Flight Details
BOAC Flight 911 was a scheduled service from San Francisco to Hong Kong, with intermediate stops in Honolulu and Tokyo. The aircraft, a Boeing 707, was expected to arrive at Tokyo Airport at 16:45 on 4 March. However, due to poor meteorological conditions and the precision approach radar (PAR) of the GCA being out of service, the flight diverted to Fukuoka, landing at 18:00. After an overnight stay, Flight 911 departed Fukuoka for Tokyo at 11:25, arriving at 12:43. The aircraft was then prepared for the next leg to Hong Kong. A flight plan was filed for instrument flight rules via Oshima on airway JG6 at flight level 310.
Accident Sequence
At 13:42, the crew contacted air traffic control requesting engine start and clearance for a VMC climb via Fuji-Rebel-Kushimoto. The aircraft left the ramp at 13:50 and was instructed to make a right turn after takeoff. It departed Tokyo Airport at 13:58. After takeoff, the aircraft flew over Gotemba City on a heading of approximately 298 degrees at an altitude of about 4900 meters and an indicated airspeed of 320 to 370 knots. The aircraft was trailing white vapor. It then suddenly lost altitude over the Takigahara area, and parts of the aircraft began to break away over Tsuchiyadai and Ichirimatsu. Over Tarobo at an altitude of approximately 2000 meters, the forward fuselage broke away. The mid-aft fuselage together with the wing entered a slow flat spin to the right and crashed into a forest at the foot of Mount Fuji. The forward fuselage crashed into the forest approximately 300 meters west of the main impact site and caught fire. All 124 occupants were killed.
Probable Cause
The official investigation determined that the aircraft suddenly encountered abnormally severe turbulence over Gotemba City, which imposed a gust load considerably in excess of the design limit.