Hi,I have a problem aligning the IRS Position.Everytime after alignment is completed the FMC IRS Position resets itself and asks me to set IRS Position again, when I align againthe same thing happens again. I would be thankful If anyone could give some clue on this issue.Patrick Henneke

How are you aligning the IRS's?

Hi PatrickThis happens to me too, but I assumed that as there are 3 IRS's the fmc will ask 3 times for each time you turn the controls in turn from off to nav.(thats how i set them) After the third asking its ok. Thought this was normal so would appreciate any other comments.regardsJohn Calleja

Hi Steve,I turn the IRS switches to OFF then to NAV and then to ALIGN.I wate until the assigned minutes have elapsed and show 0,0,0.Meanwhile I enter the IRS position in the FMC as indicated in the manual.regards,Patrick Henneke

>Hi Steve,>>I turn the IRS switches to OFF then to NAV and then to ALIGN.>I wate until the assigned minutes have elapsed and show>0,0,0.>Meanwhile I enter the IRS position in the FMC as indicated in>the manual.>>regards,>>Patrick Hennekehttp://forums.avsim.net/user_files/162745.jpgBest,Randy J. Smith<<>>

Hi thereFor a full IRS alignment (i.e. not just a quick 30 second one) from a state where the IRUs were not aligned, correct procedure I believe is to turn the IRS swithces first OFF, then to NAV.Then enter your position in the FMC and wait for a while (10 minutes), and they should, providing no fault, be aligned and ready to go. Works for me every time.If your IRUs are already "aligned", then when on the ground and parked at the gate, you can rotate the switches to "ALIGN", then enter your position in the FMC, and then rotate the IRS switches back to NAV. This provides a 30-second alignment, useful if you are performing a quick turn-around, or when a full IRS align is not necessary. I don't imagine this feature is often used on the 747-400, it is probably more useful on aircraft such as the 737, although I could be mistaken.CheersRudy

Rudy and Randy thank you very much for your kind help, I am going tofollow your recomendations.Best regards,Patrick Henneke

Hi,You should select IRS to Off then through ALIGN to NAV only.AND NOT BACK TO ALIGN (I think this an error in the manual, which I'm sure I read somewhere).This instigates a full alignment, takes about 10mins and you must enter your POS.If message ENTER IRS POS appears after position entry, check POS REF page 3/3 to verify all IRUs took position correctly and re-enter you POS. (FMC User's Guide).Amongst others, you should try and obtainPMDG-747-400-Checklist-NP-1.1 by Hans-Ruediger Gorzollahttp://library.avsim.net/download.php?DLID=91642Boeing 747-400 Advanced Operational Tutorial by Holger Seilzhttp://library.avsim.net/download.php?DLID=86332Regards Kenny.

Hi Kenny,Thank you for your advise and information, it has helped me tosolve my problem.Regards,Patrick Henneke

>(I think this an error in the manual, which I'm sure I read >somewhere).It's mentioned in the TRC lesson 1 ;-)

>You should select IRS to Off then through ALIGN to NAV only.>AND NOT BACK TO ALIGN I always do this and it always works out for me. Sometimes I get an ENTER IRS POSITION on the FMC, but I re-enter the position and the alignment completes. Then I turn the switch back to NAV once I get three +0s on the ND. But if this is the way it's supposed to be done, I'll do it from now on.About the fast alignment, I don't think it's done on the 744 very often since it usually has about a 90min turn around time. I think you could spare 10min to do a full alignment.Ryan Gamurothttp://www.precisionmanuals.com/images/forum/supporter.jpg

Also keep in mind that the FMC remembers where it was last. If you re-morph at a different airport, the FMC will say "This is not where I was. Are you sure you want to use this new present position?"But it will say this in its own FMC way. As usual, the FMC will ask, Enter Present Position. Down-select your GPS lat/long to the scratch pad then up-select to the IRS PP line (4R?)as usual. The FMC will seem to reject this as it will ask again, Enter Present Position . . . but its really just asking "Are you sure?" Just re-enter your present position into the IRS PP line, and you'll be good to go. Realism is fine, but after a while, that 10 minute wait will get old. That 30 second option works just fine. (Wish I could get that in the real airplane!) That's a well considered option. Thanks.