N102SHBell 47G-4A · 1971

The aerial application helicopter had completed applying liquid chemical to a corn field and the hopper was empty. The pilot was flying the helicopter back to the loading truck at approximately 100 ft agl and 60 mph when a total loss of engine power occurred. The pilot performed an autorotation to a flat alfalfa field, the helicopter landed hard, the right side skid collapsed, and the helicopter came to rest upright. During the hard landing, the main rotor blades severed the tail boom. The pilot was able to egress from the helicopter without further incident.

After the accident, about 5 total gallons of Jet A fuel were found in the two saddle-type fuel tanks, that are located above the turboshaft engine. There was no fuel leak due to the accident sequence. The pilot reported the helicopter was last fueled about 1 hour and 35 minutes before the accident occurred and about 30 gallons of fuel was added. For the most recent takeoff prior to the accident, the pilot reported that the cockpit fuel gauge was indicating between 8 to 18 gallons of fuel onboard.

The helicopter sustained substantial damage to the main rotor system, the tail boom, and the tail rotor system. The pilot reported there were no preimpact mechanical malfunctions or failures with the airframe or the engine that would have precluded normal operation.

The make and model of helicopter has a fuel capacity of 61.6 gallons of which 57.5 gallons of fuel is useable, and 4.1 gallons of fuel are unusable. The fuel delivery port or tube on both saddle-type fuel tanks is located at the aft, lower end of each fuel tank, and both fuel tanks deliver fuel to the engine simultaneously. There is no pilot-controlled fuel selector valve located in the cockpit. A pitch attitude change such as a banking turn or a nose-down attitude, would likely cause a disruption in fuel flow to the engine with the low fuel levels that were found in the fuel tanks, resulting in fuel starvation.