There are lots of threads here on the B747’s autopilot, all of which appear to have been written about a year ago. (nov2020)
But it’s weird this is not fixed.
The problem is, as it has always been, that the plane fails to maintain altitude, and oscillates at least 1,000 feet above and below the cruise altitude. Autothrottle is not in sync, and chases after the oscillations, almost in opposite phase.
During climb, the plane after a while enters a fairly severe descent, before slowly moving back into positive climb. This repeats itself and will cause a crash if I do not intervene. The autothrottle is also here completely out of sync.
I have noticed that the flight director’s horisontal indicator is constantly changing up and down for no reason, and the autopilot probably tries to follow this.
But, I have also occasionally experienced that the plane behaves normally, but I can not figure out what is different when it happens. Now one year after this problem was described, I guess it’s not unreasonable to expect the developers have tried to do something about it?
Or am I missing someting?
Using V/S mode to overcome the problem helps, but it’s still very erratic.
For the record, I used to be a pilot, so I know how to operate tne MCP and FMS.
Have you checked your General Options → Flight Model? Make sure it’s set to Modern. Not Legacy.
I haven’t flown the 747 post SU6 yet, but prior to SU6, there were a couple of quirks. VNAV will do your climb/descent, but it doesn’t adjust your cruise speed. So you need to set your speed manually during cruise. The second thing is you may be overloaded on payload and trying to reach an altitude that isn’t optimal. Usually, you need to do a step climb profile if you are at high gross weights.
This is super annoying.
Yeah, I just don’t use the 747, as you say it is close to unusable. Luckily we have PMDG’s 747 coming next year, so we just need to wait a bit more.
With 747 Salty development, yesterday was imposible to put again AP.
Are you using the very latest version of the Dev mod? Salty released one a few days after SU6 to fix the AP button bugs.
Yes I am using the one after SU6.
Sorry for the delay in getting back to you. There definitely seems to be some issues with the autopilot after SU6. It’s hard to say what exactly as some of the time it’s ok and others not. And it’s not only the function of the buttons but the behaviour in certain modes, including LNAV and APP mode.
I’ll post something on their GitHub.
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