BOAC Flight 911 Totally Explained

Everything about Boac Flight 911 totally explained

BOAC Flight 911 (Speedbird 911) was a round-the-world flight operated by British Overseas Airways Corporation. The Boeing 707 operating as flight 911 on March 5, 1966, was commanded by Captain Bernard Dobson, 45, from Dorset, an experienced 707 pilot who had been flying these aircraft since November 1960.
The aircraft disintegrated and crashed near Mount Fuji, Japan shortly after departure from Tokyo International Airport, at the start of the Tokyo-Hong Kong segment. All 113 passengers and 11 crew members were killed in the disaster, including a group of 75 Americans associated with Thermo King Corporation of Minneapolis, Minnesota, on a 14-day company sponsored tour of Japan and Southeast Asia. There were 26 couples traveling together in the group, leaving a total of 63 children orphaned.

Accident investigation results

The accident aircraft arrived in Tokyo at 12:40 hours on the day of the accident from Fukuoka Airport where it had diverted the previous day due to conditions on the ground in Tokyo. The weather there had since improved behind a cold front with a steep pressure gradient bringing cool dry air from the Asian mainland on a strong west-northwest flow, with crystal clear sky conditions. During their time on the ground, the crew received a weather briefing from a company representative, and filed an instrument flight rules (IFR) flight plan calling for a southbound departure via the island of Izu Ōshima, then on airway JG6 to Hong Kong at flight level 310 (31,000 feet).
   At 13:42 hours the crew contacted air traffic control requesting permission to start engines, and amending their clearance request for a visual meteorological conditions (VMC) climb westbound via the Fuji-Rebel-Kushimoto waypoints, which would take them nearer to Mount Fuji, possibly to give the passengers a better view of the landmark. The aircraft began taxiing at 13:50 and took-off into the northwest wind at 13:58. After takeoff, the aircraft made a continuous climbing right turn over Tokyo Bay, and rolled out on a southwest heading, passing north of Odawara. It then turned right again toward the mountain, flying over Gotenba on a heading of approximately 298°, at an indicated airspeed of 320 to 370 knots, and an altitude of approximately 4,900 m (16,000 ft), well above the 3,776 m (12,388 ft) mountain peak.
   While flying into the wind, approaching Mount Fuji from the downwind side, the aircraft encountered severe clear-air turbulence associated with lee waves, causing a sudden structural failure that initiated the in-flight breakup sequence. At the time of the accident, winds at the summit of Mount Fuji were measured at 60 to 70 knots from the northwest. Lenticular clouds associated with lee waves were observed on weather satellite photos taken 30 minutes before the accident some 240 km (150 mi) to the south, but were not visible in the vicinity of the accident where the skies were clear.
   A U.S. Navy A-4 Skyhawk that was sent up shortly after the accident to search for the wreckage encountered extreme turbulence in the accident area. The cockpit accelerometer display registered peak acceleration values of +9 and -4 g-units, causing temporary loss of control, and leading the Navy pilot to believe his aircraft would also break-up in the turbulence. The pilot regained control and landed safely, but the aircraft was grounded for post-flight inspection by maintenance personnel. Many other aircraft that passed near Mount Fuji that day also reported moderate to severe turbulence.
   The accident was photographed by Japan Self-Defense Forces personnel at the nearby Fuji Training Base, and 8 mm film shot by one of the passengers during the flight also survived the crash. Witnesses on the ground reported seeing the aircraft in a flat spin trailing white "smoke" prior to breaking up in flight. The white cloud was later determined to be atomized jet fuel escaping from the fuel tanks due to the breakup. The film shot on board was developed by investigators, and showed evidence that the aircraft experienced severe turbulence just prior to the accident. No evidence was recovered from the flight data recorder, which was destroyed by fire with the rest of the nose section which fell separately. The aircraft didn't have a cockpit voice recorder, and no distress call was received from the flight.
   The aircraft left a debris field 16 km (10 mi) long. Analysis of the location of wreckage allowed the accident investigators to determine that the vertical stabilizer attachment to the fuselage failed first. It left paint marks indicating that it broke off the port side horizontal stabilizer as it departed to the left and down. A short time later, the ventral fin and all four engine pylons failed due to a leftward over-stress, shortly followed by the remainder of the empennage. The aircraft then entered a flat spin, with the forward fuselage section and the outer starboard wing breaking off shortly before impact with the ground.
   Although some stress cracking was found in the vertical stabilizer bolt holes, it was determined by subsequent testing that it didn't contribute to this accident. Still, it was potentially a significant safety-of-flight issue. Subsequent inspections on Boeing 707 and similar Boeing 720 aircraft as a result of this discovery did reveal this was a common problem, and corrective maintenance actions on the fleet eventually followed.
   The probable cause determination was: "The aircraft suddenly encountered abnormally severe turbulence over Gotemba City which imposed a gust load considerably in excess of the design limit."

Related info

This accident was one of five fatal aircraft disasters -- four commercial and one military -- in Japan in 1966, occurring less than 24 hours after Canadian Pacific Airlines Flight 402 crashed and burned upon landing at Tokyo International Airport. Flight 911 had taxied past the still smouldering wreckage of that Douglas DC-8 a short time before this accident.
Several booked passengers decided to cancel their tickets at the last moment in order to see a ninja demonstration. These passengers, Cubby Broccoli, Harry Saltzman, Ken Adam, Lewis Gilbert and Freddie Young, were in Japan scouting locations for the fifth James Bond film, You Only Live Twice.

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