Originally Posted by
Xray678
The perception is much worse than the reality. As a former LCA on the 88/90 I had lots of guys turn to me during a line check or OE and ask what's going on after the plane did something they weren't expecting. But I never saw the airplane do something they hadn't just told it to do.
I've had it do something I didn't tell it. Flying across Texas at FL330 in VNAV LVL, we were BS'ing with the jumpseater. The airplane spun the altitude down to FL320 and then started a descent on it's own. We caught it and flew it back up to FL330 before we had to file an ASAP. My best guess is that the altitude select knob wasn't in a detent and clicked over 1000 feet. But that doesn't explain why it started a descent 500+ miles from the TOD.