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rondon9898

Unaligned IRS showing instruments

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Hi guys,

 

When I power the aircraft up from cold and dark, the PFD and ND show up normally as if aligned even though the ADIRU is selected OFF on ovhd (artificial horizon/asi/altimeter/ND position indicator all present). It is only when the alignment process commences that the instruments go black and the bugs appear as one would expect. My question is: is this how it happens on the real aircraft? Not questioning PMDG accuracy on these matters, which I know to be superb. I just wondered whether this happened on the real aircraft or whether it is a teenie bug/glitch.

 

I have the latest SP installed.

 

Cheers,

John Price.

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I just wondered whether this happened on the real aircraft or whether it is a teenie bug/glitch.

 

I'd have to see a picture, but it doesn't sound right to me.

 

Did you follow the earlier guidance to delete panel states prior to updating to the earlier SPs?  This isn't necessary when going from SP1b to SP1c - I'm simply trying to find out if this is an issue that was created further back (it was necessary when going from the original to SP1, or SP1 to SP1b...I forget which one, but you had to delete panel states prior to updating, and if you did not do this, then you may get weird issues).

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Search the manual for SAARU (Secondary Attitude and Air Data Reference Unit), it will explain why turning off the ADIRU switch causes the PFD to provide attitude data.

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I have now read about the SAARU in the manual but can't quite see how that explains it. If it is an accurate simulation then that's fine but can I just get confirmation from someone that their simulation is doing this too? Just so I know it isn't a bug with my setup.

 

John Price

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can I just get confirmation from someone that their simulation is doing this too?

 

Can we get a picture of what you're seeing, precisely?

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Absolutely Kyle

 

Here is the aircraft with external power in and ADIRU off. ADIRU is off here and yet instruments on PFD still alive

 

2014-10-23_17-51-45-868_zps488d250e.png

 

confirmation of ADIRU Switch position:

 

2014-10-23_17-51-52-253_zpsa8d9292d.png

 

Then I insert the aircraft position into the FMS and instruments then go black. Also, I've noticed that even though I didn't fill the SET INERTIAL POS field, alignment still begins. Is that an accurate simulation or a bug?

 

2014-10-23_17-53-28-372_zps6475d29b.png

 

Once SET INERTIAL POS inserted, instruments are black on PFD as I'd expect

2014-10-23_17-53-47-112_zps7911e5e7.png

 

My question is should the instruments be present on the PFD with ADIRU selected off and position not inserted?

 

It might well be, in which case that's cool. But just wanted to now if it's an accurate simulation, a PMDG bug or a bug with my setup.

 

John Price

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My question is should the instruments be present on the PFD with ADIRU selected off and position not inserted?

 

That's SAARU supplying attitude, air data and heading (manually set) when ADIRU fails (or is turned off). Absolutely normal behavior. 

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Righto chaps thank you for that. Yes I've seen your photo now Bryan and it's obviously standard. Excellent work! Thank you.

 

John

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Also, I've noticed that even though I didn't fill the SET INERTIAL POS field, alignment still begins. Is that an accurate simulation or a bug?

Completely accurate. For the first stages of alignment at least, the 777 doesn't need to know the actual position it's at.

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FCOM2 pdf p. 864 says that the ADIRU, upon power up, removes heading/track or attitude data from the PFDs.  This implies that the data was displayed before the ADIRU was switched on and began alignment. 

 

Mike

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Absolutely Kyle

 

The others got to your question, but I wanted to say thanks for the legwork, especially since I was the one who requested it.

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