CEN13FA121

The loss of engine power due to ice ingestion. Contributing to the accident was maintenance personnel’s delayed decision to install the helicopter's engine inlet cover until after the engine had been exposed to moisture and freezing temperatures and their inadequate daily preflight/airworthiness checks, which did not detect the ice formation.

The pilot reported hearing a sound like something had struck the helicopter shortly after departure while about 1,600 to 1,700 feet mean sea level. The engine lost power, and the pilot performed an autorotation to a field. While maneuvering to land, he saw a barbed wire fence obstructing the intended landing area, so he maneuvered the helicopter to clear the fence. The helicopter subsequently cleared the fence and landed hard in a field. Engine examination revealed that the four axial compressor blades exhibited significant deformation on the outboard tips of their leading edges in the direction opposite of normal rotation consistent with the ingestion of soft body foreign object debris, such as ice. A subsequent engine run did not detect any preimpact anomalies that would have precluded normal operation. For 3 days before the accident flight, the helicopter was parked outside without its engine cover installed and was exposed to light drizzle, rain, mist, and fog. The engine inlet cover was installed the day before the accident at an unknown time. The helicopter remained outside and exposed to freezing temperatures throughout the night until 2 hours before the flight. Although the helicopter was maintained in a ready status on the helipad and maintenance personnel performed daily preflight/airworthiness checks, the inlet to the first-stage of the axial compressor was not inspected to ensure that it was free of ice in accordance with the Aircraft Maintenance Manual. Based on the weather conditions that the helicopter was exposed to during the 3 days before the accident, it is likely that ice formed in the engine air inlet before the flight and that, when the pilot increased the engine power during takeoff, the accumulated ice separated from the inlet and was ingested by the engine and damaged the compressor blades.

