General Phraseology

A level message must identify the reference, the vertical action, the target, and any timing or rate condition. Flight levels use separate digits; heights and altitudes use feet with the appropriate pressure reference.

Core level forms

A pilot who needs to coordinate the start of a descent may transmit REQUEST DESCENT AT (time). WHEN READY lets the pilot choose when to start, but the pilot reports leaving the present level. AFTER PASSING makes the named point a condition that must occur first. EXPEDITE requires the best practicable rate without compromising safety. If unable, reply UNABLE and give the reason. A report of leaving is made only after the altimeter shows departure from the assigned level and a positive rate is established.

Worked level exchanges

A position report lets ATS project the aircraft along its route. Traffic information gives the pilot a compact relative picture and, when necessary, an immediate avoiding instruction.

Standard position-report order

ATC may alter the reporting pattern with NEXT REPORT AT (significant point), suspend routine reports with OMIT POSITION REPORTS, optionally UNTIL a stated point, and restart them with RESUME POSITION REPORTING.

Additional position reports

Traffic information

Traffic information begins with TRAFFIC and normally gives clock position, distance in miles, direction, type, relative level and movement when known. Useful forms include TRAFFIC (number) O'CLOCK (distance) MILES, TRAFFIC IS (information), LOOKING OUT, TRAFFIC IN SIGHT, TRAFFIC NOT SIGHTED or NEGATIVE CONTACT with a reason, CLEAR OF TRAFFIC, and NO REPORTED TRAFFIC.

For converging traffic, ATC can add direction bound, aircraft type, level, estimate over a significant point and movement. Unmanned free balloons are reported with classification, position or estimate, reported level or unknown level, movement and other pertinent information.

Avoiding action

An urgent radar instruction takes the form AVOIDING ACTION TURN LEFT or RIGHT IMMEDIATELY HEADING (three digits) TO AVOID TRAFFIC, followed by the traffic clock position and distance. Fly the heading promptly, keep looking out, and report traffic in sight or not sighted as appropriate.

Weather phraseology preserves the measurement, unit, location and operational meaning. Repeat the information that forms part of a clearance or affects runway use, and acknowledge the current ATIS designator.

Weather phrase forms

Wind is reported as mean direction and speed, together with significant variation. Where three RVR values are available, preserve the operational order: touchdown zone, midpoint, then rollout or stop-end. If one location is unavailable, state NOT AVAILABLE in its proper position so the remaining values cannot be misassigned.

ATIS acknowledgement

On first contact, report the received ATIS identification, for example INFORMATION GOLF. This tells ATC which broadcast the crew has copied. ATC supplies changes and any essential item not included. If no ATIS has been received, say so and request the required aerodrome information rather than guessing from an old broadcast.

A frequency instruction controls who should be called and when. A speed instruction controls the indicated airspeed while leaving the pilot responsible for aircraft limitations and safe configuration.

Transfer phrases

Read back the frequency and aircraft callsign. At first contact with the new unit, report any assigned speed or heading still in force. If instructed to contact at a point or level, include that condition in the read-back and do not change early.

Speed-control phrases

Worked transfer and speed exchanges

The pressure reference determines whether a vertical position is a height, altitude or flight level. The first call then gives the receiving unit just enough information to understand the aircraft's present and cleared state.

Level-reporting convention

Messages about climb or descent to a HEIGHT or ALTITUDE use whole numbers and include the appropriate QFE or QNH in the initial exchange. Flight levels are transmitted digit by digit. Do not mix a feet value and a flight-level label.

Initial call for an IFR flight

On first contact with the first en route ATS unit, an IFR departure gives callsign, aircraft type or wake category where relevant, SID or standard departure designator, current or passing level, and the initial climb level. Include an assigned speed or heading. On a channel change within the same ATS unit, aircraft identification and level normally suffice unless instructed otherwise.

Initial call for a VFR flight

A VFR initial call normally contains only the minimum needed to establish the requested service, or the clearance needed by a joining or departing flight. ATC then invites or requests further details.