What happened
On January 2, 2013, a Eurocopter EC1ly30 B4 helicopter, registration N334AM, departed from Seminole Regional Airport (KSRE) in Oklahoma, en route to Okemah. Shortly after takeoff, while climbing through approximately 1,600 to 1,700 feet mean sea level, the pilot heard an impact sound and the engine stopped producing power.
The pilot initiated an autorotation toward an open field. During the descent, the crew identified power lines and a previously undetected barbed-wire fence obstructing the landing area. The pilot maneuvered the aircraft to clear the fence, which resulted in a hard landing. The accident resulted in 4 serious injuries and no fatalities. The helicopter sustained substantial damage.
The investigation
Investigators examined the engine and found that four axial compressor blades exhibited significant deformation on the outboard tips of their leading edges. The direction of the deformation was opposite to normal rotation, which was consistent with the ingestion of soft body debris, such as ice.
Weather records indicated that for the three days preceding the accident, the aircraft was exposed to drizzle, rain, mist, and fog. While the engine inlet cover had been installed the day before the flight, the aircraft had been parked outside in freezing temperatures. Examination of the engine air intake duct showed no blockages or large debris, and the air filter was undamaged. An engine run conducted on a test stand later produced a distinct whining noise at idle, consistent with the damage found on the compressor blades.