BELL 206B

Full Narrative

On July 18, 2022, about 1849 central daylight time, a Bell 206B3 helicopter, N6BU, sustained substantial damage when it was involved in an accident near Verona, Illinois. The pilot was uninjured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight.
 
The pilot reported that this was not the first flight of the day and, before departure, he had about 30 gallons of fuel and 80 gallons of spray product. After takeoff from a load truck, he received a low rotor alarm and the helicopter began to sink. He performed an autorotation and the helicopter bounced upon landing. The tailboom was severed by the main rotor blades which resulted in substantial damage.

During a postaccident examination, the engine N1 system turned freely and was continuous from the compressor to the starter generator. The engine N2 system turned and was connected to the powertrain. No foreign object damage was noted on the first stage compressor blades or compressor inlet, and the inlet particle separator system was intact and was not blocked. The fourth stage turbine wheel was normal in appearance when viewed from the exhaust collector. Linkages from the collective to the Power Turbine Governor (PTG) and from the throttle twist grip to the Fuel Control Unit (FCU) were secure. The FCU throttle input lever was rigged appropriately and contacted the minimum and maximum stops when the throttle was rotated to the cut off and fly positions respectively. The PTG rotated through about 20° (from 60 to 80 on the indicator) when the collective was moved from full down to full up. Helicopter electrical power was switched on, and no engine chip lights were noted. The fuel quantity gage indicated 30 gallons. The fuel boost pumps were individually tested, and fuel flowed freely from both.
 
The engine was removed from the airframe and subsequently placed on a test stand. The engine started, idled, and accelerated as designed during the testing with no flame outs or uncommanded power fluctuations noted. No anomalies were observed during the exam or testing that would have precluded normal operation.