What happened
On 28 June 2025, a Bell Helicopter 47G-5 was conducting a ferry flight from Clare Valley Aerodrome, South Australia to Sydney, New South Wales. The pilot and passenger departed Clare Valley at about 0900 local time for an intended fuel stop at Renmark Airport, South Australia.
At about 0950, while in cruise flight at about 800 ft above ground level, the pilot felt a ‘couple of small kicks’ (in yaw[1]) and a ‘small shake’ alerting them to a problem. The pilot started to reduce power and altitude and scan the instruments and recalled that the carburettor[2] air temperature indicated the highest temperature on the gauge, although no carburettor heat was being applied. The engine then subsequently failed and the pilot conducted an autorotation[3] into a nearby field.
A run-on landing was conducted with forward speed, before the starboard side skid gear collapsed, causing the cabin to dig into the dirt whereby the helicopter tipped nose forward. As a result, the windscreen bubble ruptured, the advancing blade then struck the ground and severed the tail boom, with the helicopter coming to rest in an upright position, but substantially damaged (Figure 1).
Source: Operator
The pilot reported securing the cabin, switching the magnetos[4] and battery off and shutting off fuel (closing the fuel cut-off value). On exiting, the starter motor was smoking, the starter vibrator was buzzing, and the battery relay was chattering. The pilot then disconnected the battery which de-energised the starter system.
No injuries were reported by pilot or passenger.
Engineering inspection
Prior to the aircraft being recovered, engineers confirmed that the battery relay was energising, and the starter vibrator was also receiving power with the master switch in the OFF position when the battery was connected.
A subsequent engineering assessment detected heat damage in the main canon plug connector (connecting the cabin wiring loom with the airframe wiring loom) under the cabin floor, and heat damage in the wiring.
The assessment determined that corrosion in the plug wiring pins (Figure 2) has likely caused resistance to electrical current, and heat build-up. This likely resulted in several wires melting and creating a short circuit for the battery relay, starter vibrator, and instrument cluster.
The operator reported that the short circuit energised the starter vibrator and provided grounding to the magnetos which affected engine operation.
Figure 2: Corrosion in the plug wiring pins
Source: Iconic Helicopters Maintenance Pty Ltd
Safety message
Precise positioning and energy maintenance is required for a successful autorotation landing. Autorotation is a high-risk skill requiring the pilot to descend the helicopter by lowering the collective lever so that the resultant airflow provides the driving force to turn the blades. Thorough and regular training in emergency procedures is crucial for all pilots.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
[1] The motion of an aircraft about its vertical or normal axis.
[2] Device for continuously supplying the engine with optimum combustible mixture.
[3] Autorotation is a condition of descending flight where, following engine failure or deliberate disengagement, the rotor blades are driven solely by aerodynamic forces resulting from rate of descent airflow through the rotor. The rate of descent is determined mainly by airspeed.
[4] A type of electric generator using permanent magnets to supply an electric current for engine ignition.