RNAV (GNSS) vs RNAV (RNP)

[TotalBeginner]

Can someone please explain what the difference is between an RNAV (GNSS) approach and an RNAV (RNP)?

Many thanks!

[eckhard]

RNAV requires a default RNP of 0.3 for the final approach.
RNP may require a smaller (more accurate) RNP.

Not 100% sure but I think that is the main difference.

[Tom!]

Anything 0.29nm and below is RNP AR, main differences are a lot of regulatory hoops and the requirement for a crew alerting system if the RNP is not being achieved. (Usually a big UNABLE RNP on the ND)

[peekay4]

- RNAV (GNSS) or also called RNAV (GPS): Requires 1nm accuracy for initial and intermediate approach segments, and 0.3nm lateral accuracy for the final approach segment; standard vertical accuracy. Currently only has straight segments.

- RNAV (RNP): May require increased lateral accuracy in any segment (down to 0.1nm for some approaches), and/or has specific vertical accuracy requirements (e.g., using Baro-VNAV). This type of approach may also have curved segments (RF legs). Authorization Required (AR) to fly the approach... practically means redundant equipment, additional crew training and approved operating procedures.

[TotalBeginner]

Thanks everyone, much clearer now.

[underfire]

Airbus 'Getting to grips with RNP AR' (http://www.theairlinepilots.com/forumarchive/aviation-regulations/rnp-ar.pdf)

[DaveReidUK]

RNAV (GNSS) or also called RNAV (GPS)

GNSS is simply the generic term (Global Navigation Satellite System) for any satellite navigation system such as GPS, GLONASS, Galileo, etc.

[underfire]

Total beginner,

There is a Jepp webinar on RNAV on their website, RNAV revealed...that may help.

FREE Aviation Weather Webinar Event Series - Know your Wx | Jeppesen (http://ww1.jeppesen.com/main/corporate/aviation/webinar/)

[peekay4]

GNSS is simply the generic term (Global Navigation Satellite System) for any satellite navigation system such as GPS, GLONASS, Galileo, etc.

My comment was more specific. ICAO defines two different RNP approach procedures: RNP APCH and RNP AR APCH.

In the US, RNP APCH is charted as RNAV (GPS). Internationally, RNP APCH is charted as RNAV (GNSS).

RNP AR APCH is usually charted RNAV (RNP) everywhere.

[Capn Bloggs]

'Getting to grips with RNP AR'
When will the Frogs get their English right? It's "Coming to Grips with" or "Getting a grip on". :=

[underfire]

Obviously, they need a Queen to instruct them properly and keep them in line..just like...

[DaveReidUK]

https://en.wiktionary.org/wiki/get_to_grips_with

[Capn Bloggs]

Wiki... says it all.

[DaveReidUK]

Clearly you haven't got to grips with the concept of synonyms. :O

[aterpster]

Peekay4:
RNP AR APCH is usually charted RNAV (RNP) everywhere.
Seems to be the case that I have seen thus far. But, states are inconsistent about noting when RNP AR missed approaches require RNP of less than 1.0.

[oggers]

Can someone please explain what the difference is between an RNAV (GNSS) approach and an RNAV (RNP)?

Well, personally I get the difference between an RNP approach and an RNP AR approach. But can someone please explain the difference between an RNAV (GPS) approach and an RNP approach? Because the FAA are clear as mud on it:

FAA factsheet "Required Navigation Performance Approaches" says...

This fact sheet will focus on the most common navigation specification called “RNP Approach (RNP APCH)” and titled Area Navigation (RNAV), “RNAV (GPS) Rwy XX”.

As of February 2016 there are over 3,600 LPV lines of minima serving 1,762 airports...there are over 3,500 LNAV/VNAV lines of minima serving 1,669 airports...and over 6,000 LNAV lines of minima at 2,747 airports.

Note: The other approach navigation specification, or set of aircraft and aircrew requirements needed to support a navigation application within a defined airspace, is reserved for complex airspace and called RNP Authorization Required Approach (RNP AR APCH). Authorized pilots of certified aircraft can fly IAP based on RNP AR APCH, which are titled “RNAV (RNP) Rwy XX”.

...but the FAA.gov also say on their webpage “Satellite Navigation - NAS Implementation”:

At present, there are no RNP Approach IAPs that are not of type AR. This may change in the future

...and I have seen that statement reproduced elsewhere (maybe it has just been parroted, I don't know). For instance, the experts on that Jeppesson webinar underfire linked to earlier say that GA pilots can't do RNP approaches - not just RNP AR but any RNP.

Whilst according to AC 120-38D 5-1a:

There have been questions on whether GNSS is an RNAV or RNP system. The answer is GNSS is both an RNAV and RNP system because RNP is a subset of RNAV that also includes a requirement to provide on-board navigation system accuracy performance monitoring and alerting. Therefore, an RNP system is also capable of RNAV. GNSS equipment provides accuracy performance monitoring and alerting which, by definition, makes it an RNP-capable system.

