IT IS OBVIOUS that technology has its risks. But determining the hows and whys of a technical failure is often far less clear. When an airplane or a bridge goes down, or when a power plant fails, thousands of potential causes could be the culprit. And the evidence could be snarled in a mass of torn metal and concrete.
But a growing number of engineers are becoming involved in a kind of sleuthing that makes Sherlock Holmes look very primitive indeed. The emphasis on litigation in American society is one reason why such engineers, called failure analysts, are often among the first people on the scene of an accident. One reason for this is that pinpointing fault is a matter of many millions of dollars in damage awards in the aftermath of an accident.
An emphasis on public safety also makes this work--one engineer calls it
''the design process in reverse''--highly valued. Not only can failure analysts do work that can be incorporated into subsequent designs of similar machines or technologies, they can also study the likelihood of a failure so that the owners of power plants, and a variety of other critical technologies, can judge reliability and prevent accidents.
Air crashes are one of the more spectacular types of accident studied by Failure Analysis Associates, a Palo Alto, Calif., company that is known as the oldest and largest firm working in this area. It is a highly technical and interdisciplinary company, but despite the use of computers, electron microscopes and a variety of other sophisticated instruments, their assistance in solving the 1974 crash of a Turkish Airlines DC10 in Paris Orly airport was more a matter of common sense.
Sometime after the crash, in which 345 people were killed, the company was brought in on the case by the Lloyd`s of London insurance syndicate that covered Douglas Aircraft, the maker of the plane that had gone down shortly after takeoff because of an apparent sudden drop in pressure. It was hypothesized shortly after the crash that the reason for the drop in pressure was a cargo door that had blown off. An initial presumption was faulty aircraft design, one that the insurer was naturally anxious to see disproved. Shortly after Alan Tetelman of Failure Analysis arrived in Paris to inspect the wreckage, he noted that the pins on the cargo door had been filed down deliberately. By asking a few questions, he then learned that on a stop in Turkey, the ground crews had trouble closing the door, which then closed effortlessly by taking less than a quarter inch off the pins. By doing so, it was proved through tests, the door yielded to about 15 pounds of pressure, while it had been designed to withstand 300 pounds.
The discovery did not exonerate the aircraft maker entirely, according to Dr. Bernard Ross, who with Tetelman was an original founder of Failure Analysis. It fact, it was also observed that the pin-locking door was not state-of-the-art. A more secure door could have been designed into the airplane, but there had been a race to get the DC10 on the market before the Lockheed L1011. Nevertheless, his discovery enabled Tetelman (who himself later died in an airliner crash) to assist Lloyd`s in sharing the liability with those responsible at the airport in Turkey.
Such an analysis has obvious ramifications in the way airplanes are designed and serviced. But some other crash investigations are more intricate, drawing on engineers` knowledge of metallurgy and a highly computerized field known as ''fracture mechanics.''
In the case of the DC10 that went down in Chicago in 1979, killing 273 people, it was determined that the offending aircraft part was a yoke that held the engine assembly on the wing. Engineers determined that a crack in the steel of this part could not have been caused by normal stress.
They understood the properties of the metal well enough to know that the crack was introduced only as a result of an improper maintenance procedure--in this case by reattaching the engine to the wing by lifting the engine and the pylon together, and not separately. Computers deciphered how much time elapsed between the initiation of the crack and the ''final failure.''
Scientific precision used in assessing failure can serve to predict and ultimately prevent accidents as well. In the case of power plants, this can mean huge savings in an industry that can ill-afford building new plants if that can be avoided. Some engineering companies have made almost a full-time occupation out of testing the critical portions of power plants, determining the range of their remaining useful lives and giving the utilities an opportunity to make planned shutdowns.
Aptech Engineering Services, also in Palo Alto, has a Remaining Useful Life Extension (RULE) program that goes into different types of factories, doing ultrasonic testing and temperature distribution testing on critical parts such as turbines, fans, headers and main steam lines.
Such preventive measures are the growth aspect of the failure analysis business, said Geoffrey Egan, Aptech president. That aspect is a function not only of safety, but also for the changing economics of certain smokestack industries. ''There is a strong reluctance among utilities to build new fossil burning plants,'' said Egan, who does such studies for a variety of types of factories.
