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Precision RNAV (P-RNAV) requires a track-keeping accuracy of plus or minus..
  • A
    1.0 NM for 95% of the flight time.
  • B
    8.0 NM for 95% of the flight time.
  • C
    5.0 NM for 95% of the flight time.
  • D
    10.0 NM for 95% of the flight time.
RNAV 1 is the RNAV specification for Precision Area Navigation (P-RNAV). It requires a minimum navigational accuracy of ±1nm 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 FMS/autopilot. In addition, 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 GNSS. It can also be maintained for short periods using inertial reference systems (IRS) and 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 GNSS 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 flight management system (FMS).
P-RNAV is used to provide more routes and terminal area procedures and may be used down to the final approach fix (FAF) on designated approach procedures.

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