Flight Name:JAL 123

Model:BOEING 747SR-46

1 ) Summary


Boeing 747SR-46 which was operated by JAL, is an aircraft specifically configured for domestic flights with a high denseness siting agreements. The Boeing governments set safety as highest precedence on this big rider aeroplane, by planing it, utilizing methodological analysis called mistake tree analysis. To turn to the safety and flyability demands 747 was designed by incorporating the maps like structural redundancy, quadruplicate chief landing cogwheel, redundant hydraulic system and divide control surfaces. The below figure shows the graphical design of Boeing 747 theoretical account


With respects to JAL 123 clang, description of working system comes in two parts.

2.1 ) Care

The review and care of aircraft in JAL fleet is done in line with hours flown, flight frequence and age of aircraft. JAL is organizing periodical care plans to keep aircraft constituent in good on the job status. The company carries out necessary fix or serving operation in the event of malfunction or breakage.

JAL care process is divided into two parts

  1. Pre-flight care:It is conducted between set downing and takeoff and implies having study of jobs, from the crew cabin of an arriving aircraft and so treating those studies suitably. In add-on, it besides involves running predetermined cheque operation to do certain that there are no amendss like abrasions, escape of hydraulic oil or aircraft fuel.
  2. Regular care:It differs from aircraft to aircraft and is by and large carried out following the predefined flying hours of an aircraft. It is conducted under a ordinance which closely governs which portion is to be maintained and protocol used for needed undertaking.

Harmonizing to the protocol set by Boeing, an air trade when damaged demand to travel through following phases before acquiring ready for flights. They are as follows

Repairing:It ‘s a phase where skilled technicians are working to mend the harm parts every bit good as parts that are dependent on the damaged parts in order to do it work expeditiously.

Inspection:It ‘s an official scrutiny that is conducted in order to look into whether fixs made to an aircraft is done right or non.

Periodic Inspection:It ‘s a revenant phase through which an aircraft had to travel throughout its life rhythm.

2.2 ) Technical

The system description of JAL 123 and its working environment can be determined by analyzing the figure as shown below

Beginning:KOBAYASHI, HIDEO ( Yokohama National University ) , TERADA, HIROYUKI ( Japan Aerospace Technology )

The above figure describes the construction near the Tail. It ‘s a rear portion of the plane which provides stableness to an aircraft in a flight. All the parts that comprise the Empennage play an of import function in maintaining the flight in control. Their importance is described below

Central hydraulic unit: It maintains the flow of hydraulic fluid in hydraulic pipe. The chief intent of hydraulic fluid is to supply power to aircraft control. It ‘s like an lift that helps the plane to travel up and down.

Vertical five: They are use to cut down the aerodynamic side faux pas

Rudder: It helps the aircraft to take bend in any way

Aft Pressure Bulkhead: It is a critical portion of the plane whose intent is to seal the rear portion of the plane in order to keep the cabin force per unit area

Auxiliary power unit: These power units provide electrical power in the operational absence of engine-driven generators or inaccessibility of external power

Hydraulic pipe: It ‘s a medium, which allows the hydraulic fluid to flux around the aircraft.


The direct cause of air clang of JAL 123 was the loss of cardinal hydraulic commanding system, APU ( Auxiliary Power Unit ) , and box beam construction of perpendicular five as they were blown off by the immense mass of air traveling a hypersonic speed that was induced by the breakage of Aft Pressure Bulkhead.

In the yesteryear, aircraft had gone through big scale fix in June 1978, after it experienced tail work stoppage set downing at Osaka International Airport. Fatigue failure of Aft Pressure of bulkhead was due to an mistake made during the fixs at that clip. During that mending phase, Riveted articulations were falsely repaired by Engineering Staff from Boeing as it was non conducted harmonizing to the protocol of Boeing Procedure. Figure of difference between directed fix that was done and the existent fix that needed to be done is as follows:

Beginning:KOBAYASHI, HIDEO ( Yokohama National University ) , TERADA, HIROYUKI ( Japan Aerospace Technology )

As shown in the figure, the fix was made utilizing two separate splicings plate alternatively of individual home base. As a consequence, the full load was carried through the Centre stud row merely, and multiple weariness clefts propagated by cyclic pressurization of the aircraft and eventually caused the unstable break of the full construction after a sum of 12, 319 rhythms. The error made during the fix was extended across 2 bays, which is about 1 metre length and as this was longer than the critical size indispensable for the unstable failure of the construction to last, the cleft propagated by the interlinking of next little clefts without being arrested.

