Mystery noises on doomed China Airlines flight

Rescue teams have so far recovered 160 bodies

TAIPEI, Taiwan -- Taiwan investigators say that cockpit recordings from a China Airlines jet that mysteriously broke up last month, killing 225 people, reveal a series of unusual sounds.

Minutes before the Boeing 747-200 went down, the recorder picked up a noise that sounded like a human heart beat, followed by a series of "ka ta, ka ta, ka ta," wire reports quoted Kay Yong, the chief investigator at Taiwan's Aviation Safety Council, as tellling reporters on Sunday.

The last noise was a sharp "thud" before the power went off, he said.

Several Boeing 747 pilots who listened to the tape said the sounds were not normal in the cockpit, Yong said.

"I do not know what the sound is," Yong said, adding the probe into the jet's crash off Taiwan's western coast is still in the fact-finding stage.

Declining comment on possible causes for the sounds, he repeated on Sunday that the pilots' conversations did not indicate any problems.

Each sound lasts a fraction of a second. Investigators could not say if they were related to the crash, "but at this moment, we'd rather be more suspicious," Yong said.

Two sudden drops

ANALYSIS • China Airlines' troubled history    EXTRA INFORMATION Gallery: Taiwan tragedy  Timeline: Major air disasters in Asia     CNN.com Asia More news from our Asia edition

The mystery sounds follow in the wake of radar data from Chinese authorities showing that the China Airlines CI611 flight bound for Hong Kong from Taipei experienced two sudden and as yet unexplained drops in altitude before it broke into four sections and crashed on May 25.

Several theories have emerged about the crash, but officials have said that evidence so far does not confirm any of them.

The crew reported no problems before the crash, indicating that whatever happened to the aircraft happened quickly and without warning.

One theory is that structural problems or a sudden cabin depressurization caused the break up of jetliner, which the airline planned to retire from its fleet next month.

Another theory is that the plane's cargo or fuel tanks exploded, causing it to break up.

Some aviation experts have also said it could be a mid-air collision or a military accident, a theory that security officials have downplayed, saying there were no signs of terrorism or a missile attack.

Anger

Whatever happened to the aircraft happened quickly and without warning, investigators say

Air traffic control radar showed that one chunk of the jet shot backward at a high speed, as if propelled by a blast. The other three parts kept going forward.

U.S. experts who investigated the mid-air explosion of a Trans World Airlines Boeing 747 in 1996 have joined the probe to help find out why the jet broke up at an altitude of 30,000 feet and plunged into the ocean.

They have listened to the recordings dozens of times, Yong said. The recording was taken from one of two "black boxes" recovered last week.

The second black box, the flight data recorder, was still being analyzed.

The slow pace of the investigation and recovery of bodies had caused anger among families of the victims, many of whom have hit out at the government over China Airlines' poor safety record. (China Airlines' troubled history)

It was China Airlines' fourth fatal accident since 1994. Together, the accidents have claimed more than 650 lives.

Search crews are still trying to recover large parts of the plane. The wreckage might offer the best clues about why the plane crashed.

Rescue teams have so far recovered 160 bodies. Eight corpses -- including that of co-pilot Hsieh Ya-hsiung -- were found Saturday in wreckage about 200 feet under the sea.

The United Daily News quoted prosecutors as saying Hsieh's body was attached to the seat when it was found, indicating there had been no problem requiring him to get up immediately before the crash.