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Guest JohnnyBoy35

Question about PMDG 737 NG 800/900 VNAV

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Guest JohnnyBoy35

Hi there... I hope you're all having a great day! I have a question about the new 800/900 VNAV. When I create a flight plan with descent weighpoints that are lower than cruise altitude... I'm finding that the FMC is ascociating top of descent with my first descent weighpoint. Say for example I want to fly from KPDX (Portland) to CYVR (Vancouver) about 300nm. Now I program the FMC with several weighpoints such as PAE, BEZOV, HEDDE and they contain speed / atitude constraints that are well below cruise. The way the OLD 600/700 FMC would work was to calculate it's own top of descent somewhat ahead of the first altitude/speed constrained weighpoint and then descend in a very reliable manner. But what I'm finding with the new FMC is that it ascociates the first speed/altitude constrained weighpoint as it's top of descent... and then complains that the destination is unreachable!!!! Is the new FMC VNAV setup different... or am I having a problem with my software. Thanks in advance :-)Sincerely, John PerrySee attached photo... Despite cruise being set for FL200, TOD is being shown as being at the same distance as the fist weighpoint (BEZOV) where the plane should already be at 6000 ft :-(73240.jpg

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Guest amerton

Hello John,I see from pic 1 that you have no speed predictions on the legs page, meaning that you probably have not completed PERF INIT page. Is your weight related data correctly set ?Side note, as your 6000 wpt is under the 10000 airport speed limit it's default speed target would be 240 without inputting any hard speed constraint.anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

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Guest JohnnyBoy35

Thanks again.... I did have most of the perf page done, except maybe the reserves which I don't belive really mattered in the 600/700. In any case I clicked a few things on that page and now I've got descent figures that look much better. This is a case of when all else fails = read the manual (which I did for the previous version) he he he... Thanks again for your outstanding patience :-)Sincerely, John P.Vancouver, Canada

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