Brunei DCA CPL(A) Instrumentation key terms

The pressure of undisturbed outside air, sensed by the static port and used as the reference for the altimeter, vertical speed indicator and airspeed indicator.

Total pressure sensed at the forward-facing pitot tube, comprising static pressure plus the pressure rise caused by the aircraft's forward speed through the air.

Obstruction of the pitot tube, typically by ice or insects, which traps pressure in the airspeed system and causes the indicator to behave like an altimeter.

Obstruction of the static source that leaves trapped static pressure in the system, making the altimeter freeze and the airspeed and vertical speed indications erroneous.

A backup static port, usually inside the cabin, selected when the normal static source is blocked; it restores indications but introduces position and cabin-pressure errors.

Instrument error caused by local airflow around the fuselage, pitot head or static ports differing from the free-stream pressure, varying with airspeed, configuration and angle of attack.

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

Indicated airspeed corrected for position error and instrument error, representing the speed the aircraft would show with ideal pressure sensing.

Arcs and radial lines on the airspeed dial showing the white flap range, green normal range, yellow caution range and red never-exceed speed.

A pressure instrument that converts static pressure into altitude using a calibrated aneroid capsule and a mechanical or digital display of feet.

The altimeter subscale setting that, when entered, makes the altimeter read aerodrome elevation when the aircraft is on the ground at that aerodrome.

An altitude error caused by the subscale being set to a pressure value different from the correct local reference, producing a consistent over- or under-reading.

An instrument that displays the rate of climb or descent in feet per minute by sensing the pressure difference between the static source and a calibrated leak chamber.

A vertical speed indicator fitted with an accelerometer-driven pump or vane that produces an immediate indication of climb or descent, removing the normal lag.

The delay between a change in the sensed quantity and the corresponding movement of the instrument pointer, caused by damping, leaks or mechanical inertia.

The tendency of a spinning gyroscope to maintain the orientation of its spin axis in inertial space, the principle behind the attitude and heading indicators.

The movement of a gyroscope's spin axis in response to an applied torque, used in rate instruments such as the turn coordinator to indicate rate of turn.

A gyroscope spun by air drawn across its rotor by an engine-driven vacuum pump, whose suction gauge indicates whether adequate rotor speed is available.

A gyro horizon using a vertically spinning gyro to display pitch and roll relative to the real horizon, with a caging or fast-erect mechanism on many types.

A false attitude display caused by the erection mechanism following a false apparent vertical during prolonged acceleration or coordinated turns, corrected by reference to other instruments.

A direction gyro whose horizontal spin axis drives a compass card, giving a stable heading without the turning errors of a magnetic compass but requiring periodic synchronisation.

A rate gyro instrument displaying rate of turn and, through the inclinometer ball, the balance of the turn, used as the primary reference for standard-rate turns.

A gyroscope deliberately limited in freedom and precessed by a spring so that its deflection is proportional to the rate of turn about the sensed axis.

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

A turn of three degrees per second, requiring approximately airspeed divided by ten plus seven knots for a light aircraft to achieve.

A direct-reading instrument in which magnetised needles align with the Earth's magnetic field, giving heading free of power supply but subject to turning and acceleration errors.

The vertical component of the Earth's magnetic field that pulls the compass needle downward, varying with latitude and causing turning and acceleration errors.

A compass error during turns caused by dip, most pronounced on northerly and southerly headings, where the compass lags or leads the actual turn.

A compass error on easterly and westerly headings in which acceleration produces an apparent turn toward the north and deceleration an apparent turn toward the south.

An instrument displaying the absolute pressure in the engine intake manifold, used with the tachometer to set and monitor power in a constant-speed propeller aircraft.

An instrument indicating engine or propeller rotational speed, commonly driven electrically or mechanically and displayed as revolutions per minute.

An instrument measuring the rate at which fuel is delivered to the engine, used to monitor consumption, set mixture and detect leaks or blockage.

A display of usable fuel remaining, usually derived from float-type or capacitance probes and subject to errors from aircraft attitude, temperature and probe calibration.

An integrated display, such as EICAS or ECAM, that presents engine and system parameters together with alert messages on a shared electronic screen.

A glass-cockpit suite in which primary flight and navigation data are presented on electronic displays rather than mechanical instruments, often with reversionary modes.

A self-contained battery-backed display providing attitude, airspeed and altitude if the main electronic displays fail, independent of the primary display computers.

The automatic or manual transfer of flight or engine data to a remaining display after a screen or computer failure, so essential information stays visible.

Central alerting lights and associated aural signals that draw attention to a caution or warning condition and are usually cancelled after the fault is identified.

A device, often a lift transducer or reed switch on the wing, that gives an aural and sometimes visual alert as the angle of attack approaches the stall.

An aural or visual alert, commonly a clacker or horn, that sounds when airspeed approaches or exceeds the maximum operating limit.

An alerting system that uses radio altitude, barometric altitude, airspeed and landing gear or flap status to warn of excessive descent rate, terrain closure or unsafe configuration.

An enhanced ground proximity system that combines a terrain database with aircraft position to give predictive warnings and a terrain display ahead of the aircraft.

An airborne system that interrogates nearby transponders, displays surrounding traffic and issues traffic advisories and resolution advisories to reduce collision risk.

A TCAS command instructing the flight crew to climb, descend or maintain vertical speed to avoid an intruder, requiring prompt and correct response.

A system that computes steering commands and displays them as pitch and roll bars on the attitude indicator for the pilot to follow manually.

An automatic flight control system that moves the flight controls to hold a selected attitude, heading, altitude or navigation path without continuous pilot input.

A defined operating state, such as heading hold, altitude hold or approach, that determines which guidance laws and annunciations are active.

The textual or symbolic display on the flight mode annunciator showing which autopilot, flight director and autothrottle modes are engaged, armed or active.

The pilot's identification of an instrument or system malfunction by comparing indications, cross-checking redundant sources and noting abnormal flags, warnings or inconsistent readings.

A reading that lies outside normal limits or disagrees with related instruments, such as a frozen altimeter or an airspeed that does not change with power.

An instrument displaying the wing's angle of attack directly, giving stall margin information that is independent of airspeed, weight and configuration.

An instrument showing the vacuum or pressure driving the gyroscopes, used to confirm that gyro instruments are receiving adequate power.

A gravity-referenced air-jet valve inside an attitude indicator that senses the apparent vertical and erects the gyro spin axis toward it.