BDCA ATPL Knowledge Exam key terms

Weather conditions in which flight visibility and distance from cloud meet or exceed specified minima, allowing the pilot to navigate and maintain separation by visual reference to the ground and other traffic.

Conditions below the prescribed visual meteorological minima, so that navigation and separation from obstacles and traffic must be achieved by reference to instruments under an instrument flight rules clearance.

A set of rules and procedures under which a pilot operates by visual reference to the ground, maintaining the prescribed cloud and visibility minima and see-and-avoid responsibility for traffic separation.

Rules governing flight in which navigation and separation are based on cockpit instruments and ATC clearance, permitting operation in cloud and low visibility within controlled airspace.

A clearance allowing a flight to operate within a control zone in conditions below normal VMC minima, subject to ATC authorisation, ground visibility limits and the pilot remaining clear of cloud.

Controlled airspace extending upwards from the surface around an aerodrome, normally of defined lateral and vertical limits, established to protect approach, departure and aerodrome traffic movements.

Controlled airspace established above a specified lower limit, extending upwards to a defined upper limit, within which all flights require an ATC clearance and receive separation services.

The point to which an aircraft is granted an air traffic control clearance, normally expressed as a navigation aid, fix or aerodrome, beyond which further clearance must be obtained before proceeding.

The lowest altitude providing at least 300 metres (1000 feet) of obstacle clearance within a sector of 25 nautical miles radius around a navigation aid or fix, used for emergency and terrain planning.

The height above ground of the lowest broken or overcast cloud layer, or of the vertical visibility into obscuration, used to determine aerodrome operating minima and VMC compliance.

The range over which a pilot on the runway centreline can see surface markings or lights, measured instrumentally and reported in metres, used as a controlling value for low-visibility approach minima.

The acute angle between an aerofoil's chord line and the relative airflow approaching it; increasing this angle raises lift until the critical angle is exceeded and the wing stalls.

The specific angle of attack at which airflow separates from the upper wing surface and lift reaches its maximum, after which further increase produces a stall regardless of speed or attitude.

The margin between an aircraft's current angle of attack and the critical angle, expressed as speed above stall or load factor, providing protection against inadvertent stall during manoeuvring or turbulence.

The ratio of total lift generated to the aircraft's weight, expressed in g units; it rises with bank angle and manoeuvre severity and determines the speed at which the wing will stall.

A dimensionless number describing the lifting capability of an aerofoil at a given angle of attack, used with dynamic pressure and wing area to calculate total lift.

The rearward component of aerodynamic force created by the generation of lift, arising from the spanwise flow and wingtip vortices, greatest at high angle of attack and low speed.

The point at which the aircraft's total weight is considered to act; its position must remain within certified fore and aft limits to preserve stability, control and performance.

The determination of aircraft mass and centre of gravity position for a planned flight, ensuring values remain within certified limits for take-off, in flight and landing.

The mass of the aircraft including traffic load but excluding usable fuel, used as a limiting structural value and as a basis for calculating take-off and landing mass.

The maximum certified mass at which the aircraft may commence the take-off run, limited by structure, climb performance and, on a given day, by runway and obstacle considerations.

The runway length at which the accelerate-stop distance equals the take-off distance to 35 feet with one engine failed, giving the shortest field from which a given mass may safely depart.

The speed at or above which a take-off must be continued after an engine failure, and below which it must be abandoned, with sufficient runway remaining to stop.

The speed at which the pilot initiates the pitch input to raise the nose and increase attitude, chosen to achieve the required take-off safety speed by 35 feet.

The altitude or height at which a missed approach must be initiated if the required visual reference for the approach has not been established, used on precision approaches.

The lowest altitude or height to which descent is authorised on a non-precision approach before the required visual reference is established, after which a missed approach follows.

A condition in which the tissues receive insufficient oxygen, producing impaired judgement, euphoria and loss of consciousness; it becomes significant above about 10,000 feet without supplemental oxygen.

The period after loss of oxygen supply during which a person can still perform useful, purposeful actions, decreasing rapidly with increasing altitude and varying between individuals.

A false perception of the aircraft's position or motion relative to the earth, caused by conflicting or absent sensory cues in the inner ear and eyes, most likely without external visual reference.

A false sensation of pitching up or down caused by linear acceleration or deceleration, such as the apparent climb sensation during take-off acceleration, which may prompt an inappropriate control input.

Abnormally rapid or deep breathing that lowers blood carbon dioxide, producing dizziness, tingling and visual disturbance whose symptoms resemble those of hypoxia but respond to slower breathing.

The altimeter sub-scale setting that, when set on the ground at aerodrome elevation, causes the altimeter to indicate aerodrome elevation, giving altitude above mean sea level in the standard atmosphere.

The altimeter sub-scale setting that causes the altimeter to read zero when the aircraft is on the aerodrome, so indications represent height above that aerodrome reference point.

The altitude in the vicinity of an aerodrome at and below which altitude is referenced to QNH, above which the aircraft changes to standard pressure setting 1013.25 hPa.

A surface of constant atmospheric pressure related to the standard pressure datum of 1013.25 hPa, expressed in hundreds of feet and separated from other such surfaces by prescribed intervals.

A ground navigation beacon transmitting signals that allow an aircraft receiver to determine the magnetic bearing from the station, providing position lines for en-route navigation.

A transponder-based system in which the aircraft interrogates a ground station and measures slant range distance, used with VOR to provide a precise fix.

A ground station transmitting continuous signals in the low and medium frequency bands, allowing an aircraft's automatic direction finder to display a relative bearing to the station.

A satellite constellation providing position, velocity and time data to receivers, enabling area navigation, non-precision approaches and, with augmentation, precision approach guidance.