Uncommanded Feather
I keep seeing post here about "the crew unlocked the feathers...." I have gone back and watched again the NTSB briefing videos and reviewed the reports. Let's be clear about the facts:
1. "... the copilot, who was in right seat, moved the lock/unlock handle into unlock position."
2. In order for feathering to start, two things have to happen: someone has to unlock the feathering system, and someone has to activate the system with a different handle.
3. “This was what we would call an uncommanded feather, which means the feather occurred without the feather lever being moved into the feather position,” Hart said.
To me, the co-pilot removed the SAFETY LOCK so the feather handle could be moved later when needed. This might be a mechanical blocking handle that prevented the physical movement of the feathering handle. At this point we only know that some unknown failure caused the feathers to move. I see no reference to LOCKS on the feathers being removed, unlocked or actuated by the crew.