The Free Fiber Problem

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The Free Fiber Problem

Post by RTH » Fri Mar 03, 2017 12:56 am


The Free Fiber Problem-

During the early 1970s days of composite applications on commercial jets, we would put test parts on military fighters for evaluation. The thinking was that should a part fail, the pilot could eject and that was much better than having 200 passengers in jeopardy on a transport jet. At a military base one day, a mechanic was testing an F-4 engine on a plane with a composite rudder and forgot to set the brake. The plane taxied away and crashed into a wall and burst into flames. During the subsequent investigation, a colonel kicked the remains of the burned rudder and sent fibers into the air. He contacted the officials at the Air Force Lab at Wright-Patterson about the fiber liberation.

NASA and Air Force researchers hypothesized that should a large, composite plane crash and burn, carbon fibers could be liberated and float free around the country. Being conductive, they could short circuit electrical systems from computers to telephones to power stations and shutdown the whole country. All NASA composite programs around 1977 were put on hold while the research mounted to resolve whether this was actually an issue.

Government Ph’Ds debated for months, some claiming this was a genuine problem and others dismissing it, with no conclusive results forthcoming. Meanwhile, at Douglas Aircraft, we had paid staff on 6 months hold doing nothing and threatened with layoffs.

Finally, it was decided that a test would be run to once and for all determine the answer. Scrap composite panels and pieces were solicited by NASA from airframers like Douglas, Lockheed and Boeing to be taken to the atomic bomb testing area in Nevada. Facilities there had 750’ tall towers used to monitor radioactive releases from bomb tests that could be fitted with sensors to measure fiber concentrations from a bond-fire of the scrap materials. Helicopters were fitted with more sensors to fly special patterns and altitudes to check for wind-blown fibers. The whole scheme was serious business for both sides of the research community.

On the day of the test, the tower sensors were turned on, the helicopters flew, and a pile of 2500 lbs. of composite scrap was remotely ignited. The fire burned, the sensors sensed and tons of data was recorded and analyzed. Eventually, the researchers concluded that there was no problem from free fibers ruining the country. Programs resumed immediately and we built and flew more composite parts. But to this day, there are a few scientists around who are skeptical about composite planes flying over the country and still worry about the free-fiber problem.
Bob H

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