Incident
During flight, the aircraft experienced a decompression at an altitude of 30,000 feet. The pilot in command executed an unscheduled landing in response to the event.
Background
Between May 7 and May 9, flight crews had documented multiple write-ups regarding pressurization problems on the same aircraft. The aircraft had accumulated 55,437 flight hours and 39,983 cycles at the time of the decompression, making it one of the highest-time airframes in the American fleet.
Investigation
Examination of the aircraft identified a crack in the pressure bulkhead located at station 940 in the right wheel well. The crack measured 15.5 inches in length and was determined to have developed due to fatigue.
Service Bulletin Compliance
Boeing had issued a service bulletin on May 4, 1979, addressing bead cracking in the 940 station wheel well panel. The bulletin had not been complied with on this aircraft prior to the incident.