

Q98: When the right aileron deflects upward and the left deflects downward, the aircraft... ^q98

• A) rolls left with no yawing
• B) rolls right, yawing right
• C) rolls left, yawing right
• D) rolls right, yawing left

Correct: D)

Explanation: The upward right aileron reduces lift on the right wing; the downward left aileron increases lift on the left — the aircraft rolls right. Simultaneously, the down-deflected left aileron creates more induced drag, yawing the nose left (adverse yaw).

Q99: What is "adverse yaw"? ^q99

• A) Aileron input yaws the aircraft in the intended direction due to reduced drag on the down-deflected aileron
• B) Rudder input causes a roll to the opposite side due to extra lift on the faster wing
• C) Aileron input yaws the aircraft to the opposite side due to extra drag on the up-deflected aileron
• D) Aileron input yaws the aircraft to the opposite side due to extra drag on the down-deflected aileron

Correct: D)

Explanation: Adverse yaw occurs because the down-deflected aileron (on the rising wing) increases both lift and induced drag. This extra drag yaws the nose toward the descending wing — opposite to the roll direction.

Q100: Adverse yaw is caused by... ^q100

• A) the gyroscopic effect during turn initiation
• B) lateral airflow over the wing after a turn has begun
• C) increased induced drag on the aileron of the rising wing
• D) increased induced drag on the aileron of the descending wing

Correct: C)

Explanation: When entering a turn, the aileron on the rising wing is deflected downward, increasing both lift and induced drag. This extra drag yaws the nose toward the rising wing — opposite to the intended turn direction.

Q101: What is the advantage of differential aileron movement? ^q101

• A) It makes the adverse yaw effect stronger
• B) It keeps total lift constant during aileron deflection
• C) It increases the drag-to-lift ratio
• D) It reduces drag on the down-going aileron, thereby reducing adverse yaw

Correct: D)

Explanation: Differential aileron deflection gives the down-going aileron less travel than the up-going one, reducing the extra induced drag on the descending wing and lessening adverse yaw.

Q102: Which design feature can compensate for adverse yaw? ^q102

• A) Full aileron deflection
• B) Wing dihedral
• C) Differential aileron deflection
• D) A T-tail configuration

Correct: C)

Explanation: Differential aileron deflection reduces the drag imbalance that causes adverse yaw. Wing dihedral addresses roll stability; full aileron deflection would worsen adverse yaw.

Q103: What is the purpose of an aerodynamic rudder balance? ^q103

• A) To delay the stall
• B) To reduce the size of control surfaces
• C) To reduce control stick and pedal forces
• D) To improve rudder effectiveness

Correct: C)

Explanation: An aerodynamic balance (horn balance or set-back hinge) extends part of the control surface ahead of the hinge line. Aerodynamic pressure on this forward portion partially counteracts the hinge moment, reducing the force the pilot must exert.

Q104: Which design feature is intended to reduce control forces? ^q104

• A) Vortex generators
• B) T-tail
• C) Differential aileron deflection
• D) Aerodynamic rudder balance

Correct: D)

Explanation: An aerodynamic rudder balance places part of the surface ahead of the hinge, allowing aerodynamic pressure to assist the pilot and lower the required stick/pedal forces.

Q105: What is the function of a static (mass) balance on a control surface? ^q105

• A) To enable trimming with minimal force
• B) To prevent control surface flutter
• C) To limit control stick forces
• D) To increase control stick forces

Correct: B)

Explanation: A static (mass) balance places counterweights ahead of the hinge line to move the control surface's centre of mass forward. This prevents flutter — a potentially destructive resonant oscillation at high speeds.

Q106: When the elevator trim tab is deflected upward, the trim indicator shows a... ^q106

• A) laterally trimmed position
• B) neutral position
• C) nose-up position
• D) nose-down position

Correct: D)

Explanation: An upward-deflected trim tab pushes the elevator trailing edge down, forcing the elevator leading edge up — creating a nose-down pitching moment.

Q107: Regarding CG position, what must be considered? ^q107

• A) The elevator trim tab can shift the CG to its correct position
• B) The aileron trim tab can shift the CG to its correct position
• C) CG position can only be determined during flight
• D) Only correct loading ensures a safe CG position

Correct: D)

Explanation: Only proper loading — placing occupants and baggage within approved limits — ensures the CG stays within the certified range. Trim tabs adjust aerodynamic balance but cannot physically move the CG.

