DU failure and RNP approach

[FR9999]

Hi guys,

I was wondering something:

If inflight on the 737-800 your ND fails and you manage to switch it over to the lower DU, are you than still aloud to fly an RNP overlay approach?

Thanks for your thoughts.

[ACMS]

As long as you whisper and don't speak too loud I'm sure it is ok.......:cool:

I don't know, check your FCOM:ugh:

[de facto]

ACMS,
Contingency procedures are Airline dependent.(SOPS) and OP has a valid question,at least hes thinking about it.
No need to :ugh:.

The failure of an ND may make the PNF monitoring task more complicated but by no means brings the aircraft to become non RNP.
Getting the map on a lower DU would be acceptable but obviously not optimum as important items such VDS would not be in the line of sight of the PM as expected.

Some airlines require both NDs to work before the FAF and some leave it to the pilots.
FMCs scratchpad messages should be the ones taking all your attention.

I believe this is a quite good question and i will create a thread regarding RNP contigencies.

[FR9999]

de facto,

Thanks for your response. The reason I was asking is because I'm relatively new with RNP ops and I was thinking about possible failures, and this failure is not clearly explained for the operator I am flying for.

Cheers.

[B737900er]

Under EASA AMC 20-4 for RNAV 5, both pilots to have in their field of view, continuous indication of aircraft position relative to track displayed on a navigation display. So a ND display being inop should be ok if you using the lower DU.

[Denti]

Isn't the pseudo ILS display on the PFD enough for relative to track position indication?

There is nothing in my manuals that suggest we couldn't continue an approach with a failed DU as long as switching is possible.

[B737900er]

I think its up to interpolation. Boeing says the Lower DU is in the field of view. If the airliner feels the same who knows.

[172_driver]

Never heard of a contingency procedure/airline SOP/FCOM tale for a DU failure during RNP approach. That's a very specific combination?

Apart from the normal FCOM limitations I would expect all new relevant limitations following a failure to be written in the QRH.

[de facto]

The obvious are.