Incident Summary
Following departure, the pilot raised the landing gear selector handle, but the landing gear did not fully retract. Hydraulic fluid was added in an attempt to retract the gear, but the attempt was unsuccessful. The flight continued to its destination, where the pilot attempted to lower the landing gear using the emergency extension method, but was unable to do so. A gear-up landing was subsequently performed.
Examination Findings
Post-landing examination of the aircraft revealed that the piston and rod of the left main landing gear door actuator had exited the cylinder. This occurred due to incorrect installation of the retaining ring. The dislodged ring allowed hydraulic fluid to leak, depleting the supply needed for gear operation.
The actuator had been overhauled 6 hours and 3 cycles prior to the incident. Historical data from 47 service difficulty reports and accident/incident reports, spanning from January 1, 1984, to June 26, 1990, indicated 8 failures attributed to a dislodged retaining ring in this type of actuator.