History of Flight
On September 23, 2017, at approximately 1028 central daylight time, a Mitsubishi MU 2B-40 airplane, registration N73MA, was destroyed when it struck terrain about 3.5 miles northeast of Ainsworth Regional Airport (ANW) in Ainsworth, Nebraska. The private pilot, who was the sole occupant, sustained fatal injuries. The aircraft was owned by private individuals and operated by the pilot under 14 CFR Part 91. Instrument meteorological conditions were present, and an instrument flight rules (IFR) flight plan had been filed but not activated. The flight was originating at the time of the accident and was en route to Bottineau Municipal Airport (D09), Bottineau, North Dakota.
According to Federal Aviation Administration (FAA) records and the pilot's cellular telephone records, the pilot contacted the Flight Service Station (FSS) in Fort Worth, Texas, around 1015 to file an IFR flight plan. He requested an altitude of 16,000 ft and declined an offer of adverse weather and route information. No other calls to FAA ATC or FSS were made before the accident. Several NOTAMs were valid for ANW, including that the hazardous inflight weather advisory service and remote communications outlets on 122.4 and 121.5 were out of service.
The ANW airport manager reported that the airplane was fueled in a hangar just before departure due to rain. He heard both engines start, sounded normal, and watched the airplane depart from runway 35 and enter clouds. Witnesses north of ANW heard an airplane flying from southwest to northeast; one described the sound as lower than usual, while another said the engines sounded "wound up really tight, full throttle, and very loud." A witness heard a "thud" attributed to a thunderstorm. The pilot's family stated he was flying to D09 to pick up a dog; the airplane was reported missing by a friend when it did not arrive around 1200. The wreckage was located about 1800. Radar data showed no primary or secondary targets consistent with the accident airplane; low altitude radar was not operational in the area.
Personnel Information
The pilot reported no chronic medical conditions or medications on his medical certificate application. He was required to wear corrective lenses for near and distant vision. His flight logbook was not found. The co-owner estimated the pilot had about 2,500 hours in the MU-2 type. On his May 9, 2016 medical application, he reported 3,775 total hours, with 64 in the previous 6 months. Records from SIMCOM Aviation Training showed he completed initial MU-2B training in 1999 and recurrent training on June 3, 2017, including an instrument proficiency check with a simulated partial panel ILS approach. At that time he estimated 2,850 hours in MU-2B airplanes.
Aircraft Information
A flight log dated September 22, 2017, found in the wreckage, showed 1,125 cycles and a hobbs of 13,850.0 hours at takeoff from Kenosha Regional Airport (ENW), Kenosha, Wisconsin, destination ANW. The airplane was equipped with a two-screen Chelton Air Data Attitude Heading Reference System (ADAHRS) display in place of standard instruments, plus an attitude indicator and turn-and-slip indicator on the pilot side, and a second attitude indicator on the copilot side.
Meteorological Information
A weather study by the NTSB indicated a low-pressure system with a stationary front south of the accident site, favorable for low cloud development. Station models showed northerly winds 5-10 knots, overcast clouds, and restricted visibility in fog/mist. Composite reflectivity at 1025 CDT showed strong cells 59-75 miles east-northeast, with no significant echoes near the accident site. Satellite imagery showed two bands of clouds with tops around 24,000 ft; low stratiform clouds covered the accident site. The 1015 CDT observation at ANW reported wind from 360° at 10 knots, visibility 1 3/4 miles in mist, overcast ceiling at 500 ft agl, temperature and dew point both 10°C, altimeter 30.02 inHg. Convective SIGMET, Center Weather Advisory, and AIRMET Sierra were indicated for the route.
Wreckage and Impact Information
The wreckage came to rest in a grazing pasture at 2,590 ft msl, with a debris path oriented on a magnetic heading of 270°. The initial impact crater was about 3 ft deep, 10 ft wide, and 8 ft long, containing torn left wing tip tank fragments. A ground scar extended 6 ft west to a second crater about 25 ft long, 20 ft wide, and 6 ft deep, containing the left engine and propeller assembly with heat/fire exposure. Two propeller blades separated; outboard 6 inches of two blades located north. The right engine was embedded at the west end of the crater. A third crater about 3 ft deep, 8 ft long, and 7 ft wide contained fragmented metal. The debris field continued 23 ft west to the main wreckage, which included flight control cables, vertical stabilizer, rudder, and left wing center section. The left main landing gear was found 12 ft north, with actuator position indicating gear retracted. The right main landing gear was with the main wreckage. Cabin seats and metal extended farther west, with the farthest component 280 ft southwest. The right elevator and flap separated. Control cables were broken in multiple locations; continuity could not be confirmed. Flaps were set at zero. Fragmentation limited examination, but no preimpact failures were observed.
Additional Information
The Chelton ADAHRS was installed in 2008 per STC SA02203AK. On a flight the Wednesday before the accident, the pilot mentioned a "transient flag" on the ADAHRS to the co-owner and planned to have it checked. No avionics work was done immediately before the accident. A voice mail from the pilot to May Day Avionics on September 21 referenced a transient flag related to ADAHRS, but the manager did not speak with the pilot and could not provide details. The Chelton manual lists six ADAHRS failure modes; without details, the impact on displayed information could not be determined. It is unknown if the pilot had an issue with the system at the time of the accident. The ADAHRS was fragmented and could not be tested.
Wreckage examination showed both engines exhibited extensive impact damage with rotational scoring and blade separation. Accessories were impact damaged and could not be tested. Both propeller assemblies separated at the flange, with three of four blades separated each; blades were bowed, twisted, and showed chordwise scoring, leading edge polishing, and gouges. Damage was consistent with ground impact while engines were producing power. No anomalies were noted that would have precluded normal operations.
Medical and Pathological Information
An autopsy performed on September 26, 2017, by the Nebraska Institute of Forensic Sciences concluded the cause of death was multiple blunt force trauma, with no evidence of recent medical intervention or natural disease hazardous to flight safety. Toxicological tests by the FAA were negative for tested drugs. Liver ethanol was 12 mg/dL but no ethanol in muscle tissue; ethanol may be produced postmortem.