Accident Overview
On June 25, 2008, at approximately 1600 Pacific daylight time, a Rockwell International 690B, registration N9KG, sustained substantial damage following a collapse of the right main landing gear during the landing roll at Baker City Municipal Airport (BKE), Baker City, Oregon. The commercial pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed for the personal cross-country flight, which was operated under 14 CFR Part 91 with an instrument flight rules flight plan filed. The flight departed Portland-Hillsboro Airport (HIO) at about 1500 with destination BKE.
Pilot Report
The pilot reported that the airplane had undergone a 150-hour inspection at Aero Air, LLC facilities at HIO, and he was returning the airplane to BKE. Upon arrival at BKE, he lowered the landing gear and verified three green lights indicating down and locked. He lowered the first notch of flaps on the downwind leg, added flaps on base leg, and applied full flaps on final. He confirmed the landing gear indication again and moved the condition levers to HI RPM. After a normal landing, he moved the condition levers to ground idle and then to BETA. About midway down the runway, he applied brakes slowly, after which the right main landing gear collapsed.
Examination Findings
A Federal Aviation Administration (FAA) airworthiness inspector from the Boise Flight Standards District Office examined the airplane. The inspector found that the inboard housing boss had fractured from the main body of the right main landing gear strut. The right main landing gear retract cylinder was disconnected from the upper gear casting, with the rod end fastened to the appropriate clevis in the proper manner. The rod end jam nut was loose, and no threads were exposed between the rod end and the jam nut; however, on the auxiliary cylinder, three threads were exposed. The strut body, inboard hydraulic cylinder clevis, and housing boss were sent to the NTSB Materials Laboratory. A senior metallurgist determined that the fracture surface was consistent with overstress, with no evidence of wear or fatigue cracking on the clevis or housing boss.
The Twin Commander Engineering Manager provided a report stating that inadequate maintenance could not be a contributing factor due to the landing gear design. The report noted that the gear failure did not occur during touchdown, indicating the drag brace was locked. A failure at the clevis attach point of the actuator would not prevent locking. The report concluded that inadequate maintenance could not be a contributing factor because the failure occurred during rollout after landing.
Maintenance Records
According to the Gulfstream Commander 690A/690B Maintenance Manual, both landing gear actuating cylinders are adjusted by removing the rod end bearing attachment bolt, backing off the piston rod end bearing three turns, and tightening the check nut. Maintenance records from Aero Air for the 150-hour inspection included: performing landing gear and actuator inspections per Major Guide III and IV; compliance with Service Letter 376 (landing gear clevis and drag brace inspection), including installation of new clevises on inboard actuators and nondestructive testing of outboard clevises, trunnion bores within limits, and fluorescent penetrant inspections of trunnions and drag braces (next SL 376 due in 500 hours); and replacement of worn left and right main landing gear scissors center bushings with new part numbers.