HISTORY OF FLIGHT On January 2, 2013, about 1245 central standard time, a Eurocopter EC130 B4 helicopter, N334AM, experienced a hard landing following a loss of engine power near Seminole, Oklahoma. The commercial pilot and three crew members were seriously injured. The helicopter sustained substantial damage. The helicopter was owned and operated by Air Methods, Centennial, Colorado, under the provisions of 14 Code of Federal Regulations Part 91 as a positioning flight. Visual meteorological conditions prevailed and a company visual flight rules flight plan was filed, and activated. The flight departed from the Seminole Regional Airport (KSRE), Seminole, Oklahoma, at 1242, and was en route to a hospital in Okemah, Oklahoma. According to a statement provided by the pilot, on the morning of January 2, 2013, they received a standby call for a response to an accident scene. The pilot checked weather for the flight. He went and removed the helicopter inlet cover and the flight was requested to launch. The pilot performed a walk around inspection of the helicopter and started the helicopter normally. Shortly after takeoff, while climbing through 1,600 and 1,700 feet mean sea level (msl), the pilot heard a sound like something had struck the helicopter and the engine stopped producing power. The pilot had limited recollection of the next events but recalled that while performing an autorotation, he made a right turn to an open field. While maneuvering to land to the field he saw a previously undetected barbed wire fence. He increased the collective pitch to clear the fence, then applied aft cyclic, and increased the collective. He did not recall the landing. A crew member on board the helicopter recalled that during the climb he heard a muffled "thud" sound. The pilot notified the crew that they had lost the engine and were going down. During the descent to the field, one crew member reported the presence of power lines which the pilot acknowledged. While approaching the field, a crew member reported the presence of a fence. The pilot reported that "…that's what we've got to get over." The pilot maneuvered the helicopter over the fence and the crew member reported seeing the sky through the forward windscreen before they impacted the ground. PERSONNEL INFORMATION The pilot, age 58, held a commercial pilot certificate with ratings for airplane single engine land, helicopter, and instrument helicopter. On May 2, 2012, he was issued a second class medical certificate with the limitation that he must wear corrective lenses. His most recent flight review/Part 135 check flight was accomplished on October 24, 2012. He satisfactorily performed all the graded flight maneuvers. AIRCRAFT INFORMATION The four-seat, single engine helicopter was manufactured by Eurocopter in December 2009. It was configured for emergency medical services and powered by a 747 shaft-horse power Turbomeca Arriel 2B1 turbine engine. The last inspection was an approved helicopter inspection program inspection, which was accomplished on December 23, 2012, at a total airframe and engine time of 1,100.75 hours. The helicopter previously flew 1 hour and 14 minutes on December 30, 2012. No discrepancies were noted for the flight. A daily inspection of the helicopter was accomplished on December 31, 2012, and January 2, 2013, by an A&P mechanic. A daily inspection was not recorded for January 1, 2013. METEOROLOGICAL INFORMATION At 1235, an automated weather reporting facility located at the Shawnee Municipal Airport (KSNL), Shawnee, Oklahoma, reported wind from 280 degrees at 8 knots, visibility 10 miles, a clear sky, temperature 39° Fahrenheit (F), dew point 32° F, and a barometric pressure of 30.25 inches of mercury. When the helicopter landed on December 30, the engine inlet cover was not installed until an unknown time on January 1, 2013. A review of weather information for the accident area revealed that at 2255 on December 30, drizzle and rain began to fall and the relative humidity increased to 93%. On December 31, drizzle and rain continued to fall until 1015 when mist and fog prevailed for a majority of the day and the relative humidity remained approximately 100%. On January 1, 2013, mist and fog prevailed until about 1135 when the clouds remained overcast, temperatures decreased to 32° F, and the relative humidity ranged between 93-100%. On January 2, the day of the accident flight, temperatures stayed below freezing, relatively humidity 93% or greater, and an overcast sky until 1055. From 1055 to the time of the accident, the temperature rose to 39 degrees with a decreased relative humidity. WRECKAGE AND IMPACT INFORMATION The accident site was located in an open field about 4.8 nautical miles west-northwest of KSRE. The measureable elevation was 682 feet msl. The helicopter came to rest upright on a magnetic heading of 262 degrees. The Fenestron had separated from the helicopter and was found approximately 30 feet north of the main wreckage. Three primary ground scars near to the helicopter's final resting position were consistent with contact from the tail skid and the two landing skids. The location of the ground scars relative to the final resting position of the helicopter was consistent with a clockwise rotation of approximately 180 degrees following the initial ground impact of the landing skids and the tail skid. A barbed-wire fence was located approximately 16 feet west of the single tail skid ground scar and approximately 54 feet west of the main wreckage. All three main rotor blades remained attached to the main rotor head. The 'red' main rotor blade exhibited trailing edge separation adjacent to the blade cuff. The damage along various points on the leading edge of the 'red' main rotor blade matched that of a 45° straight-lined impact mark to the tail boom and engine exhaust duct on the right side of the helicopter. The 'blue' main rotor blade exhibited impact damage on the bottom of the blade approximately 50 inches from the blade tip end; light blue paint transfer marks were observed on some of the edges of the damaged area. The 'blue' main rotor blade also exhibited trailing edge separation along various points of the entire length of the blade. The tip of the 'blue' main rotor blade exhibited damage that was matched to damage found on the Fenestron stators. The 'yellow' main rotor blade exhibited an area of damage on its trailing edge, beginning from 51 inches from the blade tip and extending approximately 58 inches inboard. Light blue paint transfer marks were observed on the bottom side of the blade at approximately 6 inches from the tip end of the 'yellow' main rotor blade and extended inboard approximately 46 inches. Blue paint transfer marks were observed on the leading edge of the 'yellow' main rotor blade, beginning from 32 inches from the blade tip extending approximately 4 inches inboard. The helicopter was modified with an FDC/aerofilter air inlet barrier system. The air filter showed no evidence of substantial damage. No blockages or large pieces of debris were observed on either side of the air filter. The air intake duct remained attached to the engine and showed no evidence of cracks or fractures. The drain hole in the air intake duct showed no evidence of blockages. The engine remained installed on the airframe. The engine's fuel, oil, and electrical connections remained intact. The presence of fuel in the engine's hydromechanical unit (HMU) was confirmed. A sample of fuel tested negative for the presence of water. Removal of the air intake duct exposed the axial compressor (the first stage of compression). Four axial compressor blades exhibited significant deformation on the outboard tips of their leading edges; the deformation was observed to be in the direction opposite of normal rotation. Deformation observed on the four axial compressor blades was consistent with ingestion of soft body debris.