WASHINGTON - The Federal Aviation Administration plans to issue an emergency safety order on Tuesday requiring special inspections aimed at finding hidden metal fatigue in some older Boeing 737s after a large hole opened in flight in the roof of a Southwest Airlines plane.
The safety directive applies to about 175 aircraft worldwide, including 80 planes registered in the United States, the agency said in a statement released Monday.
The order will require inspections using electromagnetic, or eddy-current, technology in specific areas of the fuselage of older 737s with a high number of takeoffs and landings, the agency said.
"Safety is our number one priority," said Transportation Secretary Ray LaHood. "Last Friday's incident was very serious and could result in additional action depending on the outcome of the investigation."
FAA has authority only over U.S. operators, but government aviation agencies in most other countries usually follow FAA's safety directives with their own orders.
The 5-foot-long hole in the Southwest plane occurred near a joint in the passenger cabin Friday afternoon shortly after the Southwest plane left Phoenix for Sacramento, Calif. None of the 118 people aboard was seriously hurt as the plane descended from 34,400 feet for an emergency landing at a military base in Yuma, Ariz.
Since there had been no previous accidents or major incidents involving metal fatigue in that spot, Boeing maintenance procedures called only for a visual inspection of the joint by airlines.
But airlines, manufacturers and federal regulators have known since at least 1988, the year after an 18-foot section of the upper cabin of an Aloha Airlines 737-200 separated in flight, that planes can suffer microscopic fractures not visible to inspectors unless they use special equipment like eddy-current devices to search for them.
The order is "certainly a step in the right direction," said National Transportation Safety Board member Robert Sumwalt, who is in Yuma with the board's accident investigation team.
The focus of the new testing is on the "lap joints" which connect the skin of the plane to the outside metal, report CBS News correspondent Don Teague.
With each flight, the jet is pressurized and depressurized - in a sense, inflating and deflating like a balloon.
"When you get the expansion and contraction as a result of take-off and landing cycles, you run a risk of getting fatigue," said CBS News aviation safety expert Mark Rosenker, a former chairman of the NTSB. "You run the risk of getting cracks in the metal itself."
FAA's emergency order will require initial inspections using electromagnetic devices on some Boeing 737 aircraft in the -300, -400 and -500 series that have accumulated more than 30,000 takeoffs and landings, the agency said. It will then require repetitive inspections at regular intervals.
"The FAA has comprehensive programs in place to protect commercial aircraft from structural damage as they age," said FAA Administrator Randy Babbitt.
But Bill Voss, president of the Flight Safety Foundation in Alexandria, Va., said the safety order is an acknowledgement that previous inspection procedures were inadequate.
"There is no question this was a very serious safety event," Voss said. "This type of thing should never happen and was never expected to happen."