I85PREP
⌘ K
GCAA ATPL Theory study materials
GCAA ATPL Theory study resources

GCAA ATPL Theory practice questions

One question at a time. Build your GCAA ATPL Theory understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Air Law and ATC Procedures

Under the ICAO Convention on International Civil Aviation, which document is issued by a contracting state to certify that an aircraft is fit for flight?

  1. Certificate of Airworthiness Correct answer.
  2. Certificate of Registration
  3. Aircraft Radio Station Licence
  4. Air Operator Certificate

Explanation

The Certificate of Airworthiness is issued when an aircraft is found to meet the applicable airworthiness requirements, confirming it is fit for flight. Registration merely records nationality, the AOC authorises commercial operations, and the radio licence authorises the radio installation.

Question 2Air Law and ATC Procedures

What is the validity period of a Class 1 medical certificate for a holder who is under 40 years of age and is engaged in single-pilot commercial air transport operations carrying passengers?

  1. 12 months
  2. 24 months
  3. 3 months
  4. 6 months Correct answer.

Explanation

For single-pilot commercial air transport carrying passengers, the Class 1 medical certificate is valid for 6 months. The 12-month period applies to other commercial operations, reduced as the holder ages.

Question 3Air Law and ATC Procedures

In the standard ICAO flight plan form, what does the item designated 'E' contain?

  1. Aerodrome of departure
  2. Type of aircraft and wake turbulence category
  3. Cruising speed, level and route
  4. Emergency and survival equipment Correct answer.

Explanation

Item E of the ICAO flight plan records emergency and survival equipment information, such as radio, life jackets and dinghies. Departure aerodrome is item 13, speed/level/route is item 15, and aircraft type is item 9.

Question 4Air Law and ATC Procedures

An aircraft is on a flight within a contracting state and the pilot wishes to change from IFR to VFR. Under ICAO rules, what specific action must be taken?

  1. Commence the change without notifying ATS provided VMC are maintained
  2. Notify the appropriate ATS unit specifically that the IFR flight plan is cancelled Correct answer.
  3. Obtain a new clearance from the area control centre by radio before changing
  4. Report the change only on landing at the destination aerodrome

Explanation

When a pilot elects to change from IFR to VFR, the appropriate ATS unit must be specifically notified that the IFR flight plan has been cancelled. Simply entering VMC does not cancel the IFR flight plan.

Question 5Air Law and ATC Procedures

On the ground, an aircraft displays a flashing red light directed at it by the aerodrome control tower. What does this signal mean?

  1. Taxi clear of the landing area in use
  2. Cleared to taxi
  3. Stop Correct answer.
  4. Return to starting point on the aerodrome

Explanation

A flashing red light directed at an aircraft on the ground means stop. Steady red also means stop, while flashing white means return to starting point and flashing green means cleared to taxi.

Question 6Air Law and ATC Procedures

An aircraft in flight receives a series of red pyrotechnic flares from the ground. What is the meaning of this signal?

  1. Aircraft is flying in or near an active danger area
  2. Request for the aircraft to identify itself
  3. Notwithstanding any previous instructions, do not land for the time being Correct answer.
  4. Land here for communication

Explanation

Red flares fired from the ground toward an aircraft in flight mean that, notwithstanding any previous instructions, the aircraft should not land for the time being. This signal is used when landing would be unsafe.

Question 7Air Law and ATC Procedures

Under ICAO Annex 2, what is the minimum vertical separation that must be maintained by an aircraft flying at a level above 900 m (3000 ft) in IMC in airspace where the semicircular rule applies?

  1. 300 m (1000 ft) Correct answer.
  2. 240 m (800 ft)
  3. 150 m (500 ft)
  4. 600 m (2000 ft)

Explanation

The standard minimum vertical separation between aircraft at levels above 900 m in IMC is 300 m (1000 ft). This is the basis of the semicircular cruising level system.

Question 8Air Law and ATC Procedures

An aircraft is flying on a magnetic track of 270 degrees. Under the semicircular rule for IFR flights at levels above 900 m, which cruising level band applies?

  1. Odd thousands of feet
  2. Odd thousands plus 500 ft
  3. Even thousands plus 500 ft
  4. Even thousands of feet Correct answer.

Explanation

Tracks from 180 to 359 degrees magnetic use even thousands of feet for IFR flights above 900 m. Tracks from 000 to 179 degrees use odd thousands.

