Guidance concerning Air Navigation in and above the NAT MNPSA
The technical height-keeping accuracy of aircraft flying at RVSM levels is passively
monitored during flight over a Height Monitoring Unit (HMU) located near to Strumble in Wales. Alternatively, individual aircraft can be monitored through temporary carriage of portable GPS (Height) Monitoring Units (GMUs). Furthermore, height monitoring data is available to the NAT CMA from the 3 European HMUs. This monitoring allows the height-keeping accuracies of aircraft types and individual operator’s fleets to be assessed. Individual airframes which do not meet required performance standards can also be identified. On such occasions the operator and the State of Registry are advised of the problem and
corrective action must be undertaken before further flights in RVSM airspace are conducted.
The overall vertical navigation performance of all aircraft in NAT RVSM airspace is
continually assessed and compared to the standards established for the Region, to assess whether the relevant
TLS is being maintained.
Monitoring of Operational Height-keeping Performance
The introduction of RVSM Airspace into the NAT Region has increased the necessity for
consistent and accurate reporting by pilots and ATC units, of all deviations of 90 m (300 ft) or more from the
cleared flight level, whatever the cause.
Monitoring of Technical Height-keeping Performance
The NAT RVSM programme, from the outset, required confirmation that the RVSM
MASPS were being met programme was therefore
and would continue to be met in future years.
A technical height-keeping
(United Kingdom) and Gander (Canada), along with a number of portable GPS monitoring The Gander unit was subsequently decommissioned. The programme met its initial objectives to produce data as part of an integrated monitoring programme intended to establish RVSM
units (GMU). and continues Airspace on a
Revised Minimum Monitoring Requirements for RVSM Approval, as specified in ICAO
Annex 6, will become effective in November 2010.
Monitoring of ACAS II Performance
ACAS II can have a significant effect on ATC. Therefore, there is a continuing need to
monitor the performance of ACAS II in the developing ATM environment.
Following an RA event, or other significant ACAS II event, pilots and controllers should
complete an ACAS II RA report. Aircraft Operators and ATS authorities should forward completed reports
through established channels.
Overall Navigation (and Systems) Performance
All information relating to horizontal and vertical navigation (and systems) performance
within the NAT Region is provided to the NAT SPG via the CMA. Regular statistical assessments of system safety determine whether or not the overall target level of safety (TLS) is being met. On those occasions that summary statistics show that the TLS, in either the horizontal or vertical planes, has been exceeded, the NAT SPG is informed; in which case the NAT SPG will take appropriate action.
The introduction of modern technology into aircraft systems has lead to a gradual reduction
in the statistical risk of collision in the NAT, in spite of the continual increase in traffic.
NAT Doc 007