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Guest pilotcdc

FMC and Winds

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Guest pilotcdc

Hi all,I've posted a similar question in the ActiveSky forum, but I am posting here as well for some input.I was flying in the wonderful 737-700 and had a small issue. The wind (as shown below) was almost a direct crosswind. The TAS and GS were showing the same values, but FMC PROG 2/2 showed a headwind of 26 knots.Any thoughts...maybe an FSUIPC problem?Thanks,Christianhttp://forums.avsim.net/user_files/135352.jpg

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Guest lou ross

I've had a few drinks, but with that in mind, I'll say that the wind is 246 deg at 85kts. The FMC shows a crosswind component of 81, as it is not a 90 deg crosswind, the component is equal to 81, not 86. A strong crosswind also produces a headwind component, in this case it is apparently a component of 26 kts. If you can draw a wind triangle or have an E6B computer, you can figure the headwind component of strong crosswinds. Unfortunately, I've forgotten long ago how to draw wind triangles and I no longer have a Jepp E6B. However, I found that in actual practice, well, nevermind.louross.

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Guest pilotcdc

I got out the trustly, old E6B and it shows a groundspeed of about 428. That agrees with the FMC of a headwind of 26 knots, but why does the ND show the groundspeed to be the same as the true airspeed?-Christian

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Guest lou ross

Well, actually the groundspeed should be less.louross.

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Guest pilotcdc

Yes the GS should be less than the TAS, but the ND doesn't show that.I've also got a different screenshot in the ActiveSky forum that shows a tailwind on the ND, but a headwind in the FMC.-Christian

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Guest lou ross

Saw your AS post. I've got fsuipc 3.5 dated April of this year. I've noticed no wind problems (winds set at 0,5,8). Have not installed the new fsuipc- never do for at least several weeks of checking several forums. I get some variations from the aviationweather.gov web site and AS, but I set the "accuracy" or variance in AS options to 90%; I also have developed the belief that flight sim errors in computing ground speed when flying in strong crosswinds, whether head or tail wind componets. Maybe a prob with the new fsuipc, don't really know. louross.

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Yep the problem is only with the new FSUIPC 3.51 and ASVE. If you use FSUIPC with FS real world weather, or just one of FS's weather themes then the GS vs. TAS calc is correct. For now I'm going back to FSUIPC 3.50


Dave Paige

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