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(Nightly Build) 777 AT keeps changing to 0kts midflight

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(Nightly Build) 777 AT keeps changing to 0kts midflight

Postby ferrari 1123 » Thu Dec 05, 2019 9:15 pm

Hi Everyone,

So far the Nightly build of FG has been great and I haven't run into any problems with any other aircraft, but one new thing that keeps occurring during long-haul flights on the 777 is the autothrottle will seemingly randomly change from Mach 0.84 or any other cruising speed to 0kts, which subsequently triggers a stall if I don't then change it back to the correct cruise speed after. This sometimes also occurs during climbs as well. This may be an update to the way that the FMC processes route data; I usually just plug waypoints and altitudes into the default route manager and then hit LNAV without using the FMC.

Has anyone encountered this and figured out a way to rectify it? As far as I know this has only happened to me on the 777, A320/330 and other aircraft work perfectly fine.

Thank you very much,
-Nihar

(FlightGear 2019 2.0 Nightly Build)
(macOS Catalina)
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Re: (Nightly Build) 777 AT keeps changing to 0kts midflight

Postby Thorsten » Fri Dec 06, 2019 6:30 am

Please check if possible whether this is a regression or not - we're seeing a lot of vague issues with 2019.X and we need to understand what actually is regression and what is something else

viewtopic.php?f=4&t=36568
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Re: (Nightly Build) 777 AT keeps changing to 0kts midflight

Postby Isaak » Fri Dec 06, 2019 1:19 pm

It has to do with some change in the Route Manager code, didn't find time to find the cause. The solution that seems to work for everyone is to make sure that you put the cruise speed in the Route Manager box before the flight. It used to be at 320 kt IAS by default, but this has changed to 0 kts, so if you input 320 kts, the AT will stay at your desired cruise speed (be it mach or ias). I'm sorry I can't find the cause yet, my time is very limited at the moment.
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Re: (Nightly Build) 777 AT keeps changing to 0kts midflight

Postby ferrari 1123 » Sat Dec 07, 2019 3:33 pm

Thorsten wrote in Fri Dec 06, 2019 6:30 am:Please check if possible whether this is a regression or not - we're seeing a lot of vague issues with 2019.X and we need to understand what actually is regression and what is something else

Unfortunately since I have macOS Catalina installed, I cannot use older versions of Flightgear because aircraft keep crashing when the initializing subsystems message pops up. Unsure as to why this is, but since writing my original post I have definitely noticed a lot of faults in the Nightly Build, especially more and more crashes during long haul flights.

viewtopic.php?f=4&t=36568
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Re: (Nightly Build) 777 AT keeps changing to 0kts midflight

Postby ferrari 1123 » Sat Dec 07, 2019 3:35 pm

Isaak wrote in Fri Dec 06, 2019 1:19 pm:It has to do with some change in the Route Manager code, didn't find time to find the cause. The solution that seems to work for everyone is to make sure that you put the cruise speed in the Route Manager box before the flight. It used to be at 320 kt IAS by default, but this has changed to 0 kts, so if you input 320 kts, the AT will stay at your desired cruise speed (be it mach or ias). I'm sorry I can't find the cause yet, my time is very limited at the moment.


Thank you for this solution Isaak, I'll be sure to test it out later.
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Re: (Nightly Build) 777 AT keeps changing to 0kts midflight

Postby wkitty42 » Sun Dec 08, 2019 2:13 pm

ferrari 1123 wrote in Sat Dec 07, 2019 3:33 pm:Unfortunately since I have macOS Catalina installed, I cannot use older versions of Flightgear because aircraft keep crashing when the initializing subsystems message pops up. Unsure as to why this is,

it is because apple changed the usb interface stuff slightly... older versions of FG will likely not get this fix back-ported but it might be possible... that's up to james if it can be done without breaking non-catalina systems...
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