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RNAV Approach or RNP Approach how to read Chart?

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Hey Guys, got a question.

 

--Reference Wikipedia---

Historically, aircraft navigation specifications have been specified directly in terms of sensors (navigation beacons and/or waypoints). A navigation specification that includes an additional requirement for on-board navigation performance monitoring and alerting is referred to as a required navigation performance (RNP) specification. One not having such requirements is referred to as an area navigation (RNAV) specification. A navigation specification that includes a requirement for on-board navigation performance monitoring and alerting is referred to as an RNP specification. One not having such a requirement is referred to as an RNAV specification.

 

My question is,

how do I know on the Approach chart if an RNP Performance / equipment (performance monitoring & alerting) is required , or a traditional RNAV approach would do (sufficient)?

 

I know for a fact that many Charts do not mention "RNP" in them , but yet they demand such accuracy. 

Also I think there is a difference in the Charts codes and writing between ICAO and the FAA.

so how would I know if RNP or RNAV chart reading on ICAO (e.g. EU) and on FAA (e.g. US)?

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so how would I know if RNP or RNAV chart reading on ICAO (e.g. EU) and on FAA (e.g. US)?

 

Ours specifically state RNAV RNP. This is also usually further emphasized by "AUTHORIZATION REQUIRED" being written down near the mins. Otherwise, the chart will only refer to it as RNAV(GPS).

 

As weird as the FAA can be, we at least have that part right. Pretty simple.

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Its not an easy thing to grasp straight away and there is alot involved.

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Its not an easy thing to grasp straight away and there is alot involved.

 

Compared to the old stuff we had - VORs and NDBs - RNAV is a breeze:

RNAV - the ability to navigate from point to point without being forced to follow a radial.

RNP - a performance value related to the ability to understand a position that the aircraft must meet.

ANP - the ability of the system to be able to discern where it is on Earth

 

RNAV(GPS) - RNP not required

RNAV(RNP) - RNP required

 

Load approach. Follow dots.

 

Compare this to flying an NDB approach with wind (make sure to check the flight map to review your performance after the approach) and you'll see what I mean!

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Thats just the tip of the ice berg! Very basic run down kyle thats the best way of thinking about it, but if you want to dig even more prepare for a sore head lol

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It's complicated.

 

As I understand it:

 

If the chart says RNAV (only) this is not an RNP approach and may be carried out without any particular approval.

 

If the chart has RNAV (GNSS) (or RNAV (GPS) on older charts), it is an RNP approach and requires the aircraft to be RNP approach approved (and may require RNP values down to 0.3).

 

If the chart says RNAV RNP (AR), this is an RNP approach and special aircrew and aircraft authorisation is required. These approaches may have RNP values below 0.3.

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Thats just the tip of the ice berg! Very basic run down kyle thats the best way of thinking about it, but if you want to dig even more prepare for a sore head lol

 

Same could be said for trying to understand how a VOR generates the radials, and how the aircraft interprets them. How far one wants to go running down the rabbit hole is up to the individual. For the pilot, though, it's all pretty simple.

 

 

It's complicated.

 

As I understand it:

 

If the chart says RNAV (only) this is not an RNP approach and may be carried out without any particular approval.

 

If the chart has RNAV (GNSS) (or RNAV (GPS) on older charts), it is an RNP approach and requires the aircraft to be RNP approach approved (and may require RNP values down to 0.3).

 

If the chart says RNAV RNP (AR), this is an RNP approach and special aircrew and aircraft authorisation is required. These approaches may have RNP values below 0.3.

 

That all seems pretty simple to me, but maybe that's why I work with the people who design them now...? Perhaps the ICAO nomenclature could be a little more clear, though. RNAV, RNAV(RNP), RNAV (RNP-AR) or similar. In the States, all of our RNAV(RNP) is RNP-AR, at least at the moment.

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I suppose the confusing thing is that you can have an RNP approach which doesn't say RNP in the title (i.e. RNAV (GNSS)).

 

The charting is not necessarily consistent either -- I believe RNAV (RNP) is analogous to RNAV (RNP-AR) in that both imply the potential for RNP values below 0.3 and the requirement for special authorisation.

