What happened
Prior to departure, the pilot conducted an engine run-up on both engines and noted no discrepancies. The aircraft taxied to the runway, utilizing the full length of the pavement. During the takeoff roll, the pilot applied full power to both engines while holding the brakes. Upon releasing the brakes, the aircraft proceeded down a 3,300-foot downslope runway consisting of wet asphalt.
When the aircraft reached the halfway point of the runway, the airspeed indicator showed 60 knots. At this point, the pilot attempted to abort the takeoff, but the aircraft began to hydroplane. The aircraft continued past the end of the runway toward a 15-foot drop-off. Before reaching the edge of the pavement, the pilot applied power to both engines, which responded. The aircraft then impacted the ground in a cow pasture, eventually coming to rest in an upright position. At the time of the accident, there was moderate rain.
Findings
Post-accident weight and balance calculations revealed that the aircraft was at least 359 pounds over its maximum gross weight at the time of takeoff. This contradicted the pilot's own weight and balance calculations, which indicated the aircraft was only 3 pounds over gross weight.