Boeing Had Thought 737’s Skin Joints Were More Robust

PHOENIX — Boeing was surprised when a section of a Southwest jetliner’s fuselage ripped open in flight because the plane wasn’t old enough to be worrisome, a company official said Tuesday, as the airline cleared most of its older 737 planes to return to the skies.

Southwest said it had inspected nearly all of the jets it grounded after the accident on Friday. Five were found with the same kinds of cracks suspected of causing the 5-foot-long hole to open as the jet cruised around 34,000 feet. The planes are being repaired, the airline said.

Boeing engineers did not expect to see the cracks because they thought they had designed the joints that hold the 737-300s’ aluminum skin in place to be more robust.

They believe the planes would not need inspections for at least 60,000 pressurization cycles, the number of times that a plane takes off and lands. The company hadn’t even issued inspection specifications because none of the planes involved were anywhere near that old.

The Southwest jet was 15 years old and logged 39,000 cycles.

“I would say that it’s regrettable that we had to accelerate our plans to recommend inspections based on an event of this nature,” Boeing chief 737 engineer Paul Richter said. He said the company has given repair instructions to Southwest for three planes.

A “service bulletin” from Boeing and an emergency Federal Aviation Administration order issued on Tuesday mean inspection on 737-300s, 737-400s and 737-500s will be done starting at 30,000 cycles.

The FAA order is aimed at finding weaknesses in the metal exterior, but virtually all of the affected aircraft already were inspected by the time the order took effect.

The safety directive applies to about 175 aircraft worldwide, including 80 planes registered in the U.S., the FAA said. Of those 80, nearly all are operated by Southwest. Two belong to Alaska Airlines.

Photo Credit – the associated press
Cutline – Technicians use a device to conduct inspections on the lap joints of Southwest jets. The metal shown here being tested at Yuma National Airport on Monday is used for calibration purposes and is not part of an actual aircraft.