### Q31: True altitude is defined as... ^t20q31 - A) A height above ground level corrected for non-standard pressure. - B) A pressure altitude corrected for non-standard temperature. - C) An altitude above mean sea level corrected for non-standard temperature. - D) A height above ground level corrected for non-standard temperature. **Correct: C)** > **Explanation:** True altitude is the actual vertical distance of an aircraft above mean sea level (MSL), corrected for deviations from ISA standard temperature. It represents the real geometric height above sea level. A and D are wrong because true altitude is referenced to MSL, not to ground level (AGL). B is partially correct in mentioning the temperature correction applied to pressure altitude, but it omits the crucial MSL reference. C correctly states both the MSL reference and the temperature correction. ### Q32: When flying in air colder than ISA, the indicated altitude is... ^t20q32 - A) Equal to the standard altitude. - B) Lower than the true altitude. - C) Equal to the true altitude. - D) Higher than the true altitude. **Correct: D)** > **Explanation:** In cold air (colder than ISA), the atmosphere is denser and pressure decreases more rapidly with altitude than the ISA model predicts. The altimeter, calibrated to ISA, over-reads in cold air, indicating a higher altitude than the aircraft's actual (true) altitude. The aircraft is therefore lower than the altimeter shows, which is a significant safety concern near terrain. The memory aid is "Cold air, you're lower than you think." A and C are incorrect. B reverses the relationship. ### Q33: When flying in an air mass at ISA temperature with the correct QNH set, the indicated altitude is... ^t20q33 - A) Lower than the true altitude. - B) Higher than the true altitude. - C) Equal to the true altitude. - D) Equal to the standard atmosphere. **Correct: C)** > **Explanation:** When both the actual atmospheric pressure (set correctly via QNH) and actual temperature match ISA standard conditions exactly, the altimeter's assumptions are perfectly valid and no correction errors exist. The indicated altitude therefore equals the true altitude. This is the ideal baseline condition. A and B describe error situations that occur only when temperature or pressure deviates from ISA. D is vague and does not accurately describe the relationship between indicated and true altitude. ### Q34: Which instrument is susceptible to hysteresis error? ^t20q34 - A) Vertical speed indicator. - B) Direct reading compass. - C) Altimeter. - D) Tachometer. **Correct: C)** > **Explanation:** Hysteresis error affects the altimeter because its aneroid capsules (elastic metal bellows) have a slight mechanical lag. After expansion or contraction due to pressure changes, they do not return to exactly the same position when pressure returns to a previous value. This means the altimeter may show slightly different readings at the same altitude depending on whether the aircraft is climbing or descending. A (VSI), B (compass), and D (tachometer) do not use the same type of elastic aneroid capsules and are not subject to this specific error. ### Q35: Altitude measurement relies on changes in which type of pressure? ^t20q35 - A) Total pressure. - B) Differential pressure. - C) Static pressure. - D) Dynamic pressure. **Correct: C)** > **Explanation:** The altimeter measures altitude by detecting changes in static pressure, which decreases predictably with increasing altitude according to the ISA model. Static pressure is sensed through the aircraft's static ports and fed to the altimeter's aneroid capsules. A (total pressure) is static plus dynamic pressure, measured by the Pitot tube for airspeed. B (differential pressure) is the difference between total and static pressure, which drives the airspeed indicator. D (dynamic pressure) depends on airspeed, not altitude. ### Q36: How does a vertical speed indicator work? ^t20q36 - A) It measures total air pressure and compares it to static pressure. - B) It compares the current static air pressure against the static pressure stored in a reservoir. - C) It measures vertical acceleration using a gimbal-mounted mass. - D) It measures static air pressure and compares it against a vacuum. **Correct: B)** > **Explanation:** The VSI works by comparing current static pressure (from the static port) against a reference pressure stored in a sealed reservoir connected through a calibrated leak. When climbing, static pressure drops faster than the reservoir bleeds down, creating a pressure difference that indicates the climb rate. When descending, the reverse happens. A describes the airspeed indicator's operating principle. C describes an accelerometer. D describes a simple barometer, not a rate-of-change instrument. ### Q37: The vertical speed indicator compares the pressure difference between... ^t20q37 - A) The current dynamic pressure and the dynamic pressure from a moment earlier. - B) The current static