Japan Airlines Flight 123

..the plane fluttered towards the ground like an autumn leaf for 30 minutes before crashing into Mount Osutaka. Amazingly, there were four survivors.

August 12, 1985: Japan Airlines Flight 123. Boeing 747-SR46, registration JA8119. One of Japan Air's specially modified 747s, with 509 passengers, 12 flight attendents, and 3 crew members aboard, suffered an aft pressure bulkhead failure at 24,000 feet. Kyu Sakamoto, best known for his song "Sukiyaki," was killed in the accident. In command of this flight was Captain Masami Takahama, 49, who had been with the company for nineteen years, and had 12,500 hours of flight time.

At 520 fatalities, it was the worst single-aircraft air disaster in history. The Boeing engineer who had approved an improper repair of the bulkhead in 1978 committed suicide after the accident.

Tragically, and somewhat ironically, the flight came on the eve of Obon, the period when Japanese traditionally return to their place of birth and visit the graves of their ancestors. The flight was filled nearly to capacity. It took off from Tokyo's Haneda airport at 6:04 p.m. bound for Osaka, roughly 215 miles away. Thirteen minutes after takeoff the aircraft reached its cruising altitude.

As the Tokyo ATC was tracking the flight, the emergency transponder code 7700 appeared on their screens. This is the emergency squawk for aircraft in distress. Suddenly the crew of 123 came on the radio, saying "Tokyo...JL123. Request immediate...ah...trouble. Request return back to Haneda...descend and maintain FL220." The air traffic controller approved, and gave heading back to Haneda. The aircraft, however, seemed to be wandering and the controller again called 123 and gave it further heading instructions. News reached JAL's corporate offices in Tokyo and the company called 123 on the company frequency. 123 told them "Ah...the R5 (cabin) door is broken. Ah...we are descending now." As this gave no indication of the problems 123 was having, the company officials gave no advice.

JAL 123 had dropped in altitude to 13,500 feet. The crew called Tokyo control again at this point, saying "JL123, JL123 uncontrollable!" Crossing the Izu Peninsula and leaving it astern, it then headed out over Suruga Bay in a north-westerly direction. The aircraft began to turn left, heading down to 6800 feet, which was lower than many of the mountains in the area, then recovered to 13,000 feet. The plane veered again, this time to the right, and began a rapid descent down to 8,400 feet, and disappeared from radar. JAL 123 glanced off a ridge and impacted near the summit of Mt. Osutaka. Rescue crews could not reach the site until the next morning due to rain and darkness.

In the wreckage, searchers found letters to families, last wills, and poetry, composed by passengers contemplating their ultimate fate while floating around in the sky for those eternal minutes.

Transcripts from the flight recorders were no help in determining the cause of the accident, and terrorism was quickly ruled out when two groups tried to claim responsibility. JA8119 was an older plane, but had only half as many hours logged as the oldest 747, and regardless, there had never been a fatigue-induced structural failure in the history of the 747. A photo taken from a mountain village showed that the aircraft was missing a large portion of its vertical fin and tailcone, and a ship came across a section of the vertical fin floating in Sagami Bay. Further searches of the bay turned up several other pieces of the aircraft's tail.

Investigators came up with the idea that the rear pressure bulkhead may have ruptured, blowing off the tail assembly. No history of incidents of this type had been recorded and in fact, the pressure bulkhead had been factory tested a simulated service life of 20 years, far more than any 747 had flown. But in looking at the maintenance records of the aircraft, it was found that it had suffered tail damage on takeoff seven years prior, cracking the rear bulkhead. Boeing's protocol for such damage calls for a doubler plate to be placed over the area to be spliced and a double row of rivets put in to hold it. The wreckage showed that two doubler plates had been used, the gap between resulting in only a single row of rivets holding the splice.

Sources:
http://www.planesafe.org
http://aviation-safety.net
http://www.aviationcrashes.com
http://www.airsafetyonline.com
http://www.jal.co.jp

Japan Airlines Flight 123 (JAL123) took off from Haneda-Tokyo Airport, bound for Osaka at 6:12 p.m. on August 12, 1985. A little less than an hour ago (5:17 p.m.), the same plane, JL8119, had returned from a flight to Kyushu with no problems. The plane was refuelled, and a new flight crew came aboard. The only noticable thing being that the first officer was being promoted by a Check Captain to Captain himself.

Commanding the flight was 49 year-old, Masami Takahama, a training captain, and 19 year veteran of the company with 12,500 hours of flight time. Five minutes after take-off JAL123 requested permission for a more direct route to Osaka from Tokyo Air Traffic Control (ATC), which was granted. Six minutes after, the emergency distress transponder code 7700 appeared on the screen of the Tokyo ATC, the sign of a plane in distress.

Following this, JAL123 requested a return to Haneda, which was granted. However the controller noted that instead of making the 117° turn back to Haneda, it was only making a 50° turn. JAL123 had suffered an explosive decompression of the rear vertical tailplane above Sagami Bay and lost a 15 foot section of its leading vertical edge (which was picked up by a ship). This disabled all its hydraulics, and rendered the plane's flying controls useless and essentially uncontrollable except by use of engine thrusts.

One of the survivors, Yumi Ochiai, reported the incident as such:

There was a sudden loud noise. It was somewhere to the rear and overhead. It hurt my ears and immediately the cabin filled with white mist. The vent hole at the cabin crew seat also opened... There was no actual sound of any explosion but the ceiling panels above the rear toilets fell off. Then the passengers' oxygen masks dropped down...

For a little more than 30 minutes, the crew of JAL123 managed to keep the wounded plane aloft. As it slowly lost altitude, the plane swung around the Izu Peninsula and then headed out over Suruga Bay in a north-westerly direction before glancing off a ridge and crashing into the lower slopes of Mount Osutaka. Keiko Kawakami (12), Yumi Ochiai (28), Hiroko Yoshizaki (12), and Mikiko Yoshizaki (8) were the only survivors of 524 on board, making it the worst disaster involving a single plane.

Investigators discovered that a improperly repared rear pressure bulkhead by Boeing was the culprit after the plane had a tail scrape on landing in 1978. Another piece of evidence is the grainy photo of JAL123, taken from a mountain village, one can clearly see that the tail assembly has been completely blown off.

It should be noted that Japan Airlines agreed to take 20% responsibilty for the disaster. This is because previous pilots of JA8119 had noted that there were whistling noises from the back of the plane, but no one bothered to take any note of it. Boeing also cautioned the engineers who repaired JA8119 to be particularly careful on international flights following the disaster, as they could be taken into Japanese custody and prosecuted. However, the United States refused extradition, a practice done to allow more open and honest reports while making a investigation (Why the NTSB was doing an investigation was because of a "similar" incident on a Air India flight not too long prior... later that was found to be a bomb).

Today, a memorial stands at Uenomura Village shrine with the ashes of all the unidentified victims. On August 12, 1999, the belongings recovered from 21 victims were placed in a stainless steel container, and buried at the crash site of JAL123.

Excerpt of the Cockpit Voice Recorder (Final Moments)

Time: 18:56

"Sink rate! Pull up! Pull up! Pull up!" (Ground Proximity Warning System)
"Dame da ne!" (Roughly, "We're screwed now!" or "It's no use!")
"Pull up! Pull up! Pull up!" (GPWS)
First Impact
"Pull up! Pull up! Pull up!" (GPWS)
Second Impact, and sound of metal grinding

* This is a bit redundant, and take it as a supplement to the above writeup.