Time Running Out 
for Taiwan to Find 
Crash Black Boxes

Time Running Out for Taiwan to Find Crash Black Boxes
TAIPEI (Reuters) - Nearly three weeks after a China Airlines jet crashed mysteriously killing 225 people, Taiwan is running out of time to retrieve the "black boxes" from the ocean floor with signals from them weakening and possibly stopping in days.

Though the location of the cockpit voice and flight data recorders have been known for more than two weeks, officials said on Tuesday choppy seas and strong underwater currents have made it difficult for divers to retrieve them from waters nearly 70 meters (230 feet) deep.

A 23-year-old Hong Kong-bound Boeing 747-200, belonging to Taiwan's largest carrier, broke into four pieces at a height of 30,000 feet (9,000 meters) and fell into the Taiwan Strait near Penghu island some 20 minutes after takeoff on May 25.

The cause of the crash remains a mystery and investigators are hoping the black boxes will help explain what caused it.

Officials said signals from one of the black boxes, which normally last for up to 30 days, had begun to weaken.

Navy divers went underwater again on Tuesday, but strong undercurrents prevented efforts to recover the cockpit voice and flight data recorders.

"Undercurrent is delaying recovery," said Kay Yong, managing director of the Taiwan cabinet's Aviation Safety Council.

"Sometimes, the wind is pretty bad. Wave height is around two to four meters (6.5 to 13 feet)," Yong told Reuters.

"The weather will get worse in the next couple of days."

The Accident aircraft - 747-200 series

Salvage teams have instead focused on the retrieval of bodies and wreckage in the choppy seas, but only a fraction of the aircraft has been recovered.

Search teams recovered five more bodies on Monday, bringing to 110 the total number found so far, a spokesman for the government's disaster response center said.

The ill-fated jet's cabin chief was still strapped to his seat when his body was found, puzzling investigators.

Normally, food is served to passengers on Taipei-Hong Kong flights at around 12,000 feet (2,700 meters) because such flights are short and take only 90 minutes, but the cabin chief was still buckled to his seat when the plane broke apart at 30,000 feet, the spokesman said.

Grieving relatives have vented their anger at the government and the airline not only for the carrier's poor safety record and delays in retrieving bodies but also for giving no explanation for what caused the crash.

U.S. crash experts who investigated the mid-air explosion of a Trans World Airlines 747-100 in 1996 are in Taiwan to help determine the cause of China Airlines' fourth fatal accident since 1994 which in total have claimed more than 650 lives.

Aviation experts have floated several theories for the crash, including metal fatigue, an internal explosion, sudden loss of cabin pressure, a mid-air collision or a military accident.

June 11, 2002 - New Interest in Taiwan Crash, May be similar to Flight 800

NEW YORK (USA) - It happened half a world away. A Boeing 747 exploded in midair 20 minutes after taking off in Taipei, Taiwan, killing all 225 aboard. In the United States, there was the usual flurry of news stories but little sustained interest in a crash that did not involve U.S. passengers.

But the aviation industry and federal safety officials are paying close attention to the May 25 crash of China Airlines Flight 611. It's too early to tell why the 23-year-old plane broke apart with no warning. The circumstances have raised the possibility that the culprit could have been the same design flaw that brought down TWA Flight 800 six years ago.

"Everybody's watching this one," said Robert Clodfelter, an explosions expert and consultant in Dayton, Ohio.

The recovered cockpit

It will be weeks or months before investigators will be able to tell if the center fuel tank exploded on the China Airlines plane as it did on the TWA plane, also a Boeing 747. All that is known of the China Airlines flight is that the plane took off at 3:08 p.m., climbed to more than 30,000 feet and disappeared from radar at 3:28. There were no distress calls. Military radar recorded the aircraft breaking into four distinct pieces.

The two black boxes that record flight data and cockpit conversations have not yet been recovered. And most of the wreckage still lies beneath more than

130 feet of water in the Taiwan Strait between Taiwan and mainland China. Investigators won't know more until the boxes and the wreckage are retrieved.

In addition to the fuel tank scenario, investigators will be looking into several possibilities: a catastrophic structural failure, the failure of a door locking mechanism, or a bomb.

Authorities with the Taiwan government, which is leading the crash inves- tigation, earlier made statements that atmospheric conditions at 30,000 feet would make a fuel tank explosion impossible. But experts say that's not correct.

"I'm sitting here looking at the data," said Joe Shepherd, professor of aeronautics at the California Institute of Technology, noting that the federal government and the industry have known for more than 30 years that an explosion could take place at high altitudes. Shepherd studied fuel-air explosions for the National Transportation Safety Board after the Flight 800 crash.

