Perhaps this is a quirk of the real jet, but I doubt it. I have noticed that if I am flying manually with FDs on and I command a certain vertical speed, if the aircraft has drifted away from that vertical speed when you turn the autopilot the vertical speed target switches to the aircraft's current vertical speed and you have to re-command the prior target. For an extreme example, say I have 2000 fpm commanded in the window but am doing 1000 fpm, when I turn the autopilot on the target immediately switches to 1000 fpm.

Happy to capture a video of the behavior if needed.

I'll reach out and ask about this but please feel free to add a video as it might be something that is getting addressed in v.1.0.6

I did a basic search in the BA systems pdf. For the VS autopilot mode, the following is stated:

"Before engagement the vertical speed tape acts as a vertical speed indicator. When VS is engaged the VSI tape locks to current vertical speed, but this datum can be adjusted with the VS control wheel. This is the only pitch mode datum that can be varied with the mode engaged. Range available is +4000 to -8000 FPM."

This is an earlier version of the Tristar autopilot. However, looking at the above system, it is not out of the realm of possibility that the basic engagement parameters between this and the new ACP remain identical in that when a major mode gets engaged (engaging VS, or in this case turning ON the AP with VS mode already engaged) the system resets to the current value. It makes sense a little bit as you don't want (or back then there wasn't a proper way to) the autopilot to suddenly jump to a new VS value on a mode change. Those days G limited autopilots I believe weren't a thing.

So, again, even though I don't know the definitive answer, it MAY be designed like this.

p.s. Combing through the Delta L-1011 manual and looking at the -500 specific differences, I read the following statement:

"When an autopilot is engaged in CWS, it will automatically maintain the airplane pitch attitude and roll attitude (or heading if the bank angle is less than three degrees) existing at the moment the pilot releases the controls."

Given the fact that on the Tristar you HAVE to transit through CWS to reach CMD, it would also make sense that the autopilot captures current values instead of the ones which the FD system previously had,

Edited 3 hours ago3 hr by MD82