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Guidance concerning Air Navigation in and above the NAT MNPSA


clearances at flight levels or speeds other than those flight planned or, less frequently, may be cleared on oceanic tracks via entry or exit points other than those contained in the filed flight plan. Also it must be recognized that while a filed NAT flight plan may contain one or more step climbs for execution within the NAT Region, the initially issued oceanic clearance, or even any subsequently updated clearance (i.e. re- clearance), has only been co-ordinated for a single ( i.e. initial or current) flight level. It must therefore be appreciated that it is only the flight routing and profile contained in the current received oceanic clearance that has been guaranteed to provide conflict-free progress. Unless this oceanic clearance is precisely the same as the filed flight plan, in any lost communications situation in the NAT Region, if a pilot in receipt of an oceanic clearance unilaterally reverts to his/her filed flight plan (even by simply executing a later step climb), then a guarantee of conflict-free progress no longer exists. Consequently, if a NAT aircraft loses the possibility of communications with the relevant OAC at any time after receiving and acknowledging an oceanic clearance, and the pilot elects to continue the flight, then the aircraft must adhere strictly to the

routing and profile of the current oceanic clearance until exiting the NAT Region. unilaterally revert to their filed flight plan.

Pilots must not

Operational Procedures following Loss of HF Communications Prior to Entry into the NAT

On-Board HF Communications Equipment Failure


Due to the potential length of time in oceanic airspace, it is strongly recommended that a

pilot, experiencing an HF communications equipment failure prior to entering the NAT, whilst still in domestic airspace and still in VHF contact with the domestic ATC Unit, does not enter NAT airspace but adopts the procedure specified in the appropriate domestic AIP and lands at a suitable airport. Should the pilot, nevertheless, elect to continue the flight then every effort must be made to obtain an oceanic clearance and the routing, initial level and speed contained in that clearance must be maintained throughout the entire oceanic segment. Any level or speed changes required to comply with the Oceanic Clearance must be completed within the vicinity of the oceanic entry point.


If, however, an oceanic clearance cannot be obtained, the individual aircraft suffering radio

communications equipment failure should enter oceanic airspace at the first oceanic entry point, level and speed contained in the filed flight plan and proceed via the filed flight plan route to landfall. The initial oceanic level and speed included in the filed flight plan must be maintained until landfall. Any subsequent step-climbs included in the filed flight plan must not be executed.

HF Blackout


In the case of aircraft that lose ATC communications as a result of poor propagation

conditions HF Blackouts when approaching NAT airspace through domestic airspace where ATC communications are also conducted via HF (e.g. entering the NAT through Northern Canadian airspace into the Reykjavik OCA), it is probably less advisable to execute unscheduled landings. These poor propagation conditions are very likely to affect many aircraft simultaneously and multiple diversions of “lost comms”

aircraft might create further difficulties and risks.


As with the equipment failure situation, aircraft approaching the NAT and losing ATC

communications as a result of poor HF radio propagation conditions should, if already in receipt of an oceanic clearance, follow the routing specified in that clearance and maintain the initial cleared level and

speed throughout the oceanic segment i.e. through to landfall.


However, in these HF Blackout circumstances, if no oceanic clearance has been received, the

aircraft must remain at the last cleared domestic flight level, not only to the ocean entry point but also throughout the whole subsequent oceanic segment (i.e. until final landfall). This is in stark contrast to the equipment failure case. In such HF Blackouts, pilots must not effect level changes to comply with filed

NAT Doc 007


Edition 2010

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