Question 9Air Law and ATC Procedures

What is the definition of 'day' for the purpose of applying the rules of the air in most contracting states, unless otherwise prescribed?

  1. The period between the end of evening civil twilight and the beginning of morning civil twilight
  2. The period between sunrise and the end of evening civil twilight
  3. The period between sunrise and sunset
  4. The period between the beginning of morning civil twilight and the end of evening civil twilight Correct answer.

Explanation

'Day' is defined as the period between the beginning of morning civil twilight and the end of evening civil twilight. 'Night' is the complementary period between the end of evening civil twilight and the beginning of morning civil twilight.

Question 10Air Law and ATC Procedures

Under ICAO rules, when may an aircraft be flown over a congested area of a city at a height that does not permit an emergency landing without undue hazard to persons or property on the ground?

  1. When flying at least 300 m above the highest obstacle within 600 m of the aircraft Correct answer.
  2. When flying at a height of at least 150 m above the highest obstacle
  3. When the aircraft is engaged in commercial air transport
  4. When the aircraft is on a notified training flight

Explanation

Over congested areas, aircraft must be flown at a height that allows an emergency landing without undue hazard, which generally means at least 300 m above the highest obstacle within a horizontal radius of 600 m. Other heights apply over non-congested areas.

Question 11Air Law and ATC Procedures

Two aircraft are approaching head-on, or approximately so, in flight and there is risk of collision. What action must each take?

  1. Both alter heading to the left
  2. Both descend
  3. The higher aircraft climbs and the lower descends
  4. Both alter heading to the right Correct answer.

Explanation

When two aircraft are approaching head-on and there is risk of collision, each shall alter its heading to the right. Neither aircraft has right of way in this situation.

Question 12Air Law and ATC Procedures

Which aircraft has the right of way when two aircraft of the same category are converging at approximately the same level?

  1. The aircraft with the lower altitude
  2. The aircraft on the left
  3. The aircraft on the right Correct answer.
  4. The faster aircraft

Explanation

When two aircraft of the same category converge at approximately the same level, the aircraft on the right has the right of way. The other aircraft must give way.

Question 13Air Law and ATC Procedures

An aircraft on approach to land is at the same altitude as an aircraft in flight that is about to land. Which statement reflects the right-of-way rule?

  1. The aircraft on the ground has right of way
  2. The aircraft in flight has right of way
  3. The higher aircraft has right of way
  4. The aircraft on approach to land has right of way Correct answer.

Explanation

An aircraft on approach to land has the right of way over other aircraft in flight, including aircraft at the same level. Aircraft on the ground give way to all aircraft in flight.

Question 14Air Law and ATC Procedures

What is the purpose of the 'Alerting Service' provided by ATS units?

  1. To provide radar vectoring to aircraft in the event of an emergency
  2. To coordinate slot times at congested aerodromes
  3. To notify appropriate organisations regarding aircraft in need of search and rescue aid and to assist such organisations as required Correct answer.
  4. To provide meteorological information to aircraft in flight

Explanation

Alerting service notifies appropriate organisations when an aircraft is in need of search and rescue aid and assists those organisations as required. It is distinct from flight information and air traffic control services.

Question 15Air Law and ATC Procedures

An aircraft operating under IFR in controlled airspace fails to report at a compulsory reporting point. The ATS unit attempts to establish communication without success. What alerting phase is declared?

  1. Emergency phase
  2. Uncertainty phase
  3. Distress phase
  4. Alert phase Correct answer.

Explanation

The alert phase is declared when an aircraft fails to report at a compulsory reporting point and communication cannot be established. The uncertainty phase is declared when an aircraft fails to make an expected report but communication is still possible.

Question 16Air Law and ATC Procedures

What is the meaning of the term 'controlled airspace' under ICAO definitions?

  1. Airspace in which only IFR flights are permitted
  2. Airspace around an aerodrome within which all flights require a clearance
  3. Airspace of defined dimensions within which air traffic control service is provided to IFR flights and to VFR flights in accordance with the airspace classification Correct answer.
  4. Airspace of defined dimensions within which flight information service and alerting service are provided

Explanation

Controlled airspace is airspace of defined dimensions within which air traffic control service is provided to IFR flights and to VFR flights in accordance with the airspace classification. It does not automatically exclude VFR flights.

