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The Fluid Hammer 
and the 
China Airlines 747 Breakup

 

Posted on: 04/01/2001

Read the theory below - then reflect upon CI-611
(the China Airlines 747-200's high altitude breakup)

Engineer has alternate theory on plane disaster

By Gary Stoller, USA Today
Airplane graphic

 
Boiler expert links jet's age, design to why roof ripped off

The Aloha Airlines jet descended for landing on Maui, Hawaii, and passenger Matt Austin had noticed the luggage racks rattling and swaying when the thrust reversers came on.

It didn't startle him. He had seen that happen before on other older Aloha jets. But Austin remembered the name painted across the plane's exterior: Queen Lili'uokalani. It was a 19-year-old Boeing 737.

A week later--on April 28, 1988--the same jet's roof ripped open 24,000 feet over the Pacific Ocean, killing one flight attendant and seriously injuring seven passengers and a crew member. Austin counted himself lucky. Aloha Flight 243's last flight didn't really begin to grip him until the next year, when the National Transportation Safety Board issued its accident report.

This is a detective story. It's about a mystery that aviation professionals say was solved 12 years ago and the persistence of Austin, a former Hawaii boiler inspector, who has spent all those years and $45,000 of his money trying to prove that the experts got it wrong.

It's also about an accident that forever changed maintenance practices for old planes and about an alternative theory that could have far-reaching consequences. Finally, it's about the intriguing possible parallels between boiler safety and airplane safety.

But first it helps to know something about Austin. A mechanical engineer, Austin has no professional expertise in airplane accidents. He is an expert on boilers; the NTSB consulted him about a train boiler explosion in Gettysburg, Pa. Austin, 43, runs a consulting business,

Hawaiian Steam Engineering, which designs, inspects and restores boilers and locomotives. He also consults for the U.S. Navy on servicing nuclear submarine power plant components.

Since 1989, Austin has researched the Aloha accident independently, always maintaining that his only motivation is "engineering truth" and a conviction that sharing his insights can prevent similar accidents. He has a Web site, www.disastercity.com, where he details his theories on the Aloha accident and other disasters.

If Austin's theories are correct, a design that is intended to prevent catastrophic failures on nearly all Boeing jets could be flawed. It may even pose a danger to passengers,

Austin says. Boeing says the design meets FAA requirements and works as intended.

Austin also says his study has convinced him that:

  • Old jets are not safe to fly, even if all required maintenance has been done.

  • The FAA's aging aircraft program, which requires airlines to repair and inspect old jets, should be scrapped. The program allows planes to fly beyond their design life and relies on airline inspectors who may not detect all structural problems, he says.

To reach those conclusions, Austin purchased and pored over more than 4,000 pages of NTSB accident findings. He attended a course for airline maintenance managers on aging aircraft and studied books for aeronautical engineers. He bought special computers to study the NTSB's photos of the accident and related forensic evidence.

Austin also corresponded with NTSB investigators, FAA officials and a Boeing engineer. The investigators stand by the NTSB's conclusions but say they respect Austin's engineering knowledge.

"In every accident I ever worked, all kinds of crazies came out of the woodwork with theories about what happened,'' says former NTSB investigator Brian Richardson, who led the NTSB group that studied why the Aloha jet broke apart. ''Matt Austin is not one of those people. He has good, solid credentials, and he's not going off the deep end.''

The NTSB says it will not reopen the accident investigation, but Richardson says the FAA should study Austin's theory. Then goes a major step further.

''Matt may well have nailed the cause of the accident,'' he says. ''I don't really know.''

An important accident
Aloha Flight 243 was bound from Hilo to Honolulu when its roof tore off. An emergency landing was made in Maui.

Many aviation experts consider the flight the most significant accident in commercial aviation. It showed how inadequate airline maintenance procedures and poor FAA oversight can result in tragedy, and it prompted an FAA program to more vigilantly inspect aging airplanes.

The NTSB, which investigated the Aloha accident, concluded the jet's roof and walls tore off in flight because multiple fatigue cracks existed in the jet's skin.

Those cracks developed, the NTSB said, because lap joints that were supposed to hold the fuselage together became corroded and failed. A lap joint connects two overlapping metal sheets of the fuselage.

The role of lap joints on the Aloha plane is what first captured Austin's attention. He read a story about lap-joint failure in the accident and realized the same words had been written about a boiler explosion in Brockton, Mass., in 1905.

The boiler connection
The danger of failed lap joints is well known in the boiler industry, which stopped using them on large boilers in the 1920s. In Brockton, a shoe factory boiler explosion collapsed a building, killing 58 people and injuring 117 others.

When a boiler's lap joint fails, a hole opens in the boiler's shell. The water inside instantly turns to steam, and increased pressure causes an explosion. Such a phenomenon is known as a fluid hammer, which Austin says caused the Aloha accident.

If Austin's theory is correct, it solves a question that the accident's investigators asked: Why didn't Boeing's ''fail-safe'' design, which is supposed to prevent a massive breakup, work?

Boeing says the 737 was designed to decompress safely with as much as a 40-inch crack in the plane's skin, the 0.036-inch thick, aluminum outer layer of the fuselage. Instead of an explosive decompression, the hole in the skin is supposed to release internal pressure in a controlled way. In the Aloha accident, investigators concluded that more damage occurred--about 18 feet of the fuselage tore away--because many fatigue-caused cracks had gone undetected.

Austin says that a weakened fuselage was not the main reason for the extensive damage.

