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Southwest rip shows hazard of old planes

The fuselage rupture that prompted Southwest Airlines Co. to temporarily ground part of its fleet Saturday has highlighted an insidious hazard: potentially dangerous cracks that can develop under the aluminum skins of some older Boeing 737 jets.

Inspections by Southwest and new inspections the Federal Aviation Administration called for on Monday will change the way certain aging 737s are maintained and checked world-wide.

But the longer-term result, according to government and industry safety experts, could be that airlines and regulators broadly rethink how they deal with metal fatigue on many aircraft models.

On Friday, a five-foot gash opened in a 737 fuselage during a Southwest flight, prompting an emergency nose dive while passengers hurriedly donned oxygen masks. The plane landed safely.

After Southwest's inspections revealed fuselage cracks on four of its planes, the FAA on Monday announced a speedy, but limited, response: It said it intends to issue an emergency safety directive calling for stepped-up structural inspections affecting about 170 of aircraft giant Boeing Co.'s workhorse 737s world-wide.                             

In addition to Southwest's aircraft, the FAA's order affects some 100 other planes operated by foreign carriers, including two slightly different 737 models.

Depending on what those inspections of a relatively few planes show—and what additional details accident investigators glean from the Southwest incident Friday—there could be greater emphasis on in-depth inspections for budding structural problems in certain parts of planes that haven't received much attention in the past.

"The existing inspections procedures just weren't adequate to uncover what they eventually found under the surface," said John Goglia, a former member of the National Transportation Safety Board.

"Now, there may be moves to do more detailed inspections, and do them earlier, on various types of airplanes," he said.

The FAA said Monday that it wants airlines to begin using electromagnetic testing devices to check for tiny cracks in certain sections of the older 737s where lines of rivets join overlapping skin panels together.

In those areas, which haven't been considered especially prone to cracking due to metal fatigue, there currently aren't any repetitive inspection requirements, according to industry officials.

Government investigators and industry safety experts were surprised not only at the location where the cracks were found, but that some of the aircraft didn't have as many takeoffs and landings as might have been expected to cause such damage.

For Southwest, which initially grounded 79 of its oldest Boeing 737s and was forced to cancel hundreds of flights, the findings also were a surprise.

The company said it believes the subsurface cracks found on four of its Boeing 737-300s come from an inspection blind spot, noting Boeing hadn't issued any guidance for checking that area of the jet.

The Dallas-based budget carrier also believes it uncovered a previously unknown structural problem. "It happened to us, but we do not believe that it's a Southwest Airlines issue. We believe that we discovered something that actually is an issue for the world-wide 737-300 fleet," said Southwest spokeswoman Linda Rutherford.

She cautioned that her comments shouldn't be viewed as a final conclusion, given the continuing National Transportation Safety Board investigation.                                              

A Boeing spokeswoman said the company will issue its own service bulletin recommending stepped-up inspections of certain older 737 models.

According to government and industry officials, Boeing believes the configuration of the Southwest planes makes them more prone to such problems, but the company is working closely with the FAA to determine if additional steps are warranted

Southwest said Monday it had inspected 70 of the 79 planes it voluntarily grounded.

Of those, three aircraft were found to have "small, subsurface cracks" that would require further evaluation and possibly repairs.

The airline is "cautiously optimistic" the remaining nine planes will be inspected by Monday night, with the carrier operating "close to" a full flight schedule by Tuesday, Ms. Rutherford said. Through Monday evening, Southwest had canceled more than 620 flights and delayed 2,700 others, according to flight tracker FlightStats.com .

Detecting and repairing fuselage cracks has been a primary safety focus for more than two decades, with experts from the FAA, Boeing and other groups issuing a steady stream of maintenance rules, procedures and revisions. And there have been earlier instances of airborne ruptures involving Southwest and other carriers.

The latest in-flight incident, however, has prompted safety experts to assess whether some of Southwest's older 737s may be particularly prone to cracks because of some manufacturing issue, or the fact that they are used on shorter, more frequent flights than the industry average.

Hunter Keay, an airline analyst for Wolfe Trahan & Co., doesn't think the cancellations, delays or attention around the fuselage hole will exact a significant financial toll on the company. "This is not going to impact consumer demand," Mr. Keay said. "It's probably relatively akin to a snow storm."

Julie Roberts was forced to rebook a flight from Chicago to Los Angeles Sunday after her original flight was canceled. Despite the hassle, Ms. Roberts, a 47-year-old advertising producer, applauds Southwest for being cautious. "I'd rather wait out another flight or two than take a risk," she said, adding that she plans to continue to fly Southwest.