CEN22LA378

The pilot reported that the landing gear retracted normally on takeoff; however, when he attempted to extend the landing gear in preparation for landing, the nosewheel extended and locked into place but the main landing gear did not fully extend. The pilot completed the checklist items for “landing gear emergency operation,” but the landing gear still did not fully extend and lock into place. Unable to extend the main landing gear, the pilot elected to accomplish the landing with the nosewheel extended and the main gear out of the wheel well, but not in the down-and-locked position. The pilot shut down the engine when the landing was assured to protect the engine. After the touchdown and during deceleration, the airplane rolled slightly to the left and the left elevator and horizontal stabilizer contacted the runway, which resulted in substantial damage. Postaccident examination of the hydraulic actuator revealed a fatigue crack that initiated along the retaining ring groove of the actuator. The crack propagated in a circumferential direction outward and once the fatigue crack grew to its terminal size, the remainder of the cross-section fractured from mixed overstress and fatigue. This led to part of the housing barrel fracturing in overstress, allowing the release of the internal pressurized hydraulic fluid.

On August 9, 2022, about 1057 central daylight time, a Cessna 210B airplane, N9637X, sustained substantial damage when it was involved in an accident near Clinton, Arkansas. The pilot was uninjured. The airplane was being operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the landing gear retracted normally during takeoff; however, when he attempted to extend the landing gear in preparation for the landing, the nosewheel extended and locked into place but the main landing gear did not fully extend. The pilot completed the checklist items for “landing gear emergency operation,” but the landing gear still did not fully extend and lock into place. Unable to extend the main landing gear, the pilot elected to accomplish the landing with the nosewheel extended and the main landing gear in the trail position. The pilot shut down the engine when the landing was assured to protect the engine. After the touchdown and during deceleration, the airplane rolled slightly to the left and the left elevator and horizontal stabilizer contacted the runway, which resulted in substantial damage to both structures. Postaccident examination revealed a fracture of the hydraulic actuator which allowed the hydraulic fluid to escape the system. After removal, the hydraulic actuator was sent to the National Transportation Safety Board Materials Laboratory for a detailed fracture analysis. The barrel of the housing was sectioned to separate the cracked area from the rest of the assembly. The examination of the fracture surfaces revealed features consistent with fatigue cracking having initiated along the retaining ring groove of the actuator, propagating outward in a circumferential direction. Once the fatigue crack grew to its terminal size, the remainder of the cross-section fractured from mixed overstress and fatigue. This cracking led to part of the housing barrel fracturing in overstress, allowing the release of the internal pressurized hydraulic fluid. Maintenance records for the airplane show that overhauled main landing gear actuators were installed on June 10, 2021, about 14 months and 179 hours of airframe total time before the accident occurred.