Accident Overview
On January 14, 2018, at approximately 1445 Alaska standard time, a Cessna 210 airplane (registration N3607Y) sustained substantial damage during a landing accident at Juneau, Alaska. The pilot and passenger were not injured. The flight was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
Sequence of Events
The pilot reported that while approaching Juneau International Airport (JNU) for landing, he extended the landing gear. The nose gear extended fully, but the left and right main gear only partially extended, and the landing gear position indicator light did not illuminate. He attempted manual extension using the emergency hand pump; after a few pumps, he felt a loss of pressure feedback in the handle, and the landing gear failed to fully extend. He then extended the wing flaps, but no flap movement was evident.
During the landing roll, the left and right main landing gear collapsed. The right wing tip and right horizontal stabilizer impacted the runway, resulting in substantial damage. The pilot observed hydraulic fluid leaking from beneath the airplane as it was subsequently removed from the runway.
Examination Findings
Examination of the hydraulic system revealed that the right main landing gear hydraulic actuator (part number 1280501-2, Electrol EA1614-2) was fractured about the barrel section adjacent to the end cap. A detailed examination at the National Transportation Safety Board Materials Laboratory showed a singular thumbnail-shaped crack at the retaining ring groove. The fracture surface exhibited striations consistent with fatigue crack propagation when examined with a scanning electron microscope. Areas outside the fatigue crack showed dimple rupture, consistent with overstress fracture. The retaining ring groove also revealed multiple small corrosion pits.
Maintenance History
The airplane manufacturer issued Service Letter SE75-21 in 1975, recommending that Electrol actuators in certain Cessna 210 airplanes be modified with an actuator repair kit during the next annual or 100-hour inspection. In 1976, the Federal Aviation Administration issued Airworthiness Directive AD 76-04-01, mandating the service letter instructions. In 2011, the manufacturer issued Service Manual Supplemental Inspection Number 32-10-01, requiring visual inspection of main landing gear actuators for cracks, wear, and corrosion at regular intervals. Due to limited maintenance records, it could not be determined if the accident airplane had been maintained in accordance with the AD or supplemental inspections.