FMC Failure & BRNAV Airspace?
 

Hi all,

If after T/O you get an FMC failure, are you allowed continue to destination using conventional navigation on say a flight from Ireland to UK?

If so are there any restrictions with regard to BRNAV airspace?

Thanks.

I don't think so - certainly when I had an FMC fail on the ground a few years back I was looking at Venice to Gatwick at 10 or below:eek:. Of course you could always be economical with the truth.:)

I am not so sure. Airways are still 10 nm wide, like in the time of conventional navigation. ATC will probably accept your continuation.
If RNAV is required for the approach, you have another issue, but this could probably be resolved as well with ATC. BRNAV, or RNP5 is a not so stringent requirement. Me thinks...Correct me if I am wrong.

Well, it WAS - BRNAV mandatory above 10. Haven't looked lately but I think from Arctic's post it still is.

This is something I haven't been able to look up so been meaning to ask: What are the BRNAV requirements regarding redundancy? E.g., do you need two GPS units and if one fails you are non-BRNAV due to lack of redundancy, or do you need only one GPS unit and you are non-BRNAV if that one fails? Is there a difference in requirements if something goes unserviceable before T/O or after you are already in BRNAV airspace?

Not too likely I am going to fly in BRNAV airspace any time soon but you never know... :8

Edit: The reason I ask is because of this passage in translation of LFS 2007:58 (the Swedish regulations for private flying): "The aircraft shall be equipped with sufficient navigation equipment so that the flight, if any part of the equipment should fail during flight, can continue according to the requirements in [requirement applicable to flying over certain oceans] or [B-RNAV requirements], where applicable.".

I know it is taken from a national requirement, but I don't think the requirement as such is unique to Sweden?

Had it happen one time and we were allowed to continue with vectors from ATC and directs to certain VORs or NDBs navigating the old fashioned way. However that was a purely domestic flight. Even the flight back to maintenance was approved operating normally on a scheduled flight. The same thing on the way to our neighbors south of the border (ZRH) was not possible at all, no matter if below or above FL100, simply not possible.

So is it correct to say that you can continue once your below FL95, other factors permitting?

Well, it is difficult to say - most Euro countries mandate BRNAV above fl95 and the UK is proposing to introduce it below 95. It looks as if there are state differences and I guess the answer depends on where and perhaps how busy?

It may be that the terrain consideration in the Zurich FIR preclude it below 95.

Hi guys,

when you are already airborne and your FMS crashes I would accept you continueing and not only at low level but at normal crusing level. But if you are on ground I would say go back to the gate and get it fixed.

In Zürich (according our book) we accept non RNAV aircraft over the alpine area up to FL160 (not sure if CFMU will accept as well).

@Denti: please confirm you were airborne and ATC Zürich told you you are not accepted as long you have no RNAV?!?

greetz

Johannes