Dual fmc failure

[wilco77]

Dual fmc failure in radar environment, ie. Malaysian airspace over India, what does ATC need to be informed?

[HPbleed]

If this was me, I would make a Mayday, loss of navigational performance, loss of RVSM etc, would require radar headings, probably to nearest suitable airfield where the problem can be fixed (so need onward travel for pax, an engineering department - perferably used to dealing with company aircraft).

[Pugilistic Animus]

A Mayday???

But,

Where's your emergency?

[HPbleed]

The fact that you're no longer LNAV and VNAV compliant? Please, correct me, I'm still learning these things!

[Pugilistic Animus]

wilco77

HPbleed

I think you would just---say unable RVSM--etc.

but you should still have IRS capability on raw data STBY NAV [ususally] no
you wont lose ALL area navigation---

Bruce Wayne I don't think they are 'trolls', It is a genuine question...sometimes folks were not taught or just don't know-we don't want to put pilots off from coming here and asking genuine questions---

[Bruce Wayne]

PA,

Fair enough.. post removed

[johns7022]

By FMC I assume you mean FMS....like loosing your GPS, or GNSXL....

Um....well if your going direct...and now you have to fly by VORs, ADF, DME, ect....not an emergency...your just going to have to start pulling out charts...and using other means of navigation....

Going from SFO to Hawaii, would probably be an issue...

I always bring a little hand held GPS with me....

[Joshilini]

Why would you declare a mayday?

Switch to manual flying and request vectors to the nearest suitable airport (suitable -- up to your very own interpretation there). No offence but have a lot of airline pilots forgotten how to fly manually? "Gear up and switch on the autopilot will you?"

[Type1106]

Surely, a navigation failure of this kind would require a Pan Pan call as neither the aircraft, its occupants nor anyone else is in 'immediate need of assistance'.

If you are in a radar environment then it is now the controllers job to take whatever action he deems necessary but you should still be able to navigate using VOR/DME. Also, I'm pretty sure RVSM compliance is not dependant on nav input but I'm prepared to be corrected...

However, if you are out of ground navaid and radar coverage and you are lost then 'Mayday' would be appropriate.

BTW 77, I'm a little confused about your scenario 'Malaysian airspace over India' - last time I looked Indian and Malaysian airspace were not even adjacent.....

1106

[TolTol]

Declare to ATC "unable Rnav", RVSM should be unaffected. No mayday, no Pan, just continue using vectors or conventional navigation to destination. Should be no need to divert, unless the destination has Rnav approaches only and no radar (have never seen this).

I'm talking about operations in Europe though. MNPS airspace I'm not familiar with.

[King on a Wing]

Dual Fmc fail....
Unable RNP....infm ATC of degraded navigation performance. Consider making a PAN if in non radar environment. Try and request radar headings. All your route prior to the failure would have been copied onto your Cdu(s).Therefore following the route would be NO PROBLEM. However any new waypoints would have to be added using Lat/Long posn. Lnav/Vnav will not be avbl,however Lnav can be re-engaged later using old route. Basically revert to using good old INS system procedures.All radios ie Adf's and Vor's will have to be manually tuned thru Cdu's for navigation. No Vref/Vapp avbl.So open the ol handy dandy and dust those performance pages...
Most importantly land back at an airfield with the closest bar...
I got a feeling you'll need the drink!

[BOAC]

All a bit confusing since we have no idea which a/c we are talking about, but I think the only thing that could affect RVSM would be if the particular A/P required an FMC to function in basic height hold.

King - into which piece of kit are you planning on entering waypoints via lat and long and exactly what do you expect to get out of it afterwards?

As type 1106 says, you are already 'lost' before the failure

[B777Heavy]

I agree with BOAC here...not sure why you would not be RVSM compliant? FMC(S) failure has nothing to do with Height or Alt hold

[oceancrosser]

King on a wing has it spot on. You should even be MNPS compliant with at least 2 cdu´s/IRS´s working. More workload, but a lot less than the old 9 point INS. If not revert to the "blue spruce" routes or down to FL270 and continue. Might need PAN to get some attention in that case. Nothing at all to do with RVSM.

[Pugilistic Animus]

I don't even understand the thread anymore--RNP-RVSM RNP-MNPS which one?

whenever you can't do something---say 'unable'

[BOAC]

Unable

[latetonite]

I wonder how I survived for 25 years without even one FMC onboard...but I understand that many of the new generation pilots` best option is to declare a PAN to start with..

[Dream Land]

I agree with BOAC here...not sure why you would not be RVSM compliant? FMC(S) failure has nothing to do with Height or Alt hold

Well on the small bus Dual FM Failure would kill the A/P, please correct me if I am wrong, and that would mean no RVSM.

[BOAC]

Originally Posted by B777heavy

FMC(S) failure has nothing to do with Height or Alt hold

- there you go Never say never (as Marilyn Monroe used to say)

[MrBernoulli]

The following is taken from a Honeywell manual for the B777 FMS system. Fairly recently practised this in the sim - it is a bit startling initially (so many pages you are used to using are suddenly gone) but manageable.

I think BOAC, posting above, may have confused FMS with CDU - they are not the same thing. The CDU (boxes in the cockpit) controls inputs to, and feedback from, the FMSs (bigger boxes downstairs in the E & E bay).

Boeing 777 Flight Management System

ALTERNATE NAVIGATION

If both FMCs fail, .......

Initializing alternate navigation does not require any pilot action. It occurs automatically 2.0 seconds after the last FMC fails. Alternate navigation initializes using the last flight plan and last set of navigation radio frequencies downloaded from the FMC prior to FMC failure. Alternate lateral guidance is not enabled for an additional 3.0 seconds after alternate navigation initializes. Alternate navigation radio tuning is available as soon as alternate navigation initializes.

All CDU calculations are based on a great-circle course between waypoints. The CDU does not accept undefined waypoints or conditional waypoints. Complete departure or arrival/approach procedures cannot be manually entered or crossloaded from the FMC if they contain undefined or conditional waypoints. The CDU creates a discontinuity between such waypoints. However, individual legs of a procedure can be manually entered or crossloaded if they constitute a great-circle course.

Route changes are made on the ALTN NAV LEGS page the same as with normal FMS operations. All courses between waypoints are direct routes. Modifying the active waypoint computes a present position direct course. A route change to any one CDU crossloads the route change to the other CDU when the change is executed.

Only the active waypoint course can be referenced to magnetic north because the ADIRU can provide magnetic variation only for present position. All subsequent waypoint courses are displayed as true courses.

The radio must be manually tuned on each CDU in alternate navigation. The left CDU tunes the left VOR, DME, ADF, and left and center ILS. The right CDU tunes the right VOR, DME, ADF, and right ILS. In all cases, manual radio tuning is done on the ALTN NAV RADIO page.

The alternate navigation system operates from three CDU pages:
ALTN NAV LEGS page
ALTN NAV PROGRESS page
ALTN NAV RADIO page.
These pages are the only ones available in the alternate navigation mode. Executed flight plan modifications made on one CDU ALTN NAV LEGS page are displayed on the other CDUs