Accident Overview
On July 29, 2010, at 0930 eastern daylight time, a Hiller UH-12E helicopter, registration N104HH, operated by Haddock Flying Service Inc., collided with a tree during an autorotation near Holly Hill, South Carolina. The flight was an aerial application operation conducted under 14 Code of Federal Regulations Part 137. Visual meteorological conditions prevailed, and no flight plan was filed. The helicopter departed from a landing pad in Holly Hill at 0925.
Pilot Account
The pilot reported that as he approached a tree line for aerial application, his chemical supply was depleted. While turning back to reload, the engine experienced a total loss of power. Due to the low operating altitude, he initiated an immediate autorotation, during which the helicopter struck trees before coming to rest on the ground.
Wreckage Examination
A Federal Aviation Administration inspector examined the wreckage. The helicopter sustained substantial damage to the fuselage and main rotor assembly from the tree impact. Flight control continuity was confirmed from the cockpit to the tail rotor system and from the cyclic and collective controls to the main rotor head. Fuel was present in the fuel tank. The helicopter was recovered for further examination.
Engine and Maintenance Findings
Examination of the engine revealed that the combustion chamber fuel spray nozzle was clogged with carbon and soot deposits. A review of the engine maintenance logbooks indicated that the most recent 100-hour inspection had been completed 41 days prior to the accident. According to the aircraft Hobbs meter, the engine had accumulated 40 hours since that inspection. The logbooks did not document the inspection or cleaning of the fuel spray nozzle as required by the Rolls Royce 250-C20 series operation and maintenance schedule. Specifically, item 21.A of the 100-hour inspection states: "Remove, inspect and clean the fuel nozzle. If no airframe mounted fuel filter is installed, inspect the fuel nozzle filter." The manual also notes that operators may need to inspect and clean the fuel nozzle more often based on experience or operating conditions.