Hi Pete
Hope you've recovered health-wise?
I took off from Meigs with the default FS2K B737, climbed to 7500 ft with FSUIPC loaded and ADVDisplay disabled and Radar Contact not running...
Tried to descend to 5000 ft (previous attempt with Radar Contact was from 29000 to 24000) and same problem. FS changed descent to PLUS 1800 fpm and plane started climbing. Re-established at 7500 ft and tried climbing to 9000 ft, that worked fine. Have included FSUIPC log (with "extras" logging) for your perusal as requested - it's BIG!
Hope the info helps
Regards,
Peter Salvage
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can investigate this, but can you please see if you can get it down to basics. No Radar Contact or AdvDisplay needed. Just try setting a higher altitude with A/P Alt Hold on, and see what V/S is set, and similarly a lower one. If you can reproduce it easily that way, fine, just tell me. If not then we need to examine the details of your previous experience more. Like are these specific altitudes (what to what), and is Radar Contact's co-pilot doing anything or are you in sole command?
Sight of the FSUIPC Log would be useful too -- especially if you enable "Extras" logging first.