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voice communications with a single aircraft fail, the relevant published “lost comms procedures” normally
require that aircraft to “land at a suitable aerodrome or continue the flight and adjust level and speed in
accordance with the filed flight plan”. Communications blackouts affecting multiple aircraft, are not a
feature of this type of VHF environment.
Non-Radar Environment
6.6.17 However, in a (largely) non-radar environment such as the North Atlantic, ATC must rely
upon the Position Reports communicated by each aircraft for all position, progress and intent data. On-board
communications equipment failures and/or poor HF propagation conditions can interrupt the provision of this
information. Therefore, to mitigate against such occurrences ATC usually employs strategic traffic planning
and Oceanic Clearances issued by NAT OACs are first pre-co-ordinated with any downstream OACs, thus
ensuring that flights following a received oceanic clearance are guaranteed conflict free progress from the
oceanic entry point through to oceanic exit. By this means, safe NAT passage for all flights continuing to
adhere to their received oceanic clearance, is ensured, even if no ATS communications are subsequently
possible with any one, or even with all, of those aircraft.
6.6.18 Every effort is made by the initial NAT OAC to clear aircraft as per their filed flight plans.
However, this is not always possible, particularly during peak traffic flow periods. Aircraft may receive
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. reclearance),
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.
Operational Procedures following Loss of HF Communications Prior to Entry into the NAT
On-Board HF Communications Equipment Failure
6.6.19 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.
NORTH ATLANTIC MNPSA OPERATIONS MANUAL CHAPTER 6
NAT MNPS 35 Edition 2005
6.6.20 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. N.B. This is
the ONLY situation in which a pilot may unilaterally elect to “fly the flight plan” through the NAT Region.
“HF Blackout”
6.6.21 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
　
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