RNP specification required for U.S. FAR Part 97 RNAV (GPS) approach?

[boeing707100]

Hello!

In the United States, can an aircraft utilizing avionics with an RNAV-only specification (no RNP specification) shoot a standard FAR Part 97 RNAV (GPS) procedure? ICAO would classify this as an RNAV (RNP) non-AR approach.

My first thought was yes, of course they can. The RNAV (GPS) LNAV only level of service is now replacing the traditional stand-alone GPS procedure. But the further I research, I'm not so sure. The nav structure is RNP specific (1.0 initial and intermediate, 0.3 final), so full-scale deflection of the CDI on the final segment would violate the RNP-0.3 performance requirement.

If an RNP specification is required, then the unit must have onboard performance monitoring and alerting for this type of approach.

Any information you can provide would be helpful. Thank you.

[MarkerInbound]

In the US there are RNAV (GPS) and RNAV (RNP) approaches. The only RNAV (RNP) approaches I can find are at DCA. As you say, RNP requires not only that the box meet the standard but when it doesn't it tells you.

As I understand it, if your RNAV box is approved for approaches you can shoot RNAV (GPS) approaches. To do RNAV (RNP) requires another level of certification -AR. AC 90-101a and 105 give guidance.

[aterpster]

The U.S. probably has over 100 RNP AR approaches now. Some are "entry level" RNP 0.3 with a conventional missed approach. (IRU not required).

Others have lower, more critical RNP values and some with RNP missed approaches. Either condition: minimums predicated on RNP of less than 0.30, and/or an RNP missed approach, require at least one IRU in addition to many redundancies required for RNP AR IAPs.

Although "regular" LNAV approaches are technically RNP 0.30, they have generous containment buffers, unlike RNP AR, where containment areas have no buffers; just 2 X the RNP value.

LPV is a different beast. It is an angular scheme that emulates ILS. IMHO, LPV is better than a whole lot of CAT 1 ILSes in the U.S., but probably limited to CAT 1 minimums without local augmentation.

[MarkerInbound]

Cool, I was randomly clicking through Jepp pages and didn't see any at what I thought might be the "usual suspects." I saw the DCA charts on a FAA page explaining AR.

[underfire]

Check out Deadhorse, AK! PASC, and of course KPSP...

[aterpster]

Some good ones:

KLWS
KGPI Rwy 20
KMSO Rwy 29
KMFR Rwy 32
KGUC Rwy 24
KMRY Rwy 28L
KSDL
PHNL Rwy 26L
KBIH Rwy 30

[MarkerInbound]

Re Deadhorse, wish I could post it. The overhead break as an instrument approach. Or, "We're going to keep doing this until we do it right!"

[aterpster]

Every current FAA approach chart is viewable (and can be downloaded) at the link in the middle of this page:

digital ? Terminal Procedures Publication (d-TPP)/Airport Diagrams

Be sure to select the ICAO ID option.

[reynoldsno1]

The ICAO nav specification for RNAV(GNSS) procedures is RNP APCH. The spec can be found in the ICAO PBN manual.

[underfire]

Re Deadhorse, wish I could post it. The overhead break as an instrument approach. Or, "We're going to keep doing this until we do it right!"

More like, there is a herd of Caribou on the runway, we need to go around. Aside from that, how many coded GA's set you up for an approach?



I must say, a brilliant, brilliant design!

EDIT: BTW, there is the same procedure, using the same track using a 3.5GPA which is good from -50 to -24! How good is that!

[flyburg]

Disregard, have to start reading better!!

[boeing707100]

ATTN: aterpster

Does an RNAV (GPS) approach require onboard performance monitoring and alerting, since they all contain standard RNP levels?

[ImbracableCrunk]

The non-public RNP-AR approaches are much more fun. Juneau and Sitka are two of my favorites. Juneau is interesting in that you're winding through the mountain valleys. Sitka has a nice 90 degree turn at about a 2 mile final.

[aterpster]

Does an RNAV (GPS) approach require onboard performance monitoring and alerting, since they all contain standard RNP levels?

Yes. But, the redundancy requirements are far less.

LPV doesn't require redundancy either, but its performance alerting an monitoring is very stringent.

[boeing707100]

Thank you aterpster

Thanks for your time.

[underfire]

The non-public RNP-AR approaches are much more fun. Juneau and Sitka are two of my favorites. Juneau is interesting in that you're winding through the mountain valleys. Sitka has a nice 90 degree turn at about a 2 mile final.

Concur, the non-public RNP to SCC has a 2nm short final, 1.5nm turn, rollout is at DA...that is entertaining, but not like running the valley...

[aterpster]

Those are special instrument approach procedures predicated specifically on the performance of Alaska Airlines fleet and their specific training and qualification procedures. Those procedures often are not designed in accordance with U.S. and ICAO RNAP AR criteria.

So, picking at nits, the Alaska special RNP IAPs are not really RNP AR procedures.

[ImbracableCrunk]

So, picking at nits, the Alaska special RNP IAPs are not really RNP AR procedures.

Did not know that. We just call them RNP RNAV.

[aterpster]

Does the "we" mean you are an Alaska pilot? If so, is that the title on the Jepp charts? None of us outsiders have access to Alaska Airline's special Jepps.

[ImbracableCrunk]

Here's a title example: RNP RNAV "X" Rwy 8.