Question 17Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

In a semi-monocoque aircraft fuselage, what is the primary function of the stringers?

  1. They carry bending loads and stiffen the skin against buckling Correct answer.
  2. They form the pressure-tight boundary of the cabin
  3. They transmit engine thrust to the empennage
  4. They provide the main attachment points for the wing spars

Explanation

In semi-monocoque construction the skin carries much of the load, and longitudinal stringers stiffen the skin so it can resist buckling while helping to carry bending loads. Frames maintain the shape and support the skin, while the skin itself forms the pressure boundary.

Question 18Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

Aircraft primary flight control surfaces are operated by the pilot through which system?

  1. The secondary flight control system
  2. The high-lift device system
  3. The primary flight control system Correct answer.
  4. The trim and balance system

Explanation

Primary flight controls (ailerons, elevators, rudder) are operated directly by the pilot via the primary flight control system. Secondary controls such as flaps, slats and trim are separate systems used to modify the aircraft's configuration or trim state.

Question 19Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the purpose of a horn balance on an aircraft control surface?

  1. To reduce the hinge moment required to deflect the surface Correct answer.
  2. To increase the control surface's natural frequency
  3. To lock the surface when the aircraft is parked
  4. To provide aerodynamic damping in turbulence

Explanation

A horn balance is an extension of the control surface ahead of the hinge line; aerodynamic force on this area produces a moment that opposes the hinge moment, reducing the pilot's control forces. It is a form of aerodynamic balancing, not a structural or locking device.

Question 20Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

In a hydraulically powered flight control system, what is the function of the accumulator?

  1. To filter contaminants from the hydraulic fluid
  2. To cool the hydraulic fluid during continuous operation
  3. To convert electrical power into hydraulic pressure
  4. To store pressurised fluid and damp pressure fluctuations Correct answer.

Explanation

A hydraulic accumulator stores fluid under gas pressure, providing a reserve of energy to meet peak demands and smoothing pressure surges in the system. It does not filter, cool or generate pressure.

Question 21Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

Aircraft hydraulic systems are commonly pressurised to around 3000 psi. What is the main reason for using such high pressure?

  1. To eliminate the need for a hydraulic reservoir
  2. To reduce the size and weight of actuators and pipework for a given power Correct answer.
  3. To allow the use of incompressible fluid in the system
  4. To lower the operating temperature of the hydraulic fluid

Explanation

For a given power, higher system pressure allows smaller actuators and thinner pipework, reducing weight. All hydraulic fluids are effectively incompressible regardless of pressure, and reservoirs remain necessary.

Question 22Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the effect of a failed hydraulic system check valve in a multi-system aircraft?

  1. The accumulator will discharge instantly
  2. The reservoir will overflow
  3. The system pump will overspeed
  4. The fluid may flow backwards and allow pressure loss in the affected system Correct answer.

Explanation

A check valve permits flow in one direction only; if it fails open, fluid can flow backwards, allowing pressure to bleed off and possibly cross-feeding between systems. Pump speed and reservoir level are not directly controlled by the check valve.

Question 23Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

In a typical aircraft electrical system, what is the purpose of the busbar?

  1. To regulate the generator output voltage
  2. To convert AC to DC for the battery
  3. To protect the battery from overcharging
  4. To provide a common distribution point for electrical power to the consumers Correct answer.

Explanation

A busbar is a common conductor to which power sources and consumers are connected, allowing distribution of electrical power. Voltage regulation and rectification are performed by other components.

Question 24Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the purpose of a shunt in an aircraft DC electrical system?

  1. To convert DC to AC for the instruments
  2. To store electrical energy for emergency use
  3. To provide a low-resistance path for measuring current Correct answer.
  4. To limit the voltage supplied to the avionics bus

Explanation

A shunt is a low-resistance element placed in series with a circuit; the small voltage drop across it is proportional to current and is used by an ammeter to indicate current flow. It does not store energy or convert power.

Question 25Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

Why is a lead-acid battery capacity rated at a specific discharge rate?

  1. Because the electrolyte temperature never changes
  2. Because the battery voltage is constant regardless of load
  3. Because the available capacity depends on the discharge current Correct answer.
  4. Because the battery is only used for engine starting

Explanation

The capacity of a lead-acid battery falls as the discharge current increases, so capacity is only meaningful when quoted at a specified discharge rate. Voltage falls during discharge and electrolyte temperature affects performance.