RNAV(GPS) approaches require GPS, which includes on-board performance monitoring and alerting. Therefore, an RNAV(GPS) approach is an RNP procedure where the initial, intermediate, and missed approach segments are RNP 1.0. The LNAV final approach segment is RNP 0.3.

(c) None of the preceding statements should be confused with RNP AR that requires special aircraft and aircrew approval.


So there we have it. According to the FAA, RNAV (GPS) approaches are RNP APCH procedures and there are thousands of them. Except that currently none of them are not of the type AR. Why would anybody be confused?

[aterpster]

True RNP has containment area 2 X RNP with no secondaries. This is used only with RNP AR. The RNP AR aircraft has alerting, accuracy, redundancy, and continuity that is far better than ordinary RNAV, The initial approach segment of an RNAV approach is 6 miles wide, 2 mile primary and 1 mile secondary each side of center-line. OTOH, an RNP AR approach can have an initial approach segment as small as RNP 0.10, which is 1,215 feet each side of center-line. An RNP AR initial that small would be unusual, but 0.50 is not unusual. (1 mile each side of center-line with no secondaries.)

Secondaries in approaches other than RNP AR are necessary to provide the required target level of safety with less sophisticated (and less redundant) avionics than RNP AR. The exception is the LPV final approach segment, which is angular and identical to ILS Category 1. But, even LPV and ILS have secondaries of a sort.

[underfire]

Nov. 16, 2016

As air navigation service providers outside the U.S. implement new International Civil Aviation Organization (ICAO) naming conventions for performance based navigation (PBN) instrument approach procedures (IAP), U.S. operators are being urged to familiarize themselves with both the new standards and country-specific aeronautical information publications (AIPs) to minimize confusion.

The changes stem from ICAO’s 2014 revision to Document 8168, Procedures for Air Navigation Services – Aircraft Operations. ICAO recommends that countries retitle PBN IAPs from “RNAV” to “RNP” by Dec. 1, 2022. Specifically, the changes will see “RNAV (GNSS) RWY XX” changed to “RNP RWY XX” and “RNAV (RNP) RWY XX” to “RNP RWY XX (AR).”

http://i66.tinypic.com/2ebh1dj.jpg

While many countries have begun to make the changes or plan to comply, the FAA plans to retain the title “RNAV” in the U.S. to maintain operational safety and avoid costs related to retitling several thousand PBN IAPs, the agency said.

“There is likely to be a lot of confusion for operators flying outside the U.S., as they are not accustomed to seeing approaches titled ‘RNP’ except for ‘RNAV (RNP) AR,’” said Rich Boll, chairman of the NBAA Access Committee's ATC, Airspace and Flight Technologies Working Group.

“It is important that operators familiarize themselves with specific foreign AIPs to know their status on implementing the changes, and to recognize that, in places that have implemented the changes, ‘RNP RWY XX’ is not necessarily ‘RNP AR,’” Boll added.

While the U.S. does not intend to adopt the ICAO standard regarding the titles of PBN IAPs, the FAA is highlighting the ICAO changes in several ways. FAA is inserting a note into OpSpec/MSpec/LOA C052, Straight-In Non-Precision, APV, and Category I Precision Approach and Landing Minima – All Airports, such that authorization to fly “RNAV (GPS)” IAP should extend to procedures in foreign states titled “RNAV (GNSS) RWY XX” and/or “RNP RWY XX.”

Similarly, a note in OpSpec/MSpec/LOA C384, Required Navigation Performance Procedures With Authorization Required, will reflect ICAO changes from “RNAV (RNP) RWY XX” to “RNP RWY XX (AR),” the FAA said.

https://www.nbaa.org/ops/cns/pbn/20161116-us-operators-urged-to-follow-new-icao-approach-procedure-naming-standards.php

[peekay4]

Very interesting. I see some countries (e.g., Sweden) have adopted the new naming conventions.

But if the FAA isn't going to follow suit then this change is worthless. Instead of unifying the nomenclature we now have three naming standards through 2022:

1. US: RNAV (GPS) and RNAV (RNP)
2. Old ICAO: RNAV (GNSS) and RNAV (RNP)
3. New ICAO: RNP and RNP (AR)

Then after 2022 the best case scenario is that we'll be back to having FAA vs. ICAO, just like before. :ugh:

[FE Hoppy]

Typical ICAO
Just as people are coming to grips with their latest iteration they change it. RNAV - RNP - PBN. You just finish reading one and they scrap it and publish the next. All yours for the bargain price of MEGABUCK$$$$

[underfire]

We have spent a lot of time over the years changing the titles on the plates, and revising waypoint names...

GPS was the name of the American version, so of course, other brands had to call it something else.

There is even talk of changing it from PBN to OBN, instead of performance, it would be operations.

[naveedriaz69]

Well so much for the RNAV GPS/GNSS and RNP AR, some of the approaches r also titled RNAV. At times the clearance given for an RNAV appr is RNAV visual appr. Simply an RNAV appr would be the one without GNSS, What would be an RNAV visual appr?

[underfire]

RNAV VIS...

Something like this.

http://i66.tinypic.com/2exam9s.jpg