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CAA NZ AME Instruments study materials
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CAA NZ AME Instruments practice questions

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Question 1Instruments

In a light-aircraft direct-reading magnetic compass, what is the purpose of the compensating magnets mounted in the compass housing?

  1. To correct for deviation caused by electrical loads switching on
  2. To damp the float so the card settles quickly after a turn
  3. To cancel the aircraft's permanent magnetic field at the compass position Correct answer.
  4. To align the card with true north rather than magnetic north

Explanation

A direct-reading compass is affected by the aircraft's own hard-iron magnetism, which produces a fixed deviation for each heading. Adjustable compensating magnets in the housing are set on a compass swing to oppose that field, leaving the residual deviation recorded on the deviation card. Soft-iron effects and electrical-field effects are handled separately and are not removed by these magnets.

Question 2Instruments

Which instrument in a light aircraft is connected directly to the pitot-static system and displays rate of climb or descent?

  1. Airspeed indicator
  2. Altimeter
  3. Vertical speed indicator Correct answer.
  4. Turn coordinator

Explanation

The vertical speed indicator senses the difference between static pressure and a restricted (delayed) static pressure inside its capsule, and displays that difference as a rate of climb or descent. The airspeed indicator uses pitot pressure plus static pressure, and the altimeter uses static pressure alone. The turn coordinator is a gyroscopic instrument and is not a pressure instrument.

Question 3Instruments

An altimeter set to the local QNH reads 2,400 ft on an aerodrome. If the subscale is later set to 1013 hPa while the aircraft remains parked, what happens to the indicated altitude?

  1. It stays at 2,400 ft because the aircraft has not moved
  2. It reads the height above the aerodrome
  3. It changes to the pressure altitude for that position Correct answer.
  4. It reads zero because QNE is selected

Explanation

Setting 1013 hPa on the subscale converts the instrument to pressure altitude, referenced to the standard datum. Because the local QNH differs from 1013 hPa, the indication will shift by roughly 30 ft per hectopascal of difference. The aircraft being stationary does not prevent the indication changing, since the subscale setting directly offsets the mechanism.

Question 4Instruments

What is the primary function of the pitot heat system on an aircraft in instrument meteorological conditions?

  1. To prevent ice blocking the pitot tube and causing erroneous airspeed indications Correct answer.
  2. To warm the static ports so the altimeter does not lag
  3. To keep the gyro rotor bearings at operating temperature
  4. To stop the airspeed indicator from over-reading in cold air

Explanation

Ice forming in or over the pitot tube obstructs the total-pressure source, so the airspeed indicator gives false readings that can mislead the pilot badly. Pitot heat keeps the tube clear so total pressure continues to reach the capsule. Static ports are a separate system and gyro instruments are unrelated to pitot heat.

Question 5Instruments

During a coordinated level turn, the turn indicator shows a standard rate. What does a standard rate of turn correspond to?

  1. 6 degrees per second, giving a one-minute turn through 360 degrees
  2. 1.5 degrees per second, giving a four-minute turn through 360 degrees
  3. 2 degrees per second, giving a three-minute turn through 360 degrees
  4. 3 degrees per second, giving a two-minute turn through 360 degrees Correct answer.

Explanation

A standard rate turn is defined as 3 degrees per second, so a full 360-degree turn takes 120 seconds, or two minutes. Turn indicators are marked to show this rate, often with a doghouse or L/R mark. Pilots use this rate for timed procedure turns and holding patterns.

Question 6Instruments

A vacuum-driven attitude indicator is tumbling and its gyro is not erecting correctly. Which is the most likely cause?

  1. A blocked static port
  2. A mis-set altimeter subscale
  3. A faulty pitot heater element
  4. Insufficient vacuum or suction at the instrument Correct answer.

Explanation

Vacuum-driven gyros rely on an airflow from the vacuum pump to spin the rotor at operating speed and to provide the erection mechanism. Low suction reduces rotor speed, so the gyro precesses, drifts and may tumble. Static-port blockage and pitot heat affect pressure instruments, and the altimeter subscale has no bearing on gyro operation.

Question 7Instruments

What is the purpose of the white arc on a light-aircraft airspeed indicator?

