Word: pylons
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...Their findings last week were enough to chill the most seasoned air traveler: the key elements that destroyed American Airlines Flight 191 and killed 274 people appeared to be a bolt 3 in. long and ⅜ in. in diameter, and a cracked metal plate. Both were parts of the pylon assembly under the left wing that held one of the plane's three engines...
...flight, quickly ordered inspections of all 138 DC-10s still flying for U.S. airlines. Ernest Gigliotti, 31, and Lorin Schluter, 39, two conscientious United Airlines mechanics, found metal filings as fine as dust on one DC-10 in Chicago. Suspicious, they did the natural thing: they shook the pylon. It was loose. The two men discovered 27 fasteners that held together part of the pylon were missing or sheared. They also found that the spar web, a key pylon support, was cracked. Gigliotti told the press, "Eventually, that pylon would have separated from the plane...
...days, the NTSB put all of the blame on a broken bolt that searchers found beside the runway. It was one of five that held the pylon to the wing, and officials thought it had snapped because of "metal fatigue"-the progressive weakening that results from repeated stress. One investigator even christened it "the murdering bolt." But electron microscope studies showed the bolt had been broken by a sudden, violent strain. Meanwhile, a crack had been found in the plate that formed the aft bulkhead...
Investigators theorize that as the plane rolled down the runway, the pylon wiggled and vibrated far more than normal. Why is not yet known; the cracks in the plate may have caused-or been caused by-the vibration. In any case, the stress snapped the rear "attach" bolt and it fell out. The remaining bolts could not hold the 20 tons of thrust being generated by the General Electric CF6 engine. It yanked itself and the pylon loose from the wing and took...
...rising engine and pylon, possibly trailing yards of metal "spaghetti," apparently tore through the skin of the whig. When the engine flew off, it carried away the pumps for one of the plane's three hydraulic systems. The engine may also have cut through hydraulic lines in the front of the wing. In either case, fluid necessary to maintain pressure on controls spilled out. The leading-edge flaps that were extended from the front of the whig to supply extra lift on takeoff may have been struck and damaged by the engine. Or the lack of hydraulic pressure...