Robinson Helicopter Company R22 MARINER N42WC accident near Hollywood, Florida

Probable cause

Inadequate maintenance of the helicopter’s tail rotor blades, which resulted in a failure of the tail rotor drive system, and an inflight loss of yaw control from which the flight instructor was unable to recover.

NTSB analysis

The instructor reported hearing a popping and banging sound while hover-taxiing during an instructional flight followed by an uncommanded right yaw. The instructor attempted to regain control, but the helicopter collided with the ground and rolled over onto its right side.

Postaccident examination of the helicopter revealed that the tail rotor gearbox had fractured and that the tail rotor assembly had separated from the helicopter. Additional examination of the tail rotor blades, which had remained attached to the tail rotor drive shaft and gearbox, revealed corrosion and interior delamination of the blades. There was also erosion present on the blade leading edges, which likely provided a path for moisture to ingress, thereby resulting in the observed corrosion as well the failure of the bonding adhesive within the blade. It is likely that this condition resulted in an imbalance of the blades that imparted a vibratory loading onto the tail rotor gearbox that ultimately resulted in its failure during the accident flight. Review of partial maintenance records provided by the operator revealed that the tail rotor blades installed on the accident helicopter were not the blades that were noted in the maintenance logbooks, and the service history of the installed blades could not be determined.

Text from the NTSB. Open the NTSB docket for ERA22LA340 for the full record.