N146DU

HISTORY OF FLIGHTOn September 8, 2017, about 1120 eastern daylight time, an Airbus (formerly Eurocopter) Deutschland GmbH MBB BK117 C-2 helicopter, N146DU, powered by two Safran Helicopter (SafranHE) Arriel 1 E2 turboshaft engines, was destroyed when it was involved in an accident near Hertford, North Carolina. The commercial pilot, two flight nurses, and one patient were fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 135 air ambulance flight.

According to Air Methods Corporation (AMC), the operator of the flight, the pilot and both medical crewmembers departed at 0827 on the morning of the flight from their base at Johnston Regional Airport (JNX), Smithfield, North Carolina, for Elizabeth City Regional Airport (ECG), Elizabeth City, North Carolina, for refueling. The helicopter arrived at ECG about 0924 and departed for Sentara Albemarle Medical Center Heliport (NC98) in Elizabeth City about 1011. The helicopter arrived at NC98 about 1022, after which the patient was boarded onto the helicopter. About 1108, the pilot radioed the Duke Life Flight operations center and advised that that the helicopter was departing for Duke University North Heliport (NC92), which was 130 nautical miles (nm) away, with 2 hours of fuel and four people aboard. There were no further communications from the helicopter.

GPS tracking data transmitted from the helicopter every 60 seconds showed that it departed NC98 to the northwest, climbed to a GPS altitude of about 1,000 ft mean sea level (msl), and turned west. The helicopter then climbed to a GPS altitude of about 2,500 ft msl and continued on a westerly track at a groundspeed of about 120 knots. About 8 minutes after takeoff, the helicopter began a turn toward the south. When the transmitted data ended about 1 minute later, the helicopter was traveling on a southeasterly track at a GPS altitude of about 1,200 ft msl and a groundspeed of 75 knots. The helicopter wreckage was located about 15 nm west of ECG.

Several witnesses reported observing smoke trailing behind the helicopter while it was in flight. Some of these witnesses described the smoke as "heavy" and "dark," and others reported the color as "black," "dark blue," and "blue." One witness reported that the smoke was coming from under the rotor. Another witness reported that smoke was trailing about 20 ft behind the helicopter in “one single wide streak…like a truck would leave when it is burning oil, blue, not black”. One witness reported that the helicopter appeared to be "hovering" at an altitude of about 300 ft (based on its height relative to a nearby windmill) just before it descended straight down. Another witness reported hearing a "popping noise" and observing the helicopter turning left and right and then descending quickly. This witness further reported that the helicopter appeared "in control" with the rotors turning before he lost sight of it.

PERSONNEL INFORMATIONThe pilot had been employed with AMC since August 2009. He was the lead pilot and the safety officer at AMC’s JNX base and an AMC maintenance test pilot in the BK117 C2 helicopter. He was also current and qualified on the twin-engine Airbus EC135 helicopter, in which he had accrued 1,100 hours of total flight experience. Before his employment with AMC, the pilot flew twin-engine Sikorsky UH-60 helicopters for the US Army, accruing about 2,300 flight hours, and the EC135 helicopter for another helicopter air ambulance provider.

AMC training records indicated that the pilot had completed all required training with no deficiencies. During the pilot’s most recent recurrent training and checkride for the BK117 C2, the pilot performed one-engine-inoperative (OEI) flight procedures and a simulated OEI landing. Recurrent training typically included autorotations, which were practiced to a power recovery at a 3-ft hover, but no autorotations were specifically documented in the pilot’s recurrent training records. At the time of the accident, AMC did not have a BK117 C2 simulator training program, which would allow for practice autorotations to touchdown. According to his training records, the pilot was familiar and current with the indications associated with autorotation and OEI conditions as well as for the behavior of the aircraft. (AMC had been developing a BK117 C2 simulator training program at the time of the accident, which was subsequently implemented). Simulated OEI landings were performed in the aircraft by utilizing power limits representative of OEI performance. Engine fire light procedures were discussed during the training and were the subject of oral questions during the checkride.

The pilot’s most recent EC135 simulator training included OEI recoveries, OEI landings, and engine fire light procedures. The indications and procedures in the EC135 are similar to what is seen and performed in the EC145.

