NetJets Aviation Cessna 560XL incident

Shortly after takeoff, a tower air traffic controller notified the flight crew that fuel was pouring from the left wing. The crew also noted hydraulic and flight control annunciator messages and a gear unlocked indication. The flight remained in the traffic pattern and the airplane landed with a fuel imbalance of about 1,000 pounds. An examination of the airplane after the incident revealed minor damage in the left wing and gear well areas. The left main gear aft trunnion pivot pin was not in place, resulting in separation of the aft portion of the left main gear trunnion from the aft trunnion fitting. The end of the aft trunnion punctured the interior of the gear well, resulting in damage to surrounding structure and damage to the fuel cell and hydraulic line. The damage resulted in the fuel leak and the flight control and hydraulic messages. The pin was later found loose and undamaged in the flap track area of the left wing. The aft trunnion pivot pin retaining bolt that was intended to restrain the pivot pin was in place and secured with a nut and cotter pin. A review of maintenance records for the airplane revealed that the left main gear trunnion was removed and replaced with a new unit about six weeks before the incident. The maintenance was performed by an outside vendor. According to the airplane maintenance manual, when installing the aft main landing gear trunnion, the trunnion pivot pin must be slid forward, aligning a hole in the trunnion with a hole in the pivot pin. The trunnion pivot pin is then secured in place with the retaining bolt, washers, nut, and cotter pin. It is likely that the incorrect installation of the left main gear aft trunnion allowed the aft trunnion pivot pin to eventually exit the trunnion and attach fitting. This allowed the aft trunnion to puncture the interior of the gear well.

Verbatim NTSB analysis and probable cause from the NTSB dataset