View Full Version : PRNAV Approaches

14th Apr 2006, 18:01
Just come out of the annual LPC/OPC which included a PRNAV approach. Anyone care to offer their thoughts and opinions with regards to this? Personally I can see the merits....but how can this work in a place like LHR or LGW?


14th Apr 2006, 18:25
Can you be a bit more specific? What aspects of PRNAV procedures do you think would be a problem?

14th Apr 2006, 18:37
Its not about it being a problem, my question relates to the practicalities of the procedures..and if anyone has an opinion on this, hence I was deliberately non-specific.


14th Apr 2006, 21:40
Just did my LPC and of course came across the PRNAV approaches.

The big advantage is, that there is no need of any ground based equipment. Maybe in a place like LHR or any other big airport in an established and well run aviation environment, there is no need for this advantage immediatly, but for a lot of other places especially on the black continent, this is a major advantage.

No need for special ground based equipment, except of some lightning and a maintained runway, meens no problems regarding maintainance and of course serviceability of ground based navigation aids. How often do you find that the navaids are not working propperly or are unservicable.

One further advantage is that the PRNAV approaches is that they are usually straight in approaches and don't have an offset, like a lot of VOR based approaches have, if the VOR station is not ligned up with the runway centerline. This helps a lot, I am sure.

At the end I think in a lot of places like LHR or JFK we will see in the future that PRNAV approaches will become the backup approaches to the ILS, while NDB and VOR based approaches will become more and more unpopular, as the ground based navaids can be decomissioned, which aids also in costreduction. For places in less developed parts of our planet the PRNAV approaches will become very popular for the above mentioned reasons.

I must say I like this kind of approaches very much and think the procedures are well defined. Just my aircraft type can be a bit tricky in respect to the VNAV part, especially the speed. But this is just a matter of design and/or training.

14th Apr 2006, 21:43
haughtney1, could you tell me what you did differently during that PRNAV compared, to say, a BRNAV approach?
As for the merits, well..., from a pilot's point of view, I don't really see the point but will take vectors anytime, thanks :cool:

14th Apr 2006, 21:48
and alatnariver,
no need of any ground based equipment
is definitely a wrong argument. All the published procedures have to also support a DME-DME or even DME-VOR tuning, as not all aircraft are GPS equipped.

14th Apr 2006, 21:52
well but if the procedure is based on GPS only? As far as I know and understand it, this is possible and the aim of the game, get rid of the ground based stuff.

15th Apr 2006, 11:36
The procedure I flew in the SIM was done in LNAV/FLCH, and loosely speaking was what I thought was a BRNAV approach as it had VOR/DME derived waypoints, there was no GPS guidance. In point of fact we finished the procedure with a CAT 3B approach..(reverting to CAT 2 after the inevitable engine failure and APU fire on approach:E )

15th Apr 2006, 14:01
Surely a PRNAV approach using GPS requires a DGPS ground station.

15th Apr 2006, 14:11
Perhaps Chevron.....Im not an expert on procedure design...the plate however had PRNAV on it:ok:

15th Apr 2006, 14:24
Surely a PRNAV approach using GPS requires a DGPS ground station.

There may be an issue with semantics here, chevvron.

P-RNAV procedures are equivalant to SIDs/STARs -- i.e., they wouldn't be called "Approaches" here in the U.S.

More or less, P-RNAV is RNP-1.0.

Additional information here:

Jambo Buana
19th Apr 2006, 22:25
Lots of stuff in this subject.

You must look at the sensor requirements for the approach, ie DME/DME or GNSS or VOR/GNSS etc.

Whatever sensors are required must be serviceable prior to approach, which means more careful checking of notams.

In theory, you must deselect VOR or DME updating if your approach is based on GNSS.

You must back up LNAV posn with raw data if operating below MSA.

You may need two FMCs in certain PRNAV airspace. This allows bailout in case of FMC failure in terrain rich environments.

SOPs normal/non need to be specific to PRNAV procs.

Database of your FMC must be approved for PRNAV standards.

Proper reporting system for nav anomalies.

Training program delivered by your airline.

Benefits are purely time saving and consistency of track keeping, which will ultimately lead to 4D Nav (4th being time) introduced by around 2020!!

I think the FAA has overtaken Europe in PRNAV (suprise suprise) and they have trials in ATL, DFW and JFK.

Hope this is a reasonable summary of TGL10.

19th Apr 2006, 22:33
With the introduction of PRNAV tons of airfields around the globe which do not have a costly ILS can have precision approaches in the future which will lead to much lower minimas compared with visual and non-precision approaches. As simple as that!

Jambo Buana
20th Apr 2006, 18:22
Well kind of. LNAV/VNAV approaches will not really give much better mins than current Non Precision Approaches, but what some guys are confusing it with are GLS approaches which will require GBAS station to get rid of GNSS inherent error. Then we will see CATII/III approaches to runways without ILS/VOR/DME or anything. No more CATII/III holds or ILS protected areas etc etc... Cant wait, but loooks like Europe are miles behind as usual.

If only the LCCs heading into marginal airfields realised the potential that exists here to have precision approaches to all runways!! Now think of that molly!