ATPL 022 Instrumentation key terms

A network of probes and ports that supplies impact and static pressure to the air data instruments. The pitot tube faces the airflow to measure total pressure, while the static port senses ambient pressure.

An instrument that displays the difference between pitot (total) pressure and static pressure, calibrated to indicate the aircraft's speed through the air. It typically shows indicated airspeed and may include colour-coded speed limits.

A pressure instrument that converts static pressure into an altitude reading using the International Standard Atmosphere. It can be set to local pressure (QNH) or standard pressure (1013.25 hPa) for flight levels.

An instrument that shows the rate of climb or descent by measuring the rate of change of static pressure. It may be instantaneous (IVSI) or have a lag, and is often part of an air data computer display.

An instrument that displays the ratio of true airspeed to the local speed of sound. It uses pitot and static pressures to compute Mach number, often with a maximum operating Mach limit marked.

An electronic unit that receives pitot, static, and temperature inputs and computes airspeed, altitude, Mach, and other air data for display and for use by autopilot and navigation systems.

An electrical heating element in the pitot tube that prevents ice formation, which could block the total pressure port and cause erroneous airspeed indications. It is typically controlled by a switch and monitored for current draw.

An opening on the aircraft fuselage that senses ambient static pressure for the altimeter, airspeed indicator, and VSI. Blockage or icing can cause altitude and airspeed errors, so ports are often heated.

A sensor that measures the temperature of the air brought to rest at the probe, including kinetic heating. It provides total air temperature, which is used to compute true airspeed and engine parameters.

The actual temperature of the undisturbed air surrounding the aircraft. It is derived from total air temperature by correcting for kinetic heating, and is used for performance calculations and true airspeed computation.

A sensor that detects the presence of icing conditions, often by measuring vibration frequency change or electrical conductivity. It alerts the crew and may automatically activate ice protection systems.

A spinning mass that maintains its orientation in space due to angular momentum. In instruments, it provides a stable reference for attitude and heading, and can be used to measure rates of rotation.

An instrument that displays the aircraft's pitch and roll relative to the horizon, using a gyroscope as a stable reference. It may be vacuum-driven or electrically driven, and is a primary flight instrument.

A gyroscopic instrument that shows the aircraft's heading relative to a fixed reference, often adjustable to align with the magnetic compass. It precesses over time and must be periodically synchronized.

A gyroscope configured to measure angular rate rather than maintain a fixed orientation. It is used in turn coordinators and in inertial reference systems to sense rotation about an axis.

An instrument that displays rate of turn and slip/skid, using a rate gyro and an inclinometer. It helps the pilot maintain coordinated flight and is used for partial-panel attitude control.

A direct-reading instrument that aligns with the Earth's magnetic field to indicate magnetic heading. It is subject to turning and acceleration errors, and is used to synchronize the heading indicator.

A heading system that uses a magnetic sensing element (flux valve) to continuously correct a gyroscopic heading indicator, reducing precession errors and providing a stable magnetic heading display.

A sensor that detects the direction of the Earth's magnetic field and provides signals to a slaved compass system or inertial reference system for heading alignment and correction.

The angular difference between true north and magnetic north at a given location, varying with position and time. It is applied to convert between true and magnetic headings.

A system of accelerometers and gyroscopes that computes aircraft position, velocity, and attitude without external aids. It requires alignment before flight and drifts over time, often blended with GPS.

A gyroscope that measures rotation by detecting a phase shift between two laser beams travelling in opposite directions around a closed loop. It has no moving parts and is used in modern inertial systems.

A sensor that measures linear acceleration along a specific axis. In inertial systems, accelerometer outputs are integrated to obtain velocity and position, and are corrected for gravity and Earth rotation.

A satellite-based navigation system that provides position, velocity, and time by ranging signals from multiple satellites. It is used for en-route and approach navigation, often augmented for integrity.

A display system that provides computed pitch and roll commands to guide the pilot along a selected flight path or altitude. It may be used alone or coupled with the autopilot.

A system that automatically controls aircraft attitude and flight path by moving the flight controls in response to commands from the flight director or selected modes, reducing pilot workload.

A system that automatically adjusts engine thrust to maintain a selected speed, Mach number, or thrust setting. It is often integrated with the autopilot and flight management system.

A cockpit display system that presents flight and navigation information on electronic screens, replacing mechanical instruments. It typically includes primary flight and navigation displays.

The main electronic display showing attitude, airspeed, altitude, heading, and flight director or autopilot status. It consolidates critical flight parameters in a single screen for the pilot.

An electronic display that shows the aircraft's position, route, waypoints, weather radar, and other navigation data. It can present different modes such as map, plan, or approach.

A system that displays engine parameters and other system data, and generates alert messages for the crew. It prioritises warnings, cautions, and advisories on a dedicated screen.

A prominent visual and aural alert that indicates a condition requiring immediate action, such as fire or critical system failure. It is often accompanied by a red master caution light and specific messages.

An amber alert that indicates a condition requiring attention but not immediate action. It is typically accompanied by a caution message and may be reset after the condition is acknowledged.

A communication pathway that carries digital data between aircraft systems, such as ARINC 429 or 629. It defines the format, speed, and protocol for exchanging information among avionics units.

A widely used avionics data bus standard that transmits digital data over a twisted pair of wires using a bipolar return-to-zero format. It typically supports one transmitter and multiple receivers.

An electronic unit that processes data and performs specific functions such as flight management, air data computation, or autopilot control. It interfaces with other systems via data buses.

A computer system that manages navigation, flight planning, performance, and guidance. It integrates data from sensors and databases to provide lateral and vertical navigation and to control autopilot and autothrust.

A condition where an instrument or system stops providing valid information, often indicated by a warning flag or blank display. Pilots must recognise the failure and use backup instruments or alternate procedures.

A visual indicator, such as a red flag or message, that appears on an instrument when its data is invalid or unreliable. It alerts the pilot to disregard the indication and seek alternate information.

An operating state in which a system continues to function with reduced capability or accuracy after a failure or fault. It allows continued operation while alerting the crew to limitations.