ERA22LA340

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.

On July 27, 2022, about 1345 eastern daylight time, a Robinson R22 helicopter, N42WC, was substantially damaged when it was involved in an accident near Hollywood, Florida. The flight instructor was not injured, and the student pilot received minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the instructor, after completing an engine run-up, he “picked up” the helicopter and was air-taxiing to the practice area to conduct some hover work. Before reaching the practice area, a “popping” and “banging” sound was heard from behind the helicopter, 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. The instructor and student pilot exited the helicopter. Examination of the helicopter by a Federal Aviation Administration inspector revealed that the tail rotor assembly was separated; both tail rotor blades remained attached and the output shaft was also attached. Both tail rotor blades were bent and were impact damaged. The tail rotor gearbox was fractured, with half of the casing missing. The main rotor blades were bent down and curled, with multiple kinks and creasing from leading edge to trailing edge. Multiple impact signatures were noted on the ground within the rotor diameter of the helicopter. Examination of the tail rotor gear box and tail rotor blades revealed corrosion within both blades. The exam revealed that erosion of the leading edge provided a path for moisture to ingress into the bond joint and deteriorate the adhesive. The owner and the mechanic stated that the helicopter’s maintenance records were previously damaged by water and had to be reconstructed digitally. The records provided appeared to show that most life-limited parts had been overflown by 374.1 hours. The pilot stated that he had noted damage on the helicopter’s tail rotor blades during a preflight inspection about two weeks before the accident and that the operator had replaced the blades. Review of the available maintenance records for the helicopter revealed that the serial numbers of the tail rotor blades installed did not match that noted in the maintenance records. The available records also did not document any replacement of the tail rotor blades.