Accident Overview
On August 1, 2023, at approximately 1530 eastern daylight time, a Bell Helicopter Textron Canada 407, registration N31PB, was substantially damaged in an accident near North Charleston, South Carolina. The commercial pilot sustained minor injuries. The helicopter, operated by the Charleston County Sheriff's Office, was being used as a public aircraft.
Flight and Incident
The helicopter was on a positioning flight from Sumter Airport (SMS) to Charleston AFB International Airport (CHS). After about 35 minutes of flight, the helicopter began to yaw slowly to the right. The pilot applied left pedal but received no response, stating that it felt as if the pedals were not attached. He contacted CHS tower and declared an emergency, setting up for a straight-in approach to runway 15.
While crossing the runway threshold at about 20 feet above ground level, the helicopter started to yaw to the right. The pilot lowered the collective, but the yaw continued. He then reduced the throttle and attempted to maintain a level attitude. The helicopter struck the ground adjacent to runway 15 at a high rate of descent, coming to rest in the grass. The tail rotor boom was severed during the impact sequence.
Post-Accident Examination
Federal Aviation Administration (FAA) inspectors examined the wreckage and confirmed substantial damage to the fuselage, main rotor system, and tail rotor system. Inspection revealed that one of the two bolts securing the tail rotor pitch change lever assembly was missing, with the lever assembly disconnected from the trunnion. The other bolt connecting the levers to the rod assembly was in place but loose, and its cotter pin was missing.
Maintenance Review
A review of maintenance records showed that a 300-hour/3-month inspection was performed on the helicopter on June 28, 2023. The helicopter had been flown about 15.4 hours since that inspection. According to Bell Helicopter technical support personnel, the inspection/lubrication procedure that was accomplished on June 28 would not have required removal of the lever assembly bolts; however, the nuts and bolts should have been clearly visible during inspection of the area. The mechanic who performed the inspection stated that he must have overlooked them.