Originally Posted by chornedsnorkack
While flying with transponder left turned off is illegal, it is probably not that big deal, compared to the safety of airframe in respect to things like overspeeding, upsets and structural integrity of the plane. "Aviate, navigate, communicate"... one guesses that a pilot regaining control of cockpit would not think of switching on the transponder until after dealing with a lot of other urgent business!
What if you had two guys, a traffic controler and a commercial pilot? Was it more plausible for the traffic controler to switch on the tranponder while the pilot handling the other urgent business than the tranponder turned on by itself?
On reverse thinking, what did possiblly turn on the tranponder if it was not a human being? Any possible reason which had happened before or possiblly could happen.
If the tranponder gave the correct reading and id, could the switch mulfunction due to the violent movement of the plane? Or some kind of fight, someone or something fall on the control panel. As an accident investigation, one can not ignore such details. Every solid evidence has to be explained with plausible reason (even remotely plausible).