Cessna 310J N3123L accident near Tucson, Arizona

Probable cause

The insufficient right main landing gear (MLG) down-lock tension due to maintenance personnel's failure to perform a rigging procedure during the airplane's most recent inspection, which resulted in the right MLG collapsing during landing.

NTSB analysis

The commercial pilot and his passenger were returning to the airport after a 30-minute personal flight. The pilot reported that he configured the airplane for landing but that the landing gear down indication did not illuminate. The pilot cycled the landing gear several times, but the landing gear down indication still did not illuminate. After an air traffic controller confirmed that the landing gear was down, the pilot chose to initiate the landing. The airplane touched down uneventfully, but, about 3 seconds later, the right main landing gear (MLG) collapsed. The airplane subsequently veered right and departed the right side of the runway, which resulted in substantial damage to the right aileron and elevator.

A postaccident examination of the landing gear system revealed that the right MLG down-lock tension was about 30 lbs less than the tension prescribed by the airplane's service manual. The fork bolt normally used to adjust the down-lock tension was covered in dirt and oil. Examination also revealed that the MLG nonadjustable drive tube had separated outboard a few inches from a clevis fitting. The signatures on the tube indicated that it failed in compression on the forward/aft plane.

A review of maintenance records revealed that the airplane's last annual inspection occurred about 4 months before the accident. The condition of the fork bolt indicates that it had not been adjusted during this inspection. Further, the pilot reported that the rigging procedure in the service manual, which included an item to verify the landing gear down-lock brace tension, was not used during any recent inspections. Maintenance personnel's failure to perform the rigging procedure during the airplane's most recent annual inspection likely led to the insufficient down-lock tension and the drive tube's failure and the subsequent collapse of the right MLG due to the compression forces experienced upon touchdown.

Text from the NTSB. Open the NTSB docket for WPR16LA015 for the full record.