Cessna 402C N769EA incident near Nantucket, Massachusetts

Probable cause

Installation of an improper bearing in the landing gear actuator.

NTSB analysis

The pilot lowered the landing gear and the left main landing gear would not extend. He recycled the landing gear and completed the checklist items with negative results. The left landing gear subsequently collapsed during the landing roll out. A landing gear retraction test was conducted and the failure was duplicated. The extend inlet port for the up lock actuator was then removed for inspection. A small ball bearing was in the wrong position with respect to the larger ball bearing. The smaller ball bearing jumped the larger ball bearing causing a blockage. The up lock actuator and the main gear actuator were removed and examined at an authorized repair facility. Disassembly of the up lock actuator confirmed the initial finding, and revealed that the smaller ball bearing was too small. The main gear actuator was tested and was within manual limits. The operator stated that the up lock actuators are a condition item. The mechanic who performed the last inspection stated that he did not replace any bearings. The investigation could not determine who replaced the bearings or when they were replaced.

Text from the NTSB. Open the NTSB docket for ERA09IA267 for the full record.