How much certainty exists in this high-tech detective work? Dr. Roger McCarthy, the 33-year old president of Failure Analysis, says that it is getting better all the time by virtue of increasingly detailed study of metallurgy and increasingly complex computer codes. Indeed, powerful computers and larger data bases make a clear matter of some problems that before hand were shrouded in mystery.
The automobile accident is one area where society can benefit from knowing with statistical accuracy the dangers involved in certain automotive designs. For example, the company was commissioned recently by General Motors to determine if their X-car braking system caused skids, as had been alleged by the National Highway Traffic Safety Administration. The verdict was no.
By running through a database of more than 11 million police reports (the largest such database in the country) Failure Analysis determined that the X car was no more likely to skid, given the same road conditions, than ''peer vehicles'' that were otherwise similar. The discovery avoided a massive recall that a nonscientific concern or hysteria might otherwise have mandated.
With more powerful computers ''probabilistics and probabilistic distributions is an increasingly powerful concept in the real world,'' said McCarthy, who suggests that learning the probability of certain events affects not just engineering but other aspects of public policy, which seek answers to otherwise imponderable questions.
Why and when things fracture is a real world problem that gets its most rigorous examination in the otherworldly arena of the space shuttle. Even the most careful casting of metal and other parts for the space ship cannot be made with absolute perfection, but the analysis of the materials used and the stresses that they are meant to undergo determines how large a defect (however microscopic) can be tolerated.
A computer model (with three-dimensional computer graphics) comprehends both the properties of the materials and the stresses to which they will be subjected, and can project and pinpoint any likely failures.
No system is foolproof, of course, but it is apparent that technology is ahead of practice in many cases that have resulted in tragic failures. The 1982 collapse of scaffolding at the site of an access ramp in East Chicago, Ind., is one example where more attention to the details of the metal scaffolding could have avoided the accident.
When Failure Analysis engineer Piotr Moncarz arrived at the scene of that accident, he noticed that one of the the vertical legs of a 60-foot tower had a smooth bend (the rest of the metal was mangled and jagged), apparently due to stress.
Assuming that the tower, which held the concrete casting for the ramp, lacked stability, the engineer ran computer models to determine if ''the deformation was consistent with mathematical functions that nature likes to use.'' The conclusion was that the height and weight of the towers caused the support to bow and then break.
The failure was exacerbated by the fact that the scaffolding had no redundancy--as one tower went it cause a chain reaction bringing down the rest of the towers in ''an unfortunate sequence of events that is hard to imagine by even the most imaginative engineer,'' Moncarz said.
As mechanical error is more and more predictable, the element of human error becomes more a concern. Some are rather obvious, as in the case of Ann- Margret falling off a platform onto a stage during a 1972 performance at Lake Tahoe, Calif. The platform, shaped like a hand, was obviously unstable if the actress stepped away from dead center, and that is what happened.
This is the kind of accident that frustrates failure engineers when they are brought in by insurance companies because it was a show routine that
''never should have been done in the first place,'' according to the analayst who was assigned to it.
Other errors of neglect occur when the design of a building is altered while construction is in progress, which was the case with the Hyatt Regency in Kansas City, where a walkway collapsed onto a dance floor in 1981, killing 113 people. In that case, said Moncarz, a hanger--a rod from which the walkway was suspended--was handling twice the load it was designed to after the contractor and designer agreed to alter the original hanger configuration.
''Human factor engineeering'' is another aspect of failure analysis that predicts human error. In some cases this means making sure that safety switches and lights are visible, and that two buttons doing drastically different things are sufficiently apart. In other cases, this means rewriting service manuals, which in one case reduced accidents to truck wheels by 70 to 80 percent.
But so far, there is still a human behavior problem that will not allow engineers and scientists to reduce the accident rate of the high- tech world as low as it could go.
Because of the constraints of litigation, ''the lessons that we are learning are not going back into the design process,'' said Egan of Aptech. Because of court orders, ''everything is under lock and key for 10 years. And sometimes when there is a settlement out of court, it is part of the agreement that (potentially life-saving information) will never come out.''