### Q26: QFE refers to the... ^t20q26 - A) Barometric pressure corrected to sea level using the international standard atmosphere (ISA). - B) Altitude referenced to the 1013.25 hPa pressure level. - C) Barometric pressure at a reference datum, typically the runway threshold of an airfield. - D) Magnetic bearing to a station. **Correct: C)** > **Explanation:** QFE is the atmospheric pressure at a specific reference point, typically the runway threshold. Setting QFE on the altimeter causes it to read zero on the ground at the aerodrome, showing height above the field during flight. Option A describes QNH (sea level corrected pressure). Option B describes the flight level datum (1013.25 hPa). Option D describes QDM/QDR radio navigation terminology. ### Q27: What is the function of the altimeter subscale? ^t20q27 - A) To correct the altimeter for instrument system errors. - B) To set the reference datum for the transponder altitude encoder. - C) To reference the altimeter reading to a chosen level such as mean sea level, aerodrome elevation, or the 1013.25 hPa pressure surface. - D) To compensate the altimeter reading for non-standard temperatures. **Correct: C)** > **Explanation:** The altimeter subscale (Kollsman window) lets the pilot set a reference pressure: QNH for altitude above sea level, QFE for height above the airfield, or 1013.25 hPa for flight levels. Option A (system errors) requires calibration, not subscale adjustment. Option B (transponder encoder) operates on standard pressure independently. Option D (temperature correction) requires a separate mathematical calculation. ### Q28: How can an altimeter subscale set to an incorrect QNH lead to a dangerous altimeter error? ^t20q28 - A) Setting a lower pressure than actual causes the reading to be too low, meaning greater height above ground than intended. - B) Setting a lower pressure than actual causes the reading to be too high, bringing the aircraft closer to the ground than indicated. - C) Setting a higher pressure than actual causes the reading to be too high, bringing the aircraft closer to the ground than indicated. - D) Setting a higher pressure than actual causes the reading to be too low, meaning greater height above ground than intended. **Correct: C)** > **Explanation:** Setting a higher pressure than actual QNH causes the altimeter to over-read -- it shows a higher altitude than the aircraft's true position. The aircraft is actually closer to the ground than indicated, creating a dangerous terrain clearance illusion. The memory aid: "High to Low, look out below." Options A and B incorrectly describe the effect of a low pressure setting. Option D reverses the consequence of a high setting. ### Q29: A temperature lower than the ISA standard may cause... ^t20q29 - A) An altitude reading that is too high. - B) A correct altitude reading provided the subscale is set for non-standard temperature. - C) An altitude reading that is too low. - D) Pitot tube icing that freezes the altimeter at its current value. **Correct: A)** > **Explanation:** In colder-than-standard air, the atmosphere is denser and pressure drops faster with altitude than ISA assumes. The altimeter over-reads, indicating a higher altitude than the aircraft's actual position -- the pilot is lower than they think. "Cold air = lower than you think." Option B is wrong because altimeter subscales cannot correct for temperature. Option C reverses the error. Option D describes an icing issue separate from temperature-induced altimeter error. ### Q30: A flight level is a... ^t20q30 - A) True altitude. - B) Pressure altitude. - C) Density altitude. - D) Altitude above the ground. **Correct: B)** > **Explanation:** A flight level is a pressure altitude expressed in hundreds of feet with the altimeter set to 1013.25 hPa (standard pressure). FL100 = 10,000 ft on standard setting. All aircraft above the transition altitude use this common datum for vertical separation regardless of local pressure variations. Option A (true altitude) is actual MSL height. Option C (density altitude) is a performance calculation parameter. Option D (above ground) is height AGL. ### 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 geometric height of the aircraft above mean sea level (MSL), obtained by correcting indicated altitude for deviations from the ISA temperature profile. The altimeter assumes standard ISA conditions; when actual temperature differs, the indicated reading diverges from the real MSL height. A and D are wrong because true altitude is referenced to MSL, not above ground level (AGL). B mentions temperature correction but is imprecise — true altitude is the actual MSL height, not merely a pressure altitude with a temperature factor applied. Only C correctly defines true altitude. --- ### 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 colder-than-ISA air the atmosphere is denser, so pressure decreases more rapidly with altitude than the altimeter assumes. The altimeter therefore over-reads and shows a higher value than the aircraft's actual MSL height — the aircraft is physically lower than the instrument indicates. This is a serious terrain clearance hazard, summarized by the memory aid "High to low (temperature), look out below." B states the opposite of what occurs. A and C only apply under exact ISA conditions. Only D is correct. --- ### 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:** The altimeter is calibrated to the ISA standard temperature lapse rate. When