Accident Overview
An instrument-rated private pilot departed on a cross-country flight without receiving an instrument clearance or opening a filed IFR flight plan. The departure occurred in instrument meteorological conditions (IMC) with an overcast ceiling at 500 ft above ground level and visibility restricted to 1 ¾ miles in mist.
Flight Details
The airport manager observed the airplane depart from runway 35 and enter the clouds. There was an outage of the ground communications system at the airport, and investigators found no evidence that the pilot attempted to open the flight plan via cellular telephone. A low-level outage of radar services in the vicinity prevented determination of the airplane's route before impact.
Witness Accounts
Witnesses located north of the accident site did not see the airplane but reported hearing an airplane depart around the time of the accident. One witness reported hearing a low-flying airplane with engines operating at full power, then heard a thud that was attributed to a thunderstorm in the area.
Wreckage and Examination
The airplane impacted a field about 3.5 miles northeast of the departure end of Runway 35, off the track for the intended route. The airplane was massively fragmented, with debris scattered over approximately 300 ft. Damage and ground scars were consistent with a left-wing-low, nose-low attitude and relatively high energy at impact. Postaccident examination of the engines and propeller assemblies revealed no preimpact anomalies that would have precluded normal operation. Signatures were consistent with both engines producing power and propellers developing thrust at impact. Although massive fragmentation precluded functional testing, no damage or failure suggested preimpact anomalies with the airframe or flight controls.
Previous Issues
Several days before the accident flight, the pilot encountered a "transient flag" on the air data attitude heading reference system (ADAHRS). The pilot reported the flag to both the co-owner of the airplane and an avionics shop, but exact details are unknown. The unit was destroyed and could not be tested. The instrument panel had adequate standby instrumentation for flight continuation if the flag affected attitude display after takeoff. Investigators could not determine if the unit failed during takeoff or what role, if any, the transient issue played.
Probable Cause
Based on reported weather conditions, wreckage location, and impact attitude, investigators determined that the pilot likely experienced spatial disorientation shortly after takeoff, resulting in a loss of control and descent into terrain. The probable cause is the pilot's loss of airplane control due to spatial disorientation.