SEA04LA146

The helicopter was conducting corn pollination operations. The pilot reported that he experienced an engine failure while executing a turn to reverse direction. He further reported that there was a loss of main rotor RPM, and although the pilot attempted to increase rotor RPM by lowering the collective and rolling the throttle "into the overtravel spring," he was unsuccessful in recovering from the low RPM condition. The helicopter landed hard, and the main rotor blades severed the helicopter's tail boom. Initial examination of the engine revealed low compression readings on the cylinders. Partial disassembly of the engine indicated that the low compression was due to loose carbon deposits found on the seating surface of the valves and seats. The carbon was most likely knocked loose during the impact. No other anomalies were noted during the engine examination, and no signatures or conditions were observed consistent with any pre-mishap mechanical malfunction. The reason for the loss of engine power was not determined.

On July 26, 2004, approximately 0900 mountain daylight time, a Schweizer 269C helicopter, N62126, sustained substantial damage when it landed hard following a loss of engine power while conducting corn pollination operations near Homedale, Idaho. The commercial pilot was not injured. The helicopter was being operated by Silverhawk Aviation LLC of Caldwell, Idaho, under the provisions of Title 14, CFR Part 91 when the accident occurred. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed from the Caldwell Industrial Airport approximately 0900.

The pilot reported that he experienced an engine failure while executing a turn to reverse direction. He further reported that there was a loss of main rotor RPM, and although the pilot attempted to increase rotor RPM by lowering the collective and rolling the throttle "into the overtravel spring," he was unsuccessful in recovering from the low RPM condition. According to the pilot, he set up to land and was able to "land and keep it on the skids. However due to the drooped condition, the aircraft was destroyed." An FAA inspector, who traveled to the accident site, reported that the main rotor blades had contacted and severed the helicopter's tail boom.

According to the operator, the Lycoming HIO-360-D1A engine had accumulated 810.1 hours since major overhaul and 55.9 hours since its most recent 100 hour inspection on July 13, 2004.

The operator recovered the helicopter to their facility in Caldwell, where the engine was examined under the supervision of an FAA inspector. The examination revealed low compression readings on all four cylinders. Two cylinders indicated 10/80 pounds, one indicated 25/80 pounds, and one indicated 30/80 pounds during a differential compression test. The FAA inspector did not note any other discrepancies with the engine during the examination.

At the request of the NTSB investigator-in-charge (IIC), the operator removed the engine from the helicopter. On September 9, 2004, under the supervision of an NTSB investigator, the engine was partially disassembled in order to determine the reason for the low compression readings on the cylinders. The disassembly revealed loose carbon deposits on the seating surface of the valves and seats. No other anomalies were noted during the examination, and no signatures or conditions were observed consistent with any pre-mishap mechanical malfunction.

On October 20, 2004, under the supervision of the NTSB IIC, the fuel injection servo was bench tested and partially disassembled at the facilities of Precision Airmotive Corporation in Marysville, Washington. No discrepancies that would have contributed to a loss of engine power were found.