Incident Overview
On June 25, 2009, at 1815 Pacific daylight time, a Robinson R22 Beta, registration N836SH, experienced a loss of engine power during cruise flight and subsequently landed hard near Lewiston, Idaho. Lewis and Clark Aviation LLC operated the helicopter under 14 Code of Federal Regulations Part 91. The certified flight instructor (CFI) and student pilot were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the instructional flight.
Pilot Account
According to the CFI, he and the student were on the student’s first instructional flight. During cruise, the rotor rpm dropped suddenly. The CFI lowered the collective and rolled on the throttle but received no response. The rpm continued to decrease, and the oil light illuminated as the helicopter impacted the ground. He attempted a run-on landing, but the skids dug into the ground, causing the helicopter to come to rest on its side with the tail boom separated.
Carburetor Heat and Examination
In a phone conversation after the accident, the CFI reported that he had applied full carburetor heat approximately two minutes before the power loss. At the accident site, the carburetor control was found about 1 inch from its stop. It is unknown whether the control position changed during the accident sequence. The Federal Aviation Administration (FAA) accident coordinator examined the helicopter at the site and after recovery. The carburetor heat linkage was continuous and functional. The engine was test-run on the accident helicopter, and no mechanical anomalies were observed.
Weather Conditions
At 1756, the nearest aviation weather reporting facility reported a dew point of 5 degrees Celsius and a temperature of 25 degrees Celsius. According to the FAA’s icing probability chart, icing conditions existed at glide and cruise power at the time of the accident.