Japan Air Lines 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 (including all 15 crew members), 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.

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 more than 500 deaths in history.

## Background 
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. 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.

## 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. 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. Four people survived, all of whom 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.

## References