  1. It marks the normal operating range from VS1 to VNO
  2. It marks the caution range up to VNE
  3. It marks the never-exceed speed
  4. It marks the flap operating range from VS0 to VFE Correct answer.

Explanation

The white arc shows the range in which flaps may be extended, from the stall speed in the landing configuration (VS0) at the lower end to the maximum flap extended speed (VFE) at the upper end. The green arc marks the normal operating range, the yellow arc the caution range, and the red line VNE.

Question 8Instruments

An aircraft climbs at a constant indicated airspeed while the altimeter shows increasing altitude. What happens to the true airspeed?

  1. It decreases because the pitot head receives less total pressure
  2. It increases because air density decreases with altitude Correct answer.
  3. It stays exactly equal to the indicated airspeed
  4. It falls to zero once the aircraft leaves the troposphere

Explanation

The airspeed indicator is calibrated for sea-level density, so at higher altitude the lower density means the same dynamic pressure corresponds to a higher true speed. Indicated airspeed therefore under-reads true airspeed as altitude increases. The relationship is roughly a 2 percent increase in TAS per 1,000 ft for a constant IAS.

Question 9Instruments

Which failure mode causes an airspeed indicator to read zero while the aircraft is in flight?

  1. A blocked static port with the pitot clear
  2. A completely blocked pitot tube with an unblocked static port Correct answer.
  3. A leaking static line inside the cabin
  4. A failed vacuum pump

Explanation

If the pitot tube is fully blocked, total pressure trapped in the capsule equals the static pressure entering the case, so the indicator reads zero regardless of actual speed. A blocked static port causes the indicator to behave like an altimeter, rising in a climb and falling in a descent. Vacuum failure affects gyroscopic instruments only.

Question 10Instruments

On a compass swing, the engineer records the deviation on various headings. What does deviation represent?

  1. The error caused by the compass fluid expanding with temperature
  2. The angular difference between the compass indication and magnetic north Correct answer.
  3. The angular difference between the aircraft heading and the track made good
  4. The angular difference between magnetic north and true north

Explanation

Deviation is the error in a magnetic compass caused by the aircraft's own magnetic fields, measured as the angle between the compass reading and magnetic north. Variation, by contrast, is the angle between magnetic north and true north at a location. Track error and fluid expansion are separate concepts.

Question 11Instruments

Why is a magnetic compass subject to turning and acceleration errors during manoeuvres?

  1. The card is affected by the aircraft's electrical alternator field
  2. The compass card is pendulous and its centre of gravity is below the pivot Correct answer.
  3. The compensating magnets lose strength in flight
  4. The compass fluid becomes less viscous at altitude

Explanation

The compass card and magnet assembly is deliberately pendulous so it stays level, but this means accelerations tilt it away from the horizontal. When tilted, the vertical component of the earth's field produces a turning error, which is largest on northerly and southerly headings. Acceleration errors occur on east and west headings when speed changes.

Question 12Instruments

What does the slip indicator (the ball) in a turn and slip instrument show?

  1. The rate of turn in degrees per second
  2. The aircraft's angle of bank
  3. The aircraft's pitch attitude
  4. Whether the aircraft is skidding or slipping in a turn Correct answer.

Explanation

The ball is a simple pendulum in a curved glass tube filled with damping fluid. In a coordinated turn, centrifugal force holds it centred; if it moves to the outside or inside of the turn, the aircraft is skidding or slipping. Rate of turn is shown by the gyro indicator, and bank and pitch are shown by the attitude indicator.

Question 13Instruments

A VSI is showing a steady climb indication while the aircraft is in level flight. Which fault is most consistent with this?

  1. A pitot tube blocked by ice
  2. A failed attitude gyro
  3. A mis-set heading bug
  4. A blockage in the instrument's metering unit or static line Correct answer.

Explanation

The VSI compares static pressure with a delayed static pressure inside its capsule; if the metering orifice or static line is blocked, the delayed pressure never equalises and a false climb or descent is shown. Pitot blockage affects the airspeed indicator, and gyro or heading-bug faults are unrelated. A blocked static line can also cause the VSI to freeze at its last reading.

