What happened
During a run on landing, the pilot of a Schweizer helicopter experienced a sudden loss of control. The pilot reported hearing a loud bang, followed immediately by a loss of control over the anti-torque rotor pedals. As the aircraft approached the ground, it yawed to the right and completed a 360-degree turn before impacting the terrain.
The investigation
The FAA investigation determined that a cargo strap located in an external basket blew out of its container. This strap then wrapped around the tail rotor, causing damage to the 90 degree gearbox and the pitch change links. The pilot attempted to maintain a hover during the run on landing, at which point the helicopter began spinning.
Safety message
According to the Schweizer Aircraft Corp. Pilot's Flight Manual, pilots should enter autorotation in the event of a tail rotor failure. Furthermore, FAA Advisory Circular 61-13B specifies that during a run on landing procedure, directional control should be managed using cyclic control and throttle applications to swing the nose to the right. The circular also notes that attempting to hover during a run on landing should be avoided because it places the helicopter at a high power setting; autorotation is required if tail rotor failure occurs during a hover or if dangerous attitudes are induced by adding power.