Q108: A shift of the centre of gravity occurs by... ^q108

• A) changing the angle of attack
• B) changing the angle of incidence
• C) moving the load
• D) changing the position of the aerodynamic centre

Correct: C)

Explanation: The CG shifts when mass is physically redistributed — moving ballast, passengers, or baggage.

Load Factor, Turns, and Speed Limits

Q109: Exceeding the never-exceed speed (VNE) may result in... ^q109

• A) an unusable airspeed indicator due to excessive total pressure
• B) a better lift-to-drag ratio and improved glide angle
• C) reduced drag with increased control forces
• D) flutter and structural damage to the wings

Correct: D)

Explanation: VNE is the red-line speed above which aeroelastic failure becomes possible. Control surfaces and structures may enter flutter — a self-reinforcing oscillation causing rapid structural disintegration.

Q110: In severe turbulence, airspeed must be reduced to... ^q110

• A) normal cruising speed
• B) a speed within the yellow arc of the ASI
• C) the minimum constant speed in landing configuration
• D) below the manoeuvring speed VA

Correct: D)

Explanation: VA is the maximum speed at which full control deflections or severe gusts will not exceed the structural limit load. Below VA, the wing stalls before the load limit is reached, protecting the structure.

Q111: Which factor causes the load factor to increase during cruise flight? ^q111

• A) Higher aircraft weight
• B) Lower air density
• C) A forward centre of gravity
• D) An upward gust

Correct: D)

Explanation: An upward gust suddenly increases the wing's angle of attack, momentarily generating extra lift beyond what is needed for level flight, increasing the load factor above 1.

Q112: In a coordinated level turn, how are load factor (n) and stall speed (Vs) affected compared to straight-and-level flight? ^q112

• A) n < 1 and Vs increases
• B) n > 1 and Vs decreases
• C) n > 1 and Vs increases
• D) n < 1 and Vs decreases

Correct: C)

Explanation: In a banked turn, the lift vector must support both weight and centripetal force, so load factor n = 1/cos(bank) exceeds 1. The higher effective loading raises the stall speed.

Q113: How does the minimum speed in a level turn at 45° bank compare to straight-and-level flight? ^q113

• A) It decreases
• B) It stays the same
• C) It depends on aircraft type
• D) It increases

Correct: D)

Explanation: At 45° bank, n ≈ 1.41. Stall speed increases by √1.41 ≈ 1.19 — roughly 19% higher than in straight flight.

Q114: Why must back pressure be applied to the elevator in a coordinated, altitude-maintaining turn? ^q114

• A) To reduce speed and centrifugal force
• B) To prevent an outward sideslip
• C) To increase lift and balance centrifugal force
• D) To prevent slipping inward

Correct: C)

Explanation: In a level banked turn, the lift vector is tilted. Total lift must exceed weight to provide both vertical support and centripetal force, requiring back pressure to increase the angle of attack.

Q115: How is the balance of forces affected during a turn? ^q115

• A) A lower lift force compensates for a lower net force than in level flight
• B) The horizontal component of lift equals the centrifugal force
• C) The net force results from superposition of gravity and centripetal forces
• D) Lift must be increased to balance the combined centrifugal and gravitational forces

Correct: D)

Explanation: In a banked turn, the pilot must increase total lift above the straight-and-level value. The increased lift must balance both weight (vertical component) and provide centripetal force (horizontal component).

Q116: The speed range authorised for slotted flap use is... ^q116

• A) unlimited
• B) limited at the upper end by the manoeuvring speed VA
• C) limited at the lower end by the bottom of the green arc
• D) stated in the Flight Manual and normally marked on the ASI

Correct: D)

Explanation: The permissible speed range for flap extension varies by aircraft type and is specified in the AFM, normally shown on the ASI as a white or light-green arc.

Q117: In a sideslip, the permitted flap position is... ^q117

• A) flaps fully retracted
• B) specified in the aircraft flight manual
• C) flaps fully extended
• D) dependent on the downward vertical component of airspeed

Correct: B)

Explanation: The permitted flap configuration during a sideslip depends on the specific aircraft and is always specified in the AFM/POH.

