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... :ok:

[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 (http://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/dtpp/)

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?

http://i61.tinypic.com/24etj12.jpg

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]

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]

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.

[aterpster]

Crun:

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

That's a bit different than the FAA public RNP AR IAPS:

RNAV (RNP) X RWY 8,

followed with the bold note" AUTHORIZATION REQUIRED."

[Capn Bloggs]

Back to the OP (sorry RNP-AR willy-wavers! :E), here in Australia we have been doing GPS-NPAs for years with standalone TSO-129 boxes. Not connected to any FMS/IRU, only warning system in the box is RAIM.

Our CASA has recently moved to ICAO designations and so our old GPS NPAs are now called (and are the equivalent of) RNP APCH LNAV. So my answer to the OP's question would be Yes (if the USA's "GPS" approaches are/were done with a TSO 129 box) as only the name of the approach type has changed. While it ("RNP") sounds impressive, it means nothing different as far as the actual original GPS approach is concerned. Obviously, there are various other types of RNP APCH approaches (sorry for the stutter), the highest level being RNP-AR.

Willy-wavers may now recommence WW! :D

[underfire]

for AA aren't they RNAV (GPS) X,Y,Z RWY 08 ?

Authorization required is in a box at the top, but these were internal plates, have not seen what the Jepp plates look like, and the terminology between Countries keeps changing.

Bloggs, do you have an example, all I see in AUS is stuff like RNAV-Z (GNSS) RWY 28 or GNSS arrival (at least they got rid of the M, N, Q stuff!)

[aterpster]

Bloggs:

Still lots of TSO 129 boxes in use in the U.S. For approaches they are good for the LNAV line of minimums only and RAIM is required. If the airplane has IFR certified Baro VNAV then its good for the LNAV/VNAV line of minimums where they are charted.

[Capn Bloggs]

Bloggs, do you have an example, all I see in AUS is stuff like RNAV-Z (GNSS) RWY 28
Sorry UF, I don't understand. An example of what exactly?

Still lots of TSO 129 boxes in use in the U.S. For approaches they are good for the LNAV line of minimums only and RAIM is required.
In that case, the answer to the OP's question is Yes (assuming that a RNAV (GPS) approach in the US is now the equivalent of an RNP APCH-LNAV (as it is here).

[aterpster]

Bloggs:

A 129 box can fly this approach but not to LPV minimums:

http://aeronav.faa.gov//d-tpp/1405/05310RY24.PDF

And, not to LNAV/VNAV minimums unless the bird has IFR certified Baro VNAV.

[c100driver]

RNP APCH is the general ICAO designator for PBN approach procedures that are not Authorization Required operations.
As GNSS fulfils the basic requirement of RNP for on-board performance and monitoring, both RNAV (GNSS) and SBAS LPV procedures are types of RNP APCH operations.
RNP APCH procedures will be identified as:
• RNP APCH – LNAV
• RNP APCH – LNAV/VNAV (where a vertical guidance system is used)
• RNP APCH – LPV (Localiser Performance with Vertical Guidance)
• RNP APCH – LP (SBAS approach where vertical guidance is not available)

and

The main characteristics of RNP APCH LNAV operations are:
• IAL chart tiled RNAV (GNSS)
• Approach path constructed as series of straight segments
• Descent to an MDA which is published as an LNAV minima
• Can be flown using basic GNSS (TSOC129a) equipment or RNP 0.3 capable aircraft
• Obstacle clearance lateral tolerances not based on RNP value
• Vertical flight guidance (e.g. Baro-VNAV) may be added

and

Although RNAV (GNSS) approach procedures are designated in the PBN concept as RNP APCH – LNAV procedures there has been no change to the method of procedure design which is in accordance with PANS-OPS RNAV(GNSS) design criteria.
Instrument approach charts continue to include RNAV (GNSS) in the title, and descent is made to a minimum descent altitude which is shown as an LNAV minimum, or LNAV/VNAV where vertical guidance is available.
RNAV (GNSS) procedure design criteria is not currently based on an RNP requirement but on the performance capability of a basic TSO C129a GPS receiver. However it is considered that an aircraft with RNP 0.3 capability has at least equivalent performance and a number of States have authorised RNAV (GNSS) operations based on RNP 0.3 capability.

[underfire]

Bloggs, you said RNP APCH LNAV, I was looking for plates called this...

but it appears C100 answered this with Although RNAV (GNSS) approach procedures are designated in the PBN concept as RNP APCH – LNAV procedures there has been no change to the method of procedure design which is in accordance with PANS-OPS RNAV(GNSS) design criteria.

RNAV (GNSS) is designated as RNP APCH LNAV seems very odd...

[Capn Bloggs]

RNAV (GNSS) is designated as RNP APCH LNAV seems very odd...
What's odd about it? Same design standard and using the term "RNP APCH LNAV ..." as an operational term name/describe an approach on a chart or in the FMS is obviously impractical, hence the name "RNAV (RNP)..." on the chart you posted.

http://www.airservicesaustralia.com/aip/pending/dap/AYEGN01-138.pdf

[underfire]

What seems odd to me (on the AUS plates) is the VNAV requirement or lack thereof...

[reynoldsno1]

Proabaly little or no operational requirement for aircraft going to YEGN to have VNAV capability - the underlying LNAV design would not change anyway. Baro-VNAV is an "add-on" that uses a different assessment method for the vertical element.

[Capn Bloggs]

What seems odd to me (on the AUS plates) is the VNAV requirement or lack thereof...
Eh? It is an RNP APCH LNAV approach, not an RNP APCH LNAV/VNAV.

[underfire]

What I meant was, looking thru quite a few plates, they are all RNP APCH LNAV..didnt see any with VNAV minima...seems a bit of a waste

[reynoldsno1]

There have been a number of issues regarding the PANS OPS VNAV criteria, and their perceived deficiencies, and some States have stopped developing them - I believe Australia may be one of them.
There are significant changes to the procedure design criteria due to become effective this November, which will probably mean all existing baro VNAV procedures will require review.

[underfire]

Reynolds,

Interesting. There were some serious issues with the calcs, one calculation was completely wrong, but you could figure out what they meant to say.
The obstacle clearance surfaces did not match between the standards, and the procedure design calculations.

Typically, this was just fixed with exemptions, and since the procedure design criteria was based on FAA criteria (they just had to make the calcs look different) you would get virtually the same answer when you 'corrected' the formulas.

I do know that the turn calcs based on a curve distance over the geoid were wrong, and did not translate easily to the aircraft FMC resultants, requiring multiple iterations to get the criteria results to jive with the ac. This would only come into play with AR procedures.

The obstacle clearance areas were probably the biggest issue, as they were completely different than the FAA method. The criteria for the obstacle clearance areas was about as clear as mud, and I am not sure if anyone ever really complied without exemption. This may be why States are using the horizontal guidance only.

Do you have any links to the new criteria?

[reynoldsno1]

I think we are at cross purposes here - I believe you are talking about the RNP(AR) criteria, which are not part of PANS OPS. A VNAV element is integral to RNP(AR), and, yes, the design criteria are deficient. They are under review, but it will take some time for them to change

The previous thread discussion was referring to the baro-VNAV criteria in PANS OPS, which is always associated with a 2D LNAV procedure. It is these criteria that have been substantially amended - due for publication Nov 2014.
I understand there may be delays in the amendments (Nov 2013 amendment not released yet).

Don't have a link I'm afraid ....