Status: | Accident investigation report completed and information captured |
Date: | Monday 20 August 2007 |
Time: | 10:33 |
Type: | Boeing 737-809 |
Operator: | China Airlines |
Registration: | B-18616 |
MSN: | 30175/1182 |
First flight: | 2002 |
Total airframe hrs: | 13664 |
Engines: | 2 CFMI CFM56-7B26 |
Crew: | Fatalities: 0 / Occupants: 8 |
Passengers: | Fatalities: 0 / Occupants: 157 |
Total: | Fatalities: 0 / Occupants: 165 |
Aircraft damage: | Destroyed |
Aircraft fate: | Written off (damaged beyond repair) |
Location: | Okinawa-Naha Airport (OKA) ( Japan)
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Crash site elevation: | 4 m (13 feet) amsl |
Phase: | Landing (LDG) |
Nature: | International Scheduled Passenger |
Departure airport: | Taipei-Taiwan Taoyuan International Airport (TPE/RCTP), Taiwan |
Destination airport: | Okinawa-Naha Airport (OKA/ROAH), Japan |
Flightnumber: | 120 |
Narrative:China Airlines flight 120 departed Taipei at 08:14. It landed at Naha Airport (OKA) at 10:27 and taxied to the apron. Reaching the stand, ground engineers saw fuel gushing from an area near the no. 2 engine pylon. The pilot shut off the fuel supply to the engines after he was alerted by the ground engineer about the leak. Fuel from the leak flowed beneath the aircraft towards the no. 1 engine. The fuel ignited and the fire engulfed the airplane.
When all occupants had evacuated, a large explosion occurred in the centre of the airplane. The airplane burned out completely.
Probable Cause:
PROBABLE CAUSE: "It is considered highly probable that this accident occurred through the following causal chain: When the Aircraft retracted the slats after landing at Naha Airport, the track can that housed the inboard main track of the No. 5 slat on the right wing was punctured, creating a hole. Fuel leaked out through the hole, reaching the outside of the wing. A fire started when the leaked fuel came into contact with high-temperature areas on the right engine after the Aircraft stopped in its assigned spot, and the Aircraft burned out after several explosions.
With regard to the cause of the puncture in the track can, it is certain that the downstop assembly having detached from the aft end of the above-mentioned inboard main track fell off into the track can, and when the slat was retracted, the assembly was pressed by the track against the track can and punctured it.
With regard to the cause of the detachment of the downstop assembly, it is considered highly probable that during the maintenance works for preventing the nut from loosening, which the Company carried out on the downstop assembly about one and a half months prior to the accident based on the Service Letter from the manufacturer of the Aircraft, the washer on the nut side of the assembly fell off, following which the downstop on the nut side of the assembly fell off and then the downstop assembly eventually fell off the track. It is considered highly probable that a factor contributing to the detachment of the downstop assembly was the design of the downstop assembly, which was unable to prevent the assembly from falling off if the washer is not installed.
With regard to the detachment of the washer, it is considered probable that the following factors contributed to this: Despite the fact that the nut was in a location difficult to access during the maintenance works, neither the manufacturer of the Aircraft nor the Company had paid sufficient attention to this when preparing the Service Letter and Engineering Order job card, respectively. Also, neither the maintenance operator nor the job supervisor reported the difficulty of the job to the one who had ordered the job."
Accident investigation:
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Investigating agency: | JTSB Japant |
Status: | Investigation completed |
Duration: | 2 years | Accident number: | AA2009-7 | Download report: | Final report
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Classification:
Wrong installation of parts
Damaged on the ground
Sources:
»
SKYbrary » China Airlines plane goes up in flames at Naha airport; nobody hurt (Japan Today, 20-8-2007)
» Jet fuel gushed from plane on landing (Asahi Shimbun, 22-8-2007)
» Investigators find hole in fuel tank of plane that exploded in Japan airport (AP, 23-8-2007)
Follow-up / safety actions
FAA issued 1 Airworthiness Directive
FAA issued 2 Emergency Airworthiness Directives
JTSB issued 2 Safety Recommendations
Issued: 25-MAY-2007 | To: Boeing 737-600, -700, -700C, -800, -900, and -900ER | AD 2007-18-51 |
Required repetitive detailed inspections of the main slat track downstop assemblies to verify that proper hardware is installed, one-time torquing of the nut and bolt, and corrective actions if necessary. (Superseded by AD 2007-18-52) |
Issued: 28-MAY-2007 | To: Boeing 737-600, -700, -700C, -800, -900, and -900ER | AD 2007-18-52 |
Detailed inspections as instructed in AD 2007-18-51 have to be performed within 10 days instead of 24 days. The compliance time was shortened because the FAA had received additional reports of parts coming off the main slat track downstop assemblies. (Superseded by AD 2011-06-05) |
Issued: 21-AUG-2009 | To: CAA Taiwan | Planning and Implementation of Maintenance Jobs |
When planning and implementing maintenance jobs, the scopes of jobs should be fully ascertained and the working conditions and environments should be appropriately evaluated, and the countermeasures to prevent maintenance errors including the actions taken in 2009 against the recurrence of this accident should be steadfastly implemented and enhanced. |
Issued: 21-AUG-2009 | To: FAA | Preparation of Maintenance Job Instructions |
The Japan Transport Safety Board recommends the Federal Aviation Administration of the United States of America to supervise the Boeing Company, the manufacturer of the Aircraft, to take the following actions: When preparing maintenance job instructions for airlines such as Service Letters/Bulletins, the scopes of jobs should be clearly defined and the working conditions and environments including accessibilities to job areas should be appropriately evaluated in order to prevent maintenance errors. |
Issued: 26-APR-2011 | To: Boeing 737-600, -700, -700C, -800, -900, and -900ER | AD 2011-06-05 |
A new requirement was added to AD-2007-18-52: Within 36 months after the effective date of this AD: Replace the hardware of the down stop assembly with new hardware, do a detailed inspection or a borescope inspection of the slat cans on each wing and the lower rail of the slat main tracks for debris, and replace the bolts of the aft side guide with new bolts. |
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Photos
accident date:
20-08-2007type: Boeing 737-809
registration: B-18616
accident date:
20-08-2007type: Boeing 737-809
registration: B-18616
accident date:
20-08-2007type: Boeing 737-809
registration: B-18616
accident date:
20-08-2007type: Boeing 737-809
registration: B-18616
accident date:
20-08-2007type: Boeing 737-809
registration: B-18616
accident date:
20-08-2007type: Boeing 737-809
registration: B-18616
accident date:
20-08-2007type: Boeing 737-809
registration: B-18616
accident date:
20-08-2007type: Boeing 737-809
registration: B-18616
Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does
not display the exact flight path.
Distance from Taipei-Taiwan Taoyuan International Airport to Okinawa-Naha Airport as the crow flies is 651 km (407 miles).
Accident location: Approximate; accuracy within a few kilometers.
This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.