Question 14Instruments

What is the purpose of the erection mechanism in a vacuum-driven attitude indicator?

  1. To correct the heading indication for magnetic variation
  2. To damp out vibration from the engine
  3. To keep the gyro spin axis aligned with the local vertical Correct answer.
  4. To spin the gyro rotor up to operating speed

Explanation

The attitude indicator's gyro must remain referenced to the true vertical, so an erection system uses air jets or pendulous vanes to precess the gyro back to the vertical when it drifts. The vacuum airflow spins the rotor, but the erection mechanism is a separate function. Magnetic variation has no relevance to an attitude gyro.

Question 15Instruments

An altimeter with a subscale set to QFE will indicate what when the aircraft is on the aerodrome?

  1. Zero, or the aerodrome elevation if the instrument is set to QNH Correct answer.
  2. The pressure altitude at the aerodrome
  3. The height above the transition level
  4. The aerodrome elevation above mean sea level

Explanation

QFE is the pressure at the aerodrome reference point, so an altimeter set to QFE reads zero when the aircraft is on that aerodrome. Setting QNH instead makes the altimeter read aerodrome elevation above mean sea level. Pressure altitude is obtained by setting 1013 hPa.

Question 16Instruments

Aircraft static ports are often fitted with a small alternate static source inside the cabin. What is the effect of selecting the alternate source in an unpressurised aircraft in flight?

  1. The altimeter reads slightly low and the airspeed slightly low because cabin pressure is higher
  2. No instrument readings change because cabin pressure equals static pressure
  3. The altimeter reads slightly high and the airspeed slightly high because cabin pressure is lower than static pressure Correct answer.
  4. Only the VSI is affected

Explanation

In an unpressurised aircraft, cabin pressure is usually slightly below the true static pressure because of airflow over the cabin. Feeding this lower pressure to the static instruments makes the altimeter read high and the airspeed indicator read high, and the VSI shows a brief climb. All three static instruments are affected.

Question 17Instruments

Which statement correctly describes the difference between indicated airspeed and calibrated airspeed?

  1. Calibrated airspeed is indicated airspeed corrected for position and instrument error Correct answer.
  2. Calibrated airspeed is true airspeed corrected for wind
  3. Calibrated airspeed is indicated airspeed corrected for air density
  4. Calibrated airspeed is the speed at which the aircraft stalls in the landing configuration

Explanation

Indicated airspeed is what the instrument shows; calibrated airspeed is that reading corrected for installation (position) error and instrument error. Density correction produces true airspeed, and wind correction produces groundspeed. The stall speed in the landing configuration is a defined limit, not a correction of IAS.

Question 18Instruments

What does the green arc on an airspeed indicator represent?

  1. The caution range up to never-exceed speed
  2. The normal operating range from the clean stall speed to maximum structural cruising speed Correct answer.
  3. The flap operating range
  4. The range in which the aircraft may be operated in turbulence

Explanation

The green arc begins at VS1, the stall speed in the clean configuration, and ends at VNO, the maximum structural cruising speed. Flight above VNO into the yellow arc is permitted only in smooth air. The white arc marks the flap range and the red line marks VNE.

Question 19Instruments

An engineer is checking a heading indicator and finds it precesses steadily and must be reset frequently. Which cause is most likely?

  1. A blocked static port
  2. A faulty fuel quantity sender
  3. A failed pitot heater
  4. Worn gyro bearings or a rotor running below normal speed Correct answer.

Explanation

A heading gyro precesses because of friction in the gimbal bearings or because the rotor is not spinning at its designed speed, so the gyro cannot hold its reference. Frequent resetting indicates excessive drift. Static and pitot faults affect pressure instruments, and fuel senders are unrelated.

Question 20Instruments

Why must a magnetic compass be checked for deviation after major avionics or electrical work?

  1. The compensating magnets lose their magnetism when the battery is disconnected
  2. The compass fluid must be topped up after any electrical work
  3. New or moved electrical equipment changes the aircraft's magnetic field at the compass Correct answer.
  4. The compass card must be re-magnetised to the new heading

Explanation

Electrical equipment and its wiring produce magnetic fields that add to the aircraft's own field at the compass position. Adding or moving avionics can change the deviation, so a compass swing and a new deviation card are required. Fluid servicing and magnet re-magnetisation are not consequences of avionics work.