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The way i look at it is, RNAV in simple terms is just area navigation and on the other hand you have RNP which requires special monitoring system to check if you are within the required accuracy .3 or below

 

I see in my FCTM you have

 

 

NDB, NDB/DME 0.6 NM

VOR, VOR/DME 0.5 NM

RNAV 0.5 NM

RNAV (GPS)/(GNSS) 0.3 NM

 

Whats the difference between RNAV and VOR VOR/DME ?

 

Aren't they both out of the database and require the same RNP ?

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Whats the difference between RNAV and VOR VOR/DME ?

Aren't they both out of the database and require the same RNP ?

 

A published RNAV approach has the approach in the database, a GPS/GNSS overlay of a VOR approach is in the database too and it mimics the underlying VOR approach.  A VOR approach is flown with reference to the ground based VOR navaid and no database GPS/GNSS or computer required.

 

Required navigation performance RNP is meaningless with regard to a VOR approach.  If you provide the FCOM reference page maybe we can clear that up; most likely, it is referring to overlay approaches.  An approach based soley on ground based navaids (not GPS/GNSS overlay) does not have a "RNP" value. Rather, the VOR system is required to be accurate to within +/- 6 degrees and the NDB is simply "needle points to station."

 

Don't let different jurisdictions confuse the issue. GNSS is the European version, and separate from, the US GPS system but for aviation they are essentially the same.  Charts are labeled differently and vary a lot from country to country outside Europe and US. 

 

RNP does have a smaller error allowance, which is achieved with enhancements to the GPS/GNSS system and requires navigation systems certified for that required performance. In the US, RNP approaches are designed to include WAAS and in Europe it's called SBAS.  Basically, these are systems that augment GPS/GNSS to improve accuracy and are required for the on-board systems to provide the ANP (actual navigation performance) for RNP approaches.

 

The most important number on the approach is the minimum.  Note how it increases from ILS (CAT I 200 ft AGL typical) to RNP (400 ft AGL typical), RNAV(GPS) (500 ft) and VOR (600 ft).  These are typical for a location without mountains and obstructions, and vary significantly but I am using to illustrate the important point.

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Whats the difference between RNAV and VOR VOR/DME ?

Aren't they both out of the database and require the same RNP ?

 

Nope. You're confusing concepts.

 

ANP isn't an RNAV-only concept. It simply became more of an issue when we started using RNAV because RNAV does not use ground-based navigation, so accuracy issues are a big deal. The values listed in the FCOM are cursory ANP values if you were to use those systems alone.

 

 

 

Think of it this way:

 

VOR/VOR or VORDME

I'm flying by IAD. I tune 113.5 and check for the ident of AML, and turn the CRS knob to get my radial of 330. That, combined with a 20DME indication means I'm 20NM NW of AML. If I didn't have DME, I could use LDN to pick up where the radials cross, again, to get a verifiable spot. There's nowhere else in the world I could be. The accuracy of this method, however, given frequency errors, widening radials over distance, and other factors, means that my ability to calculate where I am in the world is only good to about my actual position with a radius of 0.5NM. This means that my ANP is 0.5 (even if I'm not using RNAV equipment). Since VOR approaches and airway widths plan in the amount of error (and you check your VOR receiver every 30 days), it was never really a question if you were in the right position, because if you were receiving the VOR signal, and were flying the procedure, you were in the right spot. Ergo, until RNAV came into play, concentrating on ANP values wasn't necessary.

 

RNAV (INS)

I'm flying by IAD. My position is wholly contained within the navigation unit and is only updated by ded reckoning. While the initial position is pretty accurate, without position updates, this degrades over time (somewhat like the cone of uncertainty for a hurricane track). Additionally, on its own, it can only bring in about 0.5 at best for ANP. The problem is that, since there is no actual ground reference using INS alone, it becomes extremely important to be able to understand how accurately the system can calculate its position. If its accuracy is degraded, your actual position could be very different from the indicated position. As an example, using early versions of an INS, I could be sitting at MIA, enter IAD as my initial position, load the BUNZZ2, and carve the BUNZZ2 SID over the Everglades. If RAMAY is at N38°57.64' W78°12.99, but I'm physically down near MIA (N25 W80ish), how could that be possible? It's possible because I told it that my starting position was IAD. It's almost as if I shifted the entire Earth's coordinate system 13 parallels south, and 2 to the west. In other words, I shifted the coordinate system such that my INS would indicate that I was flying over the North Pole (physical) somewhere between the Resolute Bay (CYRB) and Alert (CYLT) airports. For this reason, it's very important for the system to be able to verify that its indicated position is close to actuality. This is why ANP matters so much for RNAV: without being tied to the ground, your position error could be very significant.

