BDCA Instrument Rating Knowledge Exam key terms

The lowest altitude, expressed in feet above mean sea level, to which descent is authorised on a non-precision approach or circling approach without the required visual reference. It is a floor, not a landing height.

A specified altitude in a precision or approach-with-vertical-guidance procedure at which a missed approach must be initiated if the required visual reference has not been established. It is referenced to the altimeter and expressed above mean sea level.

The point in the approach procedure at which a missed approach must be started if the required visual reference to continue has not been established. On precision approaches it coincides with the decision altitude.

A published sequence of turns, climbs and altitude limits flown when a landing cannot be completed. It protects obstacle clearance from the missed approach point until the aircraft reaches a holding fix or is vectored by ATC.

The lowest altitude providing at least 1000 feet of obstacle clearance within a sector of 25 nautical miles around a navigation aid or fix. It gives emergency and terrain awareness but does not guarantee radio or navigation reception.

The lowest published altitude along an airway segment that meets obstacle clearance requirements and assures acceptable navigation signal coverage. Flight below the MEA is not authorised without a specific clearance or procedure.

The lowest published altitude on an airway segment that meets obstacle clearance requirements but may not guarantee navigation signal reception. It is often lower than the MEA and is used with care when signal coverage is in doubt.

A published series of predetermined manoeuvres protecting an aircraft from obstacles from the initial approach fix to a point where landing is possible, or to a missed approach point. Each chart states courses, altitudes and minima.

The charted depiction of an instrument approach, showing plan view, profile view, minimum altitudes, frequencies, courses, missed approach instructions and landing minima. Pilots brief it before commencing the approach.

An approach using lateral and vertical guidance meeting international standards, such as ILS. It permits operation to a decision altitude typically lower than non-precision minima because both path dimensions are protected.

A ground-based system providing a localiser for lateral guidance and a glide path for vertical guidance, often with marker beacons or distance measuring equipment for range. It supports precision approaches to suitably equipped runways.

The lateral guidance component of an ILS, transmitting on VHF frequencies in the 108 to 112 MHz band. Its course is aligned with the runway centreline and is identified by its Morse code and identification signal.

The vertical guidance component of an ILS, normally set at about three degrees, transmitted on UHF frequencies. Following it brings the aircraft to the runway touchdown zone at a stable descent rate.

A ground navigation aid transmitting on 108 to 117.95 MHz that lets an aircraft determine its magnetic bearing from the station. It supports radials, airway navigation and distance information when paired with DME.

A magnetic bearing extending outward from a VOR station, measured clockwise from magnetic north. An aircraft on a given radial is positioned along that line from the station, regardless of its heading.

A transponder-based system that measures slant range between aircraft and a ground station by timing radio pulses. It provides distance in nautical miles and, with VOR, enables fixes and arc procedures.

A method of navigation permitting aircraft to fly any desired path within the coverage of referenced navigation aids or satellite systems, rather than being constrained to station-to-station routes. It enables direct routing and defined waypoints.

A navigation specification stating the on-board performance monitoring and alerting required to operate within a defined airspace. RNP values, such as RNP 1 or RNP 0.3, express the lateral accuracy in nautical miles.

A predetermined geographical position used for route definition or progress reporting, defined by coordinates or by reference to navigation aids. Fly-by and fly-over waypoints differ in how the aircraft turns at them.

The cockpit display showing lateral displacement from a selected course, with a centred needle meaning on course. Full-scale deflection corresponds to a defined width that narrows as the aircraft nears the station or as sensitivity increases.

An integrated flight instrument combining a heading indicator with a course deviation display and often a glide path pointer. It reduces pilot workload by presenting heading and navigation guidance in one view.

A gyroscopic instrument displaying pitch and bank relative to the horizon. It is the primary reference for aircraft control in instrument meteorological conditions and is subject to gyro erection and tumble limits.

A gyroscopic instrument showing aircraft heading, usually driven by a vacuum or electric gyro and subject to precession. It must be periodically aligned with the magnetic compass during flight.

An instrument showing rate of turn and, indirectly, bank attitude, used to establish and maintain a standard rate turn. It also indicates slip or skid when coordinated with the inclinometer ball.

A turn of three degrees per second, completing 360 degrees in two minutes. It is the reference rate for timed turns and for procedure turns and holding patterns in instrument flight.

The aircraft system supplying ram air pressure and static pressure to the airspeed indicator, altimeter and vertical speed indicator. Blockages or leaks cause characteristic and often misleading instrument errors.

The pressure value set on the altimeter subscale so the instrument indicates altitude above a chosen reference. QNH gives elevation above mean sea level, while standard pressure 1013.25 hPa is used above the transition altitude.

The altitude at or below which the aircraft's altitude is controlled by reference to the altimeter set to local pressure. Above it, pilots set standard pressure and fly flight levels.

The lowest flight level available for use above the transition altitude, chosen so that adequate vertical separation exists between aircraft flying on local pressure and those on standard pressure.

A predetermined manoeuvre keeping an aircraft within a specified airspace while awaiting further clearance. It uses standard turns, defined legs and a holding fix, with entry procedures depending on the arrival direction.

A published manoeuvre reversing the aircraft's direction to establish it on the inbound approach course. It must be flown within the protected area and at or above the published altitude.

A defined area around an RNAV approach that replaces feeder routes, allowing arrivals from different directions to transition to the initial approach fix using published altitudes and courses.

Meteorological conditions expressed in terms of visibility, distance from cloud and ceiling that are less than the minimum specified for visual meteorological conditions. Flight under IMC generally requires an instrument clearance.

Weather conditions meeting specified visibility and cloud distance minima that permit flight under visual flight rules. Maintaining VMC is the pilot's responsibility even when receiving traffic information.

The set of rules governing flight in conditions where navigation and separation depend on instruments and air traffic control. IFR flights require an appropriate clearance, equipment and pilot qualification.

An authorisation for an aircraft to proceed under specified traffic conditions, including route, altitude and any restrictions. It does not relieve the pilot of responsibility for terrain clearance or compliance with regulations.

The pilot's repetition of safety-related clearance elements, such as route, altitude, heading, speed and frequencies, to confirm correct receipt. It is required for clearances and is a key defence against communication error.

A framework in which crews identify threats, anticipate and trap errors, and manage any resulting undesired aircraft state. It treats error as normal and focuses on resilience rather than blame.

A pilot's accurate perception and understanding of aircraft state, environment and future trends. Loss of it often precedes errors and is countered by monitoring, cross-checks and verbal confirmation.

The effective use of all available resources, including people, equipment and information, to achieve safe and efficient flight. It emphasises communication, leadership, workload management and decision making.