This report aims to investigate the crash of Japan Airline's JA8119. It hopes to find the main cause and find ways to prevent such a disaster from happening again. It is also to re-assure passengers who frequent Boeing 747s that there is nothing wrong with the aircraft.
Boeing 747 (how many aircraft in service, how much impact it would have if there was a problem with the aircraft)
The information in this report was obtained via the internet, reference books and aviation publications.
The report investigates the problems encountered during the tragedy and looks at preventive measures put in place to prevent such a tragedy.
Japan Airline JA8119 experienced two accidents in its history of which included a tail-strike on June 2, 1978 and the ultimate demise of Japan Airline's JA8119 when it struck the Osutaka Ridge on August 12, 1985. Japan Airline's JA8119 tail-strike on June 2, 1978 was believed to have been the cause for the second crash. (Magnuson, 2005)
2.1 June 2, 1978
The first accident happened on a trip towards Osaka on June 2, 1978. On JA8119's approach to land, it bounced on the runway, on the second attempt to land, its nose-high attitude caused the tail to strike the runway. The aircraft suffered damage to its rear underside as a result. The rear pressure bulkhead which cracked was one of the parts that sustained damage. (Magnuson, 2005)
2.2 August 12, 1985
The second and last accident happened en route to Osaka. After achieving cruising altitude over Sagami bay, the rear bulkhead failed due and thus caused an explosive decompression. This explosive decompression ripped out the vertical tail fin which caused the leakage of hydraulic fluid. With the loss of hydraulic fluid, the pilots were unable to control the plane which later clipped a ridge before crashing into Osutaka Ridge. (Magnuson, 2005)
The tail-strike that occurred on June 2, 1978, damaged the back part of the plane. One of the parts affected was the aft pressure bulkhead (refer to figure below). The pressure bulkhead is dome-shaped; it keeps cabin pressure constant by preventing the air from the pressurized cabin from escaping into the tail assembly. It serves as the only barrier that prevents the pressurized air from ripping the tail assembly of the plane as it escapes into the atmosphere. It is placed under heavy stresses during the pressurization and de-pressurization of the plane as it takes-off or lands.
3.2 Repair done
The aircraft was then repaired by Boeing's aircraft engineers. What happened during the servicing proved to be fatal for the 502 lives on JA8119.
3.3 Pilot Error
The repair of the bulkhead was not done in accordance with Boeing's approved repair methods. Instead of using a continuous doubler plate with three rows of rivets to reinforce the damaged bulkhead, Boeing technicians used two doubler plates, one with two rows of rivets and the other with one.
Therefore, the root cause was the neglect of the Boeing technicians that worked on JA8119. Should they have done the repair according to the manual, the pressure bulkhead would have been able to sustain the stress. However, not all the blame can be put on Boeing as it was Japan Airline's responsibility to delegate their own technicians to double check the repairs done by Boeing and ensure that the plane is fully serviceable. Thus, the blame should be put on both parties.
After such a devastating event that questioned the integrity of the Boeing 747s, the Federal Aviation Administration issued a few airworthiness directives to prevent such explosive decompression from ever happening again.
5.1 Measures put in place
Many airworthiness directives (AD) were issued regarding Boeing 747s and this report will go through each of them and explain the use of such directives.
5.1.1 AD 85-22-12
All Boeing 747s were required to undergo a one-time inspection of the aft pressure bulkhead to ensure that there was no discrepancies, irregular repair or any damage due stress. Owners were required to submit a descriptive report of their inspections with the necessary diagrams. Any discrepancies found were to be repaired according to the Structural Repair Manual. (FAA, 1985)
5.1.2 AD 86-08-02
A vertical fin access cover was to be installed with Boeing Service Bulletin 747-53A2264. This AD aims to prevent failure due to stress of the vertical fin in the event that the bulkhead was unable to accomplish what it was made out to do. (FAA, 1986)
5.1.3 AD 87-12-04
To prevent the loss of control of the crucial hydraulics in the plane when the vertical stabilizer sustains large amount of damage or total loss, an addition of a hydraulic fuse to number four hydraulic system was to be accomplished. (FAA, 1987)
5.1.4 AD 2000-15-08
This AD aims to prevent the repeat of the incident on August 12, 1985 by repeat inspections.
The ADs put in place would most definitely prevent the structure from failing. However, humans make errors; errors made during a repair would render such ADs useless. Such ADs are therefore not sufficient to prevent another disaster from happening again.
This report suggests that Japan Airline's technicians are to conduct a thorough check on their aircraft which had been serviced by Boeing. This is to ensure that repairs were done in accordance with the Structural Repair Manual. This thus prevents the improper repairs to go unnoticed such as JA8119's rear pressure bulkhead repair.
5.2.2 Grounding of aircrafts
Aircrafts which are required to go for scheduled maintenance should be grounded and not allowed to fly.
Macarthur, J and Swift, 2005, JAL 123: 520 Lost - It's 20 years since the world's worst single aircraft airliner accident. In: Flight Safety Australia. - Vol. 9, no. 4 page 28-33 extracted from [http://www.casa.gov.au/fsa/2005/aug/28-33.pdf] on 20/10/2009
Magnuson E. Jun. 21, 2005, Disasters: Last Minutes of JAL 123. Times. Tuesday, extracted from http://www.time.com/time/magazine/article/0,9171,1074738-6,00.html on 20/10/2009
1996-2010, Accident Description: Aviation Safety Network extracted from http://aviation-safety.net/database/record.php?id=19850812-1 on 20/10/2009
July 13, 1987, Airworthiness Directive 87-12-04, Federal Aviation Administration extracted from http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/list/87-12-04?OpenDocument on 20/10/2009
May 19, 1986, Airworthiness Directive 86-08-02, Federal Aviation Administration extracted from http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/list/86-08-02?OpenDocument on 20/10/2009
Nov 19, 1985, Airworthiness Directive 85-22-12, Federal Aviation Administration extracted from http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/list/85-22-12?OpenDocument on 20/10/2009
July 26, 2000, Airworthiness Directive 2000-15-08, Federal Aviation Administration extracted from http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/list/2000-15-08!OpenDocument&ExpandSection=1#_Section1 on 20/10/2009
October 7, 1998, Airworthiness Directive 98-20-20, Federal Aviation Administration extracted from http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/list/98-20-20?OpenDocument on 20/10/2009