Question 21Instruments

Which instrument provides the pilot with an indication of the aircraft's pitch and roll attitude relative to the horizon?

  1. Attitude indicator Correct answer.
  2. Turn coordinator
  3. Heading indicator
  4. Altimeter

Explanation

The attitude indicator, a gyroscopic instrument, displays pitch and roll against a symbolic horizon. The heading indicator shows direction, the turn coordinator shows rate of turn, and the altimeter shows altitude. Only the attitude indicator presents pitch and roll directly.

Question 22Instruments

What is the effect on the altimeter if the static line becomes disconnected inside the cabin while the aircraft climbs?

  1. The altimeter indicates a climb that is greater than the actual climb
  2. The altimeter reads the pressure altitude regardless of subscale setting
  3. The altimeter indicates a climb that is less than the actual climb Correct answer.
  4. The altimeter reads zero throughout the climb

Explanation

If the static line leaks inside the cabin, the altimeter receives cabin pressure instead of true static pressure. In an unpressurised aircraft, cabin pressure falls more slowly than outside pressure during a climb, so the altimeter under-reads the climb. A blocked static port, by contrast, causes the altimeter to freeze at the last reading.

Question 23Instruments

In a turn and bank indicator, what does the gyro measure?

  1. Yaw rate about the lateral axis
  2. Rate of roll about the longitudinal axis
  3. Rate of turn about the vertical axis Correct answer.
  4. Pitch rate about the lateral axis

Explanation

The gyro in a turn and bank indicator is mounted with its spin axis lateral and senses rotation about the vertical axis, so it displays rate of turn. A turn coordinator uses a canted gyro so it also responds to roll rate, but the basic turn and bank instrument responds to yaw rate. Pitch rate is not measured by this instrument.

Question 24Instruments

A pilot notes that the airspeed indicator reads high on the ground and low in the air at the same true speed. Which explanation is most consistent?

  1. A faulty fuel gauge
  2. A failed vacuum pump
  3. A leaking pitot line inside the cabin Correct answer.
  4. A blocked static port

Explanation

A pitot line leak reduces the total pressure reaching the capsule, so the indicated speed falls below the true value, particularly at high speed. On the ground with zero speed, the indicator should read zero; a leak can also cause errors at low speed. A blocked static port produces altitude-dependent errors rather than a consistent under-read.

Question 25Instruments

What is the function of the damping fluid in a direct-reading magnetic compass?

  1. To steady the card and reduce oscillation Correct answer.
  2. To correct the compass for deviation
  3. To indicate the aircraft's bank angle
  4. To increase the magnetic sensitivity of the card

Explanation

The fluid supports the card and provides viscous damping so the card settles quickly after turns and turbulence. It does not increase magnetic sensitivity or correct deviation; deviation is corrected by compensating magnets. Bank angle is not shown by a magnetic compass.

Question 26Instruments

Which instrument in a light aircraft typically uses a sealed capsule and a calibrated orifice to sense rate of change of static pressure?

  1. Turn coordinator
  2. Airspeed indicator
  3. Altimeter
  4. Vertical speed indicator Correct answer.

Explanation

The VSI contains a capsule connected to the static source and a calibrated leak or orifice that delays the pressure inside the case, so the differential pressure reflects the rate of change of static pressure, which is displayed as a climb or descent rate. The altimeter responds to absolute static pressure, not its rate of change.

Question 27Instruments

In a light-aircraft airspeed indicator, which colour marking indicates the maximum speed at which the aircraft may be operated in smooth air without exceeding structural limits?

  1. The green arc
  2. The yellow arc Correct answer.
  3. The red radial line
  4. The white arc

Explanation

The yellow arc spans from the design manoeuvring speed to the never-exceed speed and marks the range where flight is permitted only in smooth air. The red radial line marks the never-exceed speed, not the smooth-air caution range.

Question 28Instruments

What does the term 'position error' describe in relation to a pitot-static system?

