What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
On February 4, 2016 at approximately 1700 hours, while test flying N395MC, a Cessna 310N, sn 310N-064, to do an autopilot test flight, the pilot noticed the gear lights would not remain on when landing gear was deployed. Coming in for the landing, the pilot would lower the landing gear and would get three green lights. After a few seconds, the two main lights would go out. The gear was recycled several times which never corrected the problem. The pilot then pulled the gear circuit breaker and hand cranked the gear down with the same results. The pilot radioed a second pilot who was about to take off and asked him if he would fly alongside the aircraft and look at the landing gear. The second pilot said that the gear appeared to be down but the right landing gear door looked like it was not completely closed. The pilot then proceeded to land. Upon landing and having rolled approximately 50 yards it appeared that the right gear collapsed. When the plane starting to veer off to the right side of the runway the slide loaded the left gear and it collapsed as well. The no. 2 propeller struck the ground but did not stop spinning. Minor damage to the right and left gear door and the foot stand was bent no other damage noted until aircraft was moved. When the aircraft was moved from the runway to the hanger, damage was done to the strap area when the aircraft was lifted during transit.
After moving the aircraft to a hanger and placing it on jacks for testing, further investigation determined that a down lock limit switch and or down lock relay on the right gear failed and would not allow the gear to lock in place. The gear would move into an over-center position not allowing it to lock in place.
Pilot was not injured during this landing. No other injuries reported.
As the FAA filed it
ON FEBRUARY 4, 2016 AT APPROXIMATELY 1700 HOURS, WHILE TEST FLYING N395MC, A CESSNA 310N, SN 310N-064, TO DO AN AUTOPILOT TEST FLIGHT, THE PILOT NOTICED THE GEAR LIGHTS WOULD NOT REMAIN ON WHEN LANDING GEAR WAS DEPLOYED. COMING IN FOR THE LANDING, THE PILOT WOULD LOWER THE LANDING GEAR AND WOULD GET THREE GREEN LIGHTS. AFTER A FEW SECONDS, THE TWO MAIN LIGHTS WOULD GO OUT. THE GEAR WAS RECYCLED SEVERAL TIMES WHICH NEVER CORRECTED THE PROBLEM. THE PILOT THEN PULLED THE GEAR CIRCUIT BREAKER AND HAND CRANKED THE GEAR DOWN WITH THE SAME RESULTS. THE PILOT RADIOED A SECOND PILOT WHO WAS ABOUT TO TAKE OFF AND ASKED HIM IF HE WOULD FLY ALONGSIDE THE AIRCRAFT AND LOOK AT THE LANDING GEAR. THE SECOND PILOT SAID THAT THE GEAR APPEARED TO BE DOWN BUT THE RIGHT LANDING GEAR DOOR LOOKED LIKE IT WAS NOT COMPLETELY CLOSED. THE PILOT THEN PROCEEDED TO LAND. UPON LANDING AND HAVING ROLLED APPROXIMATELY 50 YARDS IT APPEARED THAT THE RIGHT GEAR COLLAPSED. WHEN THE PLANE STARTING TO VEER OFF TO THE RIGHT SIDE OF THE RUNWAY THE SLIDE LOADED THE LEFT GEAR AND IT COLLAPSED AS WELL. THE NO. 2 PROPELLER STRUCK THE GROUND BUT DID NOT STOP SPINNING. MINOR DAMAGE TO THE RIGHT AND LEFT GEAR DOOR AND THE FOOT STAND WAS BENT NO OTHER DAMAGE NOTED UNTIL AIRCRAFT WAS MOVED. WHEN THE AIRCRAFT WAS MOVED FROM THE RUNWAY TO THE HANGER, DAMAGE WAS DONE TO THE STRAP AREA WHEN THE AIRCRAFT WAS LIFTED DURING TRANSIT.
AFTER MOVING THE AIRCRAFT TO A HANGER AND PLACING IT ON JACKS FOR TESTING, FURTHER INVESTIGATION DETERMINED THAT A DOWN LOCK LIMIT SWITCH AND OR DOWN LOCK RELAY ON THE RIGHT GEAR FAILED AND WOULD NOT ALLOW THE GEAR TO LOCK IN PLACE. THE GEAR WOULD MOVE INTO AN OVER-CENTER POSITION NOT ALLOWING IT TO LOCK IN PLACE.
PILOT WAS NOT INJURED DURING THIS LANDING. NO OTHER INJURIES REPORTED.