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IRS Realistic Alignment Time

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HeyI have a technical question about the IRS aligment time when set to realistic.how exactly is this modeled in the NGX ?does the plane calculate how long its supposed to take and than just wait that amount of timeor does it simulate some kind of actual alignment process in real time ?thank u.

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As I think there is no earth movement in FSX is useless to simulate the gyros/accelerometer simulation and such calculations may remove some resources to other more important things.I think it is only a counter, maybe they simulated the change of alignment time from equatorial zones to polar zones, but never tried.The only things that probably are calculated are the differences between IRS last position, or detected (so actual fs position) and the entered one.But I think that only PMDG people can answer you.

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As the earth doesn't "turn" in FSX, it doesn't simulate real alignment. In fact, even if you enter a slightly wrong position, it will "snap" to the actual FSX position. I reported this a long time ago, but I never got to know if there would be any changes (also true for the following issues). Also, alignment times are sometimes off. They depend on latitude, which is correct, but still. Try very high latitudes, there the IRS should not align at all, whereas the NGX will show 16667 minutes of alignment time and actually count down from there... very odd. Furthermore, whenever alignment time is 17 minutes, which is around the sixties or seventies of latitude (IIRC), the display should show 15 minutes for the first three minutes (from 17 thru 15), and then count down from there. Don't see this as well. Talking about the IRS, also the ISDU has a bug, because the position entry is wrong. When entering the numbers they should be right-aligned, not left-aligned. On the real thing this would eliminate the need for entering leading zeroes. On the NGX this is not possible, you have to enter leading zeroes as the numbers will get filled in from the left, not the right. BTW - Does anyone know how to trigger a VERIFY IRS POSITION message? I really don't know how to do this. sig.gif

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thank u all for your input. it would be nice if PMDG could share with us some details on exactly how this works.

Also, alignment times are sometimes off. They depend on latitude, which is correct, but still. Try very high latitudes, there the IRS should not align at all, whereas the NGX will show 16667 minutes of alignment time and actually count down from there... very odd. Furthermore, whenever alignment time is 17 minutes, which is around the sixties or seventies of laitutde (IIRC), the display should show 15 minutes for the first three minutes (from 17 thru 15), and then count down from there. Don't see this as well.
where can u see the time left for alignment ? i was looking for that.

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Perhaps making several back-to-back flights without realigning? I don't have any manuals in front of me but that's what I'd suspect first to cause excessive drift.

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Where can you guys see the IRS alignment timer? I remember on the 747 there were 3 timers on the ND. Does the NGX have this as well or is it on the IRU on the aft overhead?

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HDG/STS mode on ISDU during alignment. However make sure you don't confuse the minutes with status codes, which are usually preceded by a leading zero (again, IIRC). sig.gif

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HDG/STS mode on ISDU during alignment. However make sure you don't confuse the minutes with status codes, which are usually preceded by a leading zero (again, IIRC). sig.gif
thank u sir.

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BTW - Does anyone know how to trigger a VERIFY IRS POSITION message? I really don't know how to do this. I have not tried it with the NGX, but in the RW you just move the aircraft to a different location, after shutting it down, and then start it back up. It will since that the current IRS position is different from the position when it shut down, and it will give you the message.

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Perhaps making several back-to-back flights without realigning? I don't have any manuals in front of me but that's what I'd suspect first to cause excessive drift.
But remember that you will see position drift only if you disable radio and GPS updating. Even then, you can see the raw calculated positions by selecting the POS legend on the ND.

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(BTW - Does anyone know how to trigger a VERIFY IRS POSITION message? I really don't know how to do this.) If i recall correctly, at this current build of NGX, you can trigger that message by switching off your GPSs and Radio guidance (through NAV inhibit page),while your IRS are fully aligned but Im not sure if this is the scenario your talking about. Marcus Jian

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Verify IRS position is not present on the real NG.About IRS these are the programmed messages:CYCLE IRS OFF -NAV - irs need to be fully re-alignedENTER IRS POSITION - position not entered or IRS found a difference between entered and detected or last and detected/enteredIRS MOTION - aircraft is moved during alignmentIRS NAV ONLY - IRS is the only fmc source of position data.VERIFY POSITION - too much difference from IRS and FMC calculated position, check POS SHIFT to see what is wrong.

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