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I was recently told by a friend that as soon as RNP for an approach is below the 1.0/0.3nm standard that it is required to be RNP AR.
At least here in Australia, a curved segment anywhere on the approach will qualify it as RNP AR, even if the RNP is 1.0/0.3nm.
Is there a hard and fast rule for RNP AR?
In ICAO DOC 9905 (Required Navigation Performance Authorization Required Procedure Design Manual) you can find the following definition in Chapter 2.1
RNP APCH versus RNP AR APCH
2.1.1 RNP APCH is defined as an RNP approach procedure that requires a lateral TSE of +/-1 NM in the initial, intermediate and missed approach segments (MAS) and a lateral TSE of ±0.3 NM in the FAS. Guidance on implementing RNP APCH operations can be found in the PBN Manual, Volume II, Chapter 5, Implementing RNP APCH.
2.1.2 RNP AR APCH is defined as an RNP approach procedure that requires a lateral TSE as low as ±0.1 NM on any segment of the approach procedure. RNP AR APCH procedures also require that a specific vertical accuracy be maintained as detailed in the PBN Manual, Volume II, Part B, Chapter 6. The datum crossing point (DCP) for RNP AR procedures is the point located above the landing threshold point (LTP) or the fictitious threshold point (FTP). The RNP AR APCH criteria apply only to those aircraft and operators complying with specified additional certification, approval and training requirements. RNP AR APCH procedures are only published where significant operational advantages can be achieved while preserving or improving safety of operation. The RNP AR certification and approval requirements are contained in the PBN Manual. For the purposes of applying the criteria contained in this manual, RNP AR procedure obstacle protection is associated with RNP navigation accuracy requirements. The RNP navigation accuracy requirement is used to determine the area semi-width value (in NM) of a protection area associated with a segment of an instrument procedure.
So, yes, any procedure below the 1.0/0.3 NM standard is defined as RNP AR.
You will not normally find curved segments (RF turns) on an RNP APCH chart, as these segments require a recent FMS as noted in ICAO DOC 8168 Vol. II Part III Appendix to Chapter 5.
Note 5.— RF may only be used for RNP procedures flown by aircraft equipped with systems that are compatible with ARINC 424-17, or later.
In those cases the chart will be promulgated with RF required.
