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Guidance concerning Air Navigation in and above the NAT MNPSA


flight plans. Such aircraft should, however, enter oceanic airspace at the first oceanic entry point and speed contained in the filed flight plan and proceed via the filed flight plan route to landfall.


The rationale here must be appreciated. In such circumstances it is likely that ATC will have

simultaneously lost HF communications with multiple aircraft in the same vicinity. Should pilots then wrongly apply the “normal” radio failure procedures and “fly the flight plan”, there is a possibility that two such aircraft may have filed conflicting flight paths/levels through the subsequent oceanic airspace, and without communications with either aircraft, ATC would then be unable to intervene to resolve the conflict. Since safe aircraft level separation assurance has already been incorporated into the current domestic clearances, it is consequently imperative that under such (Domestic and Oceanic) HF-blackout circumstances, all aircraft electing to continue flight into NAT oceanic airspace without a received and acknowledged oceanic clearance, should adhere to the flight level in the last received domestic clearance. No level changes should be made to comply with a filed oceanic level that is different from

that of the domestic clearance in effect at the time that ATC air-ground communications were lost.

Operational Procedures following Loss of HF Communications after Entering the NAT


If the HF communications equipment failure occurs or HF Blackout conditions are

encountered after entering the NAT then : -

The pilot must proceed in accordance with the last received and acknowledged Oceanic Clearance, including level and speed, to the last specified oceanic route point (normally landfall). After passing this point, the pilot should conform with the relevant AIP specified State procedures/regulations and if necessary rejoin the filed flight plan route by proceeding, via the published ATS route structure where possible, to the next significant point contained in the filed flight plan. Note: the relevant State procedures/regulations to be followed by an aircraft in order to rejoin its filed Flight Plan route are specified in detail in the appropriate State AIP.


Aircraft with a destination within the NAT Region should proceed to their clearance limit

and follow the ICAO standard procedure to commence descent from the appropriate designated navigation aid serving the destination aerodrome at, or as close as possible to, the expected approach time. Detailed

procedures are promulgated in relevant State AIPs.

Summary of Operational Procedures Required following Loss of Air/Ground ATS Communications in the NAT Region

      • 6.6.28

        The foregoing detailed operational procedures can be simply summarised as follows :

        • Equipment Failure before receiving an Oceanic Clearance:- Divert or fly the Flight Plan route, speed and initial planned oceanic level to landfall.

        • Blackout encountered (in an HF comms Domestic ATC environment) before receiving an Oceanic Clearance:-

Continue at Domestic cleared level and follow flight planned route and speed to landfall.

  • Equipment Failure or Blackout after receiving an Oceanic Clearance:-

Fly that clearance to landfall.

In all cases, after landfall rejoin, or continue on, the flight planned route, using appropriate State AIP specified procedures for the domestic airspace entered.

NAT Doc 007


Edition 2010

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