Guidance concerning Air Navigation in and above the NAT MNPSA
MNPS FLIGHT OPERATION & NAVIGATION PROCEDURES
The aircraft navigation systems necessary for flying in NAT MNPS Airspace are capable of
high-performance standards. However, it is essential that stringent cross-checking procedures are employed, both to ensure that these systems perform to their full capabilities and to minimise the consequences of equipment failures and possible human errors.
Navigation systems are continually evolving and early editions of the NAT MNPSA
Operations Manual concentrated on offering specific guidance on the use of individual approved long range navigation systems. The current philosophy within ICAO is to specify the navigation system performance
required for Navigation” accuracies to
operations within a (PBN). Within this
This concept is referred to as “Performance Based
be achieved, also require on-board automatic integrity monitoring and alerting functions.
specifications are referred to as RNP-X, where X represents However, specifications requiring the same accuracies but not
an accuracy of 95% containment in X Nms. requiring on-board monitoring are referred to
MNPS has been in use in the NAT Region for more than thirty years. It does not require on-
board automatic monitoring and alerting functions. Instead, pilots must remain vigilant and are required to employ rigorous routine manual monitoring procedures. In the 1990’s a navigation requirements system was introduced for use originally in the Pacific Region. Like the MNPS, it too does not include any requirement for on-board automatic monitoring. Its introduction was long before the PBN concept was developed and it was then annotated as “RNP-10”. Large numbers of aircraft worldwide are now in receipt of “RNP-10” approvals. To conform with the PBN standard terminology, as indicated above, this system should actually
be designated as “RNAV-10”.
However, it has been recognised that re-classifying such a widespread
existing approval designation would create significant difficulties for both operators and State regulators. Consequently, it has been agreed that this designation of “RNP-10” will remain as such, even though the navigation specifications here are, in PBN terminology, effectively “RNAV-10”.
With current technology, on-board automatic performance monitoring can only be carried
out using GPS. Hence GPS is mandatory for true RNP airspace (e.g. RNP-4) but is not required for RNAV
airspace, including that historically and still designated as “RNP-10”.
MNPS was established primarily with the NAT OTS environment in mind. The defining
waypoints of OTS tracks are specified by whole degrees of latitude and, using an effective 60 NM lateral separation standard, most adjacent tracks are separated by only one degree of latitude at each ten-degree meridian. The traffic density in the OTS is higher than in any other oceanic airspace. In such a densely populated flexible track system (one that changes twice every day), it is essential that crews avoid (whole degree) waypoint insertion errors. Such errors in the NAT MNPSA will inevitably result in a conflict with traffic on an adjacent track. For this reason Minimum Navigation Performance Specifications had to include not just the technical navigation accuracy of the Long-range Navigation Systems used on the aircraft but also the crew navigation procedures employed. The MNPS statement thus involves both cockpit/flight deck procedures and crew training requirements. In the early days of the RNP concept, it was these additional requirements that separated MNPS from RNP. However, RNP has come a long way since its inception and the development of the RNP-10 approvals for PAC operations brought it much closer to the original MNPS concept. The ICAO Air Navigation Plan for the North Atlantic Region states that the intention in the future is that navigational performance is expected to be tied to a level of RNP. This will probably require the
NAT Doc 007