At approximately 1211 Eastern Standard Time on 2 April 2004, the pilot of a Bell Helicopter Company 47G Soloy helicopter, registered VH-UTY, was conducting fire-ant baiting operations at Nudgee, about 5 km north-west of Brisbane Airport. The operator's chief pilot occupied the right control position and was supervising the pilot.
Near the end of a baiting run, the chief pilot told the pilot that he wanted to demonstrate a procedural turn and asked the pilot to follow him through the manoeuvre. Both pilots reported that, during the turn, the helicopter began to yaw right. The chief pilot then said that he was taking control of the helicopter. He reduced engine power but was unable to arrest the right yaw. The helicopter continued to descend towards a canal and struck the water slightly nose down and banked to the right. Both occupants were injured in the impact but were able to exit from the helicopter unaided.
The pilot reported that he had completed two previous baiting operations in the helicopter during that day without incident.
A subsequent examination of the helicopter found that the tail rotor control pedals installed at the right control position operated in the reverse sense, compared with the tail rotor control pedals installed at the left control position. That meant that tail rotor control pedal inputs made by the chief pilot would have produced a yaw response opposite to that which would normally be expected.
The helicopter operator reported that the tail rotor control pedals for the right control position had been refitted to the helicopter before the accident flight.
In 1954, the Bell Aircraft Corporation, as it was then known, issued Service Bulletin (SB) 98. The SB required installation of a stop assembly (part number 47-722-165-1), under both control position footrests. The purpose of the stop assembly was to prevent the incorrect re-installation of the tail rotor control pedals. UTY was manufactured in 1966, and the stop assembly would have been incorporated as a standard build item during manufacture.
In October 1971, the then Australian Department of Civil Aviation issued Airworthiness Directive (AD) AD/Bell47/69 titled Tail Rotor Control Pedal Assembly Interference Bracket. That AD, which mandated the installation of the interference (stop) brackets to all Bell 47G series helicopters as introduced by Bell SB 98, was still current at the time of the accident.
Examination of the helicopter showed that only part of the tail rotor control pedal assembly bracket as specified in AD/Bell 47/69, remained fitted in the helicopter. The majority of the bracket had previously been removed. There was no evidence to indicate that the removal was as a result of wear or damage sustained in the accident. The maintenance organisation that certified for the last scheduled maintenance check advised that the bracket was in place, and that the co-pilot tail rotor control pedals were not fitted at that time.
The helicopter's maintenance documentation contained no record of the installation of the right tail rotor control pedals, or of the required independent inspection of the flight controls after the installation of the tail rotor control pedals.
The helicopter examination also found that the forward section of the tail rotor drive output shaft, from the main gearbox to just forward of the first bearing hanger assembly, had separated. The separated section was not found. Examination of the remaining broken section of the drive shaft indicated that it had separated due to overload forces that occurred during the accident impact sequence. There was no evidence found of any pre-existing fault in the shaft.
