### Q76: In a correctly executed turn without altitude loss, why is slight back-pressure on the elevator necessary? ^t80q76 - A) To prevent slipping inward in the turn - B) To reduce speed and therefore centrifugal force - C) To prevent an outward sideslip in the turn - D) To slightly increase lift **Correct: A)** > **Explanation:** In a coordinated turn without altitude loss, back pressure is needed to increase lift and balance centrifugal force (load factor > 1). Lift must compensate for both gravity and centrifugal force. ### Q77: When the frontal area of a disc in an airflow is tripled, drag increases by: ^t80q77 - A) 9 times - B) 1.5 times - C) 3 times - D) 6 times **Correct: B)** > **Explanation:** Stall occurs at a critical angle of attack (stall angle), regardless of airspeed. At this angle, airflow separation on the upper surface causes a sudden drop in lift. ### Q78: Aerodynamic wing twist (washout) is a modification of: ^t80q78 - A) The angle of incidence of the same aerofoil, from root to wing tip - B) The aerofoil profile from root to wing tip - C) The angle of attack at the wing tip by means of the aileron - D) The wing dihedral, from root to tip **Correct: B)** > **Explanation:** Airflow separation occurs at a determined angle of attack (critical angle), specific to each airfoil. It is not related to the nose attitude relative to the horizon. ### Q79: What is the average value of gravitational acceleration at the Earth's surface? ^t80q79 - A) 1013.25 hPa - B) 15° C/100 m - C) 9.81 m/sec² - D) 100 m/sec² **Correct: C)** > **Explanation:** Standard gravitational acceleration at Earth's surface is 9.81 m/s². This is the ISA value used in all performance calculations. ### Q80: The speed displayed on the airspeed indicator (ASI) is a measurement of: ^t80q80 - A) Total pressure in an aneroid capsule - B) The difference between static pressure and total pressure - C) Static pressure around an aneroid capsule - D) The weathervane effect, where pressure decreases **Correct: B)** > **Explanation:** Airspeed indicator reading is based on the difference between static pressure and total pressure (dynamic pressure). The ASI measures this difference via the Pitot tube and static port. ### Q81: The horizontal and vertical stabilisers serve in particular to: ^t80q81 - A) Control the aircraft around its longitudinal axis - B) Reduce the formation of wing tip vortices - C) Stabilise the aircraft in flight - D) Reduce air resistance **Correct: C)** > **Explanation:** The horizontal and vertical stabilizers serve primarily to stabilize the aircraft in flight (longitudinal and directional stability). Without them, the aircraft would be unstable. ### Q82: When slotted flaps are extended, airflow separation: ^t80q82 - A) Occurs at the same speed as before extending the flaps - B) Occurs at a higher speed - C) None of the answers is correct - D) Occurs at a lower speed **Correct: D)** > **Explanation:** When extending slotted flaps, airflow separation occurs at a lower speed, because flaps increase the maximum lift coefficient (CL max). Stall speed decreases. ### Q83: The aerodynamic centre of an aerofoil in an airflow is the point of application of: ^t80q83 - A) The weight - B) The resultant of all pressure forces acting on the aerofoil - C) The tyre pressure on the runway - D) The airflow at the leading edge **Correct: D)** > **Explanation:** The aerodynamic center is the point of application of the resultant of aerodynamic forces on a profile. It is distinct from the center of pressure (which moves) and the center of gravity. ### Q84: Pressures are expressed in: ^t80q84 - A) Pa, psi, g - B) Bar, Pa, m/sec² - C) Bar, psi, Pa - D) Bar, psi, a(Alpha) **Correct: C)** > **Explanation:** Pressures are expressed in bar, psi (pounds per square inch) and Pa (Pascal). g is an acceleration, not a pressure. Alpha (a) is not a pressure unit. ### Q85: TAS (True Air Speed) is the speed of: ^t80q85 - A) The aircraft relative to the ground - B) The aircraft relative to the surrounding air mass - C) The aircraft relative to the air, corrected for wind component and atmospheric pressure - D) The reading on the airspeed indicator (ASI) **Correct: B)** > **Explanation:** TAS (True Air Speed) is the aircraft's speed relative to the surrounding air mass. It is the actual speed through the air, corrected for atmospheric density. ### Q86: Yaw stability of an aircraft is provided by: ^t80q86 - A) Leading edge slats - B) The horizontal stabiliser - C) The fin (vertical stabiliser) - D) Wing dihedral **Correct: C)** > **Explanation:** Yaw stability is provided