A 10-inch-by-10-inch hole opened, he says, in the roof of the front cabin at a location known as body station 500. (Body stations are identifying points on the fuselage that are measured in inches from near the nose of the jet to the rear.) A powerful stream of air swept an Aloha flight attendant off her feet and toward the hole, Austin says. Her head and right arm went through the hole, he says, but her body momentarily plugged it, creating a jolt of pressure that ripped the jet apart. The flight attendant was swept out and her body was not recovered.

''Slamming the door on a 700-mile-per-hour jet stream creates a localized, short-duration high-pressure spike, up to several orders of magnitude (greater than) the allowable design pressure,'' Austin says. ''This is a fluid hammer.''

Forensic evidence, Austin says, shows where the flight attendant's skull struck the exterior of the plane. The location of the skull print is consistent with the location of a plugged hole at body station 500, he says.

The NTSB's official accident report says, however, that the breakup of the jet began about 5 feet farther forward, at about body station 440.

But Richardson, the former NTSB investigator, says Austin pinpointed a mistake in the NTSB's report. He says he always assumed the breakup began close to the point that Austin says.

The wreckage that could reveal where the breakup occurred is at the bottom of the Pacific Ocean.

NTSB not persuaded
USA TODAY brought Austin's analysis to NTSB Chairman James Hall, who joined the board 5 years after the Aloha accident and recently announced his resignation. He said Austin's theory makes sense, but the NTSB doesn't believe it happened that way.

''We don't disagree with Mr. Austin's explanation about how an airplane can decompress at 24,000 feet after a 10-inch-by-10-inch hole is blown open in the skin and about how devastating the 'fluid hammer' effect can be at this altitude,'' Hall said in a letter. ''We disagree, however, with his conjecture involving the role the flight attendant's body played.

''The roof of the Aloha airplane came off as a result of multiple site damage --mainly, small fatigue cracks that emanated from many chamfered rivet holes. These cracks joined together, resulting in the catastrophic separation of the skin.''

Austin agrees that the many fatigue cracks weakened the structure, but he says the plane wouldn't have ripped apart if the hole hadn't been plugged. And, Austin adds, ''The NTSB validated my fluid-hammer theory. They couldn't say anything more without reconvening a pool of experts and reopening the investigation.''

Richardson says he never heard of the fluid-hammer theory until Austin explained it. No one on his structural team, he says, ever mentioned it during the course of the investigation.

He says, though, he'll stand behind his and the NTSB's conclusions. ''We never thought that the hole in the fuselage remained small enough long enough for anything to plug it and produce the kind of pressure spike that is common to the pressure vessels that you are familiar with,'' Richardson wrote Austin.

Austin says, however, that the difference between the NTSB's findings and his analysis is, ''We're 60 inches and probably 20 thousandths of a second apart.''

He says he enlarged NTSB photos of the skull print, used a computer to view them from a different angle and pinpointed the skull print's exact location. ''The skull print is the key,'' Austin says. ''It wouldn't be there so graphically if the flight attendant didn't plug the hole. If there would have been an out-rush of air without a hole being plugged, her whole body would have been sucked out at once away from the aircraft.''

Austin also corresponded with FAA officials in 1998. He was told that the FAA intended to do studies on his theory, but the agency later said it couldn't do the work because Congress had cut the FAA's research budget. King Frey, a retired aeronautical engineer who worked for two aircraft manufacturers, Hughes and Douglas, and for Northrop Grumman, which makes fuselages for 747s, buys the fluid-hammer theory.

''Matt's reasoning and logic are right on target, and he has an excellent probable theory that should be researched,'' Frey says. The odds are very small that such a phenomenon will occur, Frey says, ''but rare things do happen.''

As 737s get older, however, it raises the possibility from an astronomically small number to a number that should be taken seriously, Frey says. The increased possibility of a fluid-hammer effect, he says, needs to be heeded by Boeing and airline mechanics.

Regardless of whether he's right about the Aloha accident, he questions whether a plane can be designed for a safe decompression when a fuselage tears open. That would cause a powerful stream of air to escape from the cabin, he says, which could sweep up persons or objects not belted down, shatter eardrums and cause more serious injuries.

''Safe decompression is a fly-it-'til-it-breaks philosophy,'' he says. ''It's stupid to have a design concept that says a plane is OK until it blows a hole at 24,000 feet.''

Boeing defends design against theory
Boeing officials say their design is sound and meets FAA regulations. Further, the company says, it tested the plane for the theory that Austin has. Boeing's Jack McGuire says computer simulations were done in 1965 to test what would happen if a 40-inch hole--one much larger than the hole that Austin believes popped open on the Aloha plane--was plugged. The tests showed that cabin pressure is maintained longer, increasing passengers' chances of survival, he says. Richardson says research is needed to study Boeing's safe-decompression design.

''I think it's worth determining if this type of scenario should be a design consideration in the future,'' says Richardson, who is now an airline pilot. ''Testing by the FAA/manufacturer is the only way to determine if it can happen in an aircraft, absent funding by some private source. The FAA should spearhead the effort to see if Boeing's fail-safe design is viable.''

FAA officials in Washington did not respond to written questions about safe-decompression design and aging aircraft.

Richardson and some other aviation experts believe the FAA should study the fluid-hammer phenomenon.

''Matt's efforts and goals are commendable,'' he says. ''The industry needs to be constantly reminded of the past so it can be ever vigilant in the future.''

That's Austin's credo. ''Disasters keep recurring because we don't learn from those that have struck in the past,'' he says. ''History is repeating itself before our eyes.''

Copyright 2001, USA TODAY. Reprinted with Permission.

from this link

and for the whole 9 yards:

http://www.disastercity.com/



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