HESLO Long Line SNAFU (Soloy Helicopters AS350B3 N589SH)
On 20 August 2025, Airbus AS350B3 N589SH of Soloy Helicopters suffered an accident during a helicopter external sling load operations (HESLO) near Skwentna, Alaska.
Wreckage of Soloy Helicopters Airbus AS350B3 N589SH (Credit: Operator via NTSB)
The US National Transportation Safety Board (NTSB) issued their safety investigation report on 23 October 2025.
The Accident
The helicopter was operating under FAA Part 133 regulations. The tasking was to deliver drilling equipment to a remote mining exploration site in mountainous terrain. The pilot had a total of 15,500 flying hours, 9900 on type.
According to the operator’s accident report form:
Pilot was told to land so a couple of drillers could get picked up and be moved after putting down the load.
The drillers had prepared a flat pad of rocks for the helicopter to land next to the drill, this allows for crew change near the pad.
After landing the pilot had gone…
…to ground idle and locked the controls so he could get out and roll the [Kevlar] longline up… [The] drillers were still over on the drill pad so was staying clear till pilot was ready for them.
[The] pilot was rolling the line up into the helicopter when it got stuck on a rock as it was very rocky off the pad.
Our regular readers will be anticipating what happened when the pilot pulled to free it:
…it released hard off a sharp rock and flipped up in the [main rotor] blades.
The main gearbox and main rotor system were ripped from the helicopter by the ensuing out of balance forces.
Detached Main Rotor and MGB of Soloy Helicopters Airbus AS350B3 N589SH (Credit: Operator via NTSB)
Operator’s Safety Recommendations
In the accident report form the operator sates that:
We have issued an Ops Directive for the company after discussions restricting pilots and passengers from rolling up lines or hose or work under the rotor system while the blades are turning. They must remain clear of the rotor disc while doing these actions.
No mention is made of risk assessment.
Safety Resources
You may find these Aerossurance articles of interest:
Snagged Sling Line Pulled into Main Rotor During HESLO Shutdown
Be Careful If You Step Outside!: Unoccupied Rotors Running AS350 Takes Off
AS350B3 Dynamic Rollover When Headset Cord Snags Unguarded Collective
Brazilian Helideck Rollover After Precautionary Landing
HESLO Dynamic Rollover in Alaska
The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn.
On error management, also see:
…and our review of The Field Guide to Understanding Human Error by Sidney Dekker presented to the Royal Aeronautical Society (RAeS): The Field Guide to Understanding Human Error – A Review
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