IRS NAV ONLY

[Guest]

Hi everybody,I want to learn, why when I am at middle of Atlantic to KMCO, in the screen of the FMC suddenly appear the word [iRS NAV ONLY] and the magenta route lose from the screen of EHSI? Can I have a comment for this.Thank you very much PAUL

[Guest]

Hi Paul,That's what you get for filing direct. If you have waypoints like on a real world route you will not loose the magenta line. Of course, it'll say IRS NAV Only bacause that's all you got... Just file an oceanic route. You can use FSBiuld or whatever program to find them and you will not have that happen to you. Pedro

[Guest]

Over the atlantic, for example, you will not be in range of any VOR's. Therefore the FMC is unable to update/verify it's position. It then uses the average of the 3 IRS positions to calculate it's FMC position, hence IRS nav only.But yes, file a plan with waypoints as well. A good site to do this is www.asalink.net/davideg/rfquery.htmlBTW your ADI looks different to mine - it has the speed tape down the side. Where did you get this ?Carl

[Guest ilh]

Pegasus EADI: PIC/Carrier Options menu.Lee Hetherington (KBOS)

[Guest HPSOV]

As others have said it is there to warn you that the FMC has not had a radio update (LOC/VOR/DME) in a given period of time, or by 15000ft on descent.This means the position is being derived totally from the IRS's, and as such may not be totally accurate.It obviously happens on oceanic flights, but also on flights in places like Australia (lot of land, not a lot of VOR's), and across the island of South East Asia.From our point of view it means terribly little, other than a button to press to clear the message...