Cessna 210 N3607Y accident near Juneau, Alaska

Probable cause

A loss of hydraulic fluid due to a fatigue failure of the right main landing gear hydraulic actuator, which resulted in the pilot's inability to fully extend the landing gear and a main landing gear collapse during the landing roll.

NTSB analysis

The pilot extended the landing gear as the airplane neared the destination airport. The nose gear fully extended and locked into place, but the left and right main landing gear only partially extended. The pilot attempted to manually extend the main landing gear; however, all hydraulic pressure was lost and the gear did not extend fully. He subsequently landed the airplane, during which the main landing gear collapsed, resulting in substantial damage to the right wing and horizontal stabilizer.

Examination of the hydraulic system revealed that the right main landing gear hydraulic actuator was fractured about the barrel section adjacent to the end cap. A fracture at the retainer clip groove exhibited striations consistent with fatigue crack propagation, and other fractures through the barrel exhibited signatures of overstress failure. It is likely that, once the fatigue crack grew to a significant depth, the housing cracked further from overstress and hydraulic fluid leaked out of the system, preventing the landing gear from descending properly. The airplane experienced a landing gear collapse accident three years prior that was caused by the left landing gear actuator failure due to a fatigue crack at the retainer ring recess, similar to this accident.

The manufacturer had previously issued instructions for modification of some landing gear hydraulic actuators installed on the accident airplane make and model, and a Federal Aviation Administration airworthiness directive (AD) was subsequently issued to mandate the modifications. The manufacturer had also issued a service letter for enhanced inspection of the landing gear actuators. The maintenance records available were insufficient to determine whether the accident airplane had been maintained in accordance with the AD and manufacturer instructions.

Text from the NTSB. Open the NTSB docket for ANC18LA019 for the full record.