the actual temperature exactly matches ISA and the correct QNH is set, all instrument assumptions are perfectly met and no error exists — indicated altitude equals true altitude. This is the ideal baseline condition from which deviations introduce errors. A and B describe situations with non-standard temperature or pressure. D is vague and not a meaningful statement about the altimeter reading. Only C is correct. --- ### 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 — thin elastic bellows that expand and contract with pressure changes — do not return to exactly the same position when pressure is restored to a previously experienced value. This mechanical lag means the altimeter may show slightly different readings at the same altitude when climbing versus descending. A (VSI), B (compass), and D (tachometer) do not rely on elastic aneroid capsules for their primary measurement and are therefore not subject to this specific error. Only C is correct. --- ### 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:** Static pressure is the ambient atmospheric pressure that decreases predictably with altitude according to the ISA model. The altimeter senses this pressure via the static port and converts it to an altitude reading using calibrated aneroid capsules. A (total pressure) equals static plus dynamic and is measured by the Pitot tube for airspeed. B (differential pressure) is the difference between total and static, which drives the ASI. D (dynamic pressure) depends on airspeed and has no role in altitude measurement. Only C is correct. --- ### 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 detects rate of climb or descent by comparing current static pressure (from the static port) against a reference pressure stored in an internal reservoir that communicates via a calibrated leak. When climbing, static pressure drops faster than the reservoir can equalize, creating a pressure difference that deflects the pointer proportional to climb rate. A describes the ASI operating principle (total minus static = dynamic). C describes an accelerometer. D describes a barometer, which cannot indicate a rate of change. Only B correctly explains VSI operation. --- ### 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 senses only static pressure, which changes as altitude changes. It compares the instantaneous static pressure arriving through the static port with the slightly delayed static pressure stored in the metering reservoir behind the calibrated restriction. The rate of pressure change indicates the rate of altitude change. A, C, and D all involve dynamic or total pressure, which are Pitot-tube quantities used for airspeed measurement and play no role in the VSI. Only B is correct. --- ### 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 ASI measures the aircraft's speed relative to the surrounding air mass, not relative to the ground. The aircraft moves through the air at 100 kt TAS, so the ASI shows 100 kt regardless of wind. A wind from 180° on a heading of 180° is a headwind, reducing ground speed to 70 kt — that is A, but ground speed is not what the ASI reads. B (130 kt) would only apply with a 30 kt tailwind. C (30 kt) is merely the wind speed, irrelevant to the ASI. Only D is correct. --- ### 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 compares total pressure from the Pitot tube (which captures all air pressure including the motion component) against static pressure from the static port (ambient pressure only). The difference is dynamic pressure (q = ½ρv²), proportional to airspeed squared — the expanding capsule converts this into an IAS reading. A describes a simple barometer. B is incorrect because the Pitot tube measures total pressure, not pure dynamic pressure. C wrongly attributes total pressure measurement to the static ports. Only D correctly describes ASI operation. --- ### 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 radial marks on aircraft instruments indicate absolute operational limits that must never be exceeded — such as VNE (never-exceed speed) on the ASI. These represent structural or aerodynamic boundaries beyond which catastrophic failure or loss of control may occur. B (caution areas) are indicated by yellow arcs, covering the speed range between maneuvering speed and VNE where smooth air is required. D (normal operating range) is shown by a green arc. A ("recommended operating ranges") is not a standard instrument marking. Only C correctly defines the red line. --- ### 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 derived from dynamic pressure, which equals total pressure (Pitot tube) minus static pressure (static port). The ASI capsule deflects in proportion to this pressure difference and the needle indicates IAS. A (total minus dynamic) would yield static pressure alone — not useful for airspeed. C (standard minus total) has no aerodynamic significance for airspeed. D (dynamic minus static) is not a meaningful Pitot-static quantity since dynamic pressure is not independently measured at a single port. Only B is correct. --- ### 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° bank. **Correct: C)** > **Explanation:** The red line marks VNE — Velocity Never Exceed — the absolute structural speed limit that must not be exceeded under any circumstances, including smooth air. Beyond VNE, the risk of aeroelastic flutter or catastrophic structural failure is unacceptable. A describes the upper boundary of the yellow arc (caution range), where turbulence must be avoided. B describes VFE (flap extension speed), marked by the top of the white arc. D does not correspond to any standard ASI color marking. Only C is correct. --- ### 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 — from steel structures, electrical wiring, and electronic equipment on board. It varies with the aircraft's heading and is tabulated on the compass deviation card after a compass swing. A (variation) and C (declination) are two names for the same geographic phenomenon: the angle between true north and magnetic north at any given location on Earth — this is not caused by the aircraft. D (inclination) refers to the vertical dip angle of Earth's magnetic field, which causes turning and acceleration errors. Only B is correct. --- ### 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:** Three instrument errors cause the magnetic compass to deviate from magnetic north: deviation (from the aircraft's own magnetic fields), turning errors (the compass card tilts due to magnetic dip during turns, especially on northerly/southerly headings), and acceleration errors (speed changes on easterly/westerly headings produce false readings due to the same dip effect). A incorrectly includes variation, which is a geographic property of Earth, not an instrument error. B is too vague. C lists physical properties of Earth's field rather than specific instrument errors. Only D correctly names all three. --- ### 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:** Only the airspeed indicator is connected to the Pitot tube, which supplies total pressure as one of the two inputs needed to compute IAS. A (altimeter) and D (VSI) are connected only to the static port — they measure changes in static pressure for altitude and climb/descent rate. B (direct-reading compass) is a self-contained magnetic instrument with no connection to the Pitot-static system. Only C is correct. --- ### Q46: An aircraft in the northern hemisphere turns from 270° to 360° via the shortest route. At roughly what compass indication should the pilot stop the turn? ^t20q46 - A) 360° - B) 030° - C) 330° - D) 270° **Correct: C)** > **Explanation:** The shortest turn from 270° to 360° is a right turn through northwest toward north. In the northern hemisphere, magnetic dip causes the compass to lead (read ahead of the actual heading) when turning toward north, so the pilot must stop early — before the compass reaches 360°. The rule of thumb is to stop approximately 30° before the target when turning to north: 360° − 30° = 330°. Waiting until the compass shows 360° (A) results in overshooting to approximately 030° (B). D (270°) is the starting heading. Only C is correct. --- ### 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:** All three Pitot-static instruments receive static pressure: the altimeter (converts static pressure to altitude), the vertical speed indicator (compares current and stored static pressure to show climb/descent rate), and the airspeed indicator (uses static pressure alongside Pitot total pressure). The direct-reading compass in B and D is a self-contained magnetic instrument with no pneumatic input. The slip indicator in B and C is an inertial/gravity instrument (a ball in liquid) that requires no connection to the static port. Only A lists the correct three instruments. --- ### Q48: An aircraft in the northern hemisphere turns from 360° to 270° via the shortest route. At approximately what compass reading should the turn be stopped? ^t20q48 - A) 300° - B) 240° - C) 360° - D) 270° **Correct: D)** > **Explanation:** The shortest turn from 360° (north) to 270° (west) is a left turn passing through northwest and west. On westerly headings in the northern hemisphere, the magnetic dip-induced turning error is minimal because the compass card tilts most significantly near north and south, not near east and west. At 270° the compass reads with acceptable accuracy, so the pilot should stop the turn when the compass shows 270°. A (300°) stops too early. B (240°) overshoots significantly. C (360°) is the starting heading. Only D is correct. --- ### 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 at a given altitude regardless of airflow velocity. It is measured by flush static ports positioned on the fuselage where local aerodynamic disturbance is minimized. A is wrong: the Pitot tube senses total pressure (static plus dynamic). B (cabin pressure) is a separately regulated quantity inside the aircraft. D more closely describes dynamic pressure, which arises from organized directed air motion. Only C correctly defines static pressure. --- ### Q50: An aircraft in the northern hemisphere turns from 030° to 180° via the shortest route. At approximately what compass heading should the turn be ended? ^t20q50 - A) 180° - B) 210° - C) 360° - D) 150° **Correct: B)** > **Explanation:** The shortest turn from 030° to 180° is a right turn through east and south. When turning toward southerly headings in the northern hemisphere, the compass lags — it under-reads the actual heading and shows a smaller value than the aircraft has actually turned through. The pilot must therefore overshoot: continue turning until the compass reads approximately 180° + 30° = 210°, at which point the actual heading is approximately 180°. Stopping at 180° on the compass (A) means the aircraft has not yet reached 180° in reality. D (150°) is far too early. C (360°) is irrelevant. Only B is correct. ---