What happened
During the approach phase of the flight, the pilot received an indication that the right landing gear was not properly secured. This status was subsequently confirmed by air traffic control. As the aircraft was performing its landing roll, the right main landing gear collapsed, causing the Fokker F27 to veer off the runway.
Findings
Post-incident inspections of the right main landing gear identified a fracture within the drag brace. The break occurred at a transition point where the internal diameter of the component changed from a smaller to a larger size. The fracture surface appeared flat and perpendicular to the longitudinal axis of the tube, displaying smooth, curved boundaries characteristic of fatigue. Investigators determined that the fatigue cracks originated from multiple points on the inner surface of the tube.
Further investigation into the component revealed that the failure was linked to an improperly machined transition radius at the inner surface of the tube. The specific drag stay tube involved had reached a total of 28,285 cycles at the time of the incident. Following these findings, the FAA issued an Airworthiness Directive (AD) to mandate ultrasonic inspections of main landing gear drag stay units to identify tubes with stepped bores.