Flaps, Washout, and Wing Features

Q118: What happens when flaps are extended, increasing aerofoil camber? ^q118

• A) Maximum permissible speed increases
• B) CG shifts forward
• C) Minimum speed increases
• D) Minimum speed decreases

Correct: D)

Explanation: Extending flaps increases wing camber and raises CLmax. Since Vs = √(2W/(ρ·S·CLmax)), a higher CL_max directly lowers the stall speed.

Q119: The high-lift device shown in the figure, extending rearward and downward from the wing, is a... ^q119

• A) Plain Flap
• B) Split Flap
• C) Slotted Flap
• D) Fowler Flap

Correct: D)

Explanation: A Fowler flap moves rearward and downward, increasing both wing area and camber. It is the most effective type of trailing-edge flap.

Q120: The trailing-edge flap shown in the figure, with a slot channelling air from the lower to upper surface, is a... ^q120

• A) Fowler
• B) Plain Flap
• C) Slotted Flap
• D) Split Flap

Correct: C)

Explanation: A slotted flap has a gap (slot) between the wing and flap that channels high-energy air to the upper surface, energising the boundary layer and delaying separation.

Q121: Extending airbrakes results in... ^q121

• A) less drag and less lift
• B) less drag and more lift
• C) more drag and more lift
• D) more drag and less lift

Correct: D)

Explanation: Airbrakes (spoilers/dive brakes) dramatically increase drag for descent path control and also disrupt upper-surface flow, reducing lift.

Q122: Geometric washout means the wing is physically twisted so that the angle of incidence decreases from root to tip. This is known as... ^q122

• A) V-form
• B) Arrow shape
• C) Aerodynamic washout
• D) Geometric washout

Correct: D)

Explanation: Geometric washout is the physical twist of the wing reducing the angle of incidence from root to tip. This ensures the root stalls first, keeping the ailerons effective.

Q123: When the wing's angle of incidence is greater at the root than at the tip, this is called... ^q123

• A) interference compensation
• B) aspect ratio
• C) geometric twist (washout)
• D) aerodynamic twist

Correct: C)

Explanation: Geometric wing twist (washout) is defined by a decreasing angle of incidence from root to tip, causing the root to stall first.

Q124: Aerodynamic wing twist (washout) involves a modification of... ^q124

• A) the wing dihedral from root to tip
• B) the AoA at the wingtip by means of the aileron
• C) the rigging angle of the same aerofoil from root to tip
• D) the aerofoil profile from root to wingtip

Correct: D)

Explanation: Aerodynamic washout achieves progressive stall behaviour by changing the aerofoil section along the span rather than physically twisting the wing.

Q125: Geometric or aerodynamic wing twist results in... ^q125

• A) a higher cruise speed
• B) simultaneous flow separation along the entire wingspan at low speed
• C) progressive flow separation along the wingspan
• D) partial compensation of adverse yaw at low speed

Correct: C)

Explanation: Wing twist varies the local angle of incidence along the span, so the root stalls first and separation progresses outward, maintaining aileron effectiveness.

Q126: What is a benefit of wing washout? ^q126

• A) It reduces form drag at high speeds
• B) The wing can withstand more torsion forces
• C) At high angles of attack, aileron effectiveness is maintained as long as possible
• D) The wing becomes more structurally rigid against rotation

Correct: C)

Explanation: Because washout ensures the wingtip (where ailerons are located) reaches its critical stall angle later than the root, the ailerons remain effective during the approach to stall.

Q127: What must be considered when operating a sailplane with camber flaps? ^q127

• A) During winch launch, camber must be set to full negative
• B) During approach and landing, camber must not be changed from positive to negative
• C) During approach and landing, camber must not be changed from negative to positive
• D) During winch launch, camber must be set to full positive

Correct: B)

Explanation: Switching from positive camber (increased lift) to negative camber during approach would dramatically reduce lift at a critical moment near the ground — potentially fatal. Positive camber should be maintained throughout the approach.

