Don’t these pilots use shoulder harnesses? If so, he couldn’t simply slump forward. That’s why I’m wondering if the seat or seatback broke loose. Also the pilot called mayday over the radio, which seems to suggest an equipment malfunction instead of a major cardiac event or a stroke.
I thought I had heard he called mayday, but have not read it in any of the account... or I missed it, which is likely. Was any other verbage provided by the Pilot at the mayday call?