Japan Airlines Flight 123

Japan Airlines Flight 123 was a scheduled domestic flight from Tokyo's Haneda Airport (also known as Tokyo International Airport) to Osaka International Airport (Also known as Osaka Itami Airport). On August 12, 1985, the Boeing 747-146SR developed mechanical problems 12 minutes after taking off. The plane then crashed into Mount Takamagahara in Gunma Prefecture 32 minutes later, after the pilots tried to control the plane, but failed. 520 people died, and only 4 survived. The crash was caused by incorrect repair after a tailstrike incident, which caused metal fatigue and eventually an in-flight structural failure, in which the whole tail of the plane separated from the plane.

Japan Airlines Flight 123

JA8119, the aircraft involved in the accident at Tokyo International Airport in 1984
Accident
Date	August 12, 1985
Summary	In-flight structural failure due to improper repair, leading to rapid decompression and loss of control
Site	Mount Takamagahara, Japan
Aircraft
Aircraft type	Boeing 747-146SR
Operator	Japan Airlines
IATA flight No.	JL123
ICAO flight No.	JAL123
Call sign	JAPAN AIR 123
Registration	JA8119
Flight origin	Tokyo International Airport
Destination	Osaka International Airport
Occupants	524
Passengers	509
Crew	15
Fatalities	520 (including all crew members)
Injuries	4
Survivors	4

The crash was the deadliest aviation accident involving single airplane within more than 500 fatalities. Tenerife airport disaster remains as the deadliest aviation accident with nearly 600 deaths in history.

What happened

Route of Japan Airlines Flight 123

The plane that crashed was a Boeing 747-146SR (SR stands for short range), with tail number JA8119. The plane was used to fly short, domestic routes within Japan. The plane first flew on January 28, 1974. It had 4 Pratt & Whitney JT9D-7A engines. Before it crashed, it had flown for 25030 hours, and took off and landed 18835 times.

On June 2, 1978, JA8119 was involved in a tailstrike accident at Osaka International Airport. When landing, the plane's tail struck the runway. The aft pressure bulkhead was damaged in the accident, as well as the rear of the plane. Later, during June 17 and July 11, repairman from Boeing repaired the plane, by replacing the lower part of the rear and a part of the bulkhead. The plane later returned to service.

While investigating the accident, the investigators realised that the repair done by Boeing 7 years before the accident was incorrect. While two rows of rivets were required for a splice plate in the bulkhead to be installed, the repairman only used one row. This increased the chance of metal fatigue by 70% and also caused the subsequent accident.

Passengers and crew

On that day, the plane was flown by three crew. The 49-year-old captain, Masami Takahama, was a very experienced pilot. He has flown for 12423 hours, with 4842 hours on 747s. The 39-year-old co-pilot, Yutaka Sasaki, was training to be a captain. On that flight, he was seated on the left-seat (which is usually for captains). He has flown 3963 hours, with 2665 hours on 747s. The last crew, 46-years-old flight engineer, Hiroshi Fukuda, has flown 9831 hours, with 3846 hours on 747s. There were also 12 cabin crew. There were 509 passengers, including the singer and actor Kyu Sakamoto, who died in the plane crash. The countries which the passengers and crew came from are listed below.

Final tally of passenger nationalities
Nationality	Passengers	Crew	Total
Japan	483	15	498
China	1	0	1
West Germany	2	0	2
Hong Kong	4	0	4
India	3	0	3
Italy	2	0	2
South Korea	3	0	3
United Kingdom	1	0	1
France	1	0	1
Canada	1	0	1
Spain	1	0	1
Peru	1	0	1
United States	6	0	6
Total	509	15	524

Accident

On the afternoon of the accident day, JA8119 has already completed two round trip flights, JL503/504 to and from Sapporo, and JL363/366 to and from Fukuoka. At 5.17pm, the plane has just completed flight JL366, and was parked at Spot 18 at Tokyo International Airport, getting ready for its flight to Osaka, JL123.

At 6.04pm, the plane started taxiing towards the runway. Takeoff was at 6.12pm, and it climbed to its cruising height of 24000ft (about 7300 metres). The flight was going smoothly up to this point.

At 6.24pm, a sudden, loud noise rocked the cabin after the failure of the pressure bulkhead resulted in explosive decompression. As air rushed out of the plane, its tail also broke completely off, which is where all four hydraulic lines are located; as a result, this meant the pilots no longer had any ability to control the aircraft.

46 seconds later, the pilots squawked 7700 (meaning that they are in an emergency) and requested to return to Tokyo International Airport. However, although the air traffic controller approved the plane to turn towards Tokyo, the plane strangely started heading towards the north-west direction. At 6.28pm, the Tokyo Air Traffic Controller asked the pilots to turn left, but received the message from the pilots, "now uncontrollable." By then, the plane was moving in a way called the phugoid motion, climbing until losing speed and stalling, then the nose goes down and gaining speed until the plane is able to climb again. The phugoid motion repeated itself until the end of the flight.

At 6.31pm, the air traffic controller asked the crew to land at Nagoya Airport, which was 72 miles (about 133 km) from their location. However, the pilots wanted to return to Tokyo. Between 6.35pm and 6.56pm, the pilots struggled to control the plane without the tail. This failed, as the plane flew uncontrollably towards the mountains.

At 6.56pm, the plane's right wing hit a ridge. The aircraft then flew on, crashed into a second ridge, and exploded. 520 people aboard died, including all 15 crew members. 4 people survived and all were females.

The time taken for the plane to crash after the bulkhead failure is 32 minutes. The accident was the worst in aviation history involving explosive decompression.