Accident Details
On July 18, 2022, at approximately 1849 central daylight time, a Bell 206B3 helicopter, registration N6BU, sustained substantial damage during an accident near Verona, Illinois. The pilot, the sole occupant, was uninjured. The helicopter was being operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight.
Pilot's Report
The pilot reported that this was not the first flight of the day. Before departure, he had about 30 gallons of fuel and 80 gallons of spray product on board. After taking off from a load truck, the pilot received a low rotor alarm and the helicopter began to sink. He performed an autorotation. During the landing, the helicopter bounced. The tailboom was severed by the main rotor blades, resulting in substantial damage.
Post-Accident Examination
A post-accident examination was conducted. 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 observed on the first stage compressor blades or compressor inlet. The inlet particle separator system was intact and not blocked. The fourth stage turbine wheel appeared normal 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 degrees (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.
Engine Testing
The engine was removed from the airframe and subsequently placed on a test stand. During testing, the engine started, idled, and accelerated as designed with no flame outs or uncommanded power fluctuations. No anomalies were observed during the examination or testing that would have precluded normal operation.