On July 23, 2016, at 1325 eastern daylight time, a privately owned and operated Cessna 310L, N3261X, was substantially damaged when its main landing gear collapsed while landing at Linden Airport (LDJ), Linden, New Jersey. The commercial pilot/owner and copilot were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local personal flight that originated at LDJ and was conducted under the provisions of 14 Code of Federal Regulations Part 91.Both pilots provided a written statement, and their versions of events were consistent throughout. The pilot stated that the purpose of the flight was to perform a functional check on all systems in advance of flying his family to North Carolina. The airplane, its radios, and the autopilot all functioned as designed, with no anomalies noted.

As the airplane approached LDJ, the pilot configured the flaps and landing gear for landing on runway 27. He said he confirmed three green landing gear lights, and visually confirmed that the nose landing gear was down and locked with the airframe-mounted mirror. At touchdown, the pilot said he heard a "noise" and the copilot described a "bang" before the airplane's tail dropped to the runway. The airplane then departed the right side of the runway and settled in the grass apron. After touchdown, the copilot "tried to feather the engines" but succeeded in feathering only the right propeller.

According to Federal Aviation Administration (FAA) records, the pilot held a commercial pilot certificate with ratings for airplane single-engine land, multiengine land and instrument airplane. He also held a mechanic certificate with ratings for airframe and powerplant. The pilot was issued an FAA second-class medical certificate on April 16, 2016. He reported 1,660 total hours of flight experience on that date.

The copilot held a commercial pilot certificate with ratings for airplane single-engine land, multiengine land and instrument airplane. He was issued an FAA second-class medical certificate on September 2, 2015. The copilot reported 1,200 total hours of flight experience on that date.

The airplane's most recent annual inspection was completed by the pilot/owner on November 11, 2015, at 3,672.1 total aircraft hours.

At deployment of the Cessna 310 landing gear, the inner main landing gear door opens as the landing gear extends. As the landing gear passes by the inner door, the door moves back toward the closed position and fully closes as the landing gear reaches the down and locked position. At retraction, the inner landing gear door opens, the landing gear retracts in its well, and the inner landing gear door closes as the landing gear reaches the up and locked position.

Examination of the airplane by an airframe and powerplant mechanic who recovered it from the runway revealed that the nose landing gear was down and locked, but that the main landing gear were partially collapsed, and would not lock when the airplane was lifted and the gear was moved by hand. The main landing gear was then blocked, and the airplane was retained for further examination.

Examination of photographs revealed substantial damage to the airframe structure in the tail section. The nose landing gear was down and locked, and the landing gear doors were partially open and therefore in a transition phase between the landing gear-retracted position, and deployed position. The right propeller blades were in the feathered position.

Later, the airplane was de-paneled under the supervision of an FAA aviation safety inspector, which revealed the landing gear actuation linkages, limit switches, and landing gear motor. The inspection revealed damage to the landing gear down-limit switch and its mount bracketry, which was bent 90° from its original horizontal position, to vertical. The landing gear actuator had been driven beyond the down limit switch, and appeared that its travel was stopped by the internal stop pin in the actuator. The actuator bell crank driven beyond the down limit, and toward the internal stop pin, released the gear from its down and locked position which allowed it to partially retract, and extinguish the green landing-gear lights.

Before the NTSB released the aircraft wreckage, the insurer inadvertently sold the wreckage to a buyer who sectioned it which precluded a more detailed landing gear system examination.

At 1315, the weather reported at LDJ included clear skies and wind from 320 degrees at 9 knots gusting to 19 knots. The temperature was 34 degrees Celsius (C), dew point was 14 degrees C, and the altimeter setting was 29.86 inches of mercury.