Investigators probing wreckage from China Airlines Flight 611, which
flew apart at 35,000 feet over the Taiwan Strait, have discovered a
series of fatigue cracks in the rear fuselage area
near a 22-year-old repair,
sources close to the investigation said today.
The Boeing 747-200 suddenly broke up May 25 about 20 minutes after
taking off from Taipei for Hong Kong, killing all 225 people aboard.
There was no distress call from the crew, and so far the plane's cockpit
voice recorder and flight data recorder have revealed no definitive
cause for the rare high-altitude disintegration.
The fatigue cracks are the first physical evidence pointing to a
possible cause, and investigative sources said that area of the fuselage
"is getting a lot of attention." But the sources stressed that much work
remains to be done before Taiwan's Aviation Safety Council can determine
whether the fatigue cracks played a role in the crash or some other
initiating event merely caused the fuselage to crack apart at that
The cracks raise two questions for investigative and regulatory
agencies from Taiwan and the United States: First, were they the
initiating event in the crash? And second, are the cracks a one-time
defect caused by a repair, or should all older 747's be inspected for
So far, several sources said, the cracks appear to be a one-time
event, but not enough wreckage has been recovered from the ocean floor
yet to make a final determination.
"We don't see a need to act yet," said one official.
The in-flight breakup does not appear to be the result of an
explosion or fire. Officials have said they do not see any telltale
burns or blast damage. Nor does it appear to be a fuel tank explosion,
like the one that brought down Trans World Airlines Flight 800 in 1996.
A fatigue crack grows over a period of time in metal, sometimes
because of damage or flexing.
The cracks found in the rear fuselage of the China Airlines plane, at
least one of which was 40 inches long, were all in the vicinity of a
two-foot-by-10-foot "doubler," essentially a metal patch used to repair
damage caused in 1980 by a "tail strike." In a tail strike, the fuselage
rubs along the runway, usually when an airplane takes off at too high an
The Taiwanese investigative agency is only now getting maintenance
paperwork that will tell who performed the repairs and exactly what was
So far, salvage operations have located only one side of the fuselage
at the fatigue crack that gave way. Investigators are anxious to locate
the mating piece.
The aircraft has been located on the ocean floor in roughly three
large debris fields. The first debris field consists mostly of the tail
section up to the area of the tail strike repair. The second debris
field, about a mile away along the flight path, appears to contain most
of the rest of the plane.
The third debris field appears to contain two engines. Sources said
it appears that the engines were not the cause of the crash, but cracked
off as the plane broke apart.
Kay Yong, managing director of Taiwan's Aviation Safety Council, said
earlier that the cockpit voice recorder contains a sound at the end of
the recording that technicians have been unable to identify, and that
the flight data recorder shows only small anomalies in the last 20
Among other things, the 747 appears to pitch up somewhat abruptly
five seconds before the end of the recording. The cockpit voice
recorder, which contains the last 30 minutes of cockpit sounds and
conversation, continued to operate for three seconds after the flight
data recorder cut off.
Yong said that in the last second before the voice recorder cut off,
there was "a not very loud 'chahhh' sound" that has not been identified.
There are also a few other unidentified sounds during the last seven
minutes of the recording that specialists find unusual for a 747, but
they have been unable to identify them.
Fatigue cracks in older aircraft are not a new issue. The Federal
Aviation Administration initiated an "aging aircraft" inspection program
after part of the roof tore off an older Aloha Airlines Boeing 737 in
April 1988. The National Transportation Safety Board found that Aloha
had failed to inspect the aircraft adequately for cracks.
The 747 also has experienced trouble with cracks in the area of its
forward door, but not at the rear of the aircraft. The cracking around
the forward door has been handled with regular inspections and repairs
to tiny cracks before they can grow bigger.