A Bell 47J helicopter was being ferried by two pilots from Lyndock SA to Kings Creek Station NT over a period of 3 days. Refuelling stops were planned for Port Augusta, Roxby Downs, Coober Pedy, Cadney Park if required, and Kulgera. Additional equipment was also carried, including a ground refuelling hose and pump unit, aircraft manuals, hand tools, additional engine oil, water, and seven 20 L jerry cans of fuel.
The flight was uneventful to Cooper Pedy where a flight plan was lodged nominating Cadney Park and Kulgera as landing points. The helicopter subsequently departed at about 0730. When it failed to arrive at Cadney Park or Kulgera, a search was initiated. The burnt-out wreckage of the helicopter was located 2 days later in flat, open, sparsely timbered country, about 1 NM south-west of Temptation Bore and approximately 152 NM from Coober Pedy, close to the direct track to Kulgera. The accident was not survivable.
At the time of the accident the weather was fine and clear, with a light breeze from the south-east, and a temperature in the vicinity of 30 degrees Celsius.
Examination of the wreckage did not reveal any pre-existing defects which may have contributed to the accident. An intense post-impact fire fuelled by the fuel from the jerry cans had consumed the cockpit and forward section of the tail boom. The engine displayed severe impact and external fire damage, but all internal components were intact, well lubricated, and capable of normal operation. The fire had destroyed the fixed emergency locator transmitter mounted on a bracket at the forward section of the tail boom. The remains of a hand-held emergency locator beacon were found in the debris of the burnt cockpit. The damage sustained by the main and tail rotor assemblies was consistent with the transmission system not being powered at the time of impact. The rotational velocity of the main and tail rotor assemblies was very low at impact and it was likely that the main rotor RPM was too low for a controlled descent. Damage sustained by the engine cooling fan indicated it was not rotating at impact. Some of the flight control systems had been consumed by the fire, but the remainder were correctly connected and functioned normally. The pilot's collective lever and cyclic control stick had separated during the impact. Both displayed bending overload failures but no fire damage was evident.
One main fuel tank had collided with a main rotor blade during the impact sequence. That tank was ruptured and deformed from collision with the blade, and contained a minute quantity of fuel, but displayed no evidence of fire damage. The other main fuel tank was ruptured and heavily sooted externally, but contained no fuel, and there was no evidence of fire internally. The remainder of the fuel system was too extensively damaged to determine if a fuel leak had existed during flight. Of the seven jerry cans, most were ruptured and heavily sooted externally. Fire and explosives experts' analyses determined that the main tanks contained only a small quantity of unusable fuel at impact. The intensity of the fire indicated that there was a substantial quantity of fuel in the jerry cans. Earth displaced from the impact craters made by the forward cockpit section and tailskid was consistent with the helicopter being in a nose-down attitude, with some forward velocity at impact.
Maintenance records for the helicopter indicated that it had been correctly maintained in accordance with an approved system of maintenance. The maintenance release was current, and there were no outstanding maintenance requirements.
Both pilots were appropriately licensed for the flight. The pilot flying at the time of the accident had about 350 hours of rotary wing flight time, but had limited experience on the Bell 47J type. The pilot in the rear seat had over 7,000 hours rotary wing flight time, but his logbook indicated that he had not operated the Bell 47 type since before September 1997.
The estimated weight and balance of the helicopter on departure from Coober Pedy indicated that the centre of gravity was within approved limits and its weight was within the authorised maximum take-off weight.
The investigation determined that the main fuel tanks of the helicopter and the seven additional 20 L jerry cans were full when it departed Lyndock. The fuel management between Lyndock and the final refuelling at Coober Pedy could not be determined. After refuelling at Coober Pedy on the evening before the accident flight, the helicopter was hover taxied to another area for overnight parking. The main tanks were therefore less than full at departure from Coober Pedy the next morning. The range of the helicopter with full main tanks was insufficient to reach Kulgera and it would have had to land en route to be refuelled from the jerry cans in order to reach its destination.
It was reported that the pilot in the rear seat had flown the route several times and was known to refuel at locations of high visibility. He had refuelled at Aston Hill, about 15 NM north-north-west of Cadney Park on previous occasions but there was no evidence to suggest that the helicopter had landed between Coober Pedy and the accident site on this occasion.
Calculations using the known fuel quantities purchased at the previous enroute refuelling stops, indicated that the range of the helicopter with full main tanks should have been sufficient to reach Temptation Bore. The pilot may have been planning to land and refuel at Temptation Bore, which would have been visible in the near distance when the engine stopped from fuel exhaustion. The reason the engine stopped from fuel exhaustion and why the helicopter then collided heavily with the ground in a nose low attitude, with the rotor system rotating well below the speed required for a controlled descent, could not be determined.
|Date:||07 March 1999||Investigation status:||Completed|
|Time:||1000 hours CST|
|Location:||282 km NNW Coober Pedy, Aero.|
|State:||South Australia||Occurrence type:||Fuel exhaustion|
|Release date:||17 March 2000||Occurrence category:||Accident|
|Report status:||Final||Highest injury level:||Fatal|
|Aircraft manufacturer||Bell Helicopter Co|
|Type of operation||Aerial Work|
|Damage to aircraft||Destroyed|
|Departure point||Coober Pedy , SA|
|Departure time||0730 hours CST|
|Role||Class of licence||Hours on type||Hours total|