FTW03FA064 · Beech BE-58

Instrument meteorological conditions prevailed for the cross-country flight for which the instrument rated commercial pilot limited his weather briefing, filed an IFR flight plan, and received an ATC clearance. Approximately 13 minutes after departure, the 1,027-hour pilot, sole occupant, reported the airplane was accumulating ice, requested and was cleared to descend the airplane from 5,000 to 4,000 feet msl. Subsequently, the pilot requested and was cleared to descend to 3,000 feet, and proceed direct to the initial approach fix for the RNAV(GPS) 36 non-precision approach for landing at an alternate airport. No distress call or additional ATC communications with the pilot were recorded. The airplane impacted trees and terrain approximately 17 nautical miles south of the airport. Tree deformation, ground scars, and craters, were consistent with a near vertical impact. The NTSB meteorological study revealed that instrument meteorological conditions with low ceilings, reduced visibility, light rain, mist, and drizzle prevailed at the departure airport and along the flight route. The low-level vertical temperature profile in the accident area was likely the following; 1 degree Celsius at the surface, minus 3 degrees at 3,000 feet, freezing level at 5,000 feet, and above freezing at 7,000-8,000 feet. SLD was likely present in the accident area at and below 5,00 feet and produced moderate to severe clear icing on the airframe in the minutes prior to the accident. The investigation revealed the airplane was equipped with alcohol propellers; however, the impact and thermal destruction precluded a determination of the operational status of the anti-ice system. Both propellers exhibited physical evidence (blade bending and twisting) consistent with high power ( at or near the low pitch range) and rotation (symmetrical energy) at impact. No evidence of an in-flight mechanical or flight control malfunction was found that would have rendered the airplane uncontrollable prior to the impact. GPS was not approved for IFR. After the accident, the RNAV(GPS) 36 approach was flight checked by the FAA, and all components were found to be operating within prescribed tolerances.

Verbatim NTSB analysis and probable cause from the NTSB dataset