4.1 Authority
4.1.1 Approach control offices and aerodrome control towers shall observe the co-ordination instructions issued by the appropriate area control centre. Aerodrome control towers shall, in addition, observe the co-ordination instructions issued by the appropriate approach control office.
4.2 Co-ordination between units providing area control service within contiguous control areas
4.2.1 Area control centres shall forward from centre to centre, as the flight progresses, necessary flight plan and control information.
Note.— See also 2.4.
4.2.2 The information specified in 4.2.1 shall be transmitted in sufficient time to permit reception and analysis of the data by the receiving centre and necessary co-ordination between the two centres concerned.
Note.— See Part IX and Appendix 3 for details regarding messages, their content and time of transmission.
4.2.3 If the departure aerodrome of an aircraft is not a sufficient distance from the boundary of an adjacent control area to permit transmission of the necessary flight plan and control information to the accepting centre after take-off and
adjacent control area, the aircraft shall be held within the transferring centre’s area until flight plan and control information can be forwarded and co-ordination can be effected with the adjacent centre.
4.2.3.2 In the case of an aircraft requesting a change in its current flight plan, or of a transferring centre proposing to change the current flight plan of an aircraft in the vicinity of the boundary in circumstances similar to that described, the revised clearance shall be withheld pending acceptance of the proposal by the adjacent centre.
4.2.4 When boundary estimate data are to be transmitted in the circumstances mentioned in 4.2.3, the time in respect of an aircraft not yet departed shall be based upon the estimated time of departure as determined by the ATC unit at the departure aerodrome. In respect of an aircraft in flight requiring an initial clearance, the time shall be based on the estimated elapsed time from the holding point to the boundary plus the time expected to be needed for co-ordination.
4.2.5 With regard to the information provided by the transferring centre in accordance with 4.2.1 and 4.2.3, the accepting centre shall notify the transferring centre either that it is able to accept the aircraft concerned under the conditions specified or it shall specify to the transferring centre which changes to the flight plan are required so that the aircraft can be accepted; however, where special arrangements exist between the ATC units concerned, this notification shall only be required if the aircraft cannot be accepted as offered by the transferring centre.
4.2.6 The primary responsibility for the control of air traffic remains with the area control centre in whose control area the aircraft is operating until the time the aircraft is estimated to cross the boundary of that control area, even when control of one or more aircraft is exercised under delegation by other air traffic control units (see Annex 11, 3.5.2). It is emphasized that the accepting centre which is in communication with an aircraft not yet having reached the incoming transfer of control point shall not alter the clearance of such aircraft without the prior approval of the transferring centre.
responsibility for control should be assumed by the accepting centre, either forthwith or, if a specified transfer of control point has been established, at the time when the aircraft passes that point. If the SSR Mode and Code currently radiated by the aircraft are known, and the accepting centre is able to make use of these data, they should be included in such notification. If transfer of radar control is to be effected, such notification shall also include information regarding the position (and track and speed, if required) of the radar position of the aircraft. Such notification shall also include significant changes in the data transmitted in accordance with 4.2.1 which have not been previously forwarded.
4.2.8 Where special arrangements exist between two area control centres which are not equipped with radar and which do not employ automatic data-processing equipment, the notification in 4.2.7 need only be made in circumstances where it is appropriate to forward a revision to previously transmitted current flight plan and control data at the time when the aircraft is in a position to be handed over to the accepting centre.
4.2.9 Where non-radar separation minima are being applied, the transfer of air-ground communications of an aircraft from the transferring to the accepting centre shall be made five minutes before the time at which the aircraft is estimated to reach the common control area boundary, unless otherwise agreed between the two area control centres concerned.
4.2.10 In circumstances where radar or ADS separation minima are being applied at the time of transfer of control, the transfer of air-ground voice and/or data communications of an aircraft from the transferring to the accepting centre shall be made immediately after the accepting centre has agreed to assume control unless the provisions of Part VI, 7.3.2 are applied.
4.2.11 A notification from the transferring centre that the aircraft will be cleared or has already been cleared to establish radio and/or data communications with the accepting centre is required in those cases where this has been agreed between the two area control centres concerned.
4.2.12 The accepting centre shall notify the transferring centre that radio and/or data communication has been estab- lished with the aircraft being transferred and control of the aircraft has been assumed, unless otherwise specified by agreement between the area control centres concerned.
4.2.13 In cases where a portion of a control area is so situated that the time taken by aircraft to traverse it does not permit the application of control by the centre concerned, agreement should be reached to provide for direct transfer between the centres responsible for the adjacent control areas, provided that the intermediate centre is fully informed of such traffic; it may also require the other centres to comply with any necessary requests to obviate interference with its own traffic.
4.2.14 In the case where a flight ceases to be operated as a controlled flight, i.e. by leaving controlled airspace or by cancelling its IFR flight and proceeding on VFR in airspace where VFR flights are not controlled, the area control centre concerned shall ensure that appropriate information on the flight is forwarded to ATS unit(s) responsible for the provision of flight information and alerting services for the remaining portion of the flight, in order to ensure that such services will, in fact, be provided to the aircraft.
4.3 Co-ordination between a unit providing area control service and a unit
providing approach control service
4.3.1 Division of control
4.3.1.1 A unit providing approach control service may issue air traffic control clearances to any aircraft released to it by an area control centre without reference to the area control centre, except that when an approach has been missed the area control centre shall be advised immediately and subsequent action co-ordinated between the area control centre and the unit providing approach control service.
