New Delhi, July 13 -- Scattered across a 1,000-foot debris field in Ahmedabad, the remnants of Air India Flight 171 provided investigators with a puzzle of twisted metal and damaged components that would prove crucial to understanding what caused the Boeing 787's catastrophic engine failure.

The Aircraft Accident Investigation Bureau's preliminary report reveals how each recovered piece-from heavily damaged flight recorders to precisely positioned cockpit controls-contributed to reconstructing the final 32 seconds of a flight that claimed 260 lives.

The investigation's breakthrough came from one of the aircraft's two Enhanced Airborne Flight Recorders (EAFR), integrated black boxes that combine traditional flight data recording with coc...