Extracted From:    AC No. 43-16A
    ALERT NO. 308
    March 2004
Cessna; Model; 402C II; Businessliner;
Frozen Main Landing Gear Up-Lock Actuator; ATA 3230

On approach to the airport, the pilot selected gear down and did not get an indication that the right gear was down-and-locked. After cycling the gear several times without seeing a down-and-locked light, he was forced to land with the right main gear still in the wheel well.

After the aircraft was ferried to a maintenance facility, the technician performed gear swings and the systems was OK. Upon further inspection, he found water in the hydraulic system, primarily in the up-lock actuator (P/N 5727110-9). He tested the fluid from the up-lock actuator and determined that it would freeze. The day of the accident, the outside air temperature on the ground was minus 40 degrees F. He determined that the fluid in the up-lock actuator froze and did not allow the up-lock actuator to release.

According to the submitter, this system’s up-lock actuator is a one-way cylinder, and the fluid does not circulate.

Since the fluid does not circulate with normal operation of the system, he recommended changing the aircraft hydraulic fluid at least once a year with the up-lock removed and drained.

Part total time: 13,949 hours.