April 4 (Bloomberg) -- U.S. aviation regulators will require carriers to inspect about 175 older Boeing Co. 737s, the world’s most widely flown jet, for fuselage cracks after a Southwest Airlines Co. plane split open in flight.
An emergency directive will be issued tomorrow, the Federal Aviation Administration said in a statement today. There are about 1,800 of those models in service. The FAA is only requiring inspections on planes that have taken off and landed more than 30,000 times.
Cracks were discovered on three Southwest 737-300s in inspections for metal fatigue after the April 1 incident over Arizona. The carrier canceled 70 flights today, following 600 over the weekend, as it worked to finish examining 79 of the jets. Airlines must make regular checks of planes for metal fatigue, which can occur as jets endure the stress of takeoffs, landings and low outside air pressure of high-altitude flight.
“Southwest’s high utilization of its aircraft and short average flight length means that its planes accumulate more takeoffs and landings than do most airlines’ fleets in a given time frame,” James M. Higgins, an analyst for New York-based Soleil Securities, said in a report. Higgins has a “buy” rating on Dallas-based Southwest.
Boeing is issuing its own service bulletin urging carriers to check lap joints on some 737-300s, 737-400s and 737-500s, said Marc Birtel, a spokesman in Seattle. Those joints are where the aluminum fuselage skin panels overlap and are attached with fasteners.
The National Transportation Safety Board is probably looking at whether checks are required often enough and whether the repetitive inspection process “actually contributes to accelerating the propagation of cracks,” said Bob Mann, president of consultant R.W. Mann & Co. in Port Washington, New York.
Airlines have been carrying out “well-established” procedures to check for fatigue since an Aloha Airlines flight attendant was sucked out of a 737 through an 18-foot hole that ripped open during a 1988 flight to Hawaii, said Hans Weber, president of Tecop International Inc. in San Diego.
Inspectors crawl all over the planes with electromagnetic instruments looking for small cracks, particularly along the lap joints.
“The whole community worked really hard after Aloha to get full control over this aging aircraft problem,” Weber said. “And until about last year, we basically had no more problems. This is not good. This is really a surprise.”
The Southwest incident follows two emergency landings since 2009 caused by planes ripping open.
In July 2009, metal fatigue was blamed for an 18-by-12-inch rip in a Southwest 737 that was flying at 35,000 feet. In January 2010, the FAA ordered fuselage checks for metal fatigue on 135 737-300s, -400s and -500s in the U.S., after Boeing recommended such checks in September 2009.
In October 2010, a 1-by-2-foot hole opened on an American Airlines Boeing 757 flying at 31,000 feet, leading to an emergency landing. That and an 11-inch crack found in an inspection the month before on a United Continental Holdings Inc. 757 prompted the FAA in January to require checks on 683 of those planes.
As of today, 67 Southwest 737-300s had been inspected and 64 returned to service, the airline said. The checks should be completed tomorrow, according to the carrier.
Southwest is the world’s biggest operator of 737s, with 548 of the planes. According to its website, it had 171 737-300s at the end of 2010, with an average age of 19 years. The airline also has 25 737-500s that are an average 20 years old.
United Continental has 34 737-500s, and all have fewer than 25,000 cycles, said Mary Clark, a spokeswoman for the Chicago-based carrier.
Deutsche Lufthansa AG checked three of its 33 737-300s and didn’t find any problems, said Christian Gottschalk, a spokesman for the carrier. The German airline is the world’s second-biggest operator of the 737-300, after Southwest, according to data from aviation consulting firm Ascend.
Lufthansa and its BMIbaby unit, which has another 11 of the 737-300, said before today’s announcements that they were awaiting further instruction from Boeing.
Alaska Air Group Inc., which operates some 737-400s, couldn’t immediately comment on whether its jets need the new inspections.
Southwest fell 21 cents, or 1.7 percent, to $12.46 at 4:15 p.m. in New York Stock Exchange composite trading. Chicago-based Boeing fell 6 cents to $73.95.
Cracking Near Hole
The NTSB said yesterday that the Southwest jet showed signs of fatigue cracking near the hole in the hull after it was inspected following the emergency landing in Yuma, Arizona. Flight 812 passengers described the hole as being 1 foot wide by 3 feet long, said Linda Rutherford, a spokeswoman.
The cracks were “no longer than a quarter of an inch,” and difficult to see without magnification, Robert Sumwalt, an NTSB member, said in a briefing late yesterday.
“Cracking is wear and tear on an airplane,” he said. “From the first time an airplane flies, we see wear and tear on it. That is the reason our fleet of airplanes has redundancy built into it, and that’s why we have maintenance and inspection requirements.”
The Flight 812 aircraft will be 15 years old in June; its fuselage skin had been inspected on March 29 and Feb. 5, said Rutherford, the airline spokeswoman. It had flown 39,781 cycles, which each include one takeoff and one landing.
The NTSB has analyzed Southwest maintenance records and found all inspections on the plane were up to date, there were no discrepancies and no outstanding maintenance items, Sumwalt said in a televised briefing today from Yuma. All FAA directives were complied with and up to date, he said.
A portion of the plane’s fuselage is en route to Washington for further analysis, Sumwalt said. Joe Sedor, the investigator in charge, said the plane has been released back to Southwest, which is working with Boeing and the FAA to return it to service.
The April 1 incident occurred as Flight 812 was bound for Sacramento, California, from Phoenix. A flight attendant and a passenger were injured, Rutherford said.
-- With assistance from Dan Hart and John Hughes in Washington, Tiffany Kary in New York, Mary Jane Credeur in Atlanta, Cornelius Rahn in Frankfurt and Steven Rothwell in London. Editors: John Lear, Stephen West
To contact the editor responsible for this story: Ed Dufner at firstname.lastname@example.org