Serious electrical short-circuits cracked or burned portions of cockpit windshields on a pair of American Airlines jets in the past two weeks, ratcheting up concerns about such hazards potentially affecting thousands of Boeing Co. aircraft.
The latest electrical problems come after at least 38 similar incidents with defective Boeing windshield-heaters over a 10-year period. The recent incidents, on widely used Boeing 767 models, didn’t result in any injuries, but a section of the windshields on both jets developed a web of cracks in the air.
They showed evidence of electrical damage and were replaced as soon as the aircraft landed, according to government and industry officials familiar with the details. On both planes, mechanics also replaced a part that controls heat to the windshield, according to one person familiar with the details.
In one case, these officials said, the pilots continued to fly hundreds of miles after the first sign of trouble, without diverting to a closer airport or declaring an emergency.
The incidents are prompting new concerns about the adequacy of federal safety rules and voluntary industry efforts to combat windshield-fire dangers on wide-body Boeing 767 and single-aisle 757 aircraft.
On Monday, American said one of the planes that experienced problems earlier this month previously had a windshield replaced with an enhanced version designed to prevent electrical malfunctions.
A spokeswoman for American Airlines, a unit of AMR Corp., on Tuesday said “neither incident involved any fire, smoke or odor, nor did the crews declare an emergency.” But part of the windshields either cracked or melted, she said.
American said the events “are not that unusual,” and the planes were repaired and are back in service. It said it is cooperating with government safety officials.
A Federal Aviation Administration spokesman said the agency was reviewing both incidents.
The latest electrical problems follow repeated recommendations by the National Transportation Safety Board, stretching back several years, to replace certain portions of windshields on various Boeing models. The design of the heating systems on many Boeing planes built before 2004 are prone to short-circuits and can cause related problems.
Over the years, Boeing and the FAA have told airlines to step up windshield inspections and spelled out when damaged or defective windshields should be replaced. But neither the manufacturer nor regulators have told airlines to swap out all suspect windshields.
The pilots of the first American jet, en route from Miami to Los Angeles on March 13 diverted to Dallas after part of the co-pilot’s windshield suffered heat damage and cracked. The spokeswoman said the FAA began looking into it because of the diversion.
The second Boeing 767, en route from Zurich to New York Saturday afternoon, landed at John F. Kennedy International Airport with the captain’s windshield burned and cracked, said people familiar with the details.
A safety board spokesman said the board was looking into both incidents. Spokesman Peter Knudson said investigators were informed the latest window problems occurred “over Canadian airspace.” Commercial pilots are trained to get a plane on the ground as quickly as possible whenever a serious or a difficult-to-diagnose electrical problem crops up.
It isn’t clear why the cockpit crew of American Flight 65 opted to continue to their destination. The American spokeswoman said there was no emergency, although there were cracks and “some melting of the laminate” associated with the different layers of glass.
The NTSB spokesman said investigators “were gathering information” about the event for their Canadian counterparts, but he declined to comment further.
As a precautionary move, American years ago voluntarily decided to gradually swap out all old-style windshields on its Boeing 757 and 767 fleets.
Boeing’s service bulletins, which aren’t binding on airlines, call for replacing windshields “only if damage is found,” at which point airlines can “choose to replace with the original design and continue inspections, or retrofit” with a newly designed version “and terminate inspections.”
Four months ago, part of the windshield of a United Airlines B757 flying from Boston to Chicago developed cracks, and the plane diverted to Buffalo, N.Y., without any injuries.
Earlier this month, the safety board released a report of an earlier United incident highlighting the safety hazards involved. About half an hour after taking off from New York in May 2010, the Boeing 757 with 112 people aboard was cruising at 36,000 feet en route to Los Angeles when the pilots “heard a hissing sound and saw smoke emanating” from part of the captain’s windshield, according to the report. It took two fire extinguishers to douse the flames, and the inner pane of the captain’s windshield cracked just before the twin-engine jet made a safe emergency landing at Dulles International Airport.
Previously, a spokeswoman for United, a unit of United Continental Holdings Inc., said that the May incident prompted a fleet-wide inspection and the carrier “implemented enhancements to the maintenance program” that went “beyond what was required ”by FAA directives.
-By Andy Pasztor
