Title: Area Navigation Systems - SKYbrary Aviation Safety
Headings: Area Navigation Systems
Area Navigation Systems
RNAV
Description
Further Reading
EUROCONTROL
CASA
DGCAA (France)
AirServices Australia
ICAO
FAA
ATSB Australia

Content: European standards for Precision Area Navigation (P-RNAV) are now also defined - a navigational accuracy of +/- 1nm (RNP=1) for 95% of the time. Qualifying systems must have the ability to fly accurate tactical offsets, P-RNAV routes must be extracted directly from the FMS data base and must be flown by linking the R-NAV system to the Flight Management System / Autopilot. As well, flight crews are restricted from manually adding waypoints to the route. This level of navigation accuracy can be achieved using DME/DME, VOR/DME or GPS. It can also be maintained for short periods using IRS (the length of time that a particular IRS can be used to maintain P-RNAV accuracy without external update is determined at the time of equipment certification). It should be noted that if GPS is not used as a source then two independent ground-based sources are required to meet P-RNAV minimum requirements apart from specified short periods of INS ‘backup’, which is a more stringent requirement than for some older FMS. P-RNAV is now being used to provide more routes and terminal area procedures and may be used down to the FAF on designated approach procedures. Since the use of a GNSS source for navigation in P-RNAV is optional, it is used only for lateral navigation and baro-VNAV. The final stage of RNAV navigational performance RNP-RNAV combines VNAV with LNAV at an RNP <1, which is expected to be between 0.3nm and 0.1nm for LNAV. This will require suitable augmented GNSS to be the source of position rather than an option for it and will deliver precision approach accuracy in both VNV an LNAV.