Introduction
On December 15, 2022, at 1420 eastern standard time, a Cessna 310R, registration N3844C, was substantially damaged in an accident at Blue Grass Airport (LEX), Lexington, Kentucky. The airline transport pilot and passenger were not injured. The flight was conducted as a personal flight under 14 Code of Federal Regulations Part 91.
Landing Gear Anomaly
During the approach for landing, the pilot reported lowering the landing gear, but only the nose gear light illuminated. Using the viewing mirror on the engine nacelle, the pilot observed no movement of the gear when he recycled the landing gear system, and all three landing gear lights remained extinguished. After performing a missed approach, the pilot attempted to lower the gear manually but felt the system was “not engaging correctly” and continued turning the manual gear extension handle until it would no longer turn.
Landing and Collapse
While the airplane was on final approach, tower controllers advised that the landing gear “appeared down.” The pilot stated that no landing gear warning horn sounded, and he completed the landing. During the landing roll, the left main landing gear collapsed, followed by the right main landing gear folding. After the airplane stopped on the runway, the pilot and passenger egressed without injury.
Post-Accident Examination
Initial examination revealed only minor damage, but a more comprehensive examination at a repair station months later revealed substantial damage to the wing spar carry-through structure. Examination of photographs taken at the scene showed the nose landing gear was down and locked, with the landing gear doors partially open, consistent with a transition between retracted and extended positions. Examination of the landing gear actuation linkages, limit switches, and landing gear motor revealed damage to the landing gear down-limit switch and its mount bracketry, which was bent 45° from its original horizontal position toward vertical. The landing gear actuator upper bellcrank had been driven beyond the down limit switch, and its travel was apparently stopped by the internal stop pin in the actuator.
According to the chief air safety investigator at Textron Aviation, postaccident photographs showed that the right main landing gear drive tube assembly contacted and deformed the down limit switch bracket, preventing it from contacting and actuating the switch. The purpose of the down limit switch is to remove electrical power from the landing gear motor when the gear reaches the down and locked position. If the switch were to fail or if contact was not made, the motor would continue running until it reached the internal sector stop pin, but the landing gear mechanism would be overdriven and the gear would be down but not locked. Postaccident inspection of the down limit switch by a repair facility revealed it was operational. The reason for the landing gear actuator overtravel was not determined.
Pilot and Aircraft Information
The pilot held an airline transport pilot certificate with ratings for airplane multi-engine land and rotorcraft helicopter, and reported 19,450 total flight hours, of which 92 hours were in the accident airplane make and model. The airplane was manufactured in 1977 and powered by two Continental IO-520-MB1, 285-horsepower engines. Its most recent annual inspection was completed on July 1, 2022, at 9,198 total aircraft hours, and the airplane had accrued about 20 hours since. The maintenance log entry for the annual inspection noted that main landing gear braces, bushings, and spacers were removed and replaced, and the landing gear system was rigged per the 310R service manual. Review of previous events identified NTSB Accident No. ERA16LA271, which presented nearly identical events and evidence.