DALLAS — If there’s anything learned since a Southwest Airlines jet blew out a panel April 1, it’s that the experts didn’t know what they thought they knew. And that’s worrisome.
An airplane that wasn’t supposed to have metal fatigue problems this soon most certainly did, frightening passengers and sending the Boeing Co., the Federal Aviation Administration and airlines scrambling to figure out what to do next.
It raises questions not just about the aircraft involved, but also about when airline executives and government regulators have to begin worrying about aging airplanes and metal fatigue.
John Goglia, a former National Transportation Safety Board member and airline maintenance expert, said Boeing’s admission that its analysis missed the possibility of cracking on a part of the 737-300 raised questions about what other risks aren’t known.
“It begs the question now: If your models are not accurate, then what do we have to do to ascertain the health of the fleet?” Goglia said.
He noted that there are thousands of other older planes that aren’t covered by an emergency inspection directive issued by the FAA last week, though precise numbers on aging aircraft are difficult to come by.
The FAA order called for the immediate inspection of 175 older-model 737s — 80 of which are flown in the U.S., mostly by Southwest — and the eventual inspection of about 570 planes worldwide.
Nobody seemed more surprised than Boeing that Southwest’s 15-year-old jet developed a 5-foot-long rip along a row of fasteners. The Boeing 737-300 had fewer than 40,000 takeoff and landing cycles.
Boeing’s chief project engineer for the older 737s, Paul Richter, told reporters last week that the analysis and testing Boeing had done on those airplanes “convinced us that we would not have an issue with this lap-joint lower row until much, much later in the life of the airplane.”
Engineers were planning to recommend that airlines inspect the lap joints — where one part of the fuselage meets and overlaps an adjoining section — when the airplanes reached 60,000 cycles. The 60,000 cycles “we felt was a very conservative number.”
It wasn’t, as it turned out.
Goglia is calling for a summit of operators, manufacturers, FAA regulators and other experts to re-examine their assumptions about metal fatigue on aging aircraft.
He said the summit should undertake a detailed inspection — using electrical “eddy” current or X-ray technology — of the fuselage of an older plane that has accumulated a high number of flight cycles and hours.
“That is the only way we are going to get a baseline that is statistically accurate,” he said. “Now that they are admitting the model is wrong, that means all of the other things they have done off that model is suspect.”
Speaking to business journalists last Friday, Southwest Chairman and Chief Executive Gary Kelly said he didn’t agree with those who say the inspection requirements aren’t thorough enough.
“The airplane is already subjected to thousands of inspections on a continual basis that are very carefully put together in terms of having a whole program to ensure the safety of the airplane,” Kelly said, adding that problems are “extremely, extremely rare.”
“There are very extensive, overlapping, conservative inspection and repair procedures that are already in place,” he said. “Every time we learn something new — and new things are learned — every time we learn something new, all that information is fed back to Boeing and then ultimately the FAA. Then there is a reflection on whether changes need to be made to the maintenance program.”
In the case of the April 1 incident, that process took only 24 hours, resulting in last week’s airworthiness directive.
“If there is some finding that suggests there is merit to expand the inspection beyond what we’ve done, well, of course, we’re going to do that,” Kelly said. “But I got to tell you, looking at almost the entire length of the airplane on … the lap joint every other month is a lot of additional inspections.
“Don’t get me wrong,” he added. “We will do anything it takes to ensure the safety of flight. It’s not a matter of it taking too long. It’s just at some point if you’re going to fly on an airplane, we gotta take off.”
Michael Goldfarb, a former FAA chief of staff, said he thinks the Southwest episode will spark greater FAA oversight of airlines that fly aging aircraft and repair stations that service them.
Indeed, FAA Administrator Randy Babbitt announced last week that he’d ordered a review of the agency’s aging aircraft program.
Older aircraft are covered by a multitude of maintenance regulations known as airworthiness directives. In effect, they are responses, based on a manufacturer’s input, to structural or mechanical problems that airplanes have experienced.
The directives order airlines to conduct inspections to look for those problems, and if they are found, prescribe a solution recommended by the manufacturer, such as Boeing. Those inspections are often performed visually, according to experts, which won’t detect subsurface cracks.
“If you had a drawing of the airplane and you laid out the (airworthiness directives) that are on there, it would look like there are Band-Aids all over the airplane,” Goglia said. “Because that is what we’ve been doing. It is like a jigsaw with pieces of the puzzle missing.”
Airlines prefer to do visual inspections because using eddy-current technology “adds many, many more man-hours to the inspection,” said Charles E. Horning, department chair for aviation maintenance science at Embry-Riddle Aeronautical University.
“When you get into a situation where you are looking for hidden cracks, you are going to require eddy-current inspections,” Horning said. “This may be the point that the industry needs to step back and increase the use of eddy-current inspections or come up with some other techniques they aren’t using.”
The FAA acknowledged last year that structural cracks can go unnoticed between inspections. The tiny cracks “may then link up and grow so rapidly that the affected structure fails before an inspection can be performed to detect the cracks,” the FAA said in announcing new rules last November.
Citing the need to avoid “widespread fatigue damage,” the regulation called for manufacturers to establish lifetime limits for aging aircraft. The rule gave the industry between 18 months and five years to establish those limits, depending on the type of aircraft. Airlines lobbied vigorously to shape the rule, which affects 4,198 planes — both newer and older models — in the U.S.
“That is the safety solution — life limits,” Goldfarb said. “That is a philosophical change. … The spirit (of the rule) was to get them out, basically retire them.”
Goldfarb said he thinks the Southwest incident will now prompt the FAA to move up that five-year deadline.
“It will become a more aggressive retirement for the older aircraft,” said Goldfarb, now an aviation consultant in Washington.
Southwest’s reputation should not be damaged by the April 1 incident, said Leeham Co. aerospace analyst Scott Hamilton. Southwest grounded airplanes and began inspecting them before Boeing recommended it and the FAA required it, he noted.
“This is not a Southwest issue,” Hamilton said. “It is a Boeing issue.”
Still, the incident raises concerns, particularly for Southwest, which flies Boeing aircraft exclusively and is the world’s largest operator of Boeing 737s.
Kelly has been publicly prodding Boeing to commit to a new generation of aircraft that are more fuel efficient, less polluting and otherwise improved.
Kelly acknowledged that Southwest officials are “very anxious” for Boeing to commit to a new aircraft to replace the current 737s. But given several opportunities to criticize Boeing, Kelly instead chose to praise the firm that built every airplane now in Southwest’s fleet.
“The Boeing Co. is one of the great companies of the world and someone we’re very pleased to be partners with, especially with an incident like this,” he said.
But Hamilton said relations between Boeing and Southwest “were kind of testy even before this.
“This could have cost Southwest Airlines an airplane or two or three and a bunch of lives, and Southwest doesn’t look kindly on that prospect.”