Word: bolt
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...Maybe they don't need all the training a doctor gets, but if you make one mistake, you might kill 273 people, not one." Says E-RAU Dean Chuck Williams: "It's a little different from working on an automobile or a truck. Students sense that the bolt they tighten down is going to be flying 400 miles per hour...
...near Chicago's O'Hare Airport, collecting pieces of metal that colleagues later examined under electron microscopes. 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...
...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...
Also being critically examined last week were the procedures of the FAA, which writes the rules for inspecting jetliners and then supervises the work. There was a growing suspicion that the FAA may have relaxed too much, lulled by the fine safety record of jetliners. Shortly after the broken bolt was discovered, the FAA stipulated that pylon inspections had to be repeated every ten days or 100 flying hours, whichever came first. Formerly, it had been done only once a month or every 400 hours...