The transport helicopter that crashed into the North Sea this month suffered a "catastrophic failure" of its main rotor gearbox that caused the blades to separate from the aircraft and slice off the tail, accident investigators said. The rotor blades detached from the helicopter and then struck the tail, causing the tail boom and pylon — which holds the tail rotor — to become severed from the fuselage, the Air Accidents Investigations Branch (AAIB) said