pressure and the static pressure from a moment earlier. - C) The current total pressure and the total pressure from a moment earlier. - D) The current dynamic pressure and the static pressure from a moment earlier. **Correct: B)** > **Explanation:** The VSI compares the current ambient static pressure (which changes as altitude changes) with the static pressure from a short time ago, stored in a metering reservoir through a calibrated restriction. The rate at which this pressure difference changes indicates the rate of climb or descent. A and D involve dynamic pressure, which is unrelated to the VSI's operation. C involves total pressure, which is the Pitot tube measurement used by the airspeed indicator, not the VSI. ### Q38: An aircraft flies on a heading of 180° at 100 kt TAS. The wind blows from 180° at 30 kt. Ignoring instrument and position errors, what will the airspeed indicator approximately show? ^t20q38 - A) 70 kt - B) 130 kt - C) 30 kt - D) 100 kt **Correct: D)** > **Explanation:** The airspeed indicator measures the aircraft's speed relative to the surrounding air mass, not relative to the ground. Since the aircraft is flying at 100 kt TAS through the air, the ASI will show approximately 100 kt regardless of the wind. The 30 kt headwind from 180 degrees affects ground speed (which would be 130 kt with a tailwind or 70 kt with a headwind) but has no effect on the indicated airspeed. A (70 kt) and B (130 kt) are ground speed values. C (30 kt) is the wind speed alone. ### Q39: What principle does the airspeed indicator use to determine speed? ^t20q39 - A) Static air pressure is measured and compared against a vacuum. - B) Dynamic air pressure is sensed by the Pitot tube and converted directly into a speed reading. - C) Total air pressure is sensed by the static ports and converted into speed. - D) Total air pressure is compared against static air pressure. **Correct: D)** > **Explanation:** The ASI works by comparing total pressure (from the Pitot tube) against static pressure (from the static port). The difference between them is dynamic pressure (q = 1/2 rho v squared), which is proportional to airspeed squared. A diaphragm inside the ASI expands in proportion to this pressure difference, driving the needle. A describes a barometer. B is incorrect because the Pitot tube measures total pressure, not dynamic pressure directly. C is wrong because total pressure comes from the Pitot tube, not the static ports. ### Q40: Red lines on instrument displays typically mark which values? ^t20q40 - A) Recommended operating ranges. - B) Caution areas. - C) Operational limits. - D) Normal operating areas. **Correct: C)** > **Explanation:** Red lines (radial marks) on aircraft instrument displays indicate never-exceed operational limits -- the absolute boundaries that must not be exceeded. On the ASI, the red line marks VNE (never-exceed speed). On engine instruments, red lines mark maximum RPM, temperature, or pressure limits. A (recommended ranges) and D (normal operating areas) are shown by green arcs. B (caution areas) are indicated by yellow arcs. C correctly identifies the meaning of red lines. ### Q41: To determine indicated airspeed (IAS), the airspeed indicator requires... ^t20q41 - A) The difference between total pressure and dynamic pressure. - B) The difference between total pressure and static pressure. - C) The difference between standard pressure and total pressure. - D) The difference between dynamic pressure and static pressure. **Correct: B)** > **Explanation:** IAS is determined from the difference between total pressure (from the Pitot tube) and static pressure (from the static port). This difference equals dynamic pressure (q = 1/2 rho v squared), which the ASI converts into an airspeed reading. A (total minus dynamic) would yield static pressure, which is not useful for airspeed. C (standard minus total) has no aerodynamic significance for speed measurement. D (dynamic minus static) is not a physically meaningful quantity in this context because dynamic pressure is itself derived from the total-minus-static calculation. ### Q42: What does the red line on an airspeed indicator represent? ^t20q42 - A) A speed limit in turbulent conditions. - B) The maximum speed with flaps deployed. - C) A speed that must never be exceeded under any circumstances. - D) The maximum speed in turns exceeding 45 degrees bank. **Correct: C)** > **Explanation:** The red line on the ASI marks VNE (Velocity Never Exceed), the absolute structural speed limit that must not be exceeded under any circumstances, even in smooth air. Exceeding VNE risks catastrophic flutter, structural failure, or loss of control. A describes the caution range (yellow arc) where flight is restricted to smooth air. B describes VFE (flap extension speed), typically marked by the top of the white arc. D describes no standard ASI marking; maneuvering speed (VA) is related to structural limits in turns but is not marked with a colour on the