Ok, I just purchased the 707 v1.3 and took off happily with minimal problems. I managed to get the INS programmed without issue as I'm pretty familiar with it having used it in the 727 quite a bit. I was able to engage the autopilot in heading mode and controlled my climb with the pitch wheel, still no issues. I engaged nav mode and began tracking my INS course just fine. Then at about FL280 or so the autopilot clicked off for no reason that I can surmise. Everything was fine up to that point. Now I'm mid flight having tried everything I can think of, but the auto pilot will not re-engage. I click the autopilot button, it makes a noise, and does not engage. What would cause it to click off after having been engaged for 3/4 of the climb and not re-engage? 2100nm is a long flight with no auto pilot...

Thanks in advance for any help.

Did the rest of the avionic pack still work then?
Sounds like you ran on batteries which were down after some time after everything worked before.

Good call! I did use external power and it looks like I forgot to tun that off after engine start. The avionics must have died a bit afterward. I disconnected the external power from the animation panel, hit a hotkey to turn avionics back on and presto chango, all works. Thanks for the push in the right direction.

No problem and welcome to the forums.  :)

I always turn the Essential Power Source Selector knob and the AC Paralleling Selector knob to one of the generators, which I have set to EXT PWR and EXTERNAL POWER, respectively, when External Power is connected. I also make sure that the DC Meters Selector knob is set on ESS TR or ESS TR#. I usually do this once I have all the engines running.

Mark