Aerodrome Control

Start-up and pushback are sequenced so that aircraft reach the holding point in a useful order and do not block adjacent stands, taxi routes or the departure runway.

Procedure for start-up and assignment of flight level

1. Before requesting start-up or pushback, the pilot ensures that the steps or aerobridge are removed and all doors are closed.
2. The start-up request includes the total persons on board, including crew, and confirmation that the security check is complete.
3. The departure sequence normally follows the taxi sequence and holding-point order. It may change for VIP handling or traffic reasons.
4. An aircraft beside another aircraft already pushing back may be delayed.
5. Take-off may be delayed by restrictions in the ATC clearance, overflying traffic or the appropriate ATS authority.
6. Same-track or same-level traffic may require delay, a climb restriction or a higher climb rate to establish separation.
7. A departure requesting the same level as an overflying aircraft may receive an alternate level or a delayed release.

Pushback and movement from the stand

Pushback, powerback or towing begins only with the required approval and after the crew confirms that the path is safe. The crew remains responsible for following the clearance, monitoring wing and tail clearance, and stopping if the movement becomes unsafe.

Take-off and landing preparation

Bali also states that cruise climb is not permitted in Indian FIRs and that transonic and supersonic phases of flight are not permitted over Indian airspace.

The tower anticipates calls at known traffic and taxi positions. Where practicable, it issues the next clearance without making the pilot ask for it.

Designated circuit positions

Taxi clearance

A taxi clearance gives concise instructions and enough information to follow the correct route, avoid aircraft or objects and prevent accidental entry onto an active runway. If the taxi limit lies beyond a runway, the clearance contains an explicit clearance to cross that runway or an instruction to hold short.

Taxiing on a runway in use

• Taxi on the runway in use is allowed only to expedite traffic and only when it creates no delay or risk.
• If the tower cannot determine that a crossing or vacating aircraft is clear, it requests a runway-vacated report. The report is made only when the entire aircraft is beyond the relevant runway-holding position.
• A pilot who needs to backtrack for departure informs ATC before taxi begins.
• The pilot-in-command does not hold on the runway in use without prior ATC permission.
• Only one aircraft is cleared to land on the runway in use at one time, except an authorised military formation.

The runway-holding position is the legal boundary of runway protection. Precision operations can require a farther holding point to protect the ILS signal.

Use of runway-holding positions

An aircraft is not permitted to line up and hold at the approach end while another aircraft is landing until the landing aircraft has passed the intended holding point.

ILS critical and sensitive areas

The critical area surrounds the localiser or glide-path antenna where an aircraft or vehicle can disturb the radiated signal. The sensitive area extends farther and protects the signal against unacceptable interference during precision operations. During low-visibility Category II or Category III operations, persons and vehicles are restricted to the essential minimum and the applicable ILS holding position is protected.

Runway incursion or obstructed runway

If an obstruction is seen after a take-off or landing clearance, the controller informs the aircraft of the obstruction and its position. The take-off clearance is cancelled if the aircraft has not begun its roll, and a landing aircraft is instructed to go around.

Uncertainty of position on the manoeuvring area

The controller applies wake-turbulence minima when required and, where avoidance rests with the pilot, advises of the expected wake or jet-blast hazard as far as practicable.

The runway in use and the information package are selected early enough for safe planning, then updated whenever a material change makes the earlier picture unreliable.

Selection of runway in use

The runway best aligned into the surface wind is normally selected, but the controller also considers runway length, traffic pattern, available approach and landing aids, ground movement, noise-abatement requirements and other local conditions. A pilot may request another runway. If traffic permits it may be approved; otherwise the aircraft waits or uses the runway in use.

Start-up time procedures

Local instructions state the criteria for calculating and issuing start-up times. The purpose is to match pushback and taxi with the departure sequence without creating unnecessary engine-running time or surface congestion.

Aerodrome and meteorological information before taxi

Before take-off, the tower adds significant changes in wind, air temperature, visibility or RVR, and significant weather in the take-off and climb-out area. This includes cumulonimbus or thunderstorm, moderate or severe turbulence, wind shear, hail, moderate or severe icing, severe squall line, freezing precipitation, severe mountain waves, sandstorm, dust storm, blowing snow, tornado or waterspout.

Information before entering the circuit or approach

Unless already received, the aircraft is given the runway to be used, surface wind including significant variations, QNH and locally or on request QFE.

Automatic terminal information service

ATIS broadcasts routine arrival or departure information continuously on a discrete channel or data link. Each issue has a phonetic alphabet designator and is replaced immediately after a significant change. The pilot reports the received designator on first contact; the controller supplies any later change and any operational item not included.

