History of Flight
On July 1, 2017, at about 2036 central daylight time, an Airbus Helicopters Deutschland MBB-BK 117 B-2 helicopter, registration N238BK, landed hard and rolled over during an emergency landing to a field near Perryville, Missouri. The pilot, three crew members, and a passenger received minor injuries, and the helicopter sustained substantial damage. The helicopter was owned and operated by Air Methods Corporation, doing business as Kids Flight, as a 14 Code of Federal Regulations Part 135 medical flight. Visual meteorological conditions (dusk) prevailed at the time, and a company visual flight rules flight plan was filed. The flight originated from St. Francis Medical Center (MO50), Cape Girardeau, Missouri, about 2019 and was en route to St. Louis Children's Hospital (2MU1), St. Louis, Missouri.
The pilot reported that at 1901, he was notified by the Air Methods Communication Center (AirCom) concerning a flight request. The pilot accepted the flight and after ensuring all necessary requirements were completed, the flight departed at 1922 for MO50, which was approximately 50 nautical miles (nm) to the southeast. The pilot reported that the helicopter departed with 140 gallons of fuel in the main fuel tanks. The flight arrived at MO50 about 1949. About 2015, the medical crew arrived at the helicopter pad and loaded the patient on board. About 2019, the helicopter departed for 2MU1, which was approximately 85 nm on a 338° heading. Sunset was about 2025 with the sun setting on a 300° azimuth. The pilot reported that there was 110 gallons in the main fuel tanks.
After about 15 minutes of flight, the pilot scanned the instruments and gauges, noting that all systems were in the normal range and fuel was transferring from the main tank. He reported that the fuel level indication was approximately 95 gallons in the main tanks and the supply tanks were just below the full indication, and that there were no illuminated lights on the warning/caution panel. The airspeed was 120 kts at an altitude of 1,600 ft above mean sea level—about 1,200 ft above ground level (agl).
When the flight was about 5 miles north of Perryville, the helicopter experienced a sharp change in attitude yawing to the left with a hard-upward bump, followed by a change in the engine noise. The pilot observed the N1 gauges both indicating below 40 percent and decreasing. The No. 1 engine low warning light, the No. 1 generator light, and the battery discharge warning lights were illuminated. He stated that the aircraft suddenly pitched nose up and rolled to the right, and he could hear the rotor begin to deteriorate. He entered an autorotation by applying right forward cyclic and lowering the collective to full down.
During the autorotative descent, he saw power lines and a ditch which required him to change his flight path to land on the far side of the ditch. He flared the helicopter about 100 ft agl and the rotor rpm began to decay rapidly. He attempted to level the helicopter as it began to fall through. The helicopter landed right skid low and skidded for about 100 ft. The main rotor blades hit the ground as the helicopter rolled onto its right side. Once the helicopter came to rest, he pulled the power levers to the stop position. The pilot and flight crew, with the patient on a stretcher, egressed the helicopter. The pilot observed fuel draining in a solid stream from one of the drains on the belly. He re-entered the cockpit and turned off all electrical and fuel switches to minimize the risk of fire.
Aircraft Information
The helicopter was an Airbus Helicopters Deutschland MBB-BK 117 B-2, serial number 7238, manufactured in 1991. According to helicopter records, the airframe had accumulated an aircraft total time of about 12,150 flight hours the day prior to the accident. The engines installed were S/Ns LE45662 AEF and LE45681 EFA, positioned as the No. 1 (left) and No. 2 (right) engines, respectively. The No. 1 engine had accumulated about 9,799.53 hours, about 27,502.20 generator cycles, and about 22,451.90 power turbine cycles around the time of the accident. The No. 2 engine had accumulated about 10,193.60 hours, 27,278.27 gas generator cycles, and 20,832.55 power turbine cycles. A night vision goggle compatible interior lighting system, manufactured by Ahlers Aerospace, Inc., was installed under FAA Supplemental Type Certificate (STC) No. SR09523RC. The night vision imaging system kit uses infrared filters installed externally to faces of instruments and displays to reduce or eliminate infrared glare. An infrared filter is also placed over the advisory, caution, and warning annunciator panel. STC SR09523RC does not affect the instrument lighting controls originally installed.
The helicopter fuel system comprises fuel storage, supply, and monitoring systems. The fuel storage consists of four flexible fuel tank bladders: an 80 kg fuel tank (26.3 gallons), forward main tank, left and right prime (supply) tanks (combined 25.5 gallons), and a rear main tank. The forward and aft main tanks combined hold 132.4 gallons, total usable capacity about 184.2 gallons. Two fuel prime pumps in each supply tank deliver fuel during engine start; two fuel transfer pumps in the forward main tank deliver fuel from main to supply tanks. The transfer pumps must be activated during operation; surplus fuel returns to main tanks via overflow tubes. Caution lights indicate pump status.
Wreckage and Impact
The helicopter's main fuselage was found resting on its right side in a farm field. The right skid had fractured and partially separated; the left skid tube appeared relatively intact. Dirt was visible on the underside. The aft-right loading door was opened; the aft-left remained closed. The front-left chin bubble was fractured and the wire strike protection cutter on the chin was partially separated. The tail boom and empennage had separated from the main fuselage but were located immediately adjacent, inverted. The tail rotor and gearbox remained attached; one tail rotor blade exhibited broomstrawed appearance. Three of the four main rotor blades were underneath the main fuselage with tips generally aft; the fourth blade tip pointed to the 4 o'clock direction.
The two fuel prime pump and two fuel transfer pump switches were in the off position. The two fuel shutoff valve switches were in the open position and switch guards remained closed. Position, anti-collision, and strobe light switches were on. The copilot, engine, and pilot instrument panel lighting dials were set to the bright position. After the helicopter was moved upright, the forward battery was reconnected, and the annunciator panel and master warning light were dim. When the instrument panel lighting dials were set to off, all expected lights illuminated. The fuel gauges for the No. 1 and No. 2 supply tanks indicated zero; the main fuel tank indicated about 25 gallons. Fuel was observed leaking from the bottom, attributed to fuel vent lines. The flexible fuel line to the No. 2 engine fuel filter was removed and less than one teaspoon of fuel was present.
Examination
On August 8-9, 2017, representatives from the National Transportation Safety Board (NTSB), FAA, German Federal Bureau of Aircraft Accident Investigation (BFU), Air Methods, Airbus Helicopters, and Honeywell examined the recovered wreckage. Cockpit instrument lighting testing revealed that rotating the pilot and engine instrument panel lighting dials resulted in dimming of annunciator lights and the master warning light. When dimmed, some caution lights were not visible. Both engine fuel filter bowls contained about 0.08–0.16 fluid ounces of fuel; filter elements were undamaged and clear of debris. Continuity of control linkages between cockpit and engine fuel controls was established. Rotation of power turbines for both engines resulted in movement of their input drive shafts and the main rotor; freewheeling unit functionality was confirmed. Inlet screens exhibited no evidence of blockages.
Medical and Pathological
The pilot was tested for drugs and alcohol about 16 hours after the accident; results were negative.