I occasionally encounter a problem that I've never seen in any forum, though maybe I've missed it. At times during a sim flight, my airspeed abruptly changes, either up or down. I suspect it may be due to weather as I cannot relate it to anything else.I use FS9, flying commercial airliners, and I always download realworld weather (snapshot), and this seems to happen once every 4-5 flights, either during cruise or descent (can't remember if it's happened during climbout or ascent).The last time this happened was in a A319, cruising FL310 at .80 Mach. Suddenly I found my airspeed was over .90 Mach, alarms going off. If I act quickly, I can reduce airspeed before the a/c breaks up. A couple minutes later, airspeed changed from .80 to .60 Mach, and I let the AP bring the airspeed back. I had several more airspeed changes after that, both up and down.This occurred over the Rockies, but I've had this happen over flat terrain as well as ocean. When I downloaded the weather, there were no fronts in this part of the country.This can happen once, multiple times, or not at all during a given flight. If I restart the flight, it usually happens in approximately the same locations, and the changes generally match (increase vs decrease in speed), and if I re-download weather it usually solves the problem.What I'm wondering is this:1) Is there some glitch in my FS9 or my original weather download?2) Does this happen in real world flying?3) If this is an actual phenomenon, is there a way I can detect it so i can adjust airspeed before I encounter it?Alex M.NWVA 0174

'Tis a known 'undocumented feature' of FS9 Alex, check out the ActiveSky forum.I find it strange that such a 'undocumented feature' sailed through testing, AFAIK it affects everyone who uses real weather.MS do test before release don't they :-hmmm :-grr (Rhetorical question)

I guess you are using Active Sky, since I had the same problem with Overspeeds killing my AC when the wind speed or direction changed.In FS2002 this is really easy to solve by setting the winds in FSUIPC to change smoothly (1 knot per second or so).In FS2004 the unregistered FSUIPC version does not have this feature so you cannot solve. I think that the registered version has it, but since I am not sure I suggest you ask before buying it.Leo

I get that too--pretty annoying. FSUIPC doesn't seem to be able to solve it.

1.people say it's a bug in fs9, i have yet to see it tho', perhaps because i don't use activesky ;-)2.oh yes3.alas, you can't see the wind :-) fortunately, you can guess more or less where you'll encounter this dangerous phenomenon; for starters google these: frontal wind shear, jet stream, mountain wave, eddies, temperature inversion, thunderstorm shear

What you may be seeing is the FS9 wind bug. IT IS NOT, let me yell it again, IT IS NOT, caused by Active Sky 2004. However, AS 2004 has done good things in smoothing these things out. BTW, don't look for FSUIPC to do anything. Pete has publicly stated that he can find no fix for this right now.Hope this helps,JimActiveSky Supporthttp://www.hifisim.com/images/as2004proudsupporter.jpg

Yes.......this is the famous "wind shift" bug. It happens whether you use Activesky, FSMeteo, FS weather, or any of the other weather programs. As Jim said, FSUIPC will not be able to fix it. So far, the only program I've seen that really helps a lot is ActiveSky2004. Its a good example of a bug that was present in FS2002 that WAS NOT fixed for FS9.

I read something recently regarding FS having issues handling GUSTS when the first wind layer is set directly adjacent to the surface layer...if there's a buffer of some size between the two, things are better. I thought it was in the FSUIPC docs, or on Pete's forum, but I can't find it at all right now...anyone help me here?My thought was that maybe real weather - either FS's or via an addon like ActiveSky - lacks this buffer, thus some of the issues.If I find that source, I'll post back.Best,sg

If you use a weather program, including dynamic weather in FS, you will get that at cruising altitude. I've seen gusts and more often, abrupt wind changes like doing a 180, certainly greater than 90 degree shifts. The reason it's more noticeable at cruise alt is that in general, winds can be quite strong above FL250.I was able to get (mostly) around it by using ActiveSky's wind smoothing, and also setting FSUIPC to force abrupt changes in barometric and wind direction to some very small number (1 degree per second or something like that - not at home right now so I can't remember). I also have FSUIPC extending winds above the max, and making sure that the weather program updates FS9 weather more often (like 2 minutes), and enabling the fix for the counterclockwise winds.I'm now at the point where I still get wind shifts, but at least I don't drop or add 100Kts to my IAS and it's quite manageable - not realistic, but manageable, because I have crashed twice because of this using RFP2 (since the AP circa 70s doesn't react to this very well), and overstressed my 737 once (I went to mach 1.2 FL370 from .78 in two seconds - that didn't last long).Check out the ActiveSky forum in the commercial section of this site for a complete description of the problem.

And yes, it does happen in real life. Only difference is in the little planes I've flown they slow down right away, or accelerate quickly to the speed of the new air mass. Usually it's a thermal going up or a downdraft that has accelerated the aircraft in a verticle state and not horizontally. Kind of spooky ;) climbing at 700fpm up under a cloud and all of a sudden you're getting 1,200fpm. The wind change is so abrupt that the stall horn is activated for a second or so. As far as the game goes, I haven't experienced it since I only use the default weather most of the time. Some times I do the real weather download for fun, but I can't remember having this problem with normal weather. I have tried flying in a thunderstorm in the game though :D, BUT I expected it then ;)