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RNAV (GNSS)

Old 13th Nov 2014, 01:15
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RNAV (GNSS)

Hi there

Can someone please advise that an RNAV (GNSS) approach requires a working GPS in all cases? I.e. with failed GPS receivers the approach cannot be flown with reference to RADIO UPDATING, INERTIAL pos etc. Silly question I know. Just trying to confirm my assumption.

Thanks
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Old 13th Nov 2014, 04:58
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Correct.

What is in the brackets is the basis of your approach. No GPS no RNAV (GNSS) approach. If it was an RNAV (RNP) you could still continue an approach as long as the ANP was within the RNP.

Last edited by c100driver; 13th Nov 2014 at 21:29. Reason: correcting jetlaged spelling
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Old 15th Nov 2014, 05:42
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Point of order there.
If it says RNAV (RNP) you certainly cannot continue without dual GPS receivers as that's an RNP AR approach or SAAR as our American friends call it and GPS is a required item.
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Old 15th Nov 2014, 15:06
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8che:

Point of order there.
If it says RNAV (RNP) you certainly cannot continue without dual GPS receivers as that's an RNP AR approach...
Absolutely correct. IRU position is for extraction in the event of a loss of GPS.

... or SAAR as our American friends call it...
We stopped using SAAR a couple years ago. They are now RNP AR.
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Old 15th Nov 2014, 22:14
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And this is where all the confusion starts, as in all aviation "it depends" on how ahead or behind your certifying authority are in the PBN world.

RNAV (RNP) is not equal to RNP APCH, it is similar in many respects but it is certainly not SAAAR or RNAV (RNP AR) or RNP AR APCH (three names for the same approach by different states).

RNAV (RNP) is not part of the ICAO PBN structure. It was an attempt to allow such equipped aircraft to operate using the current aircraft navigation capability. As such in some states RNAV (RNP) was able to be flown without GNSS, but required Radar monitoring, however many states decided (quite rightly in my view) that GNSS should be part of the aircraft system requirements. RNAV (RNP) did not have RF legs or an RNP less that 0.3:

RNAV (RNP AR), SAAAR or RNP AR APCH can have RF legs, could be below 0.3 and could be either public or tailored (private) for specific requirements.

The whole PBN debacle of nomenclature, sensor requirements etc was the result of the US and Europe heading for similar outcomes via different pathways and the slow cumbersome nature of ICAO to develop a standard.

As the ICAO contracting states start towards PBN standardisation most of the confusion "should" disappear.

The USA name for RNP AR APCH was SAAAR (three A's) Aircraft, Aircrew Authorisation.

If it says RNAV (RNP) you certainly cannot continue without dual GPS
My regulator: you cannot start an RNP AR APCH approach without Dual GNSS but after the FF you can continue with a single GNSS.
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Old 15th Nov 2014, 23:23
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Well from our newly updated operations manual :


RNAV (GNSS) APPROACHES


Definition : non-precision approaches with LNAV or LNAV/VNAV minima.


- "RNAV (GNSS) approaches" corresponds to "RNP APCH operations"


- "RNAV (RNP) approaches" corresponds to "RNP AR APCH operations"


RNP AR OPERATIONS


General


Required navigation performance instrument approach procedures with authorisation required (RNP AR) are charted as RNAV (RNP) RWY XX " and contain a special note on the chart to aircrew and operators. These procedures are commonly referred to as "RNP AR" or in the USA "RNP SAAAR".
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Old 16th Nov 2014, 01:46
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8che:

Required navigation performance instrument approach procedures with authorisation required (RNP AR) are charted as RNAV (RNP) RWY XX " and contain a special note on the chart to aircrew and operators. These procedures are commonly referred to as "RNP AR" or in the USA "RNP SAAAR".
Old or incorrect source.

The U.S. changed to RNP AR at least two years ago.

Last edited by aterpster; 16th Nov 2014 at 02:05. Reason: edit errors
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Old 16th Nov 2014, 07:41
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Originally Posted by Barronflyer View Post
Hi there

Can someone please advise that an RNAV (GNSS) approach requires a working GPS in all cases? I.e. with failed GPS receivers the approach cannot be flown with reference to RADIO UPDATING, INERTIAL pos etc. Silly question I know. Just trying to confirm my assumption.

Thanks
There are approaches which are labelled as RNAV (VOR DME) or RNAV (DME DME), although they seem to be very rare.
There are some of them in Egypt like in Sharm El Sheikh (HESH): RNAV (VOR DME) 22L and 22R.
(Other airports that have them are HELX, HEAX, HESN, ...)

