Since the recent accident with a structural failure to one of Southwest's Boeing 737-300 jets, Southwest has been in debate about how to go about testing other jets and the best way to prevent something like this from happening again. (Full article from the Chicago Tribune below.)
As Southwest Airlines inspected the last of its Boeing 737-300 jets for metal fatigue Monday, debate was beginning over the best way to prevent other planes from experiencing structural failure at 35,000 feet.
Federal regulators and Boeing Co. officials prepared for wider inspections of other Boeing narrow-body aircraft with similar wear and tear to a Southwest jet that suffered a 5-foot rip in its fuselage before landing safely Friday in Yuma, Ariz.
The thin metal skin that forms a jet's fuselage can develop cracks from the repeated stresses of pressurization and depressurization that occur with every flight. While airlines visually inspect aircraft for cracks, federal officials are mandating the wider use of imaging technology to spot tiny, dangerous cracks that are hidden from view.
The Federal Aviation Administration said it planned to issue an emergency directive Tuesday requiring operators to conduct electromagnetic inspections of 175 Boeing 737 Classics worldwide to spot fatigue damage not visible to the human eye.
The order will apply to older-model Boeing jets that have undergone more than 30,000 landings and takeoffs, or "flight cycles" in industry parlance, but wasn't expected to add further misery for U.S. travelers after three days of widespread cancellations by Southwest.
Of the 80 aircraft required to face inspection in the U.S., 78 are Southwest jets being put through a rigorous structural examination that was devised with Chicago-based Boeing's help over the weekend and that identified cracks on three other planes. Southwest said it doesn't expect to have to conduct additional testing because of the FAA's mandate.
Southwest said it expected to complete the aircraft inspections and operate a full schedule on Tuesday. The other two planes singled out by the FAA are Boeing 737-400 aircraft operated by Alaska Airlines, an airline spokeswoman confirmed.
"Safety is our No. 1 priority," said U.S. Transportation Secretary Ray LaHood. "Last Friday's incident was very serious and could result in additional action depending on the outcome of the investigation."
If they are properly maintained, aircraft can fly for decades. But a hole blown open on another Southwest Boeing 737 fuselage in 2009 and lesser but troubling framework failures at other carriers have left travelers jittery and safety experts questioning whether the FAA is moving quickly enough to address metal-fatigue problems.
Critics claim that the FAA directives and service bulletins issued by aircraft manufacturers typically focus on problem areas in piecemeal fashion, and often after jarring incidents have occurred.
"So now we're going to have another inspection," said John Goglia, a safety consultant and former board member of the National Transportation Safety Board. "What about 5 feet away from there, where we haven't inspected? Are we going to wait for that to blow up before we do something?"
The Southwest 737-300 involved in Friday's mishap was almost 15 years old, not elderly by commercial airline standards. But it had racked up many hours of flight time and was beginning to show signs of fatigue, federal records show.
By the end of March, the plane had logged 39,768 cycles and 48,722 flight hours. During a maintenance check last month, mechanics found and fixed delamination — fraying of the composite materials — on the plane's left wing fore flap, FAA records show. During heavy maintenance a year earlier, they had repaired cracks to its frame.
Southwest's aggressive scheduling, which favors shorter flights and quick turnaround times on the ground, "means their aircraft build up many more cycles than any other airline's," said Charles Horning, chairman of the Aviation Maintenance Science Department at Embry-Riddle Aeronautical University. "It's really the cycles that wear the airplane out."
The FAA emergency directive and a similar service bulletin to be issued Tuesday by Boeing are expected to focus on problem areas that caused Friday's blowout: cracks and tears surrounding lap joints in the center of the fuselage that rivet overlapping pieces of the plane's metal skin to its structure for Boeing 737-300s, -400s and -500s.
Federal officials had urged airlines to watch for cracks in the fuselage skin at certain lap joints and other areas in a March 2010 bulletin. But the cracking occurred on a separate part of the Southwest plane and would not have been addressed by the FAA directive, noted FAA spokeswoman Laura Brown.
"It's time that we look at the oldest airplanes, the fleet leaders, to see what kind of condition they're in, for the entire fuselage," Goglia said. "Maybe we can know ahead of time that there are areas that are susceptible to problems and fix them before they blow up."
Brown said that the FAA also had endorsed a comprehensive approach to the issue of metal fatigue. In a little-noticed directive in November, federal regulators instructed plane-makers such as Boeing to effectively set a limit on the lifespan of aircraft they manufacture, while helping airlines more diligently inspect older planes that are in danger of widespread metal fatigue.
The rules would apply to about 4,200 U.S.-registered airplanes, the FAA said. The aircraft manufacturers were given 18 months to 60 months to set the new limits on a rolling basis, depending on the aircraft type, with Boeing's 737 family at the front end of the process, Brown said.
Some positive news came out of Friday's incident, besides the fact that no one on board Southwest Flight 812 was seriously harmed, said Aaron Gellman, transportation professor at Northwestern University.
"The fact is that it proved how fault-tolerant this airframe really is," he said. "Perhaps it's not so bad that it's causing them to look more carefully at the lap joint that created this problem."