Report: Engine Fan Disk Had 1/2-Inch Crack
SIOUX CITY, Iowa (AP) _ Officials at a federal hearing into a jet crash that killed 112 people said Tuesday they are not ready to conclude that a hairline crack in an engine fan disk caused the DC-10′s engine to explode.
James Nall, the National Transportation Safety Board member in charge of the Sioux City hearing, said no final decision on the cause of the July 19 United Airlines crash will be issued for months, after the full NTSB meets to review testimony.
″This is simply a portion of the investigation - part of the early stages of it,″ Nall said on the first of four days of hearings.
Investigators are focusing their study on a disk from the airplane’s tail- mounted engine. They believe a flaw in the disk’s metal caused it to explode, sending pieces of metal ripping through the airplane’s tail section and severing the hydraulic lines that give pilots control of the aircraft.
A report released Tuesday said the fan disk of the jet’s rear engine had a hairline crack less than a half-inch long before the plane’s final flight.
A Federal Aviation Administration official said last week that tests on the fan disk indicated the crack was caused by a flaw in the metal that probably was present when the disk was made 18 years ago by General Electric Co.
But NTSB officials said they have drawn no final conclusions.
United Airlines spokesman Robert Doughty also said Tuesday that it is too early to pinpoint the cause of the engine explosion. Doughty said experts have only had 12 days to study the disk.
″A full analysis takes two months,″ he testified. ″It’s really premature to make a judgment.″
The NTSB report is based on detailed testing of the fan disk, found in two pieces in corn fields near Alta, about 80 miles east of Sioux Gateway Airport, where the airplane cartwheeled and burst into flames as pilots tried to make an emergency landing.
The report by NTSB Senior Metallurgist James F. Wildey II said the disk had two cracks but that only one existed before the explosion. The report said that crack was visible to the naked eye after the accident, but did not say whether the crack was detectable earlier.
NTSB spokesman Ted Lopatkiewicz said Wildey did not attempt to determine whether the crack was detectable before the crash.
Lopatkiewicz also said the report does not conclude that the crack was due to a flaw in the titanium disk that might have existed for years.
Wildley is scheduled to testify Wednesday.
In another written report to the NTSB, flight simulator expert John C. Clark said United pilot Al C. Haynes had virtually no chance to make a safe landing after the hydraulic systems lost fluid. Clark assembled a panel of experts who used flight simulators to fly a DC-10 with no hydraulic controls.
″The consensus of the group was that the pilot could fly the airplane but an adequate landing could not be accomplished within the pilot’s control,″ Clark said in the report.
Engineering Test Pilot Phillip Battaglia of McDonnell Douglas, which built the DC-10, testified that the company had not anticipated an explosion severing all three hydraulic lines.
Battaglia said that since there was no precedent, the company did not have instructions on how a pilot should deal with such a problem, and said it was unlikely any instructions could help a pilot safely land anyway.
″It’s my opinion that this is not a trainable maneuver,″ he said.
The plane cartwheeled to a stop at the edge of a cornfield on airport property, which hampered rescue efforts, said the airport’s fire chief.
Firefighters had trouble dousing the burning aircraft and locating survivors because of the standing corn, said James Hathaway of the Iowa National Guard. The Guard is in charge of firefighting at the airport.
The corn did provide refuge for those fleeing the burning plane, acting as a barrier to the radiant heat, he said.
The airport leases land along its runways to farmers. At the time of the crash the corn stood 6 feet or taller.
FAA regulations allow crops to be grown on airport land and officials say the practice is common in the Midwest. But a proposed FAA advisory to airports recommends that farming be limited and that crops not be planted within 1,200 feet of any runway center line.