What happened
The accident occurred during an aerial application flight in proximity to the city of Burlington, Colorado. The pilot was conducting a cleanup pass when the aircraft was nearly empty of both fuel and chemical spray. At approximately 300 feet above ground level, the pilot initiated a steep dive with a bank angle between 60 and 70 degrees. He descended until the aircraft was within 50 feet of the ground before beginning to flare.
The pilot estimated that the indicated airspeed was 105 knots when he started the pull-up maneuver. During this phase, the aircraft shuddered, indicating an impending stall. The pilot reported that during previous maneuvers, such as pull-ups and wing-over turns, the aircraft had not shuddered and the stall warning had not activated. Upon feeling the shudder during the dive recovery, the pilot released back pressure for approximately one second. Consequently, the aircraft impacted the ground in a three-point attitude.
The impact was severe, causing the aircraft to pancake hard and slide 75 yards across the terrain. The landing gear collapsed upon impact. The accident site was located at a ground elevation of approximately 4,178 feet. Environmental conditions contributed to the incident, with the density altitude calculated to be 7,500 feet.
The investigation
The primary mechanical finding was the collapse of the landing gear due to the hard impact. No other mechanical failures were cited as contributing factors prior to the impact. The aircraft's performance characteristics during the high-density-altitude conditions were central to the analysis of the event.
Findings
The pilot's decision to perform a steep dive and accelerated pull-up at low altitude, combined with the high density altitude, resulted in a loss of control due to aerodynamic stall. The shudder experienced by the pilot was a clear warning sign that was not acted upon sufficiently to prevent the stall. The proximity to the city likely influenced the flight path and maneuver selection.