On the ground, air conditioning packs beneath the fuel tanks of the 747 and other Boeing jets can heat up the fuel vapors in a nearly empty center tank to the flammable state. When the plane takes off and climbs, the pressure decreases and with that the temperature range at which the vapors are flammable decreases as well. At the same time, the tank is cooling as the aircraft climbs into the colder air of the upper atmosphere. As the temperature decreases, along with the pressure, the vapors can remain flammable until sometime during the cruise portion of the flight when the tank becomes too cold.

Once the vapors ignite, an explosion of the tank is inevitable. And the tank, located between the wings, is a major structural part of the aircraft.

The Federal Aviation Administration has issued dozens of orders to airlines to make fixes to prevent the ignition of the vapors. But the NTSB believes that it's impossible to identify all the ignition sources and that the only real fix will come with preventing the buildup of flammable vapors.

The FAA and the aviation industry have predicted between two and three fuel tank explosions in a 10-year period. Last year, the center fuel tank of a Thai Airways Boeing 737 - which has a similar tank design to the 747 - exploded while the plane was on the tarmac in Bangkok.

The safety board sent a five-person team to aid the investigation. Boeing sent three investigators to the scene and will send more when the wreckage is retrieved.

"We're holding back the main team until we know what we're looking at," said Boeing spokeswoman Liz Verdier. "We need to find out the answer and see if it's something that needs to be changed."

In March, an industry group that advises the FAA told the agency that methods to prevent flammable vapors in fuel tanks are effective but too expensive to justify. The FAA is continuing to study ways to put nitrogen in fuel tanks to keep the vapors from igniting.

"With all the work the industry did ... we still don't know that anything they've done will prevent another fuel tank explosion," said Kevin Darcy, a former accident investigator for Boeing who worked on the Flight 800 probe. "I'd be a little bit anxious if I were Boeing or the FAA."

 

A CI-611 Opinion

The odds are tipping equally in favour of a section 41 failure and a cargo door event (at this point). Very much doubt that it will prove to be a terrorist event but could still conceivably be a TWA800 repeat (however, read on for my clue interpretation). The bit below about the cabin service chief being found still strapped into his seat is interesting and would indicate that the CVR might hold clues to the captain having stipulated that everyone should remain seated - as a result of some unexpected vibration, noise or weird flight characteristics (such as the fuselage beginning to crack up around section 41 - or possibly a cargo door losing seal). So at this point, if it were a quiz show, I'd be going for that as my answer (but favouring the S41 theory). If it was a section 41 event then the evidence should be clear (on the physical debris plus fairly clear accelerometer and control inputs on the DFDR, as well as cabin press loss). It may prove to be another accident where an external view on CCTV might have helped out the flight-crew (inspired them to stop climbing, slow down and even perhaps to have depressurised or reduce the differential).

I am unsurprised that the section 41 Service Bulletins seem to give an option for repair by reinforcement (aka cure) or regular inspection ("inspect and repair"). As the reinforcement repair is likely to be expensive, I am willing to bet that at least 75% of operators of the Classic would have gone for the inspection option. Once a progressive fatigue-cracking flaw gets underway, it can spider-web in different directions as it progresses undetected behind linings and lavatory cubicles etc. At certain points in this process it can become accelerated by stress concentration points seeking out the paths of least resistance and coming together in a joint venture (so to speak). Once those cracks start to "work", you are then the High Plains Drifter in "Marlboro Country". (i.e.  riding high with an undetected cancer that will and must eventually bring you down).

So much for the hubris of those who insist that fatigue cracking can be NDI detected, mapped and predicted via a fatigue index. That process is fine for locating, controlling and doing battle damage repair early on (with stop-drilling and Boron fibre patches), but once it advances to a certain progressive point (the spider web weave) it is most certainly a time-fuse for loss of structural integrity. Each pressurisation and flight cycle would be another nail in the coffin - as the Marlboro Man might well have drily observed at the end. Specifying "regular" inspection for these types of cracks (below)? If you were my Principal Maintenance Inspector and gave me that as your recommendation, I'd tell you that it was you that was cracking up. Boeing might just take a bath on this one. For them, I suspect it's their turn on that AA587 vertical fin roller-coaster of discovery and regret.

Section 41 cracks

Section 41 cracks

Section 41 cracks

From a Taipei Times article:

China Airlines flight CI611 took off with its center tank
nearly empty -- a procedure that Boeing recommended be
discontinued after the US Federal Aviation Administration (FAA)
in 1998 said fuel pumps on older model 747 planes were a
possible source of faulty wiring that could have ignited the TWA
blast.

China Airlines vice president of flight safety, Samson Yeh
(SC), confirmed that the airline had received notification from
Boeing not to run the center tank dry, but that they made their
own safety modifications to eliminate any potential point of
ignition.