by the fin (vertical stabilizer/rudder). Wing sweep contributes to roll stability, not yaw. ### Q87: The trailing edge flap shown below is a: ^t80q87 ![[figures/t80_q87.png]] - A) Fowler - B) Split Flap - C) Slotted Flap - D) Plain Flap **Correct: C)** > **Explanation:** The flap shown, extending from the wing with a slot, is a Slotted Flap. The slot channels air from the lower to upper surface, delaying separation. ### Q88: The risk of airflow separation on the wing occurs mainly: ^t80q88 - A) In straight climbing flight at high speed, in atmospheric turbulence - B) In calm air, in gliding flight, at the minimum authorised speed - C) During an abrupt pull-out after a dive - D) In straight level cruise flight, in atmospheric turbulence **Correct: C)** > **Explanation:** The risk of stall/separation appears mainly during an abrupt pull-out after a dive, as the angle of attack increases very rapidly and can exceed the critical angle before the pilot can react. ### Q89: The drag of a body in an airflow depends notably on: ^t80q89 - A) The mass of the body - B) The chemical composition of the body - C) The density of the air - D) The density of the body **Correct: C)** > **Explanation:** Aerodynamic drag depends notably on air density (ρ), since F_D = Cd × 0.5 × ρ × v² × A. The body's own density, chemical composition, and mass do not directly affect aerodynamic drag. ### Q90: In the drawing below, the aerofoil chord is represented by: ^t80q90 ![[figures/t80_q90.png]] - A) M - B) K - C) H - D) A **Correct: C)** > **Explanation:** The chord line is the straight line connecting the leading edge to the trailing edge. In the figure, it is represented by H. ### Q91: The angle of attack of an aerofoil is always measured between: ^t80q91 - A) The chord line and the direction of the relative airflow - B) The longitudinal axis and the general airflow direction - C) The longitudinal axis and the horizon - D) It varies depending on the pilot's weight **Correct: A)** > **Explanation:** The angle of attack (AoA) is defined as the angle between the chord line and the direction of the undisturbed relative airflow, making A correct. Option B is wrong because the longitudinal axis is a structural reference, not an aerodynamic one; AoA is measured from the chord line. Option C confuses AoA with pitch attitude, which relates the longitudinal axis to the horizon. Option D is nonsensical — AoA is a geometric and aerodynamic property entirely independent of the pilot's weight. ### Q92: Given equal frontal area and equal airflow speed, what determines the drag of a body? ^t80q92 - A) Its weight - B) Its density - C) Its shape - D) The position of its centre of gravity **Correct: C)** > **Explanation:** When frontal area and airspeed are held constant, the remaining variable in the drag equation D = CD × 0.5 × rho × V² × S is the drag coefficient CD, which is determined entirely by the body's shape. A streamlined shape produces far less drag than a blunt one. Options A and B are wrong because weight and material density have no direct aerodynamic effect — drag depends on external geometry, not internal mass distribution. Option D is incorrect because the centre of gravity affects stability, not the aerodynamic drag coefficient. ### Q93: What is the origin of induced drag on a wing? ^t80q93 - A) The angle formed at the wing-fuselage junction - B) Airspeed - C) Pressure equalisation from the lower surface toward the upper surface - D) Pressure equalisation from the upper surface toward the lower surface **Correct: C)** > **Explanation:** Induced drag originates from the pressure difference between the lower (high pressure) and upper (low pressure) wing surfaces. At the wingtips, air flows from the high-pressure lower surface around to the low-pressure upper surface, forming trailing vortices that tilt the lift vector rearward, creating induced drag. Option D reverses the flow direction — air moves from high to low pressure, not the other way. Option A describes interference drag at the wing root, and option B is too vague — airspeed alone is not the origin of induced drag. ### Q94: What is the sea-level pressure in the ICAO standard atmosphere? ^t80q94 - A) 29.92 hPa - B) 1012.35 hPa - C) 1013.25 hPa - D) It depends on latitude **Correct: C)** > **Explanation:** The ICAO International Standard Atmosphere defines sea-level pressure as exactly 1013.25 hPa (hectopascals). Option A gives 29.92, which is the equivalent value in inches of mercury (inHg), not hPa — 29.92 hPa would be an absurdly low pressure. Option B (1012.35 hPa) is simply incorrect. Option D is