Event Summary
The aircraft departed after the landing gear hydraulic pump was replaced and reportedly checked satisfactory during an annual inspection signed off one day earlier. During the flight, after the pilot reportedly lowered the landing gear selector handle, the landing gear down and locked lights did not illuminate. The pilot cycled the navigation light switch and flew by the tower, where personnel advised that the gear appeared down and locked. The pilot then retracted the gear, reentered the traffic pattern, and again lowered the gear handle. However, the down and locked lights for the landing gears did not illuminate, nor did a gear unsafe light. The pilot landed the airplane. Reportedly, after touchdown, the left main landing gear began to collapse. The airplane veered off the left side of the runway into grass and came to rest with the left and nose landing gears down and locked; the right main landing gear was collapsed.
Post-Accident Examination
Post-accident testing of the left main landing gear revealed no evidence of failure or malfunction; the down and locked light illuminated during testing. The hydraulic pump was removed, bench tested, and found to operate normally. Testing of the hydraulic fluid revealed it was contaminated beyond allowable limits. According to the source, there was no requirement by the airplane manufacturer to replace the hydraulic fluid. The pilot reported that he did not utilize the emergency gear extension.
Findings
The accident sequence involved gear indication anomalies and a subsequent landing gear collapse on touchdown. Investigative testing showed that the left main landing gear components and the hydraulic pump functioned normally after the accident. The hydraulic fluid was found to be contaminated beyond allowable limits, though no manufacturer requirement existed for fluid replacement. No emergency gear extension was attempted.