WPR20LA187

The airplane was on final approach for landing, with the landing gear extended, when the landing gear indication light in the cockpit started to flicker. After a few seconds, the light became solid. The pilot visually verified that all three landing gear were extended and then proceeded to land. Upon touchdown, the left main landing gear (MLG) collapsed. The airplane slid off the runway and came to rest in the adjacent field, resulting in substantial damage to the wings. A postaccident examination of the landing gear system revealed several discrepancies, including missing cotter pins and other hardware, improper tension on the landing gear downlocks, and mis-rigging of the landing gear actuator. Because the most recent maintenance for the landing gear system was documented 15 days before the accident, it is likely these discrepancies were not addressed during the maintenance (which included a main landing gear wheel, tire, and brake inspection). The most severe discrepancy was likely the mis-rigged condition of the retraction system, which would have allowed the left main landing gear to enter an overcenter position and collapse during landing.

On June 18, 2020, about 1345 Pacific daylight time, a Cessna 310B airplane, N6602B, was substantially damaged when it was involved in an accident at Coeur d'Alene Airport (COE), Coeur d'Alene, Idaho. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that he was on short final with the landing gear extended when the landing gear indication light in the cockpit started to flicker. After a few seconds, the light became solid. The pilot visually verified that all three landing gear were extended and then proceeded to land. Upon touchdown, the left main landing gear (MLG) collapsed. The airplane slid off the runway and came to rest in the adjacent field. A postaccident examination of the landing gear system revealed several discrepancies. The left MLG torque link was missing cotter pins on the associated castellated nuts. The right MLG torque link center bolt was missing its nut and was backed out from its attachment point (about 2/3 of the way out). The left MLG downlock tension was measured at 11.3 pounds and the right MLG downlock tension was measured at 8.3 pounds (the Cessna 310 Service Manual required a routine maintenance tension of 40-60 pounds). The landing gear actuator appeared to be mis-rigged; the emergency crank was backed off three turns after actuation of the DOWN limit switch (the Cessna 310 Service Manual stated the emergency crank should be backed off two turns after actuation). Finally, the nose landing gear centering mechanism was broken and rusty and the left MLG drive tube was fractured at the actuator attachment lug. The left MLG drive tube was retained and sent to the NTSB Materials Laboratory for additional examination. The observed features were consistent with fracture of the landing gear drive tube from bending overstress at the end of the inboard clevis shaft. There were no indications of pre-existing fracture features or cracking. Examination of the maintenance records for the airplane revealed the most recent maintenance for the landing gear system was performed on June 3, 2020 (and included a MLG wheel inspection, tire and brake inspection).