Juneau, AK, USA
N3607Y
CESSNA 210
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.
On January 14, 2018, about 1445 Alaska standard time, a Cessna 210 airplane, N3607Y, was substantially damaged when it was involved in an accident in Juneau, Alaska. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that, while approaching 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 to manually extend the gear by use of the emergency hand pump; however, 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 and the right wing tip and right horizontal stabilizer impacted the runway, resulting in substantial damage. The pilot noted hydraulic fluid leaking from under the airplane as it was subsequently removed from the runway. Examination of the hydraulic system revealed that the right main landing gear hydraulic actuator (P/N 1280501-2, Electrol EA1614-2) was fractured about the barrel section adjacent to the end cap. (see Figure 1.) Figure 1. Right main landing gear actuator exhibiting fractures. A detailed examination was conducted at the National Transportation Safety Board Materials Laboratory. The actuator was partially disassembled, and a singular, thumbnail-shaped crack was present at the retainer clip groove. The fracture surface exhibited striations consistent with fatigue crack propagation when examined using a scanning electron microscope. Fractured surfaces outside of the fatigue crack area exhibited dimple rupture, consistent with an overstress fracture. The retaining ring groove revealed multiple small corrosion pits. The airplane manufacturer issued a service letter (SE75-21) in 1975 that recommended that Electrol actuators in certain Cessna 210 airplanes be modified with an actuator repair kit during the next annual or 100-hour inspection. The instructions required disassembly, inspection, and replacement of certain internal parts. In 1976, the Federal Aviation Administration issued an airworthiness directive (AD 76-04-01) that mandated the service letter instructions for the actuator. In 2011, the manufacturer also issued a service manual Supplemental Inspection Number 32-10-01 that required visual inspection of the main landing gear actuators for cracks, wear, and corrosion at regular intervals. Due to limited maintenance records available, it could not be determined if the accident airplane had been maintained in accordance with the AD or supplemental inspections.
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.
Source: NTSB Aviation Accident Database
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