This RNAV approach is based on an RNAV system that doesn't need GPS, but only VOR DME position updating. I believe you still need the 0.3 RNP.
However, in the FCOM of my aircraft, it is written that for any RNAV approach which doesn't require a GPS (like the RNAV(VOR DME)), you need to apply the procedures for a RNAV(GPS) approach. Hence you need a working GPS. (However, that might be a company requirement.)
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Old 16th Nov 2014, 15:01
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The HESH 22L/R RNAV IAPs state "VOR/DME or GNSS."

So, the folks with GNSS follow standard procedure.
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Old 17th Nov 2014, 15:33
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c100:

My regulator: you cannot start an RNP AR APCH approach without Dual GNSS but after the FF you can continue with a single GNSS.
That's fine for some circumstances in more conventional instrument flying, but entering the final segment in some RNP AR approaches (say RNP of .2 or less with an RNP required missed approach) is literally going into an area where extraction should be the rule when any significant part of the avionics fails.
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Old 27th Nov 2014, 22:38
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I have never come across a confusing topic such as the Rnav & rnp stuff
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Old 27th Nov 2014, 23:18
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That's fine for some circumstances in more conventional instrument flying, but entering the final segment in some RNP AR approaches (say RNP of .2 or less with an RNP required missed approach) is literally going into an area where extraction should be the rule when any significant part of the avionics fails.
A single GPS "unit" failure (in a dual GPS system supporting a dual FMS) should not affect the position solution just the redundancy. As long as ANP is less than RNP and there is no trending of the ANP increasing then risk has not increased appreciably. A single GPS "unit" failure was the only failure that we could continue with after the Final Fix. If it failed prior to the Final Fix the approach could not be continued.

It has been a few years since my airline and the regulator went down the RNP AR journey of discovery but I recall that the extraction was based on, dual GPS sensor loss, FMC failure and Engine failure at missed approach point i.e. Single FMC, IRS updating only.

This was for a RNP of 0.11 for Boeing and 0.10 for Airbus into an airport that the RNP AR approach was really the only option due to the terrain and has multiple RF legs to position into a valley.

Last edited by c100driver; 28th Nov 2014 at 03:48. Reason: clarification
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Old 28th Nov 2014, 01:20
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Our company SOP's have us continue with a single GPS failure or a single. Rad Alt failure if it occurs after the IAF. Prior to that the approach can't be commenced. That is for RNP-AR.
For RNP App LNAV / VNAV you can start the approach with only one GPS and only one Rad Alt but if you lose either you must go around.
Very very confusing evolution of terminology.
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Old 28th Nov 2014, 02:47
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RNP-AR with a single GPS.?
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Old 28th Nov 2014, 08:49
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Could you report some examples of airport with RNAV (RNP) and RNAV (AR RNP) ? To see differences in charting, title notes and minima.
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Old 28th Nov 2014, 20:28
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Could you report some examples of airport with RNAV (RNP) and RNAV (AR RNP) ? To see differences in charting, title notes and minima.
RNAV (RNP) implies AR.

To be more precise, in the context of PBN there are two types of approach specifications: RNP APCH, and RNP AR APCH.

1. RNP APCH. Generally charted as RNAV (GPS) in the US or RNAV (GNSS) internationally. This type of approach mainly consists of straight legs. Obstacle clearance and approach minimums do not require specific RNP capabilities. (Instead, minimums depend on approach type being flown, e.g., LPV, LNAV/VNAV, etc.) Example: KSFO RNAV (GPS) Z RWY 28R.

2. RNP AR APCH. Generally charted as RNAV (RNP). This type of approach may include curved (RF) legs. Obstacle clearance and approach minimums developed against specific RNP capabilities (e.g., RNP 0.3 or RNP 0.1). Special authorization is required. Minimums not necessarily lower than RNP APCH (might even be higher). Example: KSFO RNAV (RNP) Y RWY 28R.
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Old 28th Nov 2014, 20:53
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Here is a link to a full tailored type approach for RNP AR APCH even though the landing plate is is called RNAV (RNP) Y RWY 23 at Queenstown NZ

AIP New Zealand

The second link is a Public RNP AR APCH for Auckland NZ

AIP New Zealand

The third is for a straight RNAV (GNSS) Z approach at Auckland NZ

AIP New Zealand
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Old 29th Nov 2014, 00:09
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Here are approaches to Rifle (KRIL), Colorado, Runway 8. For folks with biz jets that can do RNP AR, look at the huge improvement with RNP AR, especially RNP 0.10.

The smart folks with the equipage divert to Rifle when Aspen weather is marginal.



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Old 29th Nov 2014, 02:13
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Nice approach that RNAV (RNP) Z RWY 8. Interesting the difference in GP angle achieved with the RNP by being able to reduce the altitude further out on the approach than the RNAV (GPS)
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Old 29th Nov 2014, 10:37
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RNAV (GPS) Y 08
Minima in only LNAV, not LNAV/VNAV: is consider anyway to be a APV approach?
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