ASI. ### Q43: The compass error produced by the aircraft's own magnetic field is known as... ^t20q43 - A) Variation. - B) Deviation. - C) Declination. - D) Inclination. **Correct: B)** > **Explanation:** Deviation is the compass error caused by the aircraft's own magnetic fields, produced by metallic structures, electrical equipment, and engines. It varies with heading and is recorded on a deviation card in the cockpit. A (variation) and C (declination) both refer to the angular difference between true north and magnetic north, caused by the Earth's magnetic field -- not by the aircraft. D (inclination) is the vertical dip of the Earth's magnetic field, which causes turning and acceleration errors in the compass but is not caused by the aircraft. ### Q44: What errors cause a magnetic compass to deviate from magnetic north? ^t20q44 - A) Variation, turning errors, and acceleration errors. - B) Gravity and magnetism. - C) Inclination and declination of the earth's magnetic field. - D) Deviation, turning errors, and acceleration errors. **Correct: D)** > **Explanation:** The magnetic compass is affected by three main error sources: deviation (from the aircraft's own magnetic field), turning errors (caused by the vertical component of the Earth's magnetic field tilting the compass card during turns), and acceleration errors (false readings during speed changes on east/west headings). A is incorrect because variation (the geographic difference between true and magnetic north) is a known chartable quantity applied to navigation, not an error in the compass itself. B is too vague. C lists Earth field properties but not the instrument-specific errors. ### Q45: Which cockpit instrument receives input from the Pitot tube? ^t20q45 - A) Altimeter. - B) Direct-reading compass. - C) Airspeed indicator. - D) Vertical speed indicator. **Correct: C)** > **Explanation:** The airspeed indicator is the only instrument connected to the Pitot tube, receiving total pressure to determine airspeed by comparing it with static pressure. A (altimeter) and D (vertical speed indicator) are connected only to the static port, measuring changes in static pressure for altitude and climb/descent rate respectively. B (direct-reading compass) is a self-contained magnetic instrument with no connection to the Pitot-static system whatsoever. ### Q46: An aircraft in the northern hemisphere turns from 270 degrees to 360 degrees via the shortest route. At roughly what compass indication should the pilot stop the turn? ^t20q46 - A) 360 degrees - B) 030 degrees - C) 330 degrees - D) 270 degrees **Correct: C)** > **Explanation:** The shortest route from 270 degrees to 360 degrees is a right turn through north. In the northern hemisphere, the compass leads (reads ahead of actual heading) when turning toward north due to the dip of the Earth's magnetic field. The pilot must therefore stop the turn before the compass reaches the target heading. Using the rule of thumb to stop approximately 30 degrees early: 360 minus 30 = 330 degrees. A (360 degrees) would result in overshooting past the target. B (030 degrees) represents the overshoot itself. D (270 degrees) is the starting heading. ### Q47: Which instruments receive static pressure from the static port? ^t20q47 - A) Altimeter, vertical speed indicator, and airspeed indicator. - B) Airspeed indicator, direct-reading compass, and slip indicator. - C) Altimeter, slip indicator, and navigational computer. - D) Airspeed indicator, altimeter, and direct-reading compass. **Correct: A)** > **Explanation:** Three instruments receive static pressure from the static port: the altimeter (converts static pressure to altitude), the vertical speed indicator (compares current static pressure to a stored reference to determine climb/descent rate), and the airspeed indicator (uses static pressure together with Pitot total pressure to derive dynamic pressure and thus airspeed). B, C, and D include instruments that do not use static pressure, such as the direct-reading compass (magnetic, no pneumatic input) and the slip indicator (gravity/inertia-based). ### Q48: An aircraft in the northern hemisphere turns from 360 degrees to 270 degrees via the shortest route. At approximately what compass reading should the turn be stopped? ^t20q48 - A) 300 degrees - B) 240 degrees - C) 360 degrees - D) 270 degrees **Correct: D)** > **Explanation:** The shortest turn from 360 degrees to 270 degrees is a left turn through west. When turning away from north toward west (270 degrees), the compass turning error is minimal at the westerly heading because the error is greatest on northerly and southerly headings and nearly zero on easterly and westerly headings. Therefore, the pilot should stop the turn approximately when the compass reads 270 degrees, as the compass indication is relatively accurate at this heading. A (300 degrees) would stop too early. B (240 degrees) would overshoot significantly. C (360 degrees) is the starting heading. ### Q49: