Background
The airplane arrived the day before the accident and was parked outside on the airport ramp overnight. Light to moderate snow and freezing drizzle occurred during the 12 to 24 hours preceding the accident. Low instrument meteorological conditions prevailed at the time of the accident takeoff. The pilot removed snow and ice from the wings but did not clear the horizontal stabilizer, which was inaccessible.
Accident Sequence
The airplane was loaded over the maximum certificated gross weight and beyond the aft center-of-gravity limit. There were 12 occupants on board, though only 10 seats were available; none qualified as lap children under regulations. The pilot initiated takeoff rotation at about 88 knots, approximately 4 knots slower than specified for icing conditions. After takeoff, the airplane entered a left turn. Airspeed varied between 89 and 97 knots during the initial climb but decreased to about 80 knots as altitude and bank angle peaked. The airplane reached a left bank angle of 64° at a peak altitude of about 380 feet above ground level, then began a descent that continued until impact. The stall warning and stick shaker activated about 1 second after liftoff; the stick pusher became active about 15 seconds after liftoff, and all three operated intermittently for the duration of the flight. A witness about half a mile northwest of the airport heard the takeoff in cloudy, snowy conditions. He could not see the airplane but noted a left turn based on sound, hearing the engine for about 4 or 5 seconds with what seemed normal operation until the sound stopped. The airplane struck a dormant corn field about three-quarters of a mile west of the airport.
Investigation Findings
Postaccident airframe examination revealed no anomalies consistent with a preimpact failure or malfunction. Onboard recorder data indicated normal engine operation. Performance analysis showed that snow and ice on the empennage did not significantly degrade performance after takeoff, but their effect on center-of-gravity and pitch control forces could not be determined. Simulations demonstrated that recorded pitch oscillations could be reproduced with control inputs and that flight control authority was sufficient until an aerodynamic stall about 22 seconds after liftoff (the maximum bank angle occurred after exceeding the critical angle of attack). Similar but less pronounced pitch oscillations on a previous flight with a similar CG but no snow contamination suggested that improper loading, not snow, caused the oscillations. Flight data revealed that the accident pilot rotated more rapidly and to a higher pitch angle than another pilot who regularly flew the airplane. Pilot simulations indicated that the accident pilot's rotation technique—abrupt and heavy pull on the control column—combined with extreme aft CG, heavy weight, and early rotation, contributed to a high angle of attack immediately after rotation, triggering the stall protection system and causing pitch control difficulties. These oscillations led to a deep aerodynamic stall and loss of control. Although conditions were conducive to spatial disorientation, the circumstances aligned more with the pilot's response to stall protection activation, hindered by heightened pitch sensitivity from the aft CG; spatial disorientation was not considered a factor.
Probable Cause
The pilot’s loss of control shortly after takeoff, which resulted in an inadvertent, low-altitude aerodynamic stall. Contributing to the accident was the pilot’s improper loading of the airplane, which resulted in reduced static longitudinal stability and his decision to depart into low instrument meteorological conditions.