Possibly a automation modes issue? On the aircraft I instruct on, there's a trap we've known about since we started. If you are on autopilot and autothrottle, descending in FLCH (Flight Level Change) mode, the speed is controlled by pitch, and the autothrottles go to a passive mode, called "speed on elevator". If you change autopilot modes to a different pitch mode (VS, Alt Hold, etc, or if the autopilot captures another mode, like ALT CAPTURE, GS, etc), the autothrottles revert to controlling the speed ("speed on thrust" mode). HOWEVER, (this is the trap) as I said, if you are descending on autopilot and autothrottle in FLCH, AND DISCONNECT THE AUTOPILOT, the autothrottle does NOT revert to "speed on thrust". but stays in "speed on elevator". The pilot must SELECT another pitch mode, to get the autothrottles to control speed again...if not, the autothrottles stay at idle when the pilot, say, levels off and, he expects the autothrottles to advance the throttles to maintain speed. He must either control the throttles manually, or choose another pitch mode. This sounds like the classic autothrotlle TRAP we teach about on day one of FPT, and day one of simulator. It seems he was unstable on approach; if he were in FLCH, and decided to level off, he disconnects the autopilot, levels off; he expects the throttles to maintain speed with authrottle, but they stay at idle. It seems he leveled off pretty late, and may not have had time to realize his danger, concentrating on the runway, PAPI, etc, whilst the speed bled off. Purely Speculation. Does the 777 behave this way?