Lake LA 4 N7628L accident near Byron, California

Probable cause

The pilot’s failure to activate the hydraulic system during the approach, and his failure to ensure that the landing gear was down and locked before touchdown. Contributing to the accident was the pilot's decision to operate the airplane with an inoperative landing gear position indicator light.

NTSB analysis

During landing, the nose landing gear and right main landing gear collapsed, and the airplane veered off the runway. The pilot stated that it was likely that he switched the hydraulic pump off during the accident flight. Although both the hydraulic switch position and checking the hydraulic system pressure were included in his before-landing checklist, he could not recall their position and indication, respectively, during the accident approach. The pilot also reported that he had been experiencing issues with the landing gear microswitches, and the airplane's landing gear indicator light was inoperative as a result. Postaccident examination of the airplane and landing gear system revealed no evidence of mechanical malfunctions or anomalies that would have precluded normal operation.

It is likely that the pilot's failure to properly configure the hydraulic switch, and his subsequent failure to recognize the error during his before-landing check, resulted in inadequate hydraulic pressure to extend and lock the landing gear. The airplane's inoperative landing gear indicator light likely contributed to the pilot's failure to recognize that the landing gear was not fully extended and locked before landing.

Text from the NTSB. Open the NTSB docket for WPR17LA165 for the full record.