747 AP crash after switching flight phase

Hi there
Does anyone already experienced a switching flight phase on the 747 ? I can master the AP from T/O to CRZ, but as soon as I switch to descent phase, there’s nothing I can do anymore with it ! The AP seems just broken :

  • Nose up like if it was climbing at 3500ft/mn, even when it descending at 2500ft/mn :crazy_face: :no_mouth:
  • ALT hold doesn’t work anymore
  • V/S is “working” with a perpetuel delta of 500 to 1000ft
  • When I finaly get stabilized, if I dare to touch to even 1° of flaps, I totally lose the altitude AP again…

I had to attempt a manual landing, by night, with low altitude clouds and mountains… Guess how it ended…

I don’t think I’m able to stay in front of my PC for a 9h-flight. I mean I HAVE to switch navigation phases for some routes. But since it seems to crash everything, this aircraft looks just unflyable at the moment for me.

Did someone experience the same type of issues here ? Did you manage something, or any trick to share ?

Thank you for your replies.

Yeah, switching flight phase does horrible things to the AP. As a temporary workaround, here are the things I expect the AP to do so that I’m ready to catch them:

  • ALT will be set back to 5,000 ft. So immediately hit VS mode and hold VS to zero while you dial back in the correct altitude (this can sometimes be different to the altitude that you were cruising at just prior to changing flight phase)
  • If you’re in Mach hold, this will drop to around .65, so I immediately switch to IAS mode and dial up to 280kts, then switch back to Mach hold.
  • Sometimes the autothrottle will disarm as well (this seems to be more an issue in the Airbus) so be ready to rengage that if the engines don’t respond.

Having done it a couple of times I can now have it that the 747 doesn’t fall out of the sky the moment I forward to the descent point. Hope this helps.

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I tried to make a flight on the 787 from KPAE to SAEZ and it was 12 hours of flight in IFR with automatic pilot after being 4 hours from arriving it got out of hand and there was no way to control it made failures where the automatic pilot did not engage. an inverted and the weather had nothing to do with that. I have experience with this type of plane. I have flown a lot with prepard4.5 and in Xp11. And in none of them did I have those experiences of crashing like this without control as well as in KPAI there are problems of steps, tracks that when taking off measured train breakage and change track.

Thanks for the tip, I’ll try this out asap. And no issue with flaps on the approach phase ? I mean with your flaps out, does the v/s continue to work properly ?

It is still doing the same now sadly.