A37575, I think the problem on that flight goes far deeper than who engaged the autopilot! I had a situation once in a BAe146 where I (PF) engaged the A/P after takeoff and then noticed the damned thing wouldn’t turn to follow the HDG bug. The autopilot annunciation was indicating ON but when I held the column I discovered that while the pitch servo was engaged, the roll servo wasn’t and I could roll the aircraft freely. I disconnected the autopilot fully and continued the flight manually. Diagnosis and rectification of the issue took about 5 seconds and required only the barest minimum of situational awareness. I’m continually amazed how a small number of pilots will watch the autopilot try and kill them without intervening. I once had an FO sit back and watch the speed trundle back below Vapp, then Vref, with the trend well into Vmin. I had to gently remind him the autothrottles were only armed and not active (he had no idea) before he realized that he, the pilot flying, was actually going to have to fly the aeroplane.