Static pressure is defined as the pressure... ^t20q49 - A) Sensed by the Pitot tube. - B) Inside the aircraft cabin. - C) Of undisturbed airflow. - D) Produced by orderly movement of air particles. **Correct: C)** > **Explanation:** Static pressure is the ambient atmospheric pressure of undisturbed air, exerted equally in all directions by air molecules regardless of any airflow velocity. It is measured by flush static ports on the fuselage, positioned to minimise the influence of local aerodynamic effects. A is wrong because the Pitot tube senses total pressure (static plus dynamic). B (cabin pressure) is a separate, often regulated, pressure environment inside the aircraft. D describes laminar flow characteristics, not static pressure. ### Q50: An aircraft in the northern hemisphere turns from 030 degrees to 180 degrees via the shortest route. At approximately what compass heading should the turn be ended? ^t20q50 - A) 180 degrees - B) 210 degrees - C) 360 degrees - D) 150 degrees **Correct: B)** > **Explanation:** The shortest turn from 030 degrees to 180 degrees is a right turn through east and south. When turning toward southerly headings in the northern hemisphere, the compass lags behind the actual heading, reading less than the aircraft has actually turned. Therefore, the pilot must overshoot -- continuing the turn past the target heading on the compass. The rule of thumb is to add approximately 30 degrees to the target: 180 + 30 = 210 degrees. The compass will show 210 degrees when the aircraft is actually on approximately 180 degrees. A (180 degrees) would stop too early. C (360 degrees) and D (150 degrees) are incorrect stopping points. ### Q51: Which glider cockpit lever is painted red? ^t20q51 - A) Wheel brake. - B) Landing gear lever. - C) Ventilation control. - D) Emergency canopy release. **Correct: D)** > **Explanation:** In gliders, the EASA colour-coding convention assigns red to the emergency canopy release lever. Red is the universal warning colour, reserved for the most critical safety control that allows rapid pilot egress from the aircraft in an emergency. A (wheel brake), B (landing gear lever), and C (ventilation control) are not assigned the red colour under glider cockpit standardisation. ### Q52: During winter maintenance, you notice honeycomb elements inside the fuselage. What construction category does this glider belong to? ^t20q52 - A) Metal construction. - B) Wood combined with other materials. - C) Composite construction. - D) Biplane construction. **Correct: C)** > **Explanation:** Honeycomb elements are a hallmark of modern composite construction, where a lightweight honeycomb core (aluminium or Nomex) is sandwiched between composite face sheets (glass fiber or carbon fiber) to create panels with excellent stiffness-to-weight ratios. This sandwich construction technique is standard in modern high-performance gliders. A (metal construction) does not typically feature honeycomb sandwich panels in gliders. B (wood combined) would use plywood or fabric, not honeycomb. D (biplane) describes a wing configuration, not a construction method. ### Q53: The Discus B has its horizontal stabilizer mounted at the top of the fin. What type of tail configuration is this? ^t20q53 - A) V-tail. - B) Cruciform tail. - C) T-tail. - D) Pendulum cruciform tail. **Correct: C)** > **Explanation:** When the horizontal stabilizer is mounted at the top of the vertical fin, the configuration forms the shape of the letter "T" when viewed from the front, hence the name T-tail. This is a common configuration on modern gliders like the Discus B because it places the horizontal stabilizer above the wing wake, providing more effective pitch control and reduced buffeting. A (V-tail) combines horizontal and vertical surfaces into two angled panels. B (cruciform tail) places the horizontal stabilizer at mid-height on the fin. D (pendulum cruciform tail) is a free-floating stabilizer variant. ### Q54: What is the role of the fixed vertical fin and fixed horizontal stabilizer on a glider's tail? ^t20q54 - A) To trim the glider. - B) To steer the glider. - C) To stabilize the glider. - D) To trim the control forces for a desired flight condition. **Correct: C)** > **Explanation:** The fixed stabilizers of the tail assembly provide static stability, automatically restoring the aircraft to its equilibrium attitude after disturbances such as gusts. The horizontal stabilizer provides pitch stability (longitudinal) and the vertical fin provides yaw stability (directional). A and D describe the function of the trim system, not the fixed stabilizers. B (steering) is accomplished by the movable control surfaces (elevator and rudder), not the fixed stabilizers themselves. ### Q55: During winter maintenance, the equipment officer explains the CG-mounted tow hook mechanism. Why must it release the cable automatically? ^t20q55 - A) To relieve the pilot from releasing the cable during a winch launch. - B) To prevent