Beginning:KOBAYASHI, HIDEO ( Yokohama National University ) , TERADA, HIROYUKI ( Japan Aerospace Technology )

Some of the most of import points that were noticed are as follows:

Due to misidentify in fix the full membrane emphasis caused by internal force per unit area was carried through the Centre row in a fast gait. By this it can be judged that Maintenance Engineer did n’t understood the cardinal mechanism of burden transmittal

The review of fix made by the air hose representative and air transit governments was in insufficient. That is even though there was improper fix conducted ; the procedure of review should hold been able to place the job

The issue of periodical care and review conducted throughout the class of 12,319 flights was debatable, since the review was non conducted before accident


Table 1: Failures and their causes

Number Failure Causes 1 Mistake in Repair Unstable break of aft force per unit area bulkhead 2 Inspection non done decently MajorA job in the system was non identified 3 Periodic Maintenance and review of system was non conducted Expiry day of the month of the fix made in yesteryear was non known 4 Fatigue failure of aft force per unit area bulkhead Burst in Aft force per unit area bulkhead due to which cardinal hydraulic system and APU ( Auxiliary Power Unit ) which are located at the dorsum of bulkhead and box watercourse construction of the Vertical five were blown off by immense mass of air. 5 Loss of Hydraulic force per unit area and Vertical five Aircraft went out of control and eventually crashed near the ridge of Mt Osutaka.


In 1989 a similar type of accident occurred in USA. A DC 10 theoretical account with Flight figure 232 operated by United Airlines lost the hydraulic force per unit area due to failure of engine ‘s fan disc. However, in contrast to JAL 123 instance where the cockpit crew did n’t recognize the badness of state of affairs and insisted on returning to original airdrome, the cockpit crew of DC 10 recognised that hydraulic unit was damaged. Therefore they decided to set down to the nearest airdrome every bit shortly as possible and eventually stop up with clang landing. Because of this 60 % of people on board survived. If the cockpit crew of JAL 123 would hold assessed the state of affairs similar to what cockpit crew in DC10 did, so it would hold been a different narrative overall.

In 2002, another similar bad luck happened with air Flight CI611 due to chase work stoppage and miss fix. In instance of JAL 123, it had severely repaired aft force per unit area bulkhead which explosion and resulted in blowing off the perpendicular five. While CI611 had fuselage harm due to chase work stoppage and was repaired with a faulty process which resulted in failure of lower rear side of the fuselage, and later separated the whole tail of the plane.

It is besides analysed that multiple site clefts were responsible for JAL clang due to the usage of old stud holes at the fix without sing resizing the holes. So it showed the possible danger of multiple site clefts. Three old ages subsequently an accident caused by multiple site harm happened on 4th April 1988 in Hawaii, This clip, major portion of fuselage construction of B-737 operated by Aloha Airlines was blown off while cruising. These two accident caused by MSD ( Multiple site harm ) and MED ( Multiple element harm ) showed that harm tolerant design construct based on behavior of individual cleft is lacking for such instances.

6 ) Recommendation

Some of the activities that need to be followed to avoid the accident are as follows

Periodic Inspection must be done, particularly after a large-scale fix is conducted or design alteration has been carried out within the system.

Engineers working at fix site must be provided with cardinal preparation and instruction in countries like mechanics of stuffs.

The people responsible for blessing of fix should look into the site carefully to guarantee that those fixs were conducted as desired.

The stairss taken in order to avoid future accidents are as follows

The Aircraft accident probe commissioner advised the maker and operator to further beef up the construction of tortuosity box by put ining a home base to halt the high velocity air flow from come ining the box beam in the effect of bursting of aft force per unit area bulkhead. The advice was put into pattern

7 ) Mention

KOBAYASHI, HIDEO ( Yokohama National University ) , TERADA, HIROYUKI ( Japan Aerospace Technology ) , Crash of Japan Airlines B-747 at Mt Osutaka [ Online ] Available hypertext transfer protocol: //shippai.jst.go.jp/en/Detail? fn=2 & A ; id=CB1071008 ( 22/03/10, 18:44 )

8 ) Bibliography

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