The aerodrome control service manages more than aircraft. It controls vehicles and people, protects low-visibility routes and reports any surface or facility condition that can change braking, guidance or clearance.

Condition of the movement area and related facilities

Control of persons and vehicles

The tower controls movement of people and vehicles, including towed aircraft, on the manoeuvring area as necessary to protect them and aircraft landing, taxiing or taking off. Vehicles remain a safe distance from taxiing aircraft.

Low-visibility procedures

When low-visibility procedures operate, people and vehicles on the manoeuvring area are restricted to the essential minimum. Particular attention is given to protecting the ILS sensitive areas during Category II and Category III A precision operations. Taxi routes, holding points, stop bars and runway crossings are controlled so only one unambiguous clearance exists at a time.

Priority on the manoeuvring area

An emergency vehicle responding to an aircraft in distress has priority over all other surface movement. Where runway or taxiway lighting permits, flashing runway lights mean: vacate the runway or taxiway and observe the tower for a light signal.

Priority is assigned to protect life and urgent operations, then to move the largest useful traffic flow with the least average delay.

Priority rules

An aircraft landing or in the final stages of approach normally has priority over an aircraft intending to depart from the same or an intersecting runway.

Suspension of VFR operations

When safety requires, VFR operations on or near an aerodrome may be suspended by the approach control unit or appropriate area control centre, the aerodrome control tower, or the appropriate ATS authority. The suspension is made through or notified to the tower.

1. Hold all VFR departures.
2. Recall local VFR flights, or obtain approval for special VFR operations.
3. Notify approach control or the area control centre of the action.
4. Notify operators or their representatives of the reason when necessary or requested.

Circuit, departure and landing clearances are sequenced so that the necessary separation will exist at the point where it is needed, not merely at the moment the words are spoken.

Entry to the traffic circuit

A circuit-entry clearance is used when the aircraft should approach the landing area in the current circuit but traffic does not yet permit a landing clearance. The join may be assigned at any suitable position. An aircraft flying an instrument approach is normally cleared straight in unless visual manoeuvring to the landing runway is required.

Order of priority and departure sequence

Departures are normally cleared in the order in which they are ready. The order may be changed to achieve the maximum number of departures with the least average delay.

Separation before departure

A departure does not normally begin take-off until the preceding departure has crossed the end of the runway in use or started a turn, or until all preceding landing aircraft are clear of the runway.

Take-off clearance

A take-off clearance is issued when there is reasonable assurance that separation will exist when the aircraft begins take-off. The aircraft is ready and at or approaching the departure runway, traffic permits, and the clearance includes the runway designator. An accepted immediate take-off clearance requires one continuous movement from taxi onto the runway and into the take-off roll.

Control of arriving aircraft

A landing aircraft is not normally permitted to cross the threshold on final until the preceding departure has crossed the runway end or started a turn, or all preceding arrivals are clear. A landing clearance may be issued when there is reasonable assurance that the separation will exist at the threshold, but not before a preceding landing aircraft has crossed the runway threshold. The clearance includes the landing-runway designator.

The final group of tower duties keeps visual guidance, wind-shear warnings and runway-condition information current for every take-off and landing.

Aeronautical ground lights

Lights not intended for en-route navigation may be turned off when no regular or emergency operation is likely, provided they can be restored at least one hour before an expected arrival. Variable intensity is adjusted for visibility and ambient light and, when possible, further adjusted on request. Visual approach slope indicator lights operate by day and night whenever the associated runway is used.

Runway lighting includes edge, threshold, centre-line, end, touchdown-zone and wing-bar lights. If a controlled aerodrome does not operate runway lights continuously, one runway remains lit after take-off as long as necessary for an emergency return. At an aerodrome without ATC or central light control, one runway remains lit for the possible return, never less than 15 minutes after take-off.

Wind-shear advisories

Wind shear is a sustained change in wind velocity along the flight path that occurs faster than the aircraft can accelerate or decelerate. Bali describes low-level wind shear from the surface to about 1,500 ft. A pilot report is passed to subsequent arriving and departing aircraft until the condition is confirmed absent, or it is included in ATIS and the crew reports receiving the appropriate designator. The report is also passed to the meteorological office.

Designation of hot spot

The aerodrome operator designates movement-area locations as hot spots when extra attention is required. The hot spots are charted in accordance with Annex 4 so crews can identify them before taxi.

Coefficient of friction

Surface-friction information is assessed for each third of the runway. The first part is always the first third seen in the direction of landing.