 

 

 

...also...what Dan said...  :P

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A published RNAV approach has the approach in the database, a GPS/GNSS overlay of a VOR approach is in the database too and it mimics the underlying VOR approach.  A VOR approach is flown with reference to the ground based VOR navaid and no database GPS/GNSS or computer required.
 
Required navigation performance RNP is meaningless with regard to a VOR approach.  If you provide the FCOM reference page maybe we can clear that up; most likely, it is referring to overlay approaches.  An approach based soley on ground based navaids (not GPS/GNSS overlay) does not have a "RNP" value. Rather, the VOR system is required to be accurate to within +/- 6 degrees and the NDB is simply "needle points to station."

 

Thanks dan, i got that out of the FCTM Approach Requirements Relating to RNP section


 

 


RNAV does not use ground-based navigation, so accuracy issues are a big deal.

 

I read it does?

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I read it does?

 

In theory, it's meant to avoid being tied to the ground. Concorde, as an example, was IRU/IRU/IRU only during the Atlantic crossing, once out of DME/DME range. During this time, it was navigating point to point (RNAV) solely by internal position reference.

 

RNAV, or properly aRea NAVigation, is the concept of being able to navigate from point to point. The whole point of RNAV, initially, was to free navigation from being limited by ground based navigation reception ranges.

 

While RNAV using ground based aids is possible - LORAN, OMEGA (based on VOR) - it is now primarily satellite-based. One could also navigate by INS only, though the degrading position would be an issue, so in recent implementations, it is INS supplemented by GPS updating (and/or DME/DME). GPS by itself is also a method of RNAV, which, of course, does not reference ground stations.

 

The problem many sim pilots encounter in this realm is trying to drink from the proverbial fire hose. The 737 receives updates from the IRUs, VORs, DME, and GPS. This confuses the main issue of which of those is actually relevant to the concept of RNAV. The answer is "all of them," but not in the traditional sense. The only RNAV technologies in use by the 737 are IRU and GPS. The VOR and DME sources are only supplementary, and strengthen the certainty of the IRU and GPS reported positions.

 

 

 

 

In other words, say I eliminate all sources of information on the plane except the IRUs. I can navigate this way - without referencing ground sources - and it is considered RNAV. Those mix their positions and report that I'm at N38°47.00' W77°54.10'. How certain am I? I just started the flight, so I'm relatively certain. If I want more certainty, I can add GPS into the mix. The GPSs mix their indications and report that I'm at N38°47.84' W77°54.56'. This is just barely north and west of my IRU-calculated position, which gives me high confidence that both are indicating accurately. Again, at this point I have yet to reference ground sources, but I'm still flying RNAV. If I want more certainty I can add DME into the mix. The system does a lookup to see what DME stations are closest and picks LDN and MRB frequencies (the DME freq is independent of the VOR in actuality, which the NG will tunes with its DME sensors dedicated to that task). This lookup includes their lat/lon from the database as well, which allows the unit to triangulate a position given the DME information against the lat/lons. The solution of that triangulation results in, say, N38°48.01' W77°54.56'. This is just north of my IRU/GPS-calculated position, which again reinforces my certainty that I am in that location. The higher the confidence that I'm in a particular location, the lower my ANP value goes (as it's the radius of uncertainty around the aircraft).

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RNAV does not use ground-based navigation

 


I read it does?

 

Kyle is ahead of my... what he said.  Also, in the context of current systems RNAV is space-based augmented by WAAS/SBAS.  I am old enough to remember VOR-based RNAV using the King KNS-80 so in that context RNAV uses ground-based navaids... but, let's be reasonable with definitions and keep the context current.

