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Guidance concerning Air Navigation in and above the NAT MNPSA



The overall lateral navigation performance of all aircraft in the MNPS Airspace is

continually assessed and compared to the standards established for the Region, to ensure that the TLS is

being maintained.

Monitoring of Gross Navigation Errors


Radar stations capable of monitoring the boundaries of the NAT Region collect data on

flights within MNPS Airspace, together with that on non-MNPS Airspace flights. The former data provides a direct input into the risk modelling of MNPS Airspace, whilst the latter provides a wider appreciation of navigation in the NAT Region and allows follow-up action to be taken on a larger sample of flights believed

to have experienced navigation errors.

      • 10.2.9

        The data collection process comprises two parts:

        • a)

          continuous collection of all deviations of 25 NM or more (i.e. GNEs); and

        • b)

          collection of data on deviations of between 15 and less than 25 NM as required.

      • 10.2.10

        When a GNE or lateral deviation of less than 25NM has been detected by the ATS Provider

State or has been reported to ATC by the pilot, that ATS Provider unit will, in co-operation with the Operator, investigate its cause. It is important that all agencies react promptly to such reports of GNEs and other lateral deviations. Investigations should be made at once so that consideration can be given to the need for swift remedial action. In order that deviation reports can receive prompt attention, each airline/Operator should nominate a person to be responsible for receiving reports and to initiate investigations; the name and full address of this individual should be notified to each relevant ATS administration.

    • 10.3

      Monitoring of Height-Keeping Performance

      • 10.3.1

        The vertical navigation performance of operators within NAT MNPS Airspace is monitored

on a continual basis by the NAT CMA. Such monitoring includes both measurement of the technical height- keeping accuracy of RVSM approved aircraft and assessment of collision risk associated with all reported operational deviations from cleared levels.


All identified operational situations or errors which lead to aircraft deviating from ATC

cleared levels are subject to thorough investigation. Follow-up action after flight is taken with the operator of the aircraft involved, to establish the reason for the deviation or cause of the error and to confirm the approval of the flight to operate in NAT MNPS and RVSM Airspace. Operational errors, particularly those in the vertical plane, can have a significant effect on risk in the system. For their safety and the safety of other users, crews are reminded of the importance of co-operating with the reporting OAC in the compilation of appropriate documentation including the completion of an ‘Altitude Deviation Report Form’, as illustrated

at Attachment 2.


The detailed circumstances of all operational errors, both in the vertical and horizontal

planes, are thoroughly reviewed by the CMA, together with the Scrutiny Group of the NAT SPG, which includes current NAT pilots and controllers. Any lessons learned from this review, which may help to limit the possibility of recurrences of such errors, are communicated back to NAT operators and ATS authorities. The intent is to improve standard operating procedures, thereby reducing the future frequency of operational

errors and thus contribute to the safety of the overall system.


At RVSM levels, moderate and severe turbulence may also increase the level of system risk

and crews should report ALL occasions, whilst flying in MNPS Airspace, whenever a vertical deviation of 300 ft or more occurs. The form at Attachment 2 may also be used for this purpose.

NAT Doc 007


Edition 2010

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