RAYTHEON AIRCRAFT COMPANY 58 — Palos Hills, IL

What happened

The private pilot and two passengers departed in the multiengine airplane from a controlled airport under night, marginal visual flight rules conditions for a personal flight. Radar data showed the airplane climb to about 2,200 ft mean sea level (msl). At this altitude and when the airplane was about 3 nautical miles (nm) from the airport, it began a descending left turn, followed by a right turn, losing about 700 ft of altitude during this time. The airplane then began a climbing left turn. The left turn continued while its radius decreased until the end of the recorded data. During the final left turn, the airplane initially climbed about 400 ft, descended about 400 ft, and then climbed again about 1,300 ft before reaching its peak altitude of 2,800 ft msl. The final recorded radar point was 0.1 nm from the accident site, and the calculated descent rate between the final two radar points was more than 5,000 ft per minute. Postaccident examinations of the airframe, engines, and propellers, revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The airplane's avionics and instruments could not be functionally tested due to the extent of the impact damage.

The recorded weather conditions at the destination airport, located about 6 miles from the accident site, at the time of the accident included a broken ceiling at 1,000 ft above ground level (agl), an overcast ceiling at 1,700 ft agl, and visibility of 6 miles with mist. The radar data indicated that the airplane penetrated the cloud layers during the accident flight. The pilot held the appropriate certificates and ratings for operation of the multiengine airplane in instrument conditions, but no clearance had been issued for operation in instrument meteorological conditions. The weather and light conditions at the time of the accident were conducive to the development of spatial disorientation. Further, the flightpath, which was not consistent with the intended course; the airplane's repeated climbs and descents; and the loss of airplane control and high-speed impact were consistent with the known effects of spatial disorientation. Based on this evidence, it is likely that the pilot experienced spatial disorientation after the airplane entered the clouds at night, which led to his failure to maintain airplane control.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.