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OK, Now I am really confused.

I know what Navaids are and they are not RNAV nor RNP.

what I don't understand is, you guys saying that if a chart has RNAV (GNSS) on it it means RNP required and if no (GNSS) is present than it is a normal RNAV?

That is rather confusing, GNSS is a simple European naming for GPS.. also RNAV needs GPS to perform such navigation,

then how does GNSS (EU term for GPS) on the chart makes it RNP when all it means is that GPS  is needed on board.

Also RNAV equipped Airplanes have GPS on board or they will not be able to RNAV...  

 

RNAV (GNSS) - to me it sounds that you are required to have a GPS on board, that's it.

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OK, Now I am really confused.
I know what Navaids are and they are not RNAV nor RNP.
what I don't understand is, you guys saying that if a chart has RNAV (GNSS) on it it means RNP required and if no (GNSS) is present than it is a normal RNAV?
That is rather confusing, GNSS is a simple European naming for GPS.. also RNAV needs GPS to perform such navigation,
then how does GNSS (EU term for GPS) on the chart makes it RNP when all it means is that GPS  is needed on board.
Also RNAV equipped Airplanes have GPS on board or they will not be able to RNAV...  
 
RNAV (GNSS) - to me it sounds that you are required to have a GPS on board, that's it.

 

Told you the chart naming was confusing!

 

Firstly, as far as I'm aware, all chart providers/aviation organisations are phasing out the "GPS" wording in favour of "GNSS" -- because GPS is (as you know) a specific system run by the US military, whereas GNSS is a generic term referring to all the various satellite navigation systems.

 

To deal with the question about RNAV (GNSS) -- here's a quote from the UK CAA website that explains it:

 

 

 

The instrument approach procedures associated with RNP APCH are entitled RNAV (GNSS) to reflect that GNSS is the primary navigation system. With the inherent onboard performance monitoring and alerting provided by GNSS, the navigation specification qualifies as RNP, however these procedures pre-date PBN, so the chart name has remained as RNAV.

 

So an RNAV (GNSS) approach is an RNP approach, requiring the aircraft to be authorised for RNP APCH operations. But for historical reasons the chart does not have RNP in the title.

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RNAV (GNSS) - to me it sounds that you are required to have a GPS on board, that's it.

 

If you're in FAA-land:

RNAV(GPS) - RNP optional.*

RNAV(RNP) - requires RNP (and authorization required, or "AR").

 

*Our GNSS approaches - called WAAS or LAAS - are simply added as lower minimum versions of RNAV(GPS) approaches as "LPV." RNP is not required, but you use higher minimums. If you're flying with GPS only, then you use the highest mins. If you have LNAV/VNAV, then you can use those lower minimums. LPV is the only RNP-required min on those procedures.

 

 

Elsewhere? Good luck...but my understanding is:

RNAV - is not RNP.
RNAV (GNSS) - is RNP (down to 0.3)...probably using ground-based augmentation of some sort (GBAS/GRAS).
RNAV RNP (AR) - is RNP (from 0.3 to 0.1).

 

 


So an RNAV (GNSS) approach is an RNP approach, requiring the aircraft to be authorised for RNP APCH operations. But for historical reasons the chart does not have RNP in the title.

 

Per ICAO, maybe, but even they are falling victim to the GNSS misconception.

 

GNSS simply refers to navigation by satellite system. Putting that on a chart to indicate "RNP" seems very misguided, because it's only when you add GBAS/GRAS that it gets to the level where RNP even comes into play. That's why we have it as RNAV(GPS) with LPV (WAAS/LASS which is equivalent to GBAS/GRAS) listed as a different minimum. Since WAAS/LAAS is implemented in units that run their own RAIM checks, and their precision is much more than RNP 0.1, the RNP would be redundant. RNAV(RNP) is what we list our procedures as, because GNSS or GPS would be too vague.

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OK here is a chart that has RNAV (GNSS) on it (ICAO).

 

Is this an RNP Req' or not (Regular RNAV)?

