ICAO PBN codes

[Mustang93]

So hopefully the concept of PBN, RNP, RNAV...etc are not new topics to many of the members of this forum. I'm hoping not, since I have a question regarding ICAO's new PBN codes now part of Item 18 on ICAO flight plans. I am familiar with the concepts of PBN and RNP but where I begin to scratch my head is when it comes to determining when each code applies.

For example, I fly a C90B King Air with a PBN code of A1B2B4C2D2L1O2 which translates to RNAV10 (RNP 10), RNAV 5 GNSS, RNAV 5 VOR/DME, RNAV 2 GNSS, RNAV 1 GNSS, RNP 4, Basic RNP 1 GNSS. I can find nothing (which is clear) to indicate EXACTLY when each of these codes would be applicable. To illustrate, Enroute my stystem is RNP 2, and within 30NM of destination if refines to RNP 1. Thus, if I want to fly a STAR requiring RNP 1 I can't be assured of that RNP for the entirety of the STAR. Nor can I find anything written which would lead me to believe that if I lost GNSS I would remain RNAV 5 using only VOR/DME sources. (code B4)

Now I am aware that my RNP depends on my location, useable equipment and equipment settings, but isn't saying that I'm RNP 2 capable imply RNP 4, or 5, or 10 or 9.3 or 5.9787...etc? It's kinda like saying I'm 6' tall... so I'm also 5' tall, and also 4.5' tall...etc. I mean if the highest RNP my system will go to is RNP 2 without getting a integrity alert, isn't it safe to say that anything above that RNP is good?

[Sidebar]

PDW, can you provide any assistance?

[ahramin]

Can you not override the FMS RNP setting? If you want 1 before 30 miles can't you just plug that in? What FMS?

[pelmet]

We override for RNAV approaches. We manually enter 0.3 instead of the 1.0 that it has defaulted to. Honeywell FMS. Others I have used switch automatically. Plus for RNAV arrivals, it only switches to 1.0 below 15000 feet.

[ahramin]

Oh and about one level of RNP implying another, that's completely not the case right now. You need approval for each requirement. For example almost everyone has RNP 1, but RNP 4 is not that common.

[bamboo]

There are many differences. For example RNP 10 requires two long range navs. The requirements are clear in the ICAO PBN manual. The CARS also describe what most of the requirements are. You can meet RNP5 and not RNP 4 or 10.