Primary finding
Probable cause
The failure of the nose landing gear actuator forward hydraulic fitting, which resulted in a main landing gear collapse during landing due to the loss of hydraulic fluid and pressure.
Investigator assessment
Analysis narrative
The pilot of the experimental amateur-built airplane had completed an uneventful cross-country flight until the arrival to his destination airport. When the landing gear was lowered on approach, the pilot observed a “gear unsafe” message and the hydraulic pump continuously operated. The nose landing gear (NLG) indicated down and locked, but neither main landing gear lights illuminated. The pilot cycled the landing gear, however, there was no change in the unsafe gear condition. He then circled away from the airport and performed an emergency gear extension, but that also did not resolve the gear configuration malfunction. Subsequently, the pilot completed an emergency landing at the destination airport with only the NLG down and locked. Upon touchdown, both main landing gear collapsed, and the airplane skidded on its empennage and rudder to a stop, which resulted in substantial damage. Postaccident examination revealed that the NLG actuator forward hydraulic fitting had sheared, which allowed hydraulic fluid and pressure to empty from the system, preventing the main landing gear from fully extending and locking into place. Following the accident, the pilot identified that the hydraulic fitting had sheared. He subsequently replenished the hydraulic fluid, capped the fitting that had failed, and was able to lower the main landing gear normally and tow the airplane back to the ramp. The pilot, who was also the owner/repairman for the airplane, had replaced the nose landing gear actuator two times, with the most recent replacement occurring 3.4 hours prior to the accident. The pilot reported that the prior actuators would leak, resulting in the hydraulic pump running continuously. During the most recent installation, the pilot adjusted the hydraulic fitting because it was not aligned with the actuator. He performed several gear swings and flew six flights without issue after this maintenance.