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PRNAV and PBN

Yes, the KLN94 is approvable for IFR enroute, GPS/RNAV approaches, SIDs/STARs, but cannot be approved for PRNAV, RNAV SIDs/STARs, and of course it does not do LPV (there is no vertical output). In that respect it does everything operationally relevant in Europe today.

A few years ago I went to an ATC tour and the senior ATCO (from Heathrow) said PRNAV is a load of crap; they don't need it, they don't want it, they manage traffic tactically using radar, and that so long as I have a decent GPS I can safely ignore it

Well... that was one man's point of view back then, and he doesn't run Eurocontrol, but has anything actually changed in the way traffic is managed?

I have never come across an airport where radar is in use and where they just let traffic loose, to follow published tracks all on their own. Sure, a SID or a STAR is assigned by ATC, but ATC normally take over sooner or later, long before the assigned procedure is exhausted.

I guess LPV capability will become relevant first, maybe 5-10 years from now. PRNAV might become relevant like 8.33 i.e. when they force it through significantly, but only in a regulatory "carry the right kit and the right paperwork" sense; the flight will be done the same way.

Administrator
Shoreham EGKA, United Kingdom

Watching my x-track error to Berlin yesterday, it was generally 0.01nm, only going to 0.03nm in a wind shear or turbulence.

True, but that really underpins the justification for the operational approval (LOA). Your total system error probability distribution doesn't depend on your navigation equipment, but rather your adoption of correct operational procedures and competence to fly them. Imagine a very narrow normal distribution with large outlying spikes labelled 'pilot screw up'.

ICAO's rather conservative approach is that since most pilot training and operational procedures are predicated on conventional navigation, some proof is required of the adoption of correct operational procedures and competence to fly them. ORS 959 is effectively saying that the CAA has no intention of issuing operational approvals to non-commercial operators, and is inviting whomever it may concern to accept it as an equivalent.

Your total system error probability distribution doesn't depend on your navigation equipment, but rather your adoption of correct operational procedures and competence to fly them

I completely agree that systems and operational knowledge is key. I just don't think that the training typically required eg the King Schools course gives it to you.

Flying PRNAV with the right equipment seems to have less to do with the P than knowing how to use your GPS, autopilot and any other relevant systems well.

EGTK Oxford

Yes and that shows the stupidity of how PRNAV is being approached. You can get aircraft approval with an old GNS430 box and AFAIK no HSI and no autopilot. It's possible because Garmin support the 430 with the LOA.

Administrator
Shoreham EGKA, United Kingdom

I have never come across an airport where radar is in use and where they just let traffic loose, to follow published tracks all on their own. Sure, a SID or a STAR is assigned by ATC, but ATC normally take over sooner or later, long before the assigned procedure is exhausted.

I think the issue is a different one. Of course one can do everything with radar and headings but everything has to be setup so that in case there is a loss of communication, airplanes will happily continue on their clearances and arrive safely. With P-RNAV this allows for airways to be much closer together, it allows airways in places where RNP 5 would violate obstacle clearance, etc.

Yes and that shows the stupidity of how PRNAV is being approached. You can get aircraft approval with an old GNS430 box and AFAIK no HSI and no autopilot. It's possible because Garmin support the 430 with the LOA.

It is not so easy (or stupid!) unfortunately. Not only every component (Navaids, Autopilot/Flight Director/Crew) has to be PRNAV/RNPx compliant and capable, but the whole system consisting of all three. Additionally, there has to be constant monitoring and alerting and some kind of quality management as well to make sure that others will not make the same mistake as you. For a jet, this is not as trivial as it sounds. Navaids and autopilot have to be able to fly with the required accuracy both at cruising speed of 450Kt TAS and fully configured for landing at 110Kt. Not difficult to achieve with the "old" RNP5/BRNAV, more difficult with RNP1/PRNAV and quite difficult with the future RNP0.3, especially at high speed. Simply substituting an old BRANV FMS with a Garmin 430 (that for itself may be PRNAV compliant) will not be sufficient.

EDDS - Stuttgart

quite difficult with the future RNP0.3

I can't speak for jets, but surely for an autopilot to be certified it has to be stable through the whole envelope (loading, configuration, and speed). I know some old GA APs are not very stable but I am talking about modern stuff.

Also I do keep coming back to the fact that the simple GPS approaches, of which there are now plenty on Europe, are equivalent to RNP 0.3. For an aircraft to fly a GPS approach, it has to be damn accurate; certainly after turning onto the final approach track. I would expect to be within 0.01nm by the time the FAF is reached, this is achieved with a crappy old KLN94 whose crappy old GPS receiver sends out the data only once per second, and this accuracy should be normal for any GPS+autopilot. GPS approaches can have a DH of something like 400ft and an error of 0.15nm (half scale) could make it very difficult to land. So very high accuracies, far exceeding PRNAV, are already achievable, 100% of the time.

That's what I don't get. Why the extra gold plating for PRNAV?

Administrator
Shoreham EGKA, United Kingdom

Amsterdam Prnav manadatory??

I would doubt that.

NL AIP GEN 1.5

2.1.2 Schiphol TMAs An RNAV1 approval is required for all aircraft flying under IFR rules in the Schiphol TMAs inbound and outbound AMSTERDAM/Schiphol. A P-RNAV approval is considered equivalent to an RNAV1 approval. As a consequence all aircraft operators using AMSTERDAM/Schiphol as destination or alternate must hold:

a P-RNAV operations approval issued by their State of Registry which is compliant with the JAA Temporary Guidance Leaflet No. 10 (TGL-10) or equivalent (e.g. FAA AC 90-100); or a temporary exemption issued by CAA The Netherlands.

State aircraft are exempt from this RNAV1 mandate.

Peter wrote:

Also I do keep coming back to the fact that the simple GPS approaches, of which there are now plenty on Europe, are equivalent to RNP 0.3. For an aircraft to fly a GPS approach, it has to be damn accurate; certainly after turning onto the final approach track. I would expect to be within 0.01nm by the time the FAF is reached, this is achieved with a crappy old KLN94 whose crappy old GPS receiver sends out the data only once per second, and this accuracy should be normal for any GPS+autopilot. GPS approaches can have a DH of something like 400ft and an error of 0.15nm (half scale) could make it very difficult to land. So very high accuracies, far exceeding PRNAV, are already achievable, 100% of the time.

That's what I don't get. Why the extra gold plating for PRNAV?

The issue isn't the accuracy of the GPS navigator, the GNS430 is no more accurate than the KLN94. It obtained the LOA because it complied with the requirements, the KLN94 doesn't. If the KLN94 supported the CF terminator and included the RNAV SIDs and STARs in the database, then it could easily obtain a LOA. The requirement is to be able to load the SID or STAR from the database, the same as is required for an approach. Approaches don't require the CF terminator, however since they are permitted in the RNAV SID or STAR, the database must support this capability for RNAV 1. If it doesn't, then the GPS is not approved for flying the RNAV 1 procedures.

KUZA, United States
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