N805EH

On December 4, 2007, at 1455 Pacific standard time, a Robinson Helicopter Company (RHC) R22 Beta, N805EH, experienced a flight control malfunction as it touched down during a practice hover autorotation at Fresno Chandler Executive Airport (FCH), Fresno, California. Mazzei Flying Service, Inc., operated the helicopter under the provisions of 14 Code of Federal Regulations Part 91, as a training flight. The helicopter was not damaged. The Certified Flight Instructor (CFI) and student were not injured. Visual meteorological conditions prevailed for the local area instructional flight that departed the Fresno Yosemite International Airport (FAT), at 1405. No flight plan had been filed.

In the CFI’s written report he reported that while on approach for the third hover autorotation, he noted a slight wind shift and instructed the student to do a pedal turn into the wind. The CFI reported that the student had done a good job, with minimal drift, a flat set down, and "good collective cushion." The CFI had been following the student on the flight controls and noted no unusual control inputs for the maneuver. As the helicopter settled onto the ground, with the student inputting right anti-torque pedal to compensate for the loss of engine torque, the CFI heard a loud 'snap’ from the floor area of the student's side (right side) of the helicopter.

The CFI attempted to neutralize the anti-torque pedals, and found that they were stuck in place with the right pedal in the forward position. He reduced engine rpm’s to 75 percent, and again attempted to slowly move the pedals, but they seemed stuck. He instructed the student to begin the shut down procedures. Following a normal shutdown, they exited the helicopter and began an inspection as to the cause of the stuck right anti-torque pedal. The student pilot pointed out broken metal structure adjacent to the restraining block that retains the anti-torque pedals. The CFI reported that it appeared to be the actual metal structure that the entire pedal assembly bolts to.

An inspection of the helicopter by the Federal Aviation Administration (FAA), and the operator's maintenance personnel revealed that the right-hand support bracket (part number A359-2) of the tail rotor control system had failed. The operator reported that the helicopter has a total airframe time of about 13,000 hours.

TESTS AND RESEARCH

The right-hand support bracket was inspected by the RHC laboratory. RHC had been notified of other failed support brackets on the R22 with over 7,500 hours in service. As a result, the support bracket was redesigned by RHC by increasing the thickness of the material. RHC also changed the overhaul procedures that require the A359-1 and -2 supports to be replaced at overhaul for all R22 and R44 helicopters. RHC also issued service bulletin (SB) SB-97 for the R22 and SB-63 for the R44, which require the addition of a safety tab on the older thinner support brackets.