"At the time ... I remember we changed the procedure. In terms
of empty fuel tanks we were not supposed to use the fuel pumps
[when we flew with dry tanks], otherwise you will overheat it. I
believe [the maintenance department] also put some insulation on
the wiring, to isolate [potential sparks]," Yeh said.


Yeh did concede that while an overheated fuel tank was "one of
the possibilities" behind the sudden mid-air break up, "this case is
different from [TWA 800] because that one was caused by the
center fuel tank overheating, whereas this one was a sudden
explosion -- which means it's totally different."

Aviation experts have floated several theories for the crash, including metal fatigue, an internal explosion, sudden loss of cabin pressure, a mid-air collision or a military accident."................................but still NOT an encounter with severe weather??

Which might help explain why, "The ill-fated jet's cabin chief was still strapped to his seat when his body was found, puzzling investigators".

Excerpted From Aviation Week

NTSB Team Examines the wreckage



Crash Spurs Revamp Of China Airlines

MICHAEL A. DORNHEIM/LOS ANGELES

The search for victims' bodies is occupying the imited recovery resources at the China Airlines Flight 611 crash site, and slowing the retrieval of wreckage and the "black boxes." The flight data
and cockpit voice recorders were located on May 29, but had still not been recovered as of late last week.

Military radar shows debris falling in several different directions, grouped by color, over a 4-min. period (3:27:56 to 3:31:55 p.m.) following loss of the beacon signal (except the dot marked *, which was observed 7 sec. before loss of signal). [Chart omitted]

Investigators are anxious to retrieve them as their beacon batteries may get weak around June 14. Ocean currents and weather also have been hampering recovery from 130-260-ft. depths.

Shortly after the accident, the ASC obtained primary radar data of the falling debris from the military, but it was in a processed form that did not show individual pieces, and it stopped below about 31,000-ft. altitude. The last transponder return indicates the 747 came apart at 33,500 ft. Since then, raw skin returns going down to almost the ocean have been obtained from two civil radars, one
nearby and the other about 150 naut. mi. away.

The new civil data generally confirm the military tracks, which show the debris initially falling in about four different heading groups, including some that are opposite to the airplane's direction, Yong said. But he cautioned that the calculated speed is
questionable because the radar could be hopping between pieces.

China has provided a transponder track to the ASC. It is overall similar to the Taiwanese transponder track with some minor shifts in reported altitude and speed, possibly caused by timing differences. "It shows an altitude dip of 100 meters (330 ft.) 5
sec. before the transponder signal disappears, which we didn't see," Yong said. But neither track shows any rapid maneuvers.

The new skin returns give a more precise location of where pieces hit the ocean. An initial imaging sonar survey shows the major wreckage is in a rectangle about 4 naut. mi. north-south by 5 naut. mi. east-west, surrounding the data recorders, which are at 23 deg. 35 min. N. Lat., 119 deg. 24 min. E. Long. The resolution of the broad search was too low to identify anything, and a higher resolution survey is now being made.

A remote control submersible took pictures of what was suspected to be a large fuselage piece, but it turned out to be a 40 X 10-meter field of smaller debris, including either first- or business-class seats. Most of the recovered wreckage, 454 pieces
as of late last week, has been parts of control surfaces floating on the ocean. These include the vertical stabilizer leading edge and parts of flaps, slats and ailerons.
 

Wreckage Recovery


The year-round ocean current of 2-4 kt. makes underwater operations difficult, and the recovery crew will try to take advantage of roughly half-hour periods when the current stagnates, Yong said. The Taiwan Straits are also windy and choppy.

Maintenance records show that the aircraft, tail No. B18255, had its last full heavy maintenance in December 1993. The D check takes place every 25,000 flight hours and was subsequently split into two staggered "mid-period" half D checks, Yong said. The last mid-period D check took place in January 1999 and included corrosion work, though it is not clear whether that meant prevention or repair. The check was done by CAL during a 40-day period. The 1979-vintage aircraft had about 64,800 hr.

The last C check was done in November 2001. "We can't say yet what was done in the C check, but we're looking at it very carefully," Yong said. The Taiwanese Civil Aeronautics Administration principal maintenance inspector for CAL has been
interviewed, and "we are seeing how they comply with all the airworthiness directives, service bulletins, and so on," he said.

A major maintenance item on 747-200s is ensuring that the "section 41" fuselage nose is not weakened by cracks. This can be accomplished by repetitive inspect-and-repair, or by extensive reinforcement that can cost $5 million. "It seems it was done from a first look at the records," Yong said, but it was not clear yet whether it was by inspection or reinforcement. "We haven't gotten further because we are short on people." The ASC will also look at how CAL's other four 747-200s were maintained.


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