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.