Question 26Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What happens to the output of a DC generator if the aircraft's voltage regulator fails and the field current is not controlled?

  1. The generator will stop producing output
  2. The generator will reverse its polarity
  3. The generator output frequency will increase
  4. The generator output voltage will rise excessively Correct answer.

Explanation

The output voltage of a generator is controlled by regulating the field current; if that regulation is lost, the field current and hence the output voltage can rise excessively, risking overvoltage damage. A generator produces DC, so output frequency is not a relevant parameter.

Question 27Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the primary function of the magneto in a piston engine ignition system?

  1. To advance the ignition timing as engine speed increases
  2. To convert low-tension DC into the high-tension pulses needed at the spark plugs Correct answer.
  3. To cool the spark plugs during high-power operation
  4. To provide a continuous low-tension supply to the battery

Explanation

A magneto is a self-contained generator that produces high-tension pulses for the spark plugs, using a rotating magnet and coil with a contact breaker. Timing changes are achieved by mechanical or electronic means within the ignition system, not by the magneto's basic function.

Question 28Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

In a four-stroke piston engine, what is the valve overlap?

  1. The time taken for the camshaft to rotate once
  2. The period when both inlet and exhaust valves are open around top dead centre Correct answer.
  3. The period when both valves are closed during compression
  4. The distance the valve lifts off its seat

Explanation

Valve overlap occurs near the end of the exhaust stroke and the start of the induction stroke, when both valves are open; it uses the gas flow to improve scavenging and filling. Valve lift and camshaft rotation are separate parameters.

Question 29Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the purpose of a turbocharger wastegate?

  1. To prevent the compressor from surging at low rpm
  2. To cool the compressed air before it enters the cylinders
  3. To drive the compressor directly from the crankshaft
  4. To bypass exhaust gas around the turbine to limit boost pressure Correct answer.

Explanation

The wastegate controls the amount of exhaust gas passing through the turbine; by bypassing gas it limits turbine speed and therefore boost pressure. Cooling of the charge is done by an intercooler, and the compressor is driven by the turbine.

Question 30Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

In a gas turbine engine, what is the function of the compressor in the cycle?

  1. To cool the turbine blades
  2. To extract energy from the exhaust to drive the fan
  3. To ignite the fuel-air mixture
  4. To raise the pressure of the air before combustion Correct answer.

Explanation

The compressor raises the pressure of the incoming air so that combustion can occur at high pressure and the turbine can extract more work. The turbine extracts energy from the gas stream, and ignition is provided by igniters.

Question 31Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the main advantage of a high-bypass-ratio turbofan compared with a low-bypass-ratio turbofan?

  1. Greater thrust at high Mach numbers
  2. Improved propulsive efficiency and lower specific fuel consumption Correct answer.
  3. Higher exhaust velocity for supersonic cruise
  4. Elimination of the need for a combustion chamber

Explanation

In a high-bypass turbofan a large proportion of the air passes through the fan rather than the core, giving a large mass flow with a modest velocity increase and hence better propulsive efficiency and lower fuel burn. High exhaust velocity is associated with low bypass ratios.

Question 32Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

During engine start, what is the purpose of the starter in a large turbofan engine?

  1. To provide ignition energy to the igniter plugs
  2. To supply fuel pressure to the fuel control unit
  3. To drive the accessory gearbox during normal operation
  4. To accelerate the compressor to a speed at which it can sustain its own operation Correct answer.

Explanation

The starter rotates the high-pressure compressor until there is sufficient airflow and compression for combustion to be self-sustaining. Ignition, fuel supply and accessory drives are separate functions.

Question 33Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the effect of an engine fire on the fire detection loop in a typical continuous-loop system?

  1. The loop generates a voltage proportional to temperature
  2. The loop resistance changes and triggers the fire warning Correct answer.
  3. The loop opens and breaks the warning circuit
  4. The loop pressure increases and closes a pressure switch

Explanation

In a continuous-loop detection system the sensing element's resistance changes with temperature, and the control unit interprets the change as a fire warning. The system is designed so that an open circuit is annunciated separately as a loop fault.

Question 34Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

Which extinguishing agent is typically used in aircraft engine fire bottles because it is effective on fuel fires and leaves little residue?

  1. Water
  2. Dry powder
  3. Halon Correct answer.
  4. Foam

Explanation

Halon is a clean agent that interrupts the combustion reaction and is effective on fuel and electrical fires, leaving no residue that would damage engine components. Water, foam and dry powder leave residues or are unsuitable for engine installations.