  1. The error caused by temperature changes in the capsule
  2. The error caused by a leaking pitot line
  3. The error introduced by a blocked static port
  4. The error caused by incorrect static pressure at the sensing ports due to airflow around the aircraft Correct answer.

Explanation

Position error arises because the static ports and pitot head do not sense true ambient pressure at all attitudes and speeds, owing to local airflow and pressure distribution over the airframe. It is corrected by applying the position error correction from the calibration data to obtain calibrated airspeed.

Question 29Instruments

Which component provides the static pressure reference used by the altimeter, airspeed indicator and VSI?

  1. The pitot head
  2. The vacuum pump
  3. The gyro rotor
  4. The static ports Correct answer.

Explanation

The static ports supply undisturbed ambient static pressure to the pressure instruments. The pitot head supplies total (impact) pressure to the airspeed indicator only, while the vacuum pump and gyro rotor are unrelated to pressure sensing.

Question 30Instruments

What is the function of the subscale (barometric setting) knob on a sensitive altimeter?

  1. To set the heading reference
  2. To damp the VSI needle
  3. To zero the airspeed indicator
  4. To adjust the indicated altitude to the local pressure reference Correct answer.

Explanation

The subscale knob moves the pressure scale relative to the capsule mechanism so the pointer indicates altitude relative to the selected reference pressure such as QNH or QFE. It does not affect airspeed, VSI damping or heading.

Question 31Instruments

Which gyroscopic property allows a heading indicator to maintain a fixed reference in space?

  1. Pendulous suspension
  2. Erection to the vertical
  3. Magnetic variation
  4. Rigidity in space Correct answer.

Explanation

A spinning gyro resists changes to the direction of its spin axis, a property called rigidity in space, which lets the heading indicator hold a stable reference. Erection to the vertical applies to attitude instruments, and magnetic variation is unrelated to gyro behaviour.

Question 32Instruments

What does a Machmeter indicate?

  1. The indicated airspeed in knots
  2. The rate of climb in feet per minute
  3. The ratio of true airspeed to the local speed of sound Correct answer.
  4. The altitude above the standard datum

Explanation

The Machmeter computes the ratio of true airspeed to the local speed of sound from pitot and static pressures, displaying it as a Mach number. It does not display knots, climb rate or altitude.

Question 33Instruments

Why is a magnetic compass fitted with compensating magnets in its corrector assembly?

  1. To increase the sensitivity of the compass card
  2. To reduce the deviation caused by the aircraft's own magnetic fields Correct answer.
  3. To damp out oscillation of the card
  4. To align the compass with true north

Explanation

The corrector magnets create a small adjustable field that opposes the field produced by the aircraft's structure and equipment, reducing residual deviation on the compass swing. Damping is provided by the fluid, and the compass indicates magnetic, not true, direction.

Question 34Instruments

An aircraft is on the ground at an aerodrome where QNH is 1013 hPa and QFE is 1000 hPa. If the altimeter subscale is set to QNH, what will the altimeter indicate when the aircraft is on the ground?

  1. The pressure altitude
  2. The aerodrome elevation Correct answer.
  3. The aerodrome elevation plus 13 feet
  4. Zero

Explanation

With QNH set, the altimeter indicates elevation above mean sea level, so on the ground it reads the aerodrome elevation. Setting QFE would make it read zero on the ground.

Question 35Instruments

An aircraft climbs at a constant true airspeed while the airspeed indicator shows a decreasing indicated airspeed. Which statement best explains this?

  1. The VSI leak is blocked
  2. The pitot heater has failed
  3. Total pressure rises with altitude, increasing the capsule differential
  4. Static pressure falls with altitude, reducing the pressure differential across the capsule Correct answer.

Explanation

As altitude increases the air density falls, so for a given true airspeed the dynamic pressure and hence the capsule differential decrease, and indicated airspeed falls. Total pressure does not rise with altitude, and heater or VSI faults would not produce this consistent trend.

Question 36Instruments

During a compass swing, the engineer finds the deviation is small on north and south headings but large on east and west headings. Which cause is most consistent with this pattern?

