By ANDY PASZTOR Structural cracks discovered recently on at least two American Airlines Boeing 767 jetliners, including one jet that air-safety regulators believe easily could have lost an engine, are prompting concerns that some of the problems may turn out to be more widespread.
Over the past two weeks, American, with oversight from the Federal Aviation Administration, has checked the bulk of its wide-body 767 fleet to look for possible cracks in critical components that attach engines to the wings. On Monday, the FAA said problems were found on three planes.
The agency said it was working with American and manufacturer Boeing Co. to "identify the source of the cracking" and was considering new industry-wide safety mandates. "We are considering additional action, including requiring more frequent inspections" of the suspect parts, called engine pylons, according to an FAA spokesman.
American spokesman Tim Wagner disputed the FAA's tally of affected planes. He said the recent flurry of inspections found two planes with pylon-related cracks and the problems "were caught when they should have been." He also said Monday that with metallurgical tests pending, "any speculation on the cause" of the cracks "isn't based on science or technical findings." Until the laboratory results are available, according to Mr. Wagner, definitive conclusions "would be a guess at best."
Boeing, which has been working closely with the FAA to identify reasons for the cracks and assess their significance, didn't have any immediate comment.
The size and type of some of the cracks discovered in the pylons surprised Boeing, which now is drafting a service bulletin that in the next few days is likely to recommend substantially stepped-up inspections by virtually all 767 operators, according to people familiar with the details. The FAA, which has authority to mandate the changes, is expected to adopt most of Boeing's guidelines.
The issue is attracting high-level attention inside the FAA, Boeing and American partly because for years there have been relatively strict requirements to inspect certain parts of all 767 engine pylons after every 1,500 flights. Despite the frequent inspections, these people say, a routine check of one American jet for a different issue found a combination of cracks that hadn't been seen before and was deemed by FAA officials to pose a significant hazard.
This aircraft, which had the most serious safety issues, had flown only about 500 trips since its last required structural inspection for pylons, according to FAA records.
Depending on the details, the anticipated FAA mandates could disrupt current maintenance timetables while increasing operating costs across the industry. Some safety experts said more-frequent inspections could conceivably result in minor schedule disruptions at some carriers.
Certain parts now under heightened scrutiny can't be easily inspected and may require removing engine pylons from aircraft
Both American and FAA officials agree the safety concerns don't result from missed or botched inspections. Rather, the issues highlight that neither government nor industry experts expected to see the emergence of such structural problems in the wake of earlier risk analyses and ramped-up inspections.
American said it expected by early Tuesday to complete checks of the last two of the 56 Boeing 767s subject to the latest inspections. The twin-engine models are used widely by carriers across the globe, including on many trans-Atlantic flights and routes across the U.S.
Engine pylons, which attach the engines to the wings, are intended to flex as planes maneuver in the air, encounter turbulence and undergo other dynamic forces. Pylons have to withstand strong and sometimes rapidly changing stresses, including sudden changes in engine thrust and aircraft attitude.
In addition to analyzing the impact of structural loads during flight, FAA officials also are examining whether specific maintenance procedures used by American on the ground could have caused or worsened some of the cracking.
The FAA's preliminary conclusion is that some of the cracks came from holes used to install certain bolts, an issue that has been recognized since the FAA issued its repetitive inspection rules five years ago.
On at least one American aircraft, however, FAA experts believe a number of cracks found on a part of the pylon near those bolts rendered certain fail-safe designs ineffective.
The FAA's upcoming safety directive is expected to call for routinely inspecting more portions of the engine pylon than is currently required. The agency and Boeing already have agreed on the broad outlines of such a step, according to people familiar with the details.
The FAA's action would directly affect about 360 Boeing 767s operated by U.S. carriers. Foreign regulators typically order their airlines to adhere to enhanced inspection standards developed by the FAA in conjunction with Boeing.
At this point, the FAA doesn't appear to favor mandating immediate inspections of 767 jets operated by other U.S. airlines.
Separately, American and the FAA are examining another complex, but unrelated structural issue that also has potentially significant safety implications for the airline's Boeing 767 fleet. Engineering experts, according to people familiar with the matter, continue to assess whether large, upwardly curved panels attached to the wingtips of some American 767s have caused or contributed to certain cracks discovered in a section of the structural backbone of a few planes.
Called winglets and installed on many types of commercial and business jets, the additions are designed to increase fuel efficiency.
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par Poncho Mar 27 Jan 2009 - 16:40
