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opherben

VNAV DES

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My observations of VNAV descent, on properly programmed FMC flights:a. During descent without altitude or speed restrictions (so the descent should be smooth and at constant angle), the rate of descent cycled between 0 and 4000 FPM, and the was aircraft unable to regain a proper descent path without pilot intervention.b. On another flight, the aircraft ignored programmed altitude restrictions and descended through them.VNAV climb worked fine.

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I had the same problem than rich09. My vnav at climb works great -- the same at descent until i reach a vor or a waypoint -- than my vnav profile shows from one second to another that i

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Yes, I have this problem in every flight...I think the FMC calculates the TOD too far from the arrival airport...about 40 mn before a normal start of the descent...another issue: Throttle Hold doesn't work...PSS team please try to answer this questionRiccardo

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I've just reinstalled FS9!! Then I installed the 757...And the 757 has the same problems!! Help me finding a solution!!Riccardo

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Confirm the issue.I used to make flight plans in FS NAvigator - export to FS. But VNAV DEC doesn't appear in a flight plan imported from FS.I guess all these FMS issues will be fixed.

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Here same problem.I think it is a bad calculation of des path by the FMC.I have notice that after always waypoints, the aircraft seem to be lower than the true path.I'm going to show what happens.Passing TEA VOR, the aircraft is lower than the true path (it was in the right path before TEA).2006sep%38%3003av7.jpgThen the 757 decrease his rate of descend from 3000ft/min to 400ft/min until establishing again on the true path after few NM. After that it starts descending again keeping the path.2006sep%38%3004ba1.th.jpgThat happens after all waypoint during VNAV DES...

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Another example:Passing PAL VOR the VNAV path became 2140 feet higher...senzatitolo4xh7.jpgRiccardo Malpica

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hi! suppurt i have the same problem can you tell our something about??

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I have noted this as well. I usually only use FLCH to do my approaches, but after reading this thread I did a couple of VNAV approaches and was able to duplicate this behavior.

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I also noticed that when using FLCHG from higher altitudes the plane is descending at up to 5000 fpm. My pax are not happy!! Once the a/c gets down to around 10,000 feet the descents become more realistic (2000 fpm or less). My way around this is to use level change with a set rate and speed, but this is not ideal because if you don't watch your speed it is very easy to overspeed.

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This particular problem is reported on several threads and PSS are fully aware of all the details - and differences with the 777 VNav performance.John Rooum

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That's exactly what I saw BUT with the 777.Thanks guysThis is clearly a bug in ToD calculation by the FMC. I hope they will find a solutionregardsYves Lefevre

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I haven't really seen this problem, only because I use a different method. Normally, I'll take the A/C out of VNAV mode, and manually set the airspeed and descent on the MCP (flight plan built with FSBuild, which imports my TOD to the FMC). This seems to work for me when I use FS Passengers. Just offering another possible work-around.....Regards,Trent

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I mentioned this bug right after the release, but seems to have gotten buried and still no reply from Norman or Steven or Graham. I don't know how any beta tester could have not caught this, as VNAV descents are the most fuel efficient and smooth for the PAX. However, real life and simulated ATC seldom seems to have the same descents in mind as the FMC's on board do. You got to love those Pilot Discretion to the IAF altitude's.But PSS, please help with this bug.Steve Park

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I dunno. I stated above I was abkle to duplicate the behavior -- yet I did some cleaning of my computer and some tweaking to my FS and the problem went away. I am now able to do smooth VNAV approaches, so the problem went away for me after cleaning my machine. So I take back what i said above about duplicating the behavior.

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