CEN13LA158

The pilot reported a total loss of engine power that occurred while flying at 50 miles per hour, at an altitude of about 200 feet above ground level during a wildlife survey. He stated that there were no unusual noises or warnings before the loss of engine power and that the engine spooled down just as if he were shutting the engine down. During the autorotation the helicopter lost rotor rpm, resulting in a hard touchdown. The main rotor blades partially severed the tail boom, and the helicopter rolled over on its left side. A postaccident examination of the airframe and engine did not reveal any anomalies that would have caused the loss of engine power. With the exception of a momentary power surge, the engine operated normally during an engine run. Both centrifugal fuel pumps were tested, and one was subsequently torn down; no anomalies with the fuel pumps were discovered that would have precluded normal operation.

On February 11, 2013, at 1030 mountain standard time, a Bell 206BIII helicopter, N360AW, experienced a loss of engine power followed by a hard landing near Ponderosa, New Mexico. The commercial pilot and two passengers were not injured. The helicopter was substantially damaged. The helicopter was registered to Aerowest Helicopter Services and was being operated under contract for the New Mexico Department of Game and Fish as a 14 Code of Federal Regulations Part 91 aerial observation flight. Visual meteorological conditions prevailed for the flight, which was not operating on a flight plan. The local flight originated in Ponderosa, New Mexico, about 0920. The pilot reported they were conducting a game survey at the time of the accident. He stated that a total loss of engine power occurred while flying at 50 miles per hour, at an altitude of about 200 feet. He stated there were no unusual noises or warnings prior to the loss of engine power, and that the engine spooled down just as if he was shutting the engine down. The pilot landed the helicopter in a small clearing in the trees. During the autorotation the helicopter lost rotor rpm resulting in a hard touchdown. The main rotor blades partially severed the tail boom and the helicopter rolled over on its left side. The wreckage was air lifted from the accident site and transported to Phoenix, Arizona, where it was examined on March 19, 2013. The left front portion of the fuselage was crushed. The tailboom and main rotor blades had been removed from the helicopter during the recovery. One main rotor blade was undamaged and the other was fractured mid-span. The tail rotor blades remained connected to the tail rotor gearbox. One tail rotor blade was not damaged and the other sustained trailing edge damage. The tail rotor drive shaft was fractured as a result of contact with the main rotor blade during the landing. The engine remained mounted to the airframe. The drive shaft was not connected to the main transmission and the splined coupling was pulled apart. The airframe adjacent to the output shaft splines was gouged. Rotational scoring was visible on the drive shaft and in the shaft tunnel area consistent with shaft rotation at impact. The power train continuity was verified from the fourth stage turbine wheel to the drive shaft. The engine oil tank was intact and the reservoir was full of oil. The oil scavenge filter element bypass button was not extended. The oil cooler and lines were undamaged. The aircraft fuel filter bowl was free of debris and the filter was clean. Fuel was present in the airframe fuel filter, the filter bowl, the engine mounted filter, and fuel line to the firewall check valve. No external damage was noted on the engine. Control continuity was established from the throttle twist grip to the engine fuel control and from the collective to the power turbine generator. The throttle was set between the "fly" and "idle" positions. All external lines and hoses were connected andthe compressor system was intact from the compressor to the starter generator fan. The helicopter was powered by a Rolls-Royce N250-C20B gas turbine engine, serial number CAE 830849. The engine was removed from the helicopter and transported to the Aeromaritime facility in Mesa, Arizona. A pneumatic leak check was performed on the engine and no anomalies were noted. The engine was installed on a test stand and was tested in accordance with the M250-C20 Series Overall Test Procedures. The engine started normally. During the acceleration testing from ground idle to 100 percent speed, the engine surged momentarily, but continued to operate. Both of the Parker Hannifan Centrifugal Fuel Pumps, part number 2C27-10, were removed from the helicopter and sent to Parker Hannifin for examination under the supervision of the Federal Aviation Administration Flight Standards District Office, in Cleveland, Ohio. The discharge check valves that were attached to the pumps were left in place for the initial testing due to concern that their removal would damage the pumps. According to Parker Hannifan, tests with the discharge check valves in place would result in some reduction in the discharge pressure to the pressure drop through the check valve. One fuel pump, serial number 4AM260, met the minimum test requirements when tested. The second fuel pump, serial number 5AE263, was tested three times and it did not meet the test requirements. The first two tests were conducted with the discharge check valve in place. During these tests the pump produced a pressure 0.03 pounds per square inch (psi) below the minimum pressure requirement of 450 pounds per hour (PPH). The check valve was removed for the third test, and the pump produced a fuel pressure 2.2 psi above the minimum required. In addition, the pump exceeded the maximum current level during all three tests by 0.7 to 0.9 amps. Pump, serial number 5AE263 was disassembled. Metallic debris was observed outlining the magnets on the inside of the field tube. Non-metallic debris was observed in the bottom exterior of the field tube. The pump motor was opened for examination. The lower brush card contained debris. The inlet seal and impeller were worn on their interface. The magnetic ends inside the field tube contained metallic debris. The anomalies found would not have prevented operation of the pump. No anomalies were identified in either the aircraft or engine examinations, or during the engine test run which would have resulted in the loss of engine power.