  1. Incorrect damping of the compass card
  2. A fluid leak in the compass bowl
  3. A permanent magnetic field in the aircraft acting along the fore-aft axis Correct answer.
  4. A worn gyro bearing in the heading indicator

Explanation

A permanent field aligned fore-aft produces deviation that varies as the sine of the heading, giving near-zero deviation on north and south and maximum deviation on east and west. Fluid leaks, damping faults and heading indicator bearings do not give this heading-dependent pattern.

Question 37Instruments

What is the effect of a partially blocked pitot tube on the airspeed indication during a climb?

  1. The airspeed indication falls to zero immediately
  2. The airspeed indication becomes erratic in turns only
  3. The airspeed indication remains accurate
  4. The airspeed indication tends to increase as altitude rises Correct answer.

Explanation

If the pitot pressure is trapped by a blockage while the static pressure continues to fall in the climb, the differential pressure across the capsule grows and the airspeed indication rises. A fully blocked static port or total pitot failure would give different results.

Question 38Instruments

An aircraft is descending at a constant rate and the VSI needle is steady. What does the VSI actually measure?

  1. The rate of change of static pressure Correct answer.
  2. The absolute static pressure
  3. The rate of change of pitch attitude
  4. The difference between pitot and static pressure

Explanation

The VSI responds to the rate at which static pressure changes, which is proportional to the rate of climb or descent. It does not measure absolute pressure, pitot-static difference or attitude.

Question 39Instruments

Which statement correctly describes the purpose of the slip indicator in a turn and slip instrument?

  1. It shows the rate of turn about the yaw axis
  2. It shows the aircraft's pitch attitude
  3. It shows the lateral acceleration acting on the aircraft, indicating coordinated flight Correct answer.
  4. It shows the aircraft's bank angle

Explanation

The slip indicator is a ball in a curved tube that responds to the resultant of gravity and lateral acceleration, showing whether the aircraft is slipping or skidding. Rate of turn is shown by the gyro, and bank and pitch attitude are shown by the attitude indicator.

Question 40Instruments

What happens to a vacuum-driven attitude indicator if the suction line becomes partially restricted?

  1. The gyro spins faster and erects more quickly
  2. The horizon bar becomes more accurate
  3. The gyro may erect slowly or the horizon bar may drift, with a warning flag or low suction indication Correct answer.
  4. The instrument becomes a rate-of-turn indicator

Explanation

A restricted suction line reduces the airflow over the gyro, lowering rotor speed and weakening the erection mechanism, so the horizon bar may drift or erect slowly. Reduced suction is often shown by a warning flag or a low reading on the suction gauge.

Question 41Instruments

Which instrument uses a gyro that is deliberately erected to the local vertical by a pendulous vane mechanism?

  1. Magnetic compass
  2. Heading indicator
  3. Turn coordinator
  4. Attitude indicator Correct answer.

Explanation

The attitude indicator uses a vertical gyro with an erection mechanism that senses the apparent vertical and torques the gyro to align its spin axis with the local vertical. The heading indicator is not erected to the vertical, and the turn coordinator and compass use different principles.

Question 42Instruments

Why is a heading indicator usually fitted with a caging or fast-erect knob?

  1. To increase the gyro spin speed for high-altitude flight
  2. To damp out the compass card
  3. To compensate for static pressure changes
  4. To align the gyro with the magnetic compass before flight and after manoeuvres Correct answer.

Explanation

The caging knob allows the pilot to align the heading indicator with the magnetic compass reference and to re-erect the gyro after the precession that occurs during manoeuvres. It does not change spin speed, static pressure or compass damping.

Question 43Instruments

An aircraft is flying at high altitude and the airspeed indicator shows a value close to the low-speed end of the white arc while the true airspeed is high. Which statement best explains this?

  1. Indicated airspeed always equals true airspeed at altitude
  2. The static ports are blocked
  3. The pitot heater is overheating
  4. Indicated airspeed falls with density altitude while true airspeed rises for the same power setting Correct answer.

Explanation

At high density altitude the dynamic pressure for a given true airspeed is lower, so indicated airspeed is lower than true airspeed. This is why the airspeed indicator can show a low value while the aircraft is actually moving quickly through the air.

