May 2002 - China Airlines 611
China Airlines Flight 611 (Callsign: Dynasty 611 (CAL611, CI611)) was
a Boeing 747-200, registration B-18255, on a regularly scheduled flight
from Chiang Kai Shek International Airport (now renamed Taiwan Taoyuan
International Airport) in Taoyuan to Hong Kong International Airport
in Hong Kong on 25 May 2002. The aircraft broke into pieces in mid-air
and crashed, killing all aboard.
About 25 minutes after takeoff, the aircraft disappeared from radar
screens, suggesting it had experienced an in-flight breakup at FL350
(approximately 35,000 feet, or 7 miles), near the Penghu Islands in
the Taiwan Strait.
The crash occurred at a time between 15:37 and 15:40; Chang Chia-juch,
the Vice Minister of Transportation and Communications, said that two
Cathay Pacific aircraft in the area received B-18255's emergency location-indicator
signals. All 19 crew members and all 206 passengers died.
At 17:05, a military C-130 aircraft spotted a crashed airliner 20 nautical
miles (37 km) northeast of Makung. Oil slicks were also spotted at 17:05;
the first body was found at 18:10.
Searchers recovered 15% of the wreckage, including part of the cockpit,
and found no signs of burns, explosives or gunshots.
There was no distress signal or communication sent out prior to the
crash. Radar data suggests that the aircraft broke into four pieces
while at FL350. This theory is supported by the fact that articles that
would have been found inside the aircraft were found up to 80 miles
(130 km) from the crash site in villages in central Taiwan. The items
included magazines, documents, luggage, photographs, Taiwan dollars,
and a China Airlines-embossed, blood-stained pillow case.
The flight data recorder from Flight 611 shows that the plane began
gaining altitude at a significantly faster rate in the 27 seconds before
the plane broke apart, although the extra gain in altitude was well
within the plane's design limits. The plane was supposed to be leveling
off as it approached its cruising altitude of 35,000 feet. Shortly before
the breakup, one of the aircraft's four engines began providing slightly
less thrust. Coincidentally, the engine was the only one recovered from
the sea floor. Pieces of the aircraft were found in the ocean and on
Taiwan, including in the city of Changhua.
The final investigation report found that the accident was the result
of metal fatigue caused by inadequate maintenance after a previous incident.
The report finds that on 7 February 1980, the accident aircraft suffered
damage from a tailstrike accident while landing in Hong Kong. The aircraft
was then ferried back to Taiwan on the same day de-pressurized, and
a temporary repair done the day after. A permanent repair was conducted
by a team from China Airlines from 23 May through 26 May 1980. However,
the permanent repair of the tail strike was not carried out in accordance
with the Boeing SRM (Structural Repair Manual). The area of damaged
skin in Section 46 was not removed (trimmed) and the repair doubler
which was supposed to cover in excess of 30% of the damaged area did
not extend beyond the entire damaged area enough to restore the overall
structural strength. Consequently, after repeated cycles of depressurization
and pressurization during flight, the weakened hull gradually started
to crack and finally broke open in mid-flight on 25 May 2002, exactly
22 years to the day after the faulty repair was made upon the damaged
tail. An explosive decompression of the aircraft occurred once the crack
opened up, causing the complete disintegration of the aircraft in mid-air.
This was not the first time, though, that an aircraft had crashed because
of a faulty repair following a tailstrike. On 12 August 1985 (17 years
earlier), Japan Airlines Flight 123 crashed after losing its tail and
hydraulic systems. That crash had been attributed to a faulty repair
to the rear bulkhead, which had been damaged in 1978 in a tailstrike
China Airlines disputed much of the report, stating that investigators
did not find the pieces of the aircraft that would prove the contents
of the investigation report.
One of the features of this metal fatigue was that pictures that were
taken during the inspection of the plane years before the disaster had
visible brown stains of nicotine around the doubler plate. This nicotine
was deposited by smoke from the cigarettes of people who were smoking
about seven years before the disaster (smoking was allowed in a pressurized
plane at that time). This doubler plate had a brown nicotine stain all
the way around it that could have been detected by any of the engineers
when they inspected the plane. The stain could also have suggested that
there could have been a sort of metal fatigue behind the doubler plate,
as this nicotine slowly seeped out due to pressure that built up when
the plane reached its cruising altitude and stained the part around
the doubler plate. However no correction was made to the doubler plate,
causing the plane subsequently to disintegrate in mid air.
Investigators inspect the recovered cockpit
Ballistic Trajectory Analysis for the CI611 Accident Investigation
the Cockpit Voice Recorder transcript