Accident
An aircraft conducted an emergency landing with the landing gear retracted after both the normal and emergency extension systems failed to operate correctly. The crew executed the gear-up landing without further incident.
Investigation
Following the landing, maintenance personnel placed the aircraft on jacks and were able to extend the landing gear by repeatedly cycling the selector switch. Examination of the landing gear hydraulic manifold assembly revealed that the solenoid had malfunctioned, causing the selector valve assembly to remain stuck in the up position.
Findings
The malfunctioning solenoid prevented the selector valve from moving to the down position, thereby inhibiting gear extension. The solenoid was identified as the component that failed.
Service Bulletin Compliance
Cessna Service Letter SE76-24 recommends replacement of the solenoid with an improved version. According to the mechanic who performed the post-accident troubleshooting, this service action had not been accomplished prior to the accident.