Glide Performance and Speed Polar

Q128: In steady (stationary) gliding flight, how can the force balance be described? ^q128

• A) The resultant aerodynamic force acts along the direction of airflow
• B) The lift force compensates the drag force
• C) The resultant aerodynamic force acts along with the lift force
• D) The resultant aerodynamic force compensates gravity

Correct: D)

Explanation: In steady gliding flight without thrust, only two forces act: gravity and the total aerodynamic force (lift + drag combined). For equilibrium, the resultant aerodynamic force exactly compensates gravity.

Q129: Which measures can improve the glide ratio of a sailplane? ^q129

• A) Forward CG position, correct speed, taped gaps
• B) Higher mass, thin aerofoil, taped gaps
• C) Cleaning surfaces, correct speed, retractable gear, taping gaps
• D) Lower mass, correct speed, retractable gear

Correct: C)

Explanation: Glide ratio (L/D) is maximised by minimising drag and flying at the optimum speed. Cleaning surfaces, taping gaps, retractable gear, and correct speed all contribute to minimising drag and maximising L/D.

Q130: On the speed polar, which tangent touches the curve at the point of minimum sink rate? ^q130

• A) Tangent (A) — from the origin
• B) Tangent (B) — from a point shifted right on the V axis
• C) Tangent (D) — horizontal line at minimum sink level
• D) Tangent (C) — from a point above the origin on the W axis

Correct: D)

Explanation: On the speed polar, the McCready tangent (C), drawn from a point above the origin on the vertical (W) axis, touches the polar at the point of minimum sink rate. The tangent from the origin gives the best L/D speed.

Q131: When approaching the next thermal, the variometer shows 3 m/s descent and you expect 2 m/s climb in the thermal. How should you set the McCready ring? ^q131

• A) Set the ring to 3 m/s; read the recommended speed at the 2 m/s mark
• B) Set the ring to 0 m/s outside thermals; read the speed at the 3 m/s mark
• C) Set the ring to 2 m/s; read the speed at the sum of sink and climb (5 m/s)
• D) Set the ring to 2 m/s; read the recommended speed at the current sink rate (3 m/s)

Correct: D)

Explanation: The McCready ring is set to the expected climb rate in the next thermal (2 m/s). The pilot reads the recommended inter-thermal cruise speed at the variometer position corresponding to the current sink rate (3 m/s).

Water Ballast

Q132: With water ballast, how do best glide angle and best-glide speed change? ^q132

• A) Best glide angle decreases; best-glide speed decreases
• B) Best glide angle stays the same; best-glide speed increases
• C) Best glide angle increases; best-glide speed increases
• D) Best glide angle stays the same; best-glide speed decreases

Correct: B)

Explanation: Water ballast increases weight, so the aircraft must fly faster to maintain lift — best-glide speed rises. The L/D ratio (and hence best glide angle) is a geometric property of the wing's aerodynamics and remains unchanged.

Q133: What must be considered when operating a sailplane with water ballast? ^q133

• A) The best glide angle decreases significantly
• B) Significant CG shifts are expected
• C) The best-glide speed decreases
• D) The aircraft should remain below the freezing level

Correct: D)

Explanation: Water ballast must stay above freezing to prevent ice forming in the wings, which could jam dump valves, shift the CG unpredictably, and damage the structure.

Engine and TMG Design

Q134: Which engine arrangement on a Touring Motor Glider (TMG) produces the least drag? ^q134

• A) Engine and propeller fixed on the fuselage
• B) Engine and propeller fixed at the nose
• C) Engine and propeller retractable into the fuselage
• D) Engine and propeller fixed at the horizontal stabiliser

Correct: C)

Explanation: A retractable engine and propeller can be folded into the fuselage when not in use, eliminating all associated parasite drag and enabling pure glider performance.

Ground Effect

Q135: What is meant by "ground effect"? ^q135

• A) Both lift and induced drag increase near the ground
• B) Both lift and induced drag decrease near the ground
• C) Lift increases and induced drag decreases near the ground
• D) Lift decreases and induced drag increases near the ground

Correct: C)

Explanation: Within approximately one wingspan of the ground, the surface restricts wingtip vortex development, reducing induced downwash. This increases the effective angle of attack (more lift) while reducing induced drag. Pilots feel this as a floating "cushion" during the landing flare.