danger if the glider flies too long near the ground during the winch launch takeoff roll. - C) To prevent danger when the glider climbs too high during aero-tow. - D) It is a safety measure -- the hook must release automatically when the glider risks flying over the winch. **Correct: D)** > **Explanation:** The CG-mounted tow hook must automatically release the cable when the glider approaches the winch and risks flying directly over it. At that point, the cable angle becomes nearly vertical, and if the cable remains attached, the abrupt change in pull direction can cause a dangerous and uncontrollable nose-down pitch. The automatic release prevents this potentially fatal scenario. A is incorrect because the pilot still has the primary responsibility to release. B describes a different phase of the launch. C describes an aero-tow scenario, not winch launching. ### Q56: Aileron deflection produces rotation around which axis? ^t20q56 - A) The yaw axis. - B) The lateral axis. - C) The vertical axis. - D) The longitudinal axis. **Correct: D)** > **Explanation:** Ailerons control roll, which is rotation around the longitudinal axis (the axis running from nose to tail through the centre of gravity). Deflecting ailerons creates differential lift between the two wings, causing the aircraft to bank. B (lateral axis) is the pitch axis, controlled by the elevator. A (yaw axis) and C (vertical axis) refer to the same axis, controlled by the rudder. Note that ailerons produce a secondary yaw effect (adverse yaw), but the primary motion is roll around the longitudinal axis. ### Q57: When the control stick is moved to the left, what happens? ^t20q57 - A) Both ailerons move upward. - B) The left aileron goes up and the right aileron goes down. - C) Both ailerons move downward. - D) The left aileron goes down and the right aileron goes up. **Correct: D)** > **Explanation:** Moving the stick to the left initiates a left roll. The left aileron deflects downward (increasing lift on the left wing, pushing it up) while the right aileron deflects upward (reducing lift on the right wing, allowing it to drop). This differential creates a rolling moment toward the left. B reverses the correct aileron positions. A and C describe both ailerons moving in the same direction, which would not produce roll but would change overall lift symmetrically. ### Q58: In mechanical brake systems, how is the braking force transmitted from the pedals or handles to the brake shoes? ^t20q58 - A) Through electric motors. - B) Through hydraulic lines. - C) Through pneumatic lines. - D) Through cables and pushrods. **Correct: D)** > **Explanation:** Mechanical brake systems in gliders use a direct mechanical linkage of cables and pushrods to transmit braking force from the cockpit controls to the brake shoes on the wheel. This system is simple, lightweight, and reliable, with no fluid or electrical components. A (electric motors) are not used in standard glider brake systems. B (hydraulic lines) are used on heavier aircraft where greater braking force is required. C (pneumatic lines) are used in some large transport aircraft but not in gliders. ### Q59: The flight manual states that the glider has balanced control surfaces. What is the main reason for this design? ^t20q59 - A) Better turning characteristics. - B) Harmonious coordination of controls. - C) Elimination of flutter. - D) Reduction of the force needed to move the controls. **Correct: C)** > **Explanation:** Mass-balanced control surfaces are designed primarily to prevent flutter, a potentially catastrophic aeroelastic oscillation that can occur at high speeds. By placing counterweights ahead of the hinge axis, the manufacturer moves the centre of gravity of each control surface to coincide with its pivot point, breaking the coupling between aerodynamic forces and structural vibration that causes flutter. A (turning characteristics) and B (control harmony) are not the primary reasons for mass balancing. D (force reduction) is a secondary benefit of aerodynamic balancing, not mass balancing. ### Q60: Why are there small holes on the fuselage sides connected to internal flexible tubes? ^t20q60 - A) They serve as static pressure ports for the instruments. - B) They are used to measure outside air temperature. - C) They equalize pressure between the fuselage interior and exterior. - D) They prevent excess humidity inside the glider in cold weather. **Correct: A)** > **Explanation:** The small flush-mounted orifices on the fuselage sides are the static pressure ports of the Pitot-static system. They sense the ambient atmospheric (static) pressure and route it via internal flexible tubing to the altimeter, variometer, and airspeed indicator. Their position on the fuselage is carefully chosen to minimise local aerodynamic disturbances that could cause pressure errors. B (temperature measurement) uses separate probes. C (pressure equalisation) and D (humidity prevention) are not functions of these ports.