Negative RNAV

[cosmo kramer]

Another discussion on this board has given rise to my curiosity to what procedures ATC has if an aircraft en-route reports that due to system failure they are no longer RNAV compliant?

[aerotech07]

In my experience ensure that any waypoints given are radio navigation aids such as a VOR or NDB that the aircraft can navigate to. If this is not possible there are always good old radar vectors.

In terms of admin, in the UK we are able to add "Non RNAV" to the flight progress strip so that following sectors getr a heads up. Personally I would also call the next sector to let them know/co-ordinate before transferring control.

[Spitoon]

It's an interesting question - but I'm afraid I can't give you an answer because I'm not operational any more.

However, there are lots of instances where the rules say the 'pilot must advise ATC' or this be done 'unless authorised by ATC'. Some of these rules come from ICAO, others from national legislation and CAAs. Sadly there are often few formal procedures in ATC unit instructions to define how such reports or requests should be handled and it often comes down to individual controllers' judgement annd decisions. This is illustrated by aerotech07's comment - and this isn't meant as any form of criticism - that starts 'In my experience....'. Whilst the actions that he/she suggests appear to be common sense and I'm sure would be fine, ideally he/she should be able to tell you what the unit procedures say.

I recall that this topic was raised with the UK CAA a few years back but there seemed to be little desire to solve the generic issue. I guess that procedures will be introduced to handle each example of undefined rules after there is an incident where the lack of procedures is a contributory factor.

[BrATCO]

I couldn't say much more than Aerotech7 :
VOR, vectors, "no R" in the computer, phone co-ordinations, wait for the pilot to say his intentions (usually, continues to destination).

That's SOP in my center, it works. I've done it more than once.

I've heard some centers refuse them... Not sure.:confused:

[5milesbaby]

aerotech07/BrATCO I agree with, use either VORs or RPs that are derived straight from a VOR or vectors if in doubt. Co-ord with the next sector and stick a message in the computer too so the other sectors are aware on the strips. Not a major problem as far as we are concerned.

For our info cosmo, what does it say in your manuals and what highlighted you to pose the question? Anything we should know from your side?

[cosmo kramer]

Thanks for the replies. Pretty much as expected.

The manual say "Resume conventional navigation". In my opinion that means VOR to VOR or NDB. If that is not convenient for ATC radar vectors is of course an option on your discretion.

What highlighted the question is a discussion in tech log forum, where some seems to believe that the best course of action is to try to remain on the RNAV routing as best as possible (which means a certain degree of guesstimation and continuous rechecking, with whatever inaccuracies it may imply). If interested the link is below:
http://www.pprune.org/tech-log/448181-dual-fmc-failure-boeing-737-ng.html

Pretty much it boils down to this:
If an aircraft reports negative RNAV, but declines re-routing or vectors, with what precision would you expect it to continue?

[Tourist]

Just a quick one.

I have spent most of the last 6 yrs flying a non rnav equiped aircraft around the airways of europe.
We almost always get treated exactly like we do have rnav and we just have to cope.

[BrATCO]

If an aircraft reports negative RNAV, but declines re-routing or vectors, with what precision would you expect it to continue?

None ! :}

More seriously, my radar system is statistically more precise than 5 NM. I expect the pilot to do the same, but it doesn't count much : I know the plane is not RNAV, I'll check a bit more often and maybe use a bit more radar vectors and/or level separation. Maybe...

Some procedures (radar hand-overs come to my mind) need to be more careful, but all in all, it doesn't differ alot from usual.