CAA NZ AME Instruments key terms

A set of externally mounted probes and lines that supply total pressure from a forward-facing pitot tube and static pressure from flush ports to the airspeed indicator, altimeter, and vertical speed indicator.

A forward-facing open-ended probe that senses total pressure, the sum of static pressure and the dynamic pressure created by the aircraft's motion through the air.

A flush-mounted opening on the aircraft skin, located in undisturbed airflow, that supplies ambient atmospheric pressure to the static line and the pressure instruments connected to it.

The pressure arising from airflow brought to rest at the pitot tube, equal to one half the air density multiplied by the square of true airspeed, and the quantity that drives airspeed indication.

An electrical heating element built into the pitot tube, controlled from the flight deck, that prevents ice blockage of the pressure inlet and its drain hole.

A differential pressure gauge that displays the difference between total pressure and static pressure, scaled to show indicated airspeed in knots or miles per hour.

A pressure instrument that converts static pressure into altitude by means of an evacuated capsule whose expansion and contraction drive a pointer across a calibrated dial.

The pressure value, either QNH, QFE, or standard pressure, set on the subscale so the altimeter indicates the intended reference datum, such as mean sea level or aerodrome level.

The altimeter subscale setting that, when applied at a given place, causes the altimeter to indicate elevation above mean sea level, derived from station pressure reduced to sea level.

The altimeter subscale setting that makes the instrument read zero when the aircraft is on the ground at the reference aerodrome, so it indicates height above that aerodrome.

The altitude displayed by an altimeter whose subscale is set to standard pressure 1013.25 hectopascals, used for flight levels and performance calculations independent of local weather.

Pressure altitude corrected for the difference between actual air temperature and standard temperature, representing the altitude at which the air density would produce the same aircraft performance.

An instrument that senses the rate of change of static pressure through a calibrated restrictor and displays climb or descent rate, typically in feet per minute.

The delay between an actual change in static pressure and the response of an instrument, caused by restricted airflow through a calibrated orifice or by volume in the static system.

An unintended opening in the static system, such as a cracked line or loose union, that admits cabin pressure and causes altimeter and airspeed errors when the aircraft is unpressurised.

A ground check in which the system is pressurised or evacuated with a test set and the indicated values are monitored for decay, confirming the integrity of lines, instruments, and connections.

The difference between the pressure sensed at the aircraft's static ports and the true ambient static pressure, arising from airflow disturbances around the fuselage at varying speeds and attitudes.

An altimeter error caused by the subscale being set to a pressure other than the true local pressure at the reference datum, so the indicated altitude differs from the actual altitude.

Markings on an airspeed indicator dial showing the white flap range, green normal operating range, yellow caution range, and the red never-exceed line, defined by the aircraft's limiting speeds.

The maximum speed at which an aircraft may be operated in any flight condition, marked by the red radial line on the airspeed indicator and denoted VNE.

Calibrated airspeed corrected for compressibility effects on the pitot-static system, equal to true airspeed multiplied by the square root of the density ratio.

A direct-reading instrument in which a magnetised assembly aligns with the Earth's magnetic field, indicating magnetic heading subject to turning and acceleration errors.

The angular error of a magnetic compass caused by magnetic fields generated by the aircraft's own structure, electrical circuits, and equipment, corrected by a compass swing and deviation card.

The angular difference between true north and magnetic north at a particular location, shown on aeronautical charts and applied when converting between true and magnetic directions.

A procedure in which the aircraft is aligned on known headings and the compass readings are compared with magnetic references so that residual deviation can be recorded on a card.

A remote sensor containing saturable magnetic cores that detects the direction of the Earth's magnetic field and supplies signals to a remote indicating compass or heading reference system.

A directional gyro whose drift is automatically corrected by signals from a magnetic flux valve, combining the stability of a gyro with the north-seeking accuracy of a magnetic reference.

A two-degree-of-freedom gyroscope whose spinning rotor maintains a fixed direction in space, providing a stable heading reference that must be set manually and periodically corrected for drift.

The property of a spinning gyroscope whereby its rotor axis tends to remain fixed in inertial space unless acted upon by an external torque, providing a stable attitude or direction reference.

The predictable tilting of a spinning gyroscope's axis when a torque is applied, occurring at right angles to the applied force in the direction of rotor rotation.

A gyroscopic instrument displaying pitch and roll relative to the horizon, using an erect gyro whose rotor axis is held vertical by an erection mechanism.

A system of pendulous vanes or torque motors that senses apparent tilt of a gyro and applies correction so its axis returns to the true vertical or horizontal reference.

An instrument that displays rate of turn, commonly by a rate gyro sensing yaw rate, often combined with a slip-skid ball to indicate coordination of the turn.

A curved glass tube containing a damping fluid and a ball that indicates slip or skid by showing whether the resultant force on the aircraft is aligned with the vertical.

The apparent slow wander of a gyroscope's axis away from its reference direction, caused by bearing friction, rotor imbalance, and the Earth's rotation, requiring periodic correction.

An instrument that indicates engine rotational speed, typically driven by a magnetic drag-cup or electrical generator system and marked with operating limits in revolutions per minute.

A mechanical tachometer in which a rotating magnet induces eddy currents in a drag cup, producing a torque proportional to speed that is balanced by a hairspring.

A temperature sensor formed by joining two dissimilar metals, which generates a small voltage proportional to the temperature difference between the hot junction and the cold junction.

Circuitry in a thermocouple measuring system that corrects the indicated temperature for changes in the temperature of the reference junction, preventing ambient temperature from corrupting the reading.

An instrument using thermocouples in the exhaust stream to display exhaust gas temperature, used to monitor engine power setting and protect turbine components from overtemperature.

A system of tank probes or float sensors and an indicator that measures and displays the amount of fuel in each tank, often with low-level warning outputs.

A tubular sensor whose capacitance changes with the fuel level between inner and outer electrodes, since fuel has a different dielectric constant from air.

An instrument that measures the rate at which fuel is delivered to the engine, displayed in litres or pounds per hour, and used to calculate range and endurance.

A central display of warning, caution, and advisory lights that alerts the crew to system faults, often paired with a master warning or master caution attention-getter.

A central attention-getting light and reset switch that illuminates when any caution-level annunciator is active, directing the crew to the specific fault message.

A flight deck display system in which cathode ray tube or liquid crystal displays replace electromechanical instruments, showing attitude, heading, airspeed, altitude, and navigation data.

The electronic display directly in front of each pilot that presents attitude, airspeed, altitude, heading, and flight director information in an integrated format.

A reconfigurable electronic display that can present navigation maps, weather radar, engine parameters, or system synoptics, selected by the crew.

A digital unit that receives pitot and static pressures and outside air temperature, computes airspeed, altitude, vertical speed, and temperature data, and feeds displays and other systems.

A solid-state pressure transducer that converts pitot and static pressures into digital signals for the air data computer, eliminating long pneumatic runs to the flight deck.

A sensor, usually a resistance element mounted in a shielded housing on the fuselage, that measures free-stream air temperature for display and for true airspeed computation.

The actual speed of the aircraft through the air mass, obtained by correcting indicated airspeed for position error, compressibility, and air density at the flight altitude.