I keep hearing all this talk about an "IRS". So what is an IRS and what does it do?Thanks, Jase Traylor

IRS stands for Inertial Reference System and is the replacement for the INS (inertial navigation system). Basically when you start up your 747 for instance, you have to tell the fms where the hell you are in the world, and to do this you align the irs's (there are three). You input the grid ref for where you are, and the laser gyro's at the heart of the system then require a set amount of time to work things out ( 13mins on the 777 I think). What they are doing during this time is sensing the rotation of the earth, which is why it will take longer at the poles. You can do a quick alighnment if the plane has not been shut down for more than a short period of time, and the system can update enroute with data from vordme's and gps. This is only a rough explanation of an extremely complex topic, and for more detail I would suggest you read Bill Bulfer's guides, or post on the ps1 forum where there are some real techie experts who will REALLY confuse you!!! But during a long flight over water you may get some map shifting occuring, and need to purge the system when you get within range of a vordme. The IRS is far more accurate than the INS used to be, anyway, hope that helped, and that I haven't made too many mistakesregards,ant

Ok that gives me a better understanding, Thanks ant. Boy I bet that would be a hell of a thing to model in Flight Sim.

Check out civa110.zip in the Avsim file library! Dick Bixler

>>>>Ok that gives me a better understanding, Thanks ant. Boy I bet that would be a hell of a thing to model in Flight Sim<<<<<<

7 and 6 are not letters mate. :(_Paul

Jase, if you'd like to see a technical drawing of such a unit with laser gyros and all that stuff, have a look here: http://www.airliners.ch/technik/systeme/adirs/adirs_e.htmBest regardsMarkus

>[snip] You can do a quick>alighnment if the plane has not been shut down for more than a>short period of time, and the system can update enroute with>data from vordme's and gps. [/snip]Just one correction: The IRS position is not updated in flight. The FMC position, however, is.Typically the FMC takes its position from GPS, then a mix of navaids (ILSDME,VORDME,VOR, etc), and then from the IRS. If you are on a non-GPS aircraft, and are out of range of any navaids, the FMC position will be soley based off of the IRS mix (in a 744 or 763, from the L, R, and C IRS).Once you get within range of navaids, the FMC will update its position based off of the navaids. The IRS, on the other hand, cannot be updated.Jon (KSEA)

>I keep hearing all this talk about an "IRS". So what is an>IRS and what does it do?>Well, here in the U.S., given the date of your post (4/14), IRS means "Show me where the money went!" :-(IRS - Internal Revenue Service - Tax Time :-(And as my wife says "The IRS" as in the money is THEIRS!-michael

>>>>>>>7 and 6 are not letters mate. :(:) :)

Thanks for all the information guys, will wilco release a PIC767 FS9 version?

"will wilco release a PIC767 FS9 version?"Last I heard, Wade, Eric, Laurent and Pedro wanted to fly solo on their next 767 project, so, no, *Wilco* probably won't be releasing PIC767v2 .... The folks formerly known as the "PIC team" will be.Cheers.Ian.

Last I heard, Wade, Eric, Laurent and Pedro Eric is no longer involved in this project, he hasnt been for quite some time.John http://homepage.eircom.net/~eamonnmca/images/logo_ba.JPGwww.bavirtual.co.uk Senior Captain Simflight.com Staff Reviewer

A brief description about what an IRS/IGS does. It's an old joke but still a good one.The aircraft knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is the greater), it obtains a difference, or deviation.The Inertial Guidance System uses deviations to generate error signal commands which instruct the aircraft to move from a position where it is to a position where it isn't, arriving at a position where it wasn't, or now is. Consequently, the position where it is, is now the position where it wasn't; thus, it follows logically that the position where it was is the position where it isn't.In the event that the position where the aircraft now is, is not the position where it wasn't, the Inertial Guidance System has acquired a variation. Variations are caused by external factors, the discussions of which are beyond the scope of this report.A variation is the difference between where the aircraft is and where the aircraft wasn't. If the variation is considered to be a factor of significant magnitude, a correction may be applied by the use of the autopilot system. However, use of this correction requires that the aircraft now knows where it was because the variation has modified some of the information which the aircraft has, so it is sure where it isn't.Nevertheless, the aircraft is sure where it isn't (within reason) and it knows where it was. It now subtracts where it should be from where it isn't, where it ought to be from where it wasn't (or vice versa) and intergrates the difference with the product of where it shouldn't be and where it was; thus obtaining the difference between its deviation and its variation, which is variable constant called "error".

:-hmmm I was getting dizzy reading that the first time.I got :-erks the second time,Now I've given up!Good post though ;)John http://homepage.eircom.net/~eamonnmca/images/logo_ba.JPGwww.bavirtual.co.uk Senior Captain Simflight.com Staff Reviewer