Incident Details
On August 28, 2017, about 1900 Pacific daylight time, a Cessna 560XL airplane, registration N503UP, sustained minor damage to the right wing during a landing roll at San Jose, California. The aircraft was operating as a Title 14 Code of Federal Regulations Part 135 air taxi flight with two pilots and three passengers on board; no injuries were reported. The pilot and copilot stated that the airplane bounced during landing roll, veered right, and the pilot corrected back to the runway centerline. The copilot observed that the right side seemed to dip as the airplane continued to pull right. The pilot noted that the right side was lower than the left, leading them to suspect a flat tire on the right main landing gear (MLG). The pilot taxied the airplane off the runway and parked on a taxiway, where passengers disembarked without incident.
Aircraft Examination
Examination revealed that the aft portion of the right MLG trunnion was protruding through the top of the wing. The MLG strut and wheel were positioned out and aft at approximately a 45° angle from their original position. The right MLG trunnion aft pivot pin was not in the trunnion but remained in the trunnion mount in the aft wing spar; it was easily removed by hand. The retaining bolt used to keep the pivot pin in the trunnion was in place and secured with a nut and cotter pin.
Maintenance History
A review of the airplane's maintenance records showed that the left and right MLG trunnions had been replaced with new trunnions and trunnion pivot pins 8 days before the incident.
Mechanic's Statement
The mechanic who performed the replacement stated that, after installing the right MLG aft trunnion pivot pin, it must have shifted aft when he attempted to install the retaining bolt through the pin. He suggested that an "air-pocket" might have developed and pushed the pin back out. He noted that the pin appeared fully engaged and that no faults were observed during postmaintenance operational checks.
Manufacturer's Revision
Following the incident, the airplane manufacturer revised the trunnion pivot pin installation procedures in the Airplane Maintenance Manual. The revision included a step requiring maintenance personnel to visually verify that the bolt is visible when looking through the pivot pin from the aft side. If the bolt is not visible, the procedure calls for removing the bolt, ensuring the pivot pin is fully installed in the trunnion assembly, and reinstalling the bolt.