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Between 2004 and 2007, NASA sent four safety alerts to the FAA and the NTSB regarding cockpit fires, smoke or arcing in the 757. It sent a similar safety alert about the 737 in July 2003. For their part, major carriers American Airlines, Delta Air Lines, United Airlines and US Airways are either replacing the old windows or stepping up inspections. Boeing spokesman Peter Conte acknowledged electrical arcing in cockpit window heaters has led to cracked windows in the 737. He said the problem was not considered dangerous because the arcing happens between window layers, unlike the incidents in other Boeing models, and doesn't cause smoke or flames. The 737's heaters require less power to warm the plane's smaller windows, he noted. However, a May 2003 report filed with NASA describes a window fire in a 737 with "blowtorch" flames, smoke and sparking. The plane, which was on a test flight, made an emergency landing. Two other reports mention smoke as well as arcing and window cracking. Two years ago, the FAA said its proposed remedy would affect 1,212 planes. That order does not include 737s. The NTSB said it learned of the window heater problems after two 757 cockpit fires in January 2004. Safety investigators traced the fires to arcing caused by a loose screw that chafed power wires connected to heating wires in the windows, which were manufactured by PPG Aerospace. But the source of the problem may have been known even earlier. A March 2002 report in the NASA database describes a 757 cockpit fire that was traced to a loose screw in the window heater terminal. The problem was uncovered by the airline involved, which was not named in the NASA report. The FAA's 2008 proposal would require airlines to check for the loose screw and replace damaged windows
-- a task that some airlines say would require extensive window disassembly because the screws are difficult for mechanics to reach. "Even with small hands it cannot be held," a Continental Airlines safety official wrote the FAA in 2008. "This, coupled with poor view ability, turns a very simple installation into a very complex installation." ___ Online:
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