Question 44Instruments

What is the purpose of the range markings on an airspeed indicator being referenced to calibrated airspeed rather than true airspeed?

  1. Because true airspeed is not measurable in flight
  2. Because calibrated airspeed is always higher than true airspeed
  3. Because the aircraft's limiting speeds are determined by dynamic pressure, which is what indicated airspeed reflects Correct answer.
  4. Because the markings are only used on the ground

Explanation

Structural and aerodynamic limits depend on dynamic pressure, which the airspeed indicator senses directly. Marking the dial in indicated/calibrated airspeed therefore gives the pilot a direct check against those limits regardless of altitude.

Question 45Instruments

A magnetic compass is being checked and the engineer notes that the card oscillates for a long time after a turn. Which cause is most likely?

  1. Incorrect subscale setting
  2. A strong permanent magnet in the aircraft structure
  3. Low fluid level or incorrect damping fluid in the compass bowl Correct answer.
  4. A failed gyro erection mechanism

Explanation

The liquid in the compass bowl provides damping; if the fluid level is low or the wrong fluid is used, the card oscillates excessively. Structural magnetism would cause deviation, not prolonged oscillation, and the other options relate to different instruments.

Question 46Instruments

An aircraft with a blocked static port is climbing. What will the airspeed indicator, altimeter and VSI most likely show?

  1. Airspeed increases, altimeter remains fixed, VSI reads zero Correct answer.
  2. Airspeed decreases, altimeter decreases, VSI reads a descent
  3. Airspeed remains correct, altimeter increases, VSI reads a climb
  4. Airspeed decreases, altimeter increases, VSI reads a climb

Explanation

With the static port blocked, the trapped static pressure cannot fall as the aircraft climbs, so the altimeter remains fixed and the VSI reads zero. The pitot pressure still falls with true airspeed but the trapped static pressure stays high, so the differential grows and the airspeed indication increases.

Question 47Instruments

An engineer is calibrating a sensitive altimeter and finds that the indicated altitude is consistently higher than the true altitude at all pressures. Which fault is most consistent with this?

  1. The static line has a leak
  2. The subscale is set to QFE
  3. The instrument is fitted with the wrong colour markings
  4. The capsule is incorrectly adjusted so the mechanism has a zero offset Correct answer.

Explanation

A consistent offset at all pressures indicates a zero or calibration error in the capsule mechanism or linkage, not a pressure leak or subscale selection. A static leak would produce a different, often transient, error pattern.

Question 48Instruments

A turn coordinator is being tested and the engineer notes that the gyro indicates a turn even when the aircraft is stationary on the ground. Which explanation is most likely?

  1. The gyro is not spinning up to speed or the instrument has a mechanical fault Correct answer.
  2. The static ports are blocked
  3. The aircraft is experiencing real yaw
  4. The compass has excessive deviation

Explanation

A turn coordinator should read zero when the aircraft is stationary because there is no rate of turn. An indication on the ground suggests the gyro is not at operating speed or there is a mechanical or electrical fault in the instrument.

Question 49Instruments

An aircraft is accelerating on the runway and the magnetic compass card swings. Which explanation best accounts for this?

  1. Damping caused by the compass fluid
  2. Acceleration error caused by the compass pivot being below the centre of gravity Correct answer.
  3. Deviation caused by the aircraft's permanent magnetism
  4. Variation caused by the earth's magnetic field

Explanation

Acceleration error occurs because the compass magnet assembly's centre of gravity is below the pivot point, so acceleration tilts the assembly and produces a false turn indication. It is most pronounced on east and west headings and is a known limitation of the direct-reading compass.

Question 50Instruments

An engineer is investigating why an airspeed indicator reads low at high angle of attack. Which factor is most relevant?

  1. Position error from the pitot head and static ports sensing pressures that differ from free-stream values Correct answer.
  2. The capsule being made of the wrong material
  3. The subscale being set to QNH
  4. The colour markings being incorrect

Explanation

At high angles of attack the local airflow around the pitot head and static ports changes, so the sensed pressures depart from free-stream values and produce position error, which is corrected by calibration data. Marking errors, capsule material and subscale setting do not explain the angle-of-attack dependence.