wrong because the ISA is a standardized model that does not vary with latitude, even though real atmospheric pressure does. ### Q95: In the aerofoil diagram below, which line represents the mean camber line? ^t80q95 ![[figures/t80_q95.png]] - A) H - B) B - C) G + J - D) A **Correct: B)** > **Explanation:** The mean camber line is the locus of points equidistant between the upper and lower surfaces of the aerofoil, representing the profile's curvature. In this diagram, line B corresponds to this curved reference line. Options A, C, and D represent other aerofoil features such as the chord line, thickness distribution, or surface contours, not the mean camber line. ### Q96: In a level turn without sideslip or altitude loss, why is back pressure on the elevator necessary? ^t80q96 - A) To prevent an inward slip during the turn - B) To slow down and reduce centrifugal force - C) To prevent an outward skid during the turn - D) To increase lift so it balances both weight and centrifugal force **Correct: D)** > **Explanation:** In a banked turn at constant altitude, the load factor exceeds 1 because lift must counterbalance both the aircraft's weight and provide the centripetal force for the curved flight path. Back pressure on the elevator increases the angle of attack and thus total lift to meet this requirement. Option A is wrong because slips are corrected with rudder, not elevator. Option B is incorrect — the purpose is not to slow down. Option C is also wrong because skid prevention is a rudder function, not an elevator function. ### Q97: A wing stall occurs: ^t80q97 - A) At the red radial line on the airspeed indicator - B) When a critical angle of attack is exceeded - C) Following a reduction in engine power - D) Only when the nose is pitched excessively above the horizon **Correct: B)** > **Explanation:** A stall occurs when the wing's angle of attack exceeds the critical value (typically around 15-18 degrees), causing flow separation from the upper surface and a sudden loss of lift. This is a fundamental aerodynamic principle independent of airspeed or attitude. Option A is wrong because the red line (VNE) relates to structural speed limits, not stall. Option C is incorrect — reducing power alone does not cause a stall if AoA remains below critical. Option D is false because a stall can occur at any pitch attitude or airspeed, as long as the critical AoA is exceeded. ### Q98: At what condition does airflow separation from an aerofoil occur? ^t80q98 - A) Only at a specific aircraft altitude - B) Only at a given nose position relative to the horizon - C) Simultaneously across the entire span - D) At a specific angle of attack **Correct: D)** > **Explanation:** Airflow separation occurs when the angle of attack reaches the critical stall angle, which is a fixed aerodynamic property of the aerofoil shape. Option A is wrong because stall AoA is independent of altitude. Option B confuses pitch attitude with angle of attack — a wing can stall at any nose position. Option C is incorrect because, thanks to wing design features like washout, the stall typically progresses from root to tip rather than occurring simultaneously across the entire span. ### Q99: What is the mean gravitational acceleration at the surface of the Earth? ^t80q99 - A) 9.81 m/sec2 - B) 100 m/sec2 - C) 1013.5 hPa - D) 15° C/100 m **Correct: A)** > **Explanation:** The standard gravitational acceleration at sea level is 9.81 m/s², used throughout aviation for weight, load factor, and performance calculations. Option B (100 m/s²) is roughly ten times too large. Option C (1013.5 hPa) is a pressure value close to the ISA sea-level pressure, not an acceleration. Option D (15°C/100 m) resembles a temperature lapse rate format but is far too high — the ISA lapse rate is 0.65°C per 100 m. ### Q100: True Airspeed (TAS) is obtained from the airspeed indicator (ASI) reading by: ^t80q100 - A) No corrections at all - B) Correcting for position and instrument errors - C) Applying corrections for both position/instrument errors and atmospheric density - D) Adjusting for atmospheric density alone **Correct: C)** > **Explanation:** TAS is derived from the ASI reading (IAS) through two successive corrections: first, position and instrument errors are removed to obtain calibrated airspeed (CAS), then a density correction accounts for the difference between actual air density and ISA sea-level density. Option A is wrong because uncorrected IAS does not equal TAS. Option B yields only CAS, not TAS. Option D omits the instrument/position error correction, which is always the first step.