Incident Overview
On February 28, 2020, at about 1151 Pacific standard time, a Piper PA-46-350P airplane, registration N304LA, sustained substantial damage during a gear-up landing near San Jose, California. The flight instructor, private pilot, and two passengers were not injured. The flight was operating under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Landing Gear Extension Attempts
According to the pilot receiving instruction, during the approach to San Martin Airport (E16) in San Martin, California, the landing gear could not be extended and locked despite multiple attempts. The flight instructor decided to divert to San Jose International Airport (SJC). En route, continued attempts to extend the gear were unsuccessful, and the instructor landed with the gear retracted.
Postaccident Examination
A Federal Aviation Administration inspector examined the airplane and found substantial damage to the fuselage. A certified airframe and powerplant mechanic inspected the landing gear system. The hydraulic power pack showed no fluid in the sight window for the reservoir. This lack of fluid was consistent with a disconnected hydraulic line, which had not been reconnected after being used to release the landing gear during recovery. The line was resecured, and the power pack was serviced with about a pint of hydraulic fluid, after which no leaks were noted. The hydraulic pump circuit breaker was reset, and the gear cycled normally from retracted to extended.
Emergency Extension System Examination
Attempts to extend the landing gear using the emergency system were unsuccessful despite full movement of the emergency extension handle. During cycling, the power lead was disconnected to reduce pressure at the emergency extension valve, but this did not affect the valve's operation or lack thereof.
The hydraulic pack, along with the emergency extension valve, was drained, removed, and shipped to the manufacturer for examination. The power pack showed no fluid in the sight glass upon arrival; the filler hole was dry. The pack had been updated per Piper SB964B. Bench testing of the pack "as received" (without adding fluid) revealed that pressure switches operated per specifications, but flow at 1325 psi was 0.15 gpm, below the minimum of 0.46 gpm. After servicing to the proper fluid level, the pack met all requirements, with flow at 0.85 gpm at 1325 psi.
The emergency release valve was intact with required fittings. Low-pressure testing showed normal flow; with the valve closed, it held 1600 psi without leakage. However, when rotated to the OPEN position, the valve did not release pressure as expected. Two bolts on the valve bracket were missing lockwire and were finger tight, with no measurable removal torque. The valve bracket and lever were at the extreme setting, producing minimal activation. Loose bracket bolts could affect valve lever position, and the valve's rigging and potential mispositioning were considered factors. After torqueing the bolts to specification, the valve functioned correctly, releasing pressure when opened. The bolts were not cut or loosened during valve removal.
Conclusion
The landing gear could not be extended due to a lack of hydraulic fluid and a malfunctioning emergency extension valve. The fluid loss resulted from a disconnected line that was not reconnected, and the valve failure was attributed to loose bracket bolts and improper rigging.