777 ADIRU Failure

[5LY]

After a failure of the 777 ADIRU, the EICAS checklist has you initialize the SAARU by entering heading info on the appropriate page in the CDU. My question is what exactly have I got to work with now. My assumption is that the a/p will work again now and that I can now navigate by steering with the HDG bug. Is this correct? Are my ND displays still normal?

Thanks in advance.

[Wizofoz]

Yes, A/P is available.

Nav display reverts to track up display (if it wasn't your companys default). You have HDG SEL Mode but NOT TRK SEL Mode.

Hope that helps!

[mru-mru]

If the ADIRU (interial part) fails, the SAARU takes over. The SAARU can provide Attitude and Air data (not position). You have to update HDG within 3 min on the POS init page. Navigation will be available via the FM's that still receive the GPS data, but you will loose the LNAV,VNAV,TK Sel, FPA, TOGA , LOC and GS modes, so you have to use HDG SEL, and VS or FLCH. You will also loose the flap maneuver speeds, and the autobrakes (no inertial data available). The autopilot can be re-engaged after entering the HDG.

[CanadaKid]

If the aircaft is in an area of Compass Unreliability, (Polar Route), heading information is lost without the 3 minutes delay. Track information may be used.

[5LY]

I'm still not sure we've got to it. What are we left with after entering the heading info. I'm steering with my heading bug with the A/P on. What am I navigating to. Do I have an L-nav line? Am I using X-track error? Am I now running this like an old INS? (Remember when 0 to 9 made your day?)

Thanks again. 5

[kijangnim]

:ok:Greetings,
The other NAV aspect to take into consideration is that you are navigating on Rhumb line (Constant heading):uhoh: No More great circle :\
For track correction use the 1 in 60 rule it works fine.