4.3.1.2 Time of take-off shall be specified by the area control centre when it is necessary to:
a) co-ordinate the departure with traffic not released to the unit providing approach control service; and b) provide en-route separation between departing aircraft
following the same route.
4.3.1.2.1 If time of take-off is not specified, the unit providing approach control service shall determine the take-off time when necessary to co-ordinate the departure with traffic released to it.
4.3.1.3 A clearance expiry time shall be specified by the area control centre if a delayed departure would conflict with traffic not released to the unit providing approach control service. If, for traffic reasons of its own, a unit providing approach control service has to specify in addition its own clearance expiry time, this shall in no case be later than that specified by the area control centre.
4.3.1.4 When weather conditions require an approach sequence, the area control centre shall clear arriving aircraft to the holding point, including holding instructions and expected approach time in such clearance. If the approach sequence is such that succeeding arrivals would be required to hold at high levels, such arrivals should be cleared to other points until lower levels are vacated in the approach sequence.
4.3.1.5 After co-ordination with the unit providing approach control service, the area control centre may clear the first arriving aircraft for approach rather than to a holding point.
4.3.1.6 After co-ordination with the unit providing approach control service, the area control centre may clear arriving aircraft to visual holding points to hold until further advised by the unit providing approach control service.
4.3.1.7 Any additional procedures necessary for proper co-ordination with reference to individual aerodromes shall be contained in local written instructions approved by the appropriate ATS authority. Where an approach control office is established, an area control centre may, after co-ordination with such office, release aircraft directly to aerodrome control towers if the entire approach will be made under visual meteorological conditions.
4.3.2 Exchange of movement and control data
4.3.2.1 From the unit providing approach control service to the area control centre. The unit providing approach control
service shall keep the area control centre promptly advised of pertinent data on controlled traffic such as:
a) lowest vacant level at the holding point available for use by the area control centre;
control service indicates a variation of five minutes or such other time as has been agreed between the two ATC units concerned;
e) arrival times over the holding point when these vary by three minutes, or such other time as has been agreed between the two ATC units concerned, from those previously estimated;
f) cancellations by aircraft of their IFR flights, if these will affect levels at the holding point or expected approach times of other aircraft;
g) departure times of departing aircraft;
h) all available information relating to overdue or unreported aircraft;
i) missed approaches.
4.3.2.2 From the area control centre to the unit providing approach control service. The area control centre
shall keep the unit providing approach control service promptly advised of pertinent data on controlled traffic such as:
a) identification, type and point of departure of arriving aircraft;
b) estimated time and proposed level of arriving aircraft over holding point or actual time if aircraft is released to the unit providing approach control service after arrival over the holding point;
c) requested type of instrument approach procedure if different to that specified in 4.3.2.1 b);
d) expected approach time issued;
e) statement that aircraft has been cleared to contact the unit providing approach control service;
f) statement that an aircraft has been released to the unit providing approach control service including, if necessary, the time and conditions of release;
g) anticipated delay to departing traffic due to conges- tion.
4.4.1 Division of control
4.4.1.1 A unit providing approach control service shall retain control of arriving aircraft until such aircraft have been cleared to the aerodrome control tower and are in communication with the aerodrome control tower. Not more than one arrival shall be cleared to a unit providing aerodrome control service during IMC, except when prior arrangements have been made by the appropriate ATS authority.
4.4.1.2 After co-ordination with the aerodrome control tower, the unit providing approach control service may clear arriving aircraft to visual holding points to hold until further advised by the aerodrome control tower.
4.4.1.3 A unit providing approach control service may authorize an aerodrome control tower to release an aircraft for take-off subject to the discretion of the aerodrome control tower with respect to arriving aircraft.
4.4.1.4 Aerodrome control towers shall obtain approval from the unit providing approach control service prior to authorizing operation of special VFR flights.
4.4.2 Exchange of movement and control data
4.4.2.1 From an aerodrome control tower to the unit providing approach control service. An aerodrome control
tower shall keep the unit providing approach control service promptly advised of pertinent data on relevant controlled traffic such as:
a) arrival and departure times;
b) statement that the first aircraft in an approach sequence is in communication with and is sighted by the aerodrome control tower, and that reasonable assurance exists that a landing can be accomplished; c) all available information relating to overdue or unre-
d) information concerning missed approaches;
e) information concerning aircraft that constitute essential local traffic to aircraft under the control of the unit providing approach control service.
4.4.2.2 From the unit providing approach control service to an aerodrome control tower. The unit providing approach
control service shall keep the aerodrome control tower promptly advised of pertinent data on controlled traffic such as:
a) estimated time and proposed level of arriving aircraft over the aerodrome, at least fifteen minutes prior to estimated arrival;
b) statement that an aircraft has been cleared to contact the aerodrome control tower and that control shall be assumed by that unit;
c) anticipated delay to departing traffic due to congestion.
4.5 Co-ordination between control positions within the same unit
4.5.1 Appropriate flight plan and control information shall be exchanged between control positions within the same air traffic control unit, in respect of:
a) all aircraft for which responsibility for control will be transferred from one control position to another;
b) aircraft operating in such close proximity to the boundary between control sectors that control of traffic within an adjacent sector may be affected;
c) all aircraft for which responsibility for control has been delegated by a procedural controller to a radar controller, as well as other aircraft affected.
5. Co-ordination between