Incident Description
The captain overflew the landing field to assess wind conditions. The windsock indicated a quartering headwind for Runway 12. During the landing rollout, when the power levers were brought into the beta range, the airplane immediately veered to the right. The captain applied rudder and braking corrections but was unable to maintain directional control. The aircraft departed the right side of the runway and collided with a ditch and an embankment.
Post-Incident Observations
After deplaning, the crew determined that the actual wind was a 60-degree tailwind on Runway 12. The windsock's pivot point on the pole was rusted and could not rotate, causing it to give a false indication. Performance calculations showed that with the same landing weight and a 60-degree 10-knot tailwind, the aircraft would require a 1,600-foot landing roll on the 2,350-foot runway, without the assistance of both propellers in beta.
Additionally, the beta pin on the left engine's beta control linkage had backed out of position. The pin, cotter pin, and washer were found in the bottom of the engine cowling.
Maintenance History
The left engine had been replaced two days prior to the incident. During installation, mechanics completed work on the beta pin area, and an inspector verified the pin was in place and properly safety wired. Following the inspector's signoff, mechanics discovered that the teleflex cable was too short for the beta valve to be flushed and needed adjustment. The director of maintenance readjusted the cable, which required disturbing the safety wire on the beta pin. One of the two mechanics instructed to re-safety the connections thought that the rear portion had already been safetied and did not recheck the area. The inspector believed the area had already been checked and did not re-examine the beta pin.