Blueskies21

All true, but again, missed information; we really don't train things like runway position updates anymore. Once you take the runway, the bottom left key on the FMS becomes "runway update" (though you could also reclick the TOGA's as that's one of the other functions of TOGA). If you click runway update or toga on the runway, then the FMS is fairly reliable for white needles navigation. If you don't (because we really don't train that) and we have been training to update the FMS position from the GPS source (rather than gate coordinates for example) then the FMS is pretty inaccurate in white needles, which has caused some people to assume we need to fly green needles. For example after ATC says "are you direct ?", someone looks at the green needle back up, says "what's it doing" and then they fly green needles and heading the rest of the time. But all of that is caused by a lack of information, which should have been provided and clarified by this point.

Assuming you do the runway update, if the FMS is off, you'll literally see the FMS map page on the MFD snap to your current position, and then the FMS is great in white needles.

There again, if you get Check Pos message in flight, mostly we ignore it when everything's working, some people may actually know there's a procedure in the CFM to update the position from a "known good" nav aid. Typically, we would use the GPS to do that, but if you're on a victor airway or a jet route (or have another reliable means to fix position with regard to the ground) you can update from a VOR which will also allow you to use the FMS in white needles if the position solution has degraded to the point to a Check Position message.

Rant off.

ninerdriver

It's page 4-110 on the 900 and page 4-119 on the 200 for those who are interested.

Folks can also update the FMS position from the gate if needed. Almost all of our airports publish gate coordinates.

For IRS planes, if the FMS position is okay after cross-referencing the gate coordinates, then update POS INIT from the FMS. YMMV.

Flogger

The CHECK POS message is not actually indicative of a need to "check positions". Rock-coll says it's very much a glitch, usually caused by certain frequencies being tuned in stby mode. You don't need to do anything when you get that message.

And read page 2-2 in the 200 CFM. No, we can't go white needles with GPS unavailable. MEL says we can. CFM says we can't.

prex8390

In this case what has a higher precedence? The memo saying we can specifically dealing with this event or the CFM?

Meow1215

Memo takes higher precedence as it is essentially a modification to the CFM. Just needed that memo a few days earlier.

Flogger

Perhaps, but STDS published that memo based on the MEL, before some A-Hole pointed out what the CFM said.

It really is ridiculous, since the thing works fine in white needles with just a single VOR?DME. That stupid table in the CFM is most likely a typo, but it is still there.

web500sjc

Don’t worry, the company just published a guide to flying no GPS... now I need to go learn about service volumes again.

TalkTurkey

That and the fact that they just hired a new fleet manager who’s just breaking into the job.

TalkTurkey

If we can’t do NOTR/GPS departures, why do we care about runway update?

ninerdriver

If you can't update the FMS position from GPS, and if you don't update the FMS position from some other known location, then the end of the runway is a pretty solid known location to update the FMS position.