Question 35Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the purpose of the pressurisation outflow valve in a transport aircraft?

  1. To regulate cabin pressure by controlling the rate at which air leaves the cabin Correct answer.
  2. To control the temperature of the bleed air
  3. To relieve excessive positive pressure only in a rapid decompression
  4. To supply conditioned air to the cabin

Explanation

The outflow valve modulates the escape of cabin air to maintain the selected cabin altitude and rate of change. Air supply is provided by the air conditioning packs, and the valve's normal function is continuous regulation, not emergency relief alone.

Question 36Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

In a vapour-cycle air conditioning system, what is the function of the expansion valve?

  1. To compress the refrigerant vapour
  2. To reduce refrigerant pressure and temperature before it enters the evaporator Correct answer.
  3. To condense the refrigerant into a liquid
  4. To remove moisture from the refrigerant

Explanation

The expansion valve throttles the refrigerant, dropping its pressure and temperature so that it can absorb heat in the evaporator. Compression and condensation occur in the compressor and condenser respectively.

Question 37Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the purpose of anti-icing of the pitot tube and static ports?

  1. To keep the cabin windows clear of ice
  2. To prevent blockage that would cause erroneous airspeed and altitude indications Correct answer.
  3. To improve the accuracy of the magnetic compass
  4. To prevent ice formation on the wing leading edge

Explanation

Ice blocking a pitot tube or static port would corrupt the pressure signals used by the airspeed indicator, altimeter and vertical speed indicator, so these probes are heated. Wing leading-edge protection is a separate anti-icing system.

Question 38Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

In a pneumatic de-icing system using boots, how is ice removed from the protected surface?

  1. By applying a chemical fluid to the surface
  2. By bleeding hot air through the surface
  3. By heating the surface electrically
  4. By inflating the boot to crack and shed the ice Correct answer.

Explanation

Pneumatic boots are inflated cyclically with air, which expands the surface and cracks the accumulated ice so that aerodynamic forces carry it away. Thermal and fluid systems are separate de-icing or anti-icing methods.

Question 39Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

An aircraft is on the ground with the battery master switch on and the generator off. What supplies the electrical loads?

  1. The static inverter
  2. The external ground power unit only
  3. The battery alone Correct answer.
  4. The generator through the reverse-current relay

Explanation

With the generator offline, the battery is the only source connected to the bus and supplies the connected loads, its voltage falling as it discharges. Ground power and the inverter are not sources unless selected or supplied.

Question 40Aircraft General Knowledge - Airframe, Systems, Electrics, Powerplant and Emergency Equipment

What is the consequence of a short circuit in an unprotected aircraft electrical circuit?

  1. The current rises rapidly and can cause overheating and fire Correct answer.
  2. The voltage rises and damages the avionics
  3. The circuit breaker opens automatically
  4. The battery voltage increases

Explanation

A short circuit provides a low-resistance path, so current rises rapidly; without protection this causes overheating, insulation damage and fire risk. Circuit breakers or fuses are fitted to interrupt the current before damage occurs.

Question 41Aircraft General Knowledge - Instrumentation

In a straight-and-level unaccelerated flight, what does an attitude indicator (artificial horizon) display?

  1. The aircraft's pitch and roll attitude relative to the horizon Correct answer.
  2. The aircraft's vertical speed in feet per minute
  3. The aircraft's rate of turn about the vertical axis
  4. The aircraft's heading relative to magnetic north

Explanation

The attitude indicator is a gyro horizon that shows pitch and bank relative to the real horizon using a vertical-axis gyroscope. It does not sense heading, turn rate, or vertical speed; those belong to other instruments.

Question 42Aircraft General Knowledge - Instrumentation

Which instrument uses a gyroscope with only two degrees of freedom and relies on the aircraft's rate of turn to produce its indication?

  1. The altimeter
  2. The turn coordinator Correct answer.
  3. The attitude indicator
  4. The heading indicator

Explanation

The turn coordinator uses a rate gyro restrained to two degrees of freedom; precession caused by a yaw rate tilts the gyro and deflects the miniature aircraft. The attitude and heading indicators use three-degree-of-freedom gyros, and the altimeter is a pressure instrument.

