Aerodrome Control 1: Start, Taxi, Departure

The departure clearance defines the route and initial constraints. The start-up request then gives ATC the operational details needed to plan ground movement and avoid unnecessary fuel burn.

Departure clearance format and read-back

A request normally includes station, full callsign, aircraft type and wake category when required, stand, flight rules and destination, ATIS designator and the words REQUEST CLEARANCE. The clearance can include destination, route, SID, runway, initial level, QNH, SSR code, slot or clearance expiry. Read it back in full and end with the callsign.

Start-up request and responses

Use aircraft location followed by REQUEST START-UP, adding the ATIS designator. Where required, state persons on board and confirmation that security checks are complete. The controller may reply START-UP APPROVED, START-UP AT (time), EXPECT START-UP AT (time), START-UP AT OWN DISCRETION, or EXPECT DEPARTURE (time) START-UP AT OWN DISCRETION.

Priority start-up

Priority may be given to an aircraft likely to become committed to land because of a factor affecting safe operation, such as engine trouble or fuel shortage; a hospital aircraft or one carrying a sick or seriously injured person requiring urgent attention; an aircraft engaged in search and rescue; and other aircraft designated by the authority. State the reason plainly, such as rescue operations, human-organ transplant or urgent medical transport.

Pushback is an aircraft movement that must be coordinated with ATC or Apron and with the ground crew. Approval never removes the crew's responsibility for obstacles, brakes and engine-start safety.

ATC and apron phraseology

Cockpit and ground-crew exchange

After ATC approval, the ground crew may call START NUMBER ONE and the cockpit answers STARTING NUMBER ONE. Maintain the agreed interphone or hand-signal discipline until the tug and headset are clear.

Time check

A taxi clearance has a limit. For a departing aircraft the normal limit is the runway holding point, and nothing in a taxi instruction grants runway entry unless that movement is stated.

Taxi requests and clearances

Holding and runway crossing

Use HOLD (direction) OF (position), HOLD POSITION, HOLD (distance) FROM (position), or HOLD SHORT OF (position). The pilot replies HOLDING or HOLDING SHORT. Holding instructions require a specific read-back.

To cross, transmit REQUEST CROSS RUNWAY (number). ATC may issue CROSS RUNWAY (number) REPORT VACATED. In low visibility or whenever the tower cannot see the crossing aircraft, the report-vacated requirement is essential. Report RUNWAY VACATED only when the entire aircraft is beyond the relevant holding position. ATC may say EXPEDITE CROSSING RUNWAY with traffic information.

Backtrack, air-taxi and surface hazards

Use REQUEST BACKTRACK, BACKTRACK APPROVED and BACKTRACK RUNWAY (number). Helicopters may request AIR-TAXI from or via a route to a location. ATC can issue AIR-TAXI TO or AIR-TAXI VIA, together with CAUTION for dust, blowing snow, loose debris, taxiing light aircraft, personnel or vehicles, and AVOID instructions. Ground hazards also use CAUTION WAKE TURBULENCE, CAUTION JET BLAST and CAUTION SLIPSTREAM.

Before the runway, the route clearance, departure instructions and line-up clearance must remain separate. The pilot reads each one back and does not infer authority for the next movement.

ATC clearance and departure instructions

SID restrictions

Use CLIMB VIA SID TO (level). ATC may state CANCEL LEVEL RESTRICTIONS, CANCEL LEVEL RESTRICTIONS AT (points), CANCEL SPEED RESTRICTIONS, CANCEL SPEED RESTRICTIONS AT (points), or CLIMB UNRESTRICTED TO (level) with cancellation of level and speed restrictions. Unless cancelled or amended, published SID restrictions remain binding.

Preparation and runway entry

ATC may say UNABLE TO ISSUE (designator) DEPARTURE with a reason, REPORT WHEN READY FOR DEPARTURE, ARE YOU READY FOR DEPARTURE, or ARE YOU READY FOR IMMEDIATE DEPARTURE. Reply READY or AFFIRM only when able to comply without delay.

Runway entry uses LINE UP RUNWAY (number), LINE UP AND WAIT, or LINE UP, BE READY FOR IMMEDIATE DEPARTURE. With multiple runways, include the runway number. If lining up from an intermediate holding point, state the designator and the remaining take-off run available, TORA.

Conditional line-up

The order is aircraft callsign, condition, identification of the subject, instruction. The read-back repeats the condition and instruction. Conditional clearances apply to one movement only. Do not use them for an active-runway movement unless both controller and pilot can see the relevant traffic.

A take-off clearance is a distinct safety-critical transmission. It is read back exactly, may include wind or traffic, and can be cancelled with repeated unmistakable words.

Clearance and immediate departure

The standard form is RUNWAY (number) CLEARED FOR TAKE-OFF, optionally REPORT AIRBORNE. Where reduced runway separation is used, traffic information precedes the clearance. If the surface wind has changed significantly, pass it separately from the clearance. ATC may ask ARE YOU READY FOR IMMEDIATE DEPARTURE. If the pilot answers AFFIRM, ATC may issue LINE UP RUNWAY (number) AND BE READY FOR IMMEDIATE DEPARTURE, followed by the actual clearance when safe.

If a cleared aircraft has not begun the take-off, ATC may use TAKE OFF IMMEDIATELY OR VACATE RUNWAY with instructions, or TAKE OFF IMMEDIATELY OR HOLD SHORT OF RUNWAY. The pilot must not accept if immediate safe compliance is impossible.

Cancellation before and after the roll

Before the roll, transmit HOLD POSITION, CANCEL TAKE-OFF, I SAY AGAIN CANCEL TAKE-OFF followed by the reason. The pilot replies HOLDING. Once the aircraft is rolling, use STOP IMMEDIATELY, repeating the aircraft callsign and instruction. The pilot replies STOPPING. If the pilot abandons take-off independently, announce STOPPING as soon as practicable, state the reason, location and intentions, then request manoeuvring instructions.

Low visibility and runway-incursion defence

In poor visibility ATC states the runway and may request REPORT AIRBORNE. The pilot reads back the runway with every line-up, crossing and take-off clearance. Use explicit holding-point designators, never infer a runway crossing from a taxi route, and question any instruction that conflicts with signs, lights or observed traffic. HOLD POSITION means stop and remain stopped.

After take-off, the crew reports airborne when requested, follows the assigned runway heading, track or turn, and transfers to Departure on the stated frequency.

After take-off phrases

For helicopter operations, a take-off clearance may identify the present position, taxiway, final approach and take-off area, runway or number. A helicopter may request departure instructions and receive AFTER DEPARTURE TURN RIGHT, TURN LEFT or CLIMB as appropriate.

Complete tower sequence

Departure flow in one view

The sequence is information and clearance, start-up, pushback, taxi to a stated limit, holding or crossing, line-up, take-off clearance, airborne report and transfer. Each stage needs its own authority. A correct clearance at one stage never silently authorises the next.