RNP Requirements

[Toga]

I have pbn endorsed on my licence and Ive flown countless rnp/rnav approaches but the required hardware / software requirements are somewhat ambiguous to me. For most a/c it means some retrofitting / updating of kit to meet the requirements. According to Boeing the following equipment is required for the B747-400 to be rnp capable:



Does the updated PSX fmc update meet the requirements and permit approaches down to rnp 0.14?

[Hardy Heinlin]

To my knowledge there's no 744 on the planet that has got the DU/EIU upgrade to show the NPS, nor the automatic go-around TO/GA-to-LNAV software update in the FCCs. It's not in the PSX upgrade either.

You just get what the NG FMC adds on this subject; that is, cross track error resolution in hundreds of NM instead of tenths, and extended radio navigation inhibit functions (second NAV RAD page).

For RNP AR, the NG FMC can also increase the LNAV bank angle limit from 25° to 30°, and for RNP < 0.30 the NG FMC increases the LNAV control gain for a more precise tracking.


|-|ardy

[Toga]

Yeah I wasn't sure if there were any flying with that config as it seems overkill and unnecessary. IAN approaches are the future tho!

T

[Toga]

Is the B744 capable of performing GPS approaches? I'm guessing not?

[Hardy Heinlin]

Even with the NG FMC installed, the 744 has not the capability for a GLS/GBAS (ground based augmentation system) approach.

[dhob]

     PBN and GPS are too vague to answer your question. The 747-400 with the Legacy or NGFMC can fly PBN RNP Specification RNAV (GPS) approaches. These approaches use a different nomenclature in Europe, and are labeled RNP approaches. In Asia they can be titled RNAV (GNSS). The RNP required to fly these approaches is 0.3 NM, and are covered under AC 90-105A Appendix A: Required Navigation Performance Approach (RNP APCH) Operations.

     RNP AR, or Required Navigation Performance Authorization Required, fall under AC 90-101A, Approval Guidance for RNP Procedures with AR. Part 121 operators must have OpSpec C384 approval to fly these approaches. The approaches are titled RNAV (RNP) in the US, and RNP AR under EASA rules. Currently the 747-8 is certified to fly these approaches and the AFM (Airplane Flight Manual) includes a statement the demonstrated RNP capabilities are covered in Boeing Document D926U050, which listed the 747-8 is in compliance with AC90-101A. The 747-400 with the NGFMC is not listed as complaint with AC 90-101A.

     We are currently working with Boeing to certify the 747-400 for RNP AR approaches which requires flight tests to collect FTE data. Once this is done, the 747-400 will be eligible to fly the RNP AR approaches, but without TOGA to LNAV, will be limited to approaches with missed approach procedures have an RNP requirement of 1.0 NM. The FTE data will determine the minimum RNP value, which could be as low as 0.1 NM.

     Further, we have switched our MMR (multi-mode receiver) from ABAS to GBAS WAAS based. This will preclude the requirement for a RAIM check.

     Finally GBAS GLS approaches are a completely different category. These fall under AC 120-118, which cover Category I/II/III approaches. Only the 747-8 is equipped for these approaches. The 747-400 would require a significant equipment upgrade and re-certification to be able to fly GLS approaches. ICAO and FAA are now using the nomenclature xLS approaches, which include ILS, GLS, and MLS approaches. All flown identical to ILS approaches. Also the GLS approaches require a LAAS to generate the approach path.

     In summary:
RNP APCH: Both 747-8 and 747-400 approved down to 0.3 NM
RNP AR: Currently 747-8 is certified, RNP 0.1 NM. 747-400 approval coming, RNP less than 0.3 NM to 0.1 NM.
GLS Approach: 747-8 only.

[Toga]

Thanks very much for taking the time to write such a thorough explanation.