Accident Sequence
The aircraft collided with the ground in a steep nose-down descent while maneuvering to return to the runway during the takeoff initial climb from the airport. The takeoff ground roll exceeded 3,000 feet, and the climb-out angle was shallower than usual. Witnesses near the impact site observed the airplane begin a steep left turn between one-quarter and one-half mile from the runway's end at a lower than normal altitude, with a bank angle estimated at 45 degrees or greater. The turn continued until the nose suddenly dropped and the airplane entered a spiraling descent to ground impact.
Witness Observations
Pilot and mechanic witnesses on the airport reported abnormal engine sounds during the takeoff. Two witnesses stated the engine sounded "like a radial engine" and believed the power output was lower than normal. One mechanic witness described the engine as surging and not developing full power, suggesting possible fuel feed problems, turbocharger surge, or an excessively lean running condition. The majority of ground witnesses near the impact site reported hearing "sputtering" or "popping" noises from the airplane.
Performance Analysis
Engineering personnel from the manufacturer developed a performance profile for a normal takeoff and climb under the ambient conditions and at gross weight. Comparing this profile to the actual aircraft performance derived from recorded radar data and witness observations, the ground roll was 1,300 feet longer than expected, and speed/acceleration and climb performance were consistently below predictions. Based on radar data and factoring in winds, the estimated indicated airspeed during the final turn was 82 knots. The stall speed at 45 degrees of bank is 82 knots and increases linearly to 96 knots at 60 degrees of bank.
Pre-Accident Circumstances
No evidence indicated that the pilot flew the airplane from December until the accident date. The airplane sat outside during the rainy season with only 10 gallons of fuel in each tank. Comparison of fueling start time and communication transcripts showed the pilot had 17 minutes 41 seconds to refuel with 120 gallons, reboard, and start the engine. The maximum nozzle discharge flow rate of the pump was 24 gallons per minute. Transcripts also revealed a 3-minute 35-second interval from taxi clearance at the fuel facility to ready for takeoff after a taxi distance of at least 2,000 feet. During the 8 seconds following the pilot's acknowledgment of takeoff clearance, a non-pertinