N193MHughes 369HS · 1969

The private pilot said the helicopter's turbine engine lost power after flying through an area of moderate to heavy snow. The pilot entered an autorotaion and landed in a field with excessive aft cyclic, which caused the main rotor blades to flex down and sever the tail boom. Weather reported in the area included snow, freezing fog, with a temperature of 16 degrees Fahrenheit. The helicopter was equipped with an automatic engine re-ignition and engine failure warning system, which was required per the rotorcraft flight manual (RFM) for operation in falling or blowing snow. The pilot said this system was armed at the time of the engine failure and the engine-out warning light illuminated before the power loss along with an audible tone. The RFM also stated that flight into known icing conditions was prohibited and fuel had to meet anti-icing capability of JP-4 when operating at 40 degrees or less. A review of fueling records revealed no anti-icing additive was added to the fuel. Examination of the engine found no mechanical anomalies.