On June 12, 1985, a Cessna T337G (registration N30S) operated by Tarr Chevrolet Co. was involved in an aviation accident near Knoxville, TN. Investigators recorded the probable cause as: The solenoid on the landing gear hydraulic manifold assembly malfunctioned, leaving the selector valve assembly stuck in the up position. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An aircraft performed an emergency gear-up landing after both normal and emergency landing gear extension systems failed. Investigation found a solenoid malfunction on the hydraulic manifold, leaving the selector valve stuck in the up position.
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.
Probable cause
The solenoid on the landing gear hydraulic manifold assembly malfunctioned, leaving the selector valve assembly stuck in the up position.