On April 15, 1984, a Cessna 421C (registration N6205X) was involved in an aviation accident near Farmington, NM. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a left turn after landing, the right main gear collapsed. Examination found contamination preventing the locking keys and switch from operating.
Incident Details
After landing, while taxiing and executing a left turn, the right main landing gear collapsed. The pilot reported that all three landing gear down-and-lock indicators showed the gear was down and locked both before and after the event.
Actuator Examination
Inspection of the right main gear actuator (part number 9910136-4) revealed contamination on the inner cylinder wall. This contamination prevented the keys from extending into the locked position. The gear system was designed to maintain hydraulic pressure on the down side of the actuator when extended. However, the contaminant also prevented the actuator's switch from operating properly.