Question 43Aircraft General Knowledge - Instrumentation

An aircraft climbs at a constant indicated airspeed while the outside air temperature is warmer than ISA. How does the true airspeed compare with the indicated airspeed?

  1. True airspeed is higher than indicated airspeed Correct answer.
  2. True airspeed is unrelated to temperature
  3. True airspeed is lower than indicated airspeed
  4. True airspeed equals indicated airspeed

Explanation

Indicated airspeed depends on dynamic pressure, which falls as air density decreases with altitude and higher temperature. To maintain the same dynamic pressure at lower density, the aircraft must move faster, so true airspeed exceeds indicated airspeed.

Question 44Aircraft General Knowledge - Instrumentation

What is the purpose of the altimeter subscale (pressure setting) window?

  1. To display the aircraft's rate of climb in feet per minute
  2. To allow the pilot to set the reference pressure so the altimeter indicates altitude above that datum Correct answer.
  3. To show the outside air temperature at the aircraft's level
  4. To indicate the Mach number at high altitude

Explanation

The altimeter is a barometer calibrated to show height; the subscale lets the pilot insert the reference pressure (QNH, QFE, or standard) so the indicated altitude is measured from the intended datum. It does not measure temperature, Mach, or rate of climb.

Question 45Aircraft General Knowledge - Instrumentation

An aircraft flies from a high-pressure region into a low-pressure region without the altimeter setting being changed. If the aircraft maintains a constant indicated altitude, what is happening to its true altitude?

  1. True altitude is decreasing below indicated altitude Correct answer.
  2. True altitude is increasing above indicated altitude
  3. True altitude is unaffected by pressure changes
  4. True altitude remains constant

Explanation

The altimeter senses static pressure; lower pressure at the same true height makes the instrument read higher. If the pilot holds indicated altitude constant while pressure falls, the aircraft must descend, so true altitude becomes lower than indicated: 'high to low, look out below'.

Question 46Aircraft General Knowledge - Instrumentation

The vertical speed indicator gives an immediate indication of climb or descent mainly because of which feature?

  1. A temperature-compensated aneroid capsule only
  2. A calibrated leak (choke) between the case and the capsule Correct answer.
  3. A magnetic vane in the airstream
  4. A gyroscope that senses vertical acceleration

Explanation

The VSI capsule senses static pressure while the case is connected through a calibrated choke; during a climb or descent the pressure difference across the choke drives the pointer, giving a near-immediate trend. The lag in steady-state reading comes from the time the pressures take to equalise.

Question 47Aircraft General Knowledge - Instrumentation

During a coordinated level turn, the turn coordinator's miniature aircraft is banked and the ball is centred. What does a centred ball indicate?

  1. The aircraft is in a slip
  2. The turn is coordinated Correct answer.
  3. The aircraft is in a skid
  4. The aircraft is climbing

Explanation

The inclinometer ball responds to the resultant of gravity and centrifugal force. When the ball is centred, the two forces align and the turn is coordinated, with no slip or skid.

Question 48Aircraft General Knowledge - Instrumentation

A direct-reading magnetic compass is subject to turning error. When is this error greatest?

  1. Only when accelerating on an easterly heading
  2. On headings near east or west
  3. On headings near north or south Correct answer.
  4. Only when the aircraft is stationary

Explanation

The compass card is pivoted and dips toward the magnetic poles; during a turn the card lags or leads. The error is largest on northerly and southerly headings and negligible on east or west headings.

Question 49Aircraft General Knowledge - Instrumentation

An aircraft accelerates on an easterly heading. What does a direct-reading magnetic compass indicate?

  1. No change in indicated heading
  2. A turn toward the east
  3. A turn toward the south
  4. A turn toward the north Correct answer.

Explanation

On an easterly heading, acceleration causes the compass card to swing, indicating a turn toward north (the 'ANDS' rule: Accelerate North, Decelerate South on east/west headings). This is acceleration error caused by the compass's centre of gravity being below its pivot.

Question 50Aircraft General Knowledge - Instrumentation

What is the primary quantity measured by a Machmeter?

  1. The ratio of true airspeed to the local speed of sound Correct answer.
  2. True airspeed in knots
  3. The static pressure altitude
  4. The dynamic pressure only

Explanation

The Machmeter computes the ratio of true airspeed to the local speed of sound using pitot and static pressures. Because the speed of sound depends on temperature, the instrument accounts for this through pressure relationships.