Hi thereFirst post here. Have bought the PMDG NG 737-700 for FS9 and getting to grips with the FMC but something very frustrating is happening and I don't know why. I fly from Amsterdam to London Gatwick following all the procedures and entering correct information into the FMC, observing all the obligatory alt limits and speeds and letting the FMC calculate the rest for me. I approach Gatwick using TIMBA 2E STAR. Evry time that I reach LARCK wpt, where according to the STAR I turn 310 to TIMBA wpt, the aircraft starts wobbling and carrying on southwards out to sea. Funny thing is VNAV PATH is still lit up in the FD yet the aircraft is not following it. It just wobbles and carries on! In the end I have to manually turn the aircraft around so that it hits the path again. And it isn't just a case of not following the path for a few seconds or so, it carries for ages and still doesn't make an effort to back turn round by itself.Any ideas why it should be doing this?Any tips gratefully received.Thanks in advanceBrian

Welcome to the family Brian.Well, I presume LNAV is activated.But,that seems the typical behaviour of having a discontinuity in the ROUTE or LEGS page. Have you checked that you have cleaned all discos ?In any case, if you could post some screenshots of the panel that would be very helpful.

Thank you Jose. I must admit I can't remember if LNAV was active at that moment or not. I'm going to repeat the flight again and check everything. It could also have been that I entered the wrong transition wpt and that would have given me a disco.Thanks anyway for the tips.Brian

If you don't have disco errors, then one possibility is the STAR procedure by Navigraph might have a bug. I can't check that right now but yesterday I found a procedure at EGSS that did have a problem that would cause the symptoms you have.Specifically, if the procedure uses a FLYOVER followed by a TURN LEFT|RIGHT DIRECT commands both the 737/747 FMCs display a pretty route on the ND but can't fly it.That being said, be sure to make sure all disco errors are cleared before starting the flight. These pop up for even the most experienced of us.

Was that turn a Vectored waypoint?

Also, screenshots of the panel and FMC are very helpful with this type of problem

Thank you all for your advice. I think I discovered what the problem was: I had entered the wrong transition wpt for the STAR TIMBA2E. I entered MAY and it should have been TIMBA. I flew it the other night and it was fine.Thanks once again