hi, in reallife, how do pilot obtained coordinate information to be dialed into the IRS. Do they have to carry a portable GPS device with them so that they could do the startup procedure?

As far as im aware the airport diagrams(ramp diag's) give the co-ordinates of the individual gates which is plugged in.RegardsRottnest

Some airports have the coordinates displayed on the sign carrying the gate number - they're my favourites, as it's just a question of looking out of the window...Cheers,Gosta.http://hifi.avsim.net/activesky/images/wxrebeta.jpg

On our 737NG's Marvel , when I power up the aircraft and prep it for flight, I will select the iru's to nav and usually within a few minutes I will have a gps position on page 2 of the pos page, I then down select it to the scrathpad and then enter it in the IRS FMC position lsk. Usually though our fmc databases have the gate positions anyway for the gate your in. Of course your aircraft has to have gps receivers to do this and not all 757/767's have this although some do, most still use vor updates.

I think that the 767 also automatically updates the position when you push N1 hold for takeoff. The 744 does this, based on the position of the runway in the FMC database.

"Otherwise, once in the air, the VOR and GPS update (if equipped) make the IRS position exact."Just a slight amendment from a technical POV...The aircraft (MAP) position is usually the FMC-computed position... The FMC looks at raw data provided by the IRS's and Nav Radios. The IRS's position itself is not being changed. The IRS's continue to drift without alteration. Even IRS triple mixing (weighted averaging) is done within the FMC.When GPS is put into the equation, the FMC is updated by the GPS at all times (in the air and on the ground). The TOGA/ N1 update only occurs if the aircraft does not have GPS (or GPS is inoperable). The TOGA/N1 update uses the applicable runway threshold position taken from the FMC Nav Database. To refine the TOGA updating process, FMC's allow the insertion of a distance value to compensate for takeoffs which are not started at the runway threshold (e.g. during a taxyway departure)By VOR updating, I guess you mean DME-DME and VOR-DME updating? VOR signals alone cannot update the FMC position.Hope this helps.Cheers.Ian.P.S. It may be company policy that you should not use the Lat/Long shown on the sign at the gate. These may not be updated as often as your paper navigation charts or FMC databases.