ATS.OR.135 Contingency arrangements

The various circumstances surrounding each ATS contingency situation preclude the establishment of exact detailed procedures to be followed.

RADIO COMMUNICATION CONTINGENCIES IN AIR TRAFFIC CONTROL SERVICE

(a)General Air traffic control contingencies related to communications, i.e. circumstances preventing an air traffic controller from communicating with aircraft under control, may be caused by either a failure of ground radio equipment, a failure of airborne equipment, or by the control frequency being inadvertently blocked by an aircraft or a ground transmitter, or any unauthorised use. The duration of such events may be for prolonged periods and appropriate action to ensure that the safety of aircraft is not affected should therefore be taken immediately.

(b)Complete ground radio failure

(1)In the event of complete failure of the ground radio equipment used for air traffic control service, the air traffic controller should:

(i)attempt to establish radio communications on the emergency frequency 121.500 MHz;

(ii)without delay inform all adjacent control positions or air traffic control units, as applicable, of the failure;

(iii)apprise such positions or units of the current traffic situation;

(iv)request their assistance, in respect of aircraft which may establish communications with those positions or units, in establishing and maintaining separation between such aircraft; and

(v)instruct adjacent control positions or air traffic control units to hold or re-route all controlled flights outside the area of responsibility of the position or air traffic control unit that has experienced the failure until such time that the provision of normal services can be resumed, unless able to continue to provide air traffic services by means of other available communication channels.

(2)In order to reduce the impact of complete ground radio equipment failure on the safety of air traffic, the air traffic services provider should establish contingency procedures to be followed by control positions and air traffic control units in the event of such failures. Where agreed between affected air traffic services providers, such contingency procedures should provide for the delegation of control to an adjacent control position or air traffic control unit in order to permit a minimum level of services to be provided as soon as possible, following the ground radio failure and until normal operations can be resumed.

(c)Blocked frequency In the event that the control frequency is inadvertently blocked by an aircraft transmitter, the following additional steps should be taken:

(1)attempt to identify the aircraft concerned;

(2)if the aircraft blocking the frequency is identified, attempts should be made to establish communication with that aircraft, e.g. on the emergency frequency 121.500 MHz, by SELCAL, through the aircraft operator’s company frequency if applicable, on any VHF frequency designated for air-to-air use by flight crews or any other communication means or, if the aircraft is on the ground, by direct contact; and

(3)if communication is established with the aircraft concerned, the flight crew should be instructed to take immediate action to stop inadvertent transmissions on the affected control frequency.

(d)Unauthorised use of ATC frequency Instances of false and deceptive transmissions on air traffic control frequencies which may impair the safety of aircraft can occasionally occur. In the event of such occurrences, the air traffic control unit concerned should:

(1)correct any false or deceptive instructions or clearances which have been transmitted;

(2)advise all aircraft on the affected frequency(ies) that false and deceptive instructions or clearances are being transmitted;

(3)instruct all aircraft on the affected frequency(ies) to verify instructions and clearances before taking action to comply;

(4)if practical, instruct aircraft to change to another frequency; and

(5)if possible, advise all aircraft affected when the false and deceptive instructions or clearances are no longer being transmitted.

CONTINGENCY PROCEDURES FOR AIR TRAFFIC SERVICES UNITS WHEN A VOLCANIC ASH CLOUD IS REPORTED OR FORECAST If a volcanic ash cloud is reported or forecast in the airspace for which the air traffic services unit is responsible, the following actions should be taken, as appropriate:

(a)relay pertinent information immediately to flight crews whose aircraft could be affected to ensure that they are aware of the ash cloud’s current and forecast position and the flight levels affected;

(b)accommodate requests for re-routing or level changes to the extent practicable;

(c)suggest re-routing to avoid or exit areas of reported or forecast ash clouds when requested by the pilot or deemed necessary by the air traffic controller; and

(d)when practicable, request a special air-report when the route of flight takes the aircraft into or near the forecast ash cloud and provide such special air-reports to the appropriate agencies.

Guidance on contingency planning for air navigation services providers, including air traffic services providers, may be found in:

(a)ICAO Annex 11 - Attachment C ‘Material relating to contingency planning’; and

(b)the ‘EUROCONTROL Guidelines for Contingency Planning of Air Navigation Services (including Service Continuity)’ Edition 2.0 of 06/04/2009, available at: https://www.eurocontrol.int/sites/default/files/article/content/documents/nm/safety/safety-guidelines-contingency-planning-ans-2009.pdf, and in its complementary document named ‘Reference Guide to EUROCONTROL Guidelines for Contingency Planning of Air Navigation Services (including Service Continuity)’ Edition 2.0 of 06/04/2009, available at: https://www.eurocontrol.int/publication/eurocontrol-guidelines-contingency-planning-air-navigation-services