Accident Summary
On June 14, 2020, about 2030 central daylight time, a Bell 47G helicopter, registration N473TT, was substantially damaged during a forced landing near Burnett Heliport (59TN) in Atoka, Tennessee. The pilot and two passengers were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Pilot Report
The pilot reported that he was providing short, nonrevenue passenger flights, each lasting 7 to 8 minutes. He had completed eight uneventful flights. Before the eighth flight, he added 20 gallons of fuel (10 gallons to each tank), bringing the total to about 39 gallons. During the ninth flight, while the helicopter was about 1.5 miles north of 59TN and descending through 900 ft mean sea level, the engine lost all power. The pilot executed an autorotation to a field. During touchdown, the main rotor blade struck the tailboom, severing the aft 20 inches of the tailboom, including the tail rotor, from the airframe.
Postaccident Examination
Postaccident examination revealed that the helicopter came to rest upright in the field. All major components were accounted for. The engine showed no evidence of a preimpact malfunction. The crankshaft was rotated using a tool inserted in the pump drive pad after removing the hydraulic pump. Continuity of the crankshaft, camshaft, and valve train was confirmed. Borescope inspection of the cylinders found no anomalies. Both magnetos rotated normally with timing within limits. All ignition leads and spark plugs appeared functional. The air filter and induction system showed no obstruction. The throttle had a normal operating range.
Fuel System Examination
The fuel line to the carburetor appeared collapsed; after disconnecting, about 4 ounces of fuel drained from the system. Borescope inspection of the fuel line showed no light passing through, but when the borescope was pushed through, no contaminants were found. Both left and right fuel tanks tested normal for 100LL fuel with no contamination. Fuel from the support truck's supply system was uncontaminated. The fuel line was subsequently examined by the National Transportation Safety Board's Materials Laboratory. No blockages were observed; the interior of the hose appeared undamaged and intact; no evidence of kinks, creases, or material creep was found on the exterior.