Aircraft Section That Failed May Not Have Been Covered By 2004 AD

The NTSB Investigation of a Southwest Airlines Boeing 737-300 which experienced a cabin depressurization earlier this week may hinge on an old maintenance violation the airline thought it had covered with a design improvement.

A 2004 AD (2004-18-06) "...applicable to certain Boeing Model 737-200, -200C, -300, -400, and -500 series airplanes, requires repetitive inspections to find fatigue cracking of certain upper and lower skin panels of the fuselage, and follow-on and corrective actions, if necessary. This amendment also includes terminating action for the repetitive inspections of certain modified or repaired areas only. This action is necessary to find and fix fatigue cracking of the skin panels, which could result in sudden fracture and failure of the skin panels of the fuselage, and consequent rapid decompression of the airplane. This action is intended to address the identified unsafe condition." There are then several pages of clarifications.

"It looks like that would apply," Peter Knudson, an NTSB spokesman, told the Dallas Morning News Wednesday. "We are going to look at the maintenance records and the maintenance practices, and we are going to want to know if all of these [regulations] were followed."

Southwest was fined $7.5 million in 2008 when it was discovered it was continuing to fly 46 aircraft that were due for inspection for structural damage. 6 of those were found to have stress fatigue cracks. The case was settled earlier this year, negotiated down from an original fine of $10.2 million.

File Photo

FAA officials told the paper that a service bulletin issued by Boeing recommends that inspections should focus on areas where two major skin panels join, but did not specify inspection of the long panels at the top of the aircraft.

The paper also reports that NTSB may investigate whether the aircraft was damaged during re-painting. A Southwest spokeswoman said the most recent inspection of the aircraft had revealed no problems. She declined to comment on the re-painting issue, citing an ongoing NTSB investigation into an incident that took place with another airline in 2003.

FMI: www.ntsb.gov, www.faa.gov