Incident Overview
Shortly after departure, the flight crew heard a loud noise and felt a vibration when the landing gear was retracted. Declaring an emergency, the crew returned to Salt Lake City International Airport. During the approach, 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. After a low pass over the airport, maintenance personnel advised the crew that the landing gear appeared to be down and locked, and an uneventful landing was subsequently made.
Maintenance Findings
Following the incident, maintenance personnel informed the crew that the landing gear retract actuator had sheared and could not be pinned for towing. The part was removed and examined. Examination revealed that 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.
Investigation Details
The investigation focused on the metallurgical failure of the actuator. The stress corrosion cracking was attributed to the faulty seal, which permitted moisture intrusion over time. The actuator's prior rework did not prevent the corrosion process. No other contributing factors were identified in the source material.