WASHINGTON — A United Airlines plane with 112 people aboard was allowed to take off last May without repairs despite indications during two previous flights that the cockpit window was overheating, a condition long known to cause fires, according to evidence gathered by federal investigators.
The Boeing 757 was about 30 minutes into a flight from New York to San Francisco, and had just leveled off at 36,000 feet, when pilots said they heard a hissing noise followed seconds later by 14- to 16-inch flames shooting from the cockpit window near the captain, documents recently released by the National Transportation Safety Board show.
Capt. Boyd Hammack, who had been flying the plane, told investigators he got out of his seat, grabbed a Halon fire extinguisher and put out the flames. But he said they quickly reignited. A flight attendant brought him a second fire extinguisher, which he emptied on the flames, putting them out again.
Shortly before making an emergency landing at Washington Dulles International Airport in Virginia, the inner pane of the window in front of Hammack shattered, the documents show. He turned over control of the plane to the first officer, who safely landed the aircraft.
Another United captain who had flown the same plane earlier that day told investigators he reported fumes and an overheated electrical connection when he landed at John F. Kennedy International Airport in New York, according a summary of his interview with investigators.
Capt. Robert Caponetti told investigators he showed a mechanic an electrical connection at the window on the captain's side of the cockpit that appeared blackened or charred and was hot. He also said the plane had made an unscheduled landing in Las Vegas the previous day because of smoke and fumes in the cockpit.
The mechanic, also interviewed by investigators, said he OK'd the plane to fly without repairs because United's maintenance manual says planes can be flown another 50 hours after a blackened or burned window heater electrical connector had been found. A blackened, burned or hot electrical connection is a sign of uncontained electricity, which can cause fires.
"We did a full inspection and believed the plane was flight worthy," United spokeswoman Megan McCarthy said.
Federal aviation officials have known for years that cockpit window heaters in some Boeing planes catch fire. But prior to the United incident they hadn't required airlines to fix the problem, even after dozens of incidents that unnerved pilots and, in many cases, forced emergency landings.
Accident investigators had traced the problem to a simple loose screw. NTSB has urged the Federal Aviation Administration since 2004 to require airlines to replace the windows with a new design.
Nearly two months after the United incident, FAA ordered airlines to inspect the cockpit window heaters on 1,212 Boeing airliners. But the order doesn't require airlines to replace the windows unless evidence of damage is found.
The order also gives airlines a choice of installing windows of the same design or the new design. Carriers that choose old design replacements must continue to inspect windows at regular intervals.
McCarthy said United has complied with FAA's order for inspections and is replacing windows with the new design "when they are up for replacement." She said she didn't know what would trigger a replacement.
United has also made "enhancements to our maintenance program," she said.