Chris, I think the autopilot engineers didn't want the AP flying the airplane if there were two competent pilots to take over if the inputs to the computer were lost. The AP if programmed to keep flying without airspeed input would have held 3 degrees nose up until altitude hold required a different attitude, and the last N1. The AT would eventually have no way to know if it needed to change with no AS. I think that is why they wouldn't let it keep flying level. It could get too fast or too slow with no AT help. Letting the pilots fly it manually to keep it in proper speed range was their solution.
Last edited by bubbers44; 27th August 2011 at 02:16.
Reason: clarify