KCAA IR Theory key terms

A licence endorsement permitting a pilot to fly under instrument flight rules in instrument meteorological conditions, granted after meeting KCAA knowledge, experience and flight-test requirements for IFR operations.

Rules governing flight conducted by reference to instruments, requiring an ATC clearance, filed flight plan and adherence to specified routes, altitudes and separation minima in controlled airspace.

Meteorological conditions expressed in terms of visibility, distance from cloud and ceiling that are below the minima specified for visual meteorological conditions, requiring instrument flight.

Weather conditions meeting prescribed visibility, cloud distance and ceiling minima that permit flight by visual reference to the ground and allow VFR operations.

An authorisation for an aircraft to proceed under specified traffic conditions, containing instructions such as route, altitude, speed and departure or arrival procedure; it does not by itself confer terrain separation responsibility.

The lowest altitude providing a specified terrain clearance within a defined area, often shown on approach charts for a 25 nautical mile sector around a navigation aid.

The lowest published altitude for an airway or route segment that meets obstacle clearance requirements and, where applicable, navigation signal coverage for the whole segment.

A specified altitude in a precision or vertically guided approach at which a missed approach must be initiated if the required visual reference to continue has not been established.

The lowest altitude, in a non-precision approach, to which descent is authorised until the required visual reference is established, after which descent may continue to land.

The point on a published approach procedure at which the missed approach must be flown if the required visual reference has not been established, defined by fix, distance or navigation aid.

An instrument approach procedure using lateral guidance only, without electronic vertical guidance, terminating at a minimum descent altitude rather than a decision altitude.

An instrument approach providing both lateral and vertical guidance meeting specified accuracy standards, such as ILS, allowing operation down to a decision altitude.

A ground-based precision approach aid radiating a localiser for lateral guidance and a glidepath for vertical guidance, with marker beacons or distance measuring equipment for range information.

The vertical guidance signal of a precision approach system, typically set at about three degrees, defining a descent path to the runway touchdown zone.

The lateral guidance component of an ILS, transmitting on VHF frequencies to define the extended runway centreline within a narrow course sector.

A ground navigation beacon transmitting on 108 to 117.95 MHz that enables an aircraft receiver to determine the magnetic bearing from the station and track to or from it.

A magnetic bearing from a VOR or similar station, expressed in degrees, along which an aircraft may track inbound or outbound; the aircraft's position is a point on a radial.

A transponder-based system measuring slant range from the aircraft to a ground station by timing interrogations and replies, usually paired with a VOR or ILS.

The display element showing lateral deviation of the aircraft from a selected navigation course, with full-scale deflection representing a defined width in degrees or nautical miles.

An integrated display combining a heading reference with a course deviation indicator and glideslope pointer, reducing pilot workload during instrument approaches and tracking.

A gyroscopic instrument showing pitch and roll relative to the horizon, serving as the primary reference for aircraft attitude during instrument flight.

A gyroscopic instrument displaying aircraft heading, subject to precession and requiring periodic alignment with the magnetic compass during flight.

An instrument showing rate of turn and, through a ball, coordination of rudder input, used to maintain standard-rate turns and detect slips or skids.

The system of pressure sources and lines supplying pitot and static pressure to the airspeed indicator, altimeter and vertical speed indicator.

The pressure value set on the subscale so the altimeter indicates altitude relative to a chosen datum, such as QNH, QFE or standard pressure 1013.25 hPa.

The altitude at or below which the aircraft's altitude is controlled by reference to the local altimeter setting and above which standard pressure is used.

The lowest flight level available for use above the transition altitude, ensuring at least the required separation from the transition altitude.

A turn through three degrees per second, completing 360 degrees in two minutes, used as a reference for timed turns and procedure turns under instrument flight.

A published manoeuvre allowing an aircraft to reverse direction and establish on the inbound approach course, flown within protected airspace at a specified altitude.

A racetrack manoeuvre flown at a specified fix and altitude, with defined inbound leg, turn direction and leg timing or distance, used to absorb delay or sequence arrivals.

A deep convective cloud producing heavy showers, hail, severe turbulence, icing and lightning, and often embedded in frontal or tropical systems; it must be avoided by instrument flights.

A change in wind speed or direction over a short distance or time, including microbursts and frontal shear, which can cause sudden airspeed and lift changes on approach.

A concentrated downdraft producing divergent surface winds over a small area, capable of causing severe performance loss close to the ground during departure or approach.

Accumulation of ice on airframe surfaces from supercooled water droplets, degrading lift and increasing drag and weight; structural icing is a major hazard in instrument conditions.

The altitude at which the ambient air temperature is zero degrees Celsius, a key planning figure for icing exposure and for setting climb or descent profiles.

A pilot's mistaken perception of aircraft attitude or motion, typically arising from conflicting vestibular and visual cues in low visibility, and countered by reliance on instruments.

A false sensation of pitch caused by linear acceleration or deceleration, which may lead a pilot to push or pull incorrectly after a rapid acceleration or go-around.

Insufficient oxygen reaching body tissues, causing impaired judgement, vision and coordination at altitude; it is insidious and demands prompt use of supplemental oxygen.

The period after loss of cabin pressurisation or oxygen supply during which a pilot can still perform useful tasks before incapacitation, decreasing rapidly with altitude.

The fuel required beyond trip fuel, comprising contingency, alternate, final reserve and, where applicable, additional fuel, ensuring safe diversion and holding capability.

An aerodrome specified in the flight plan to which an aircraft may proceed if landing at the intended destination becomes inadvisable or impossible.