The pilot's work schedule included 12-hour workdays from 0800 to 2000, with a 6-days-on/6-days-off format. The accident occurred on the third flight leg of the second day of the pilot’s work schedule.

According to his wife, the pilot had no issues with his sleep during the 3 days preceding the accident. He was in good health and was not taking any medications. She further reported that he was happy with his life and did not have any major life stressors. The pilot was not employed outside of AMC, enjoyed his job with the company, and had not mentioned any concerns about the company or its helicopters.

The pilot's coworkers and managers provided positive feedback about his performance. He was described as professional, well prepared, thorough, and team oriented, and he exhibited good pilot skills.

AIRCRAFT INFORMATIONMaintenance

The helicopter was maintained by the operator using a Federal Aviation Administration (FAA) Approved Aircraft Inspection Program. According to AMC maintenance records, the helicopter’s most recent 30-hour engine inspection was completed on August 15, 2017. At that time, the helicopter and both engines had accrued a total of 2,673 hours. Several routine maintenance and inspection tasks were completed on both engines during a ten-day period prior to the accident which include such items as engine power assurance checks, compressor wash, and zonal inspections; no unusual finds were reported. The most recent daily inspection occurred on the morning of the accident at which time, the helicopter and engines had accrued a total of about 2,714 hours.

According to AMC, in addition to scheduled inspections, a daily airworthiness check of the helicopter was performed by a mechanic. A review of all engine and engine indication related maintenance records for the 6 months preceding the accident revealed no discrepancies.

AMC’s maintenance program specified the time between overhaul (TBO) for different engine components; the engine was normally not overhauled completely at one time. The TBO for the gas generator section was every 3,600 hours; the gas generator sections for the accident engines were not due to be overhauled for another 886 hours. Review of the maintenance records for the last 9 months prior to the accident revealed that AMC conducted multiple routine and scheduled gas generator oil system tasks which included rear bearing lubrication inspections, oil line inspections, and electric magnetic plugs inspections with no anomies reported. The engine manufacturer's specification for an engine oil change was every 800 hours. Maintenance records indicated that the operator replaced the engine oil at least every 300 hours. In addition, the Fuel Control Units (FCU) of both engines were last checked in mid-August with no anomalies reported.

In the period February 22nd, 2017 through March 31, 2017 (at 2,406 hours), both engines were removed from the airframe during a major helicopter maintenance.

On May 22nd, 2017 (at 2,521 hours), a flight crew reported an electrical burning smell in the cabin. Maintenance troubleshooting did not reveal any discrepancies.

Engine Procedures

Each engine was equipped with four chip detectors, two of which were electric, to alert the pilot with a cockpit indication (ENG CHIP) when a metal particle is detected in the engine oil. One of the electric detectors was positioned in a strainer downstream of the rear bearing housing. The cockpit indication for a chip detection is a master caution light, an audible gong, and an amber caution message on the caution and advisory display panel showing the chip detection and the engine that was affected. The helicopter was optionally equipped with a pulse chip detector, or “fuzz burn” system. This system can clear small insignificant debris from the chip detector contacts by applying an electrical current to the detector to ‘burn’ the debris. According to the BK117 C-2 Flight Manual (FLM), with this system installed, the first procedure after receiving an ENG CHIP indication, is to depress the FUZZ BURN switch for 1 second, and monitor engine parameters. If the ENG CHIP indication extinguishes, no further action is required. If the ENG CHIP indication occurs again later in flight, the fuzz burn system may be activated a second time. If the ENG CHIP indication does not extinguish, the emergency procedures included two options for resolving the issue: either (1) perform a single-engine emergency shutdown or (2) reduce the affected engine slowly to idle power, and monitor indications. The FLM indicated that the second option would enable a pilot to use the affected engine for landing, as long as engine parameters remained within limits. A decision for this option requires the pilot to continuously monitor engine parameters N1 (gas generator speed), TOT (turbine outlet temperature), TRQ (engine torque), oil pressure and temperature, and be prepared for immediate engine shutdown.

According to the Airbus Helicopters training content and the FLM, emergency procedures in bold face with a grey background are generally me...