WEEK 34
H2F brings you the ‘helicopter mayday of the week’ with a short accident report summary. I tell you what happened. You think more about why it happened. We all learn from it. Because that’s what accident reporting is for.
TITLE
Unexpected descent and longline contact during firefighting water collection flyaway.
WHAT?
A Bell 412 conducting firefighting operations experienced an unanticipated loss of height during water collection while using a 150-ft longline and bucket. The pilot attempted to fly away, but the already submerged bucket restrained the helicopter’s movement, causing the longline to contact and damage the aft fuselage, damaging flight and engine control systems.
WHERE?
Murchison River, approximately 57 km north-east of Strahan Airport, Tasmania, Australia.
WHEN?
10 March 2025. Final report published on 6 October 2026.
HOW?
At the bottom of an approach to hover approximately 150 ft above the river, with the bucket submerged, the helicopter unexpectedly sank about 50 ft.
Flight-data analysis showed that the preceding approach was a steep, powered descent at low airspeed, creating conditions conducive to incipient vortex ring state.
On recognising the descent the pilot initially raised collective, but realised that available power would not arrest the descent. He then lowered collective and applied forward cyclic to gain airspeed in an attempted fly away. However, the bucket was already submerged. An attempt to jettison the longline failed when the protective ring guard surrounding the release button was pressed instead of the button itself. As the helicopter transitioned forward, the bucket resisted movement through the water, and the line became taut, stopping the forward transition abruptly. The longline, now under tension, contacted the underside of the aft fuselage near the cargo hook.
The pilot was able to recover to a hover approximately 30 ft above the water, and then fly backwards to empty and retrieve the bucket.
CONDITIONS?
The pick up site was a narrow section of river bordered by tall trees, restricting escape options. Initially light winds had increased in strength and changed direction.
Externally fitted cameras and extended flight steps on the helicopter restricted downward visibility of the bucket for the pilot, which encouraged steeper approach profiles.
OUTCOME?
On recovering control, the aircraft was flown back to base with the longline and bucket still attached, despite stiff tail-rotor pedals and abnormal engine indications.
Post-flight examination revealed extensive damage beneath the aft fuselage, around and behind the external cargo hook. Tail rotor controls had been damaged with control rod and supporting structures fractured. Both engine controls had been damaged at the bell crank reducing pilot control input to the engine. Other elements of the airframe and transmission components had impact damage.
WHY?
The investigation identified several interacting factors:
A steep, powered, low-speed approach created conditions conducive to incipient VRS.
The unsuccessful jettison attempt left the helicopter connected to the submerged bucket during the recovery manoeuvre.
Restricted visibility of the bucket encouraged steeper approaches, increasing the risk of the flight profiles flown.
The operator’s risk-assessment tool inadequately addressed aircraft-specific and mission-specific hazards, while weaknesses in oversight, occurrence reporting and specialist recency management reduced preventive defences.
REFERENCE?
Australian Transport Safety Bureau. (2026). Loss of control and equipment contact with water involving Bell 412EP, VH-VJF, 57 km north-east of Strahan Airport, Tasmania, on 10 March 2025 (AO-2025-013).
Note:
Accident reports selected from the following open source databases: US NTSB; UK AAIB; Flight Safety Foundation’s Aviation Safety Network; Australia’s ATSB. Ireland’s AAIU; Taiwan’s TTSB; France’s BEA; Spain’s CIAIAC. Germany’s BFU.
