N3844CCessna 310R

On December 15, 2022, at 1420 eastern standard time, a Cessna 310R, N3844C, was substantially damaged when it was involved in an accident at Blue Grass Airport (LEX), Lexington, Kentucky. The airline transport pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

During the approach for landing, the pilot reported that he lowered the airplane’s landing gear and only the nose gear light illuminated. Using the viewing mirror on the engine nacelle, the pilot detected no movement of the gear when he recycled it, and all three landing gear lights remained extinguished. After performing a missed approach, the pilot attempted to manually lower the gear, but felt the system was “not engaging correctly” and he continued to turn the manual gear extension handle until it would no longer turn.

While the airplane was on final approach, the 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 “folding” of the right main landing gear. After the airplane stopped on the runway, the pilot and his passenger egressed the airplane without injury.

Initial examination of the airplane 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 revealed that the nose landing gear was down and locked, and the landing gear doors were partially open, consistent with a transition phase between the 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 it appeared that its travel was stopped by the internal stop pin in the actuator. (See Figure 1.)

Figure 1 - Note main landing gear down-limit switch and bracketry in bottom-right corner of frame, bent 45° from original horizontal position towards vertical.

According to the chief air safety investigator at Textron Aviation, review of postaccident photographs showed that the right main landing gear drive tube assembly contacted and deformed the down limit switch bracket, which prevented it from contacting and actuating the switch. The purpose of down limit switch is to remove electrical power from the landing gear motor when the landing gear reaches the down and locked position. If the switch were to fail or if contact from the right main landing gear drive tube assembly was not made with the down limit switch, the motor would continue to run until it reached the internal sector stop pin. However, when this occurs the landing gear mechanism will have over driven, and the landing gear will be down but not be in the down and locked position.

Postaccident inspection of the landing gear down limit switch by a repair facility revealed that it was operational. The reason for the landing gear actuator overtravel was not determined.

The pilot held an airline transport pilot certificate with ratings for airplane multi-engine land and rotorcraft helicopter. The pilot reported 19,450 total hours of flight experience, of which 92 hours were in the accident airplane make and model.

According to Federal Aviation Administration and maintenance records, the airplane was manufactured in 1977 and was powered by two Continental IO-520-MB1, 285-horsepower engines. The airplane’s most recent annual inspection was completed July 1, 2022, at 9,198 total aircraft hours. The airplane had accrued about 20 hours since the inspection.

According to the maintenance log entry for the annual inspection, main landing gear braces, bushings, and spacers were removed and replaced, and the landing gear system was rigged “per 310R service manual.”

Review of previous events identified NTSB Accident No. ERA16LA271, which presented nearly identical events and evidence.