Robinson R22 N194HC accident near Fort Myers, Florida

Probable cause

Foreign object damage of the turning tailrotor by a soft-bodied object, which resulted in the sudden stoppage of the tailrotor and the catastrophic failure of the tailrotor assembly and its mount structure.

NTSB analysis

The flight instructor and pilot receiving instruction had just started the helicopter when, as the engine accelerated to near its operating rpm, both pilots heard a loud “bang.” The pilot receiving instruction leaned out his door and announced that “the tail was hanging off the back of the aircraft.” The pilots shut down the helicopter and reported the event to the helicopter’s owner and his mechanic.

Examination of the tailrotor driveshaft, tailrotor gearbox, tailrotor blades, and the tailcone section forward of the tailrotor gearbox all revealed signatures consistent with overstress fracture on the fracture surfaces. There was no evidence of fatigue or foreign object damage (FOD). The fractures and impact signatures were consistent with the fracture of the tailrotor gearbox mount structure (bulkhead) of the tailcone, followed by impact signatures of the rotating tailrotor assembly against the vertical and horizontal stabilizers.

The impact signatures were consistent with a soft-bodied object (such as a plastic shopping bag or Mylar balloon) striking the turning tailrotor, which resulted in sudden-stoppage and overstress fractures of the tailrotor gearbox mount and the associated parts of the tailrotor assembly.

Text from the NTSB. Open the NTSB docket for ERA20LA310 for the full record.