Accident Sequence
The pilot was conducting an IFR flight in instrument meteorological conditions (IMC). After receiving clearance to climb and maintain flight level (FL) 220, the pilot informed air route traffic control center (ARTCC) that they were having a problem. When asked to repeat, the pilot began the same reply, but no further radio communication was received. The aircraft subsequently experienced an inflight breakup, scattering wreckage over a wide area.
Wreckage Examination
Examination of the wreckage revealed that the right outboard wing panel, horizontal stabilizer, elevators, right aileron, and parts of the rudder were found at a distance from the main wreckage. These components displayed evidence of overstress failure. No preexisting cracks or fatigue were found.
Flight Path Analysis
Radar and weather data indicated that deviation from normal flight began at or near a moderate convective weather echo (VIP level 2) as the aircraft was climbing through 17,300 feet in freezing conditions. At that time, the rate of climb was approximately 200 feet per minute and the ground speed was between 150 and 160 knots. At 1032:18, a descent commenced. Over the next two to three minutes, the aircraft's altitude, heading, and speed deviated. At 1035:17, additional primary radar targets appeared, after which radar contact was lost.
Weight and Balance
The estimated gross weight of the aircraft was 4,311 pounds, exceeding the maximum allowable weight of 4,100 pounds. The center of gravity was estimated to be 1.59 inches behind the aft limit. All four occupants died in the accident.
Probable Cause
The official probable cause was the pilot's failure to activate the pitot heat before ascending above the freezing level in IMC, followed by an improper response to erroneous airspeed indications that resulted from blockage of the pitot tube by atmospheric icing. A contributing factor was the pilot's lack of currency in flying in IMC.