If true how did you determine this apart from the Title "RNAV (GNSS)"

 

 

[Jepps are copyrighted]

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is this an RNP Req' or not (Regular RNAV)?

 

No.

 

 

 

if true how did you determine this apart from the Title "RNAV (GNSS)"

 

The only mins listed are LNAV-only. Plus, the M in the vertical profile shows that there's a missed approach point (the threshold of the runway). Both of these mean that the approach is a non-precision approach. I've never seen an RNP non-precision approach.

 

The mins box would also say "RNP" if it was RNP (instead of LNAV).

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GNSS simply refers to navigation by satellite system. Putting that on a chart to indicate "RNP" seems very misguided, because it's only when you add GBAS/GRAS that it gets to the level where RNP even comes into play. That's why we have it as RNAV(GPS) with LPV (WAAS/LASS which is equivalent to GBAS/GRAS) listed as a different minimum. Since WAAS/LAAS is implemented in units that run their own RAIM checks, and their precision is much more than RNP 0.1, the RNP would be redundant. RNAV(RNP) is what we list our procedures as, because GNSS or GPS would be too vague.

 

I agree -- the chart titling is confusing!

 

As I've found the quote about RNP (AR) per the UK CAA, I'll reproduce it here for completeness:

 

 

RNAV (RNP) approach operations are GNSS-based and flown using chart procedures titled RNP. Note: FAA charts may be labelled RNP (SAAAR). This type of approach operation is typically flown at aerodromes with difficult terrain or in challenging ATC environments and may require an RNP as low as 0.1 NM. The required RNP will be labelled on the chart next to the minima. Aircraft will require certification in accordance with EASA AMC 20-26 and crews should be specifically trained for each RNAV (RNP) Approach operation.

Any EASA AOC or private operator wishing to carry out such approach operations must hold an approval issued by the State of aircraft registry and may require special permission from the State of the aerodrome.

 

 

 

OK here is a chart that has RNAV (GNSS) on it (ICAO).

is this an RNP Req' or not (Regular RNAV)?

 

if true how did you determine this apart from the Title "RNAV (GNSS)"

 

You'd have to check the Jeppesen chart legend to see how they title their charts!

The only mins listed are LNAV-only. Plus, the M in the vertical profile shows that there's a missed approach point (the threshold of the runway). Both of these mean that the approach is a non-precision approach. I've never seen an RNP non-precision approach.

 

The mins box would also say "RNP" if it was RNP (instead of LNAV).

 

Not necessarily true:

 

 

Approach Applications

Approach Applications which are classified as RNP Approach (APCH) in accordance with ICAO Doc 9613 Performance Based Navigation (PBN) Manual (and ICAO state Letter SP 65/4-10/53) give access to minima (on an Instrument Approach Procedure) designated as:

  • LNAV (Lateral Navigation) – This is a Non-Precision Approach with Lateral navigation guidance provided by Global Positioning System (GPS) and an Aircraft Based Augmentation System. (ABAS) Receiver Autonomous Integrity Monitoring (RAIM) is a form of ABAS.  

 

Full information (and a handy diagram): http://www.caa.co.uk/default.aspx?catid=1340&pageid=13338

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That chart is what it says RNAV (GNSS) RNP. Whats in the brackets is what you need to carry out that 3D APV

Also that chart is NPA 2D approach with an MDA. You will have to add company mins to that MDA.

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No.

 

 

 

 

The only mins listed are LNAV-only. Plus, the M in the vertical profile shows that there's a missed approach point (the threshold of the runway). Both of these mean that the approach is a non-precision approach. I've never seen an RNP non-precision approach.

 

The mins box would also say "RNP" if it was RNP (instead of LNAV).

 

 

It is not RNP, even though it has RNAV (GNSS) on the chart tile?

 

so in that case the claim that was heard here before that claims if a chart has RNAV (GNSS) in the tile is an RNP Req, is not true?

we back to score one.

how do we know for ICAO charts what is RNP Req or not?  :mellow:  :(

 

Just in case you might suspect JEPPESEN Chart is the issue, here is the Original AIP Chart.

it also states RNAV (GNSS) 

 

1z48nih.jpg

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