NCAA Air Traffic Controller Licence key terms

An authorisation from a controller for an aircraft to proceed under specified conditions. It does not guarantee terrain or traffic separation unless explicitly stated, and the pilot remains responsible for safe flight.

The spacing maintained between aircraft, or between an aircraft and terrain or obstacles, to reduce collision risk. It is achieved through vertical, lateral, longitudinal or radar-based methods.

Separation between aircraft expressed as a minimum altitude or flight level difference, commonly 1000 feet above a specified transition altitude and 2000 feet at high flight levels where reduced margins apply.

Separation applied using observed radar positions, where controllers ensure aircraft are separated by a minimum horizontal distance or altitude. It requires identified targets, serviceable equipment and defined airspace.

The process by which a controller positively determines that a radar target corresponds to a specific aircraft, using methods such as position reports, turn instructions, transponder codes or identifier features.

A four-digit octal code set in the aircraft transponder so that secondary radar replies carry a discrete identity. Codes are assigned by ATC, with standard emergency codes reserved for distress and radio failure.

Airborne equipment that replies to interrogations from secondary surveillance radar, transmitting identity and often pressure altitude. Mode C provides altitude, while Mode S allows selective addressing and data exchange.

A secondary surveillance radar data-link standard using selective interrogation of individual aircraft by unique address. It supports altitude reporting, aircraft identification and data communications with reduced frequency congestion.

A surveillance technique in which aircraft automatically transmit position and other data derived from onboard systems. ADS-B broadcasts to ground stations and other aircraft, while ADS-C uses contract-based reporting to specific recipients.

A surface of constant atmospheric pressure related to a standard datum of 1013.25 hectopascals, expressed in hundreds of feet. Aircraft at or above the transition altitude use flight levels rather than altitudes.

The altitude above which aircraft set the standard pressure datum and report flight levels instead of altitudes. It is published for each aerodrome or area and may vary between locations.

The rule assigning flight levels according to magnetic track direction, typically odd levels for eastbound tracks and even levels for westbound tracks. It provides a common basis for vertical separation between opposing traffic.

Controlled airspace extending upwards from the surface around an aerodrome, usually within a defined radius and up to a specified upper limit. It protects aerodrome traffic and requires clearance for entry.

Controlled airspace extending upwards from a specified lower limit above the surface, often serving en-route traffic. Its dimensions and classification determine the rules and clearances required for entry.

A lettered system (A to G) defining the rules for flight, clearance requirements, separation provision and services within a volume of airspace. Classes differ in whether VFR and IFR flights are permitted and how they are separated.

A published corridor of controlled airspace along defined tracks between radio navigation aids or waypoints, used for en-route navigation. Aircraft normally require clearance and follow the published alignment and level rules.

A specified geographical location, defined by coordinates or a navigation aid, used to structure routes and procedures. Waypoints may be fly-by or fly-over points and are referenced in clearances and flight plans.

A published instrument procedure linking the departure runway to the en-route structure, including track, altitude and speed constraints. A clearance may include a SID by name, and pilots must follow its published restrictions.

A published instrument procedure guiding arriving aircraft from the en-route structure to a point where approach begins. It may include speed and level constraints and is normally cleared by name.

A published series of manoeuvres for landing under instrument conditions, including initial, intermediate, final and missed approach segments. It specifies courses, altitudes, minima and a missed approach point.

An authorisation for an aircraft to conduct a specified instrument approach, which may include the procedure name, runway and any restrictions. It does not by itself authorise landing, which requires a separate clearance.

A manoeuvre flown when an approach cannot be completed to landing, following the published missed approach procedure or controller instructions. Controllers must protect the missed approach path and issue instructions as needed.

The altitude at which a pilot on a precision approach must decide to continue or initiate a missed approach if the required visual reference is not established. It is referenced to a specified altimeter setting.

The lowest altitude permitted on a non-precision approach before the required visual reference is established. Descent below it is not allowed unless the pilot can continue safely to land.

An event in which an aircraft, vehicle or person is incorrectly present on a protected runway area, creating a collision risk. Prevention relies on clearances, read-backs, signage and situational awareness.

The repetition by a pilot or controller of essential clearance elements to confirm correct reception and understanding. Safety-critical items must be read back, and any discrepancy must be corrected before action.

The standardised words and sentence patterns used for aeronautical communications to minimise ambiguity and misunderstanding. Standard phraseology is prescribed internationally, with plain language used only when it is unavailable.

The identifier used in radiotelephony to identify an aircraft or station, such as a registration, flight number or controller unit name. Correct use reduces confusion when several aircraft share a frequency.

An instruction or request to move communication from one radio channel to another, typically specifying the next unit or channel. Pilots should confirm the change and establish contact with the new unit as instructed.

The agreed process by which responsibility for providing air traffic control service for an aircraft passes from one controller or unit to another. It requires coordination and normally includes a specified point or time.

The ATC service responsible for traffic on and in the vicinity of an aerodrome, including runway operations and aerodrome traffic circuits. It issues clearances for take-off, landing and movement on manoeuvring areas.

An authorisation for an aircraft to land on a specified runway, issued when the runway is available and separation requirements are met. It may be issued before the aircraft reaches the runway but can be cancelled.

A manoeuvre in which an aircraft abandons an approach to landing and climbs away, either voluntarily or on instruction. Controllers must anticipate the flight path and provide separation from other traffic.

A predetermined manoeuvre keeping an aircraft within a specified airspace while awaiting further clearance. It follows defined inbound tracks, turn directions, leg times or distances and minimum holding altitudes.

A phrase advising a pilot of the time or point at which a revised onward clearance can be expected, often while holding. It helps crews manage fuel and plan for contingencies.

A situation in which an aircraft declares that fuel is critically low and requires priority handling. Controllers must give maximum assistance and priority, and the declaration triggers specific emergency procedures.

Standard radiotelephony signals indicating escalating levels of need for assistance: MAYDAY for distress, PAN PAN for urgency. Controllers apply prescribed procedures, protect the aircraft and notify appropriate services.

Loss of two-way communication between aircraft and ATC, requiring the pilot to follow published communication failure procedures. Controllers must apply separation safeguards and anticipate the aircraft's likely route and level.