CEN17FA362

The pilot's loss of airplane control due to spatial disorientation.

The instrument-rated private pilot departed on a cross-country flight in instrument meteorological conditions (IMC) with an overcast cloud layer at 500 ft above ground level (agl) and visibility restricted to 1 ¾ miles in mist, without receiving an instrument clearance or opening his filed instrument flight rules flight plan. There was an outage of the ground communications system at the airport and there was no evidence that the pilot attempted to open his flight plan via his cellular telephone. In addition, there was a low-level outage of the radar services in the vicinity of the accident site and investigators were unable to determine the airplane's route of flight before impact. The airport manager observed the accident airplane depart from runway 35 and enter the clouds. Witnesses located to the north of the accident site did not see the airplane but reported hearing an airplane depart about the time of the accident. One witness reported hearing a low-flying airplane and commented that the engines sounded as if they were operating at full power. The witness heard a thud as he was walking into his home but attributed it to a thunderstorm in the area. The airplane impacted a field about 3.5 miles to the northeast of the departure end of the runway and off the track for the intended route of flight. The airplane was massively fragmented during the impact and debris was scattered for about 300 ft. The damage to the airplane and ground scars at the accident site were consistent with the airplane impacting in a left wing low, nose low attitude with relatively high energy. A postaccident examination of the engines and propeller assemblies did not reveal any preimpact anomalies that would have precluded normal operation. Signatures were consistent with both engines producing power and both propellers developing thrust at the time of impact. While the massive fragmentation precluded functional testing of the equipment, there was no damage or failure that suggested preimpact anomalies with the airframe or flight controls. Several days before the accident flight, the pilot encountered a "transient flag" on the air data attitude heading reference system. The pilot reported the flag to both the co-owner of the airplane and an avionics shop; however, exact details of the flag are not known. The unit was destroyed by impact forces and could not be functionally tested. If the flag affecting the display of attitude information had occurred with the unit after takeoff, the instrument panel had adequate stand-by instrumentation from which the pilot could have continued the flight. It is not known if this unit failed during the takeoff and investigators were unable to determine what role, if any, this transient issue may have played in the accident. Based upon the reported weather conditions, the location of the wreckage, and the attitude of the airplane at the time of impact with the ground, it is likely that the pilot experienced spatial disorientation shortly after takeoff which resulted in a loss of control and descent into terrain.

The Nebraska Institute of Forensic Sciences, Inc. performed the autopsy on the pilot on September 26, 2017, as authorized by Brown County Nebraska. The autopsy concluded that the cause of death was "multiple blunt force trauma," and the report listed the specific injuries. There was no evidence of recent medical intervention or natural disease that could pose a hazard to flight safety. The FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological tests on specimens that were collected during the pilot's autopsy. Carbon monoxide and cyanide tests were not performed. Results were negative for tested drugs. Testing of the liver revealed 12 mg/dL ethanol; however, no ethanol was detected in the muscle tissue. When ethanol is ingested, it is quickly distributed throughout the body's tissues and fluids fairly uniformly. Ethanol may also be produced in the body after death by microbial activity. A weather study was conducted by the National Transportation Safety Board in support of this accident investigation and the detailed weather study is available in the public docket. The National Weather Service Surface (NWS) Surface Analysis Chart for 1000 CDT depicted a low-pressure system and an associated stationary front south of the accident site, with the accident site in an area of favorable overrunning conditions for low cloud development. The station models in the vicinity of the accident site, north of the front, indicated northerly winds of 5 to 10 knots, overcast cloud cover, and restricted visibility in fog or mist. A review of the NWS Composite Reflectivity image taken at 1025 CDT depicted several strong to intense cells between 59 and 75 miles to the east-northeast of ANW and the accident site with no significant echoes in the immediate vicinity of the accident site. The Geostationary Operational Environmental Satellite depicted two bands of clouds with a radiative cloud top temperature consistent with 24,000 ft; the bands were on either side of the accident site. Low stratiform clouds were over the accident site. The ANW weather observation taken at 1015 CDT reported wind from 360° at 10 knots, visibility 1 3/4 miles in mist, ceiling overcast at 500 ft agl. Temperature 10° Celsius (C), dew point temperature 10 C, and altimeter 30.02 inches of mercury. Similar conditions continued to be reported. A Convective SIGMET for an area of embedded thunderstorms, a Center Weather Advisory for an area of heavy rain showers, and AIRMET Sierra for an extensive area of IFR conditions, were indicated for the route of flight. At the time of medical certificate application, the pilot reported no chronic medical conditions and no medications. The pilot was issued a medical certificate that contained the limitation "must wear corrective lenses for near and distant vision." The pilot's flight logbook was not located during the investigation. The co-owner of the airplane stated that he had co-owned several MU-2 airplanes with the pilot since 2000, and he estimated that the pilot had logged 2,500 hours in the make and model of the accident airplane. According to the pilot's application for medical certificate, dated May 9, 2016, he estimated his total pilot time was 3,775 hours; 64 of which were logged in the previous 6 months. According to records provided by SIMCOM Aviation Training, the pilot had completed initial Mitsubishi MU-2B training at Flight Safety in 1999. The pilot's most recent recurrent training was completed on June 3, 2017, at SIMCOM. The pilot also successfully completed an instrument proficiency check at that time. The instrument training included a simulated partial panel instrument landing system (ILS) approach. At the time of the most recent recurrent course, the pilot estimated his time on the prerequisite form as 2,850 hours in MU-2B airplanes. The wreckage came to rest in a grazing pasture vegetated with tall grass. The accident site was at an elevation of 2,590 ft msl, and the debris and wreckage path were oriented on a magnetic heading of 270°. Torn and fragmented remains of the left wing tip tank were located in the initial impact crater. The crater was about 3 ft deep, 10 ft wide, and 8 ft long. A long narrow ground scar extended from the initial impact crater west 6 ft to a second crater. The scar was about 3 ft at its widest point and about 1 ft deep. The second crater was about 25 ft long, 20 ft at its widest point, and 6 ft deep. The second crater contained the left engine and left propeller assembly. The assembly exhibited signatures consistent with exposure to heat and fire. Two propeller blades separated from the propeller assembly and were embedded in the crater. The outboard 6 inches of two blades separated and were located north of the crater. The crater also contained torn and fragmented metal consistent with the left wing and fuselage, engine tubing and components, and the counter weight for the left horizontal stabilizer. The right engine was located at the west end of the crater and was embedded in the ground. A ground scar extended 6 ft west to a third crater. The crater was about 3 ft deep, 8 ft long, and 7 ft at its widest point. The crater contained fragmented metal, tubing, and components. The debris field continued from the third crater west about 23 ft to the main piece of wreckage. The left main landing gear assembly was located 12 ft north of the main wreckage. The landing gear actuator position was consistent with the landing gear being retracted. The right main landing gear was with the main wreckage. The main wreckage included flight control cables, electrical wiring, tubing, the vertical stabilizer, rudder, and center and left side of the wing. Cabin seats, electrical wiring cables, and torn and fragmented metal extended farther west from the main wreckage. The farthest component was located about 280 ft southwest of the wreckage on the adjacent dirt farm road. The right elevator separated and was located 4 ft west of the main piece of wreckage. The right flap was separated and located about 10 ft farther west. The control cables were broken in multiple locations and continuity could not be confirmed. Separated cable ends illustrated broomstraw signatures consistent with overload separation due to impact forces. The fuselage was fragmented. The wing flaps were set at zero based upon the actuator position and was consistent with damage signatures on the cockpit flap selector. The scope of the examination was limited by fragmentation due to impact damage; however, no anomalies consistent with a preimpact failure or malfunction were observed. A flight log for the accident airplane, located in the wreckage and dated September 22, 2017, showed the airplane cycles at 1,125, and the hobbs at takeoff as 13,850.0 hours. The hobbs landing and flight time fields were not populated on the form. The departure airport was Kenosha Regional Airport (ENW), Kenosha, Wisconsin, and the destination was ANW. According to a photograph of the instrument panel provided by the co-owner, the airplane was equipped with a two-screen Chelton Air Data Attitude Heading Reference System (ADAHRS) display in place of the standard 6 primary flight instruments on the pilot-side of the instrument panel. Below the two-screen Chelton display, from left to right, the pilot had an attitude indicator and a turn and slip indicator. A second attitude indicator was mounted on the co-pilot's side of the instrument panel, on the upper right corner. On September 23, 2017, about 1028 central daylight time, a Mitsubishi MU 2B-40 airplane, N73MA, was destroyed when it impacted terrain 3.5 miles northeast of the Ainsworth Regional Airport (ANW), Ainsworth, Nebraska. The private pilot was fatally injured. The airplane was owned by private individuals and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Instrument meteorological condi