NTSB Identification: DEN00IA023.
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Scheduled 14 CFR DELTA AIR LINES, INC.
Incident occurred Monday, December 06, 1999 in SALT LAKE CITY, UT
Probable Cause Approval Date: 08/13/2001
Aircraft: Boeing 767-232, registration: N111DN
Injuries: 85 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
The crew heard a loud noise and felt a vibration when the landing gear was retracted after takeoff. An emergency was declared, and the flight returned to Salt Lake City. When the landing gear was lowered, the nose and right main landing gear DOWN AND LOCKED lights illuminated, but a GEAR UNSAFE light illuminated for the left main landing gear. Following a low pass over the airport, maintenance personnel advised the landing gear appeared to be down and locked. An uneventful landing was made. Maintenance personnel informed the crew that the landing gear actuator had sheared and could not be pinned for towing. The part was later removed and examined. Stress corrosion cracking had occurred through 75% of the piston, followed by ductile separation. The corrosion had formed when a faulty fillet seal around the base of the rod end allowed moisture to enter the joint. The retract actuator was an original part, but it was determined that it had previously been reworked.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: Total failure of the main landing gear retract actuator due to stress corrosion caused by the use of a faulty sealant by company maintenance personnel that allowed moisture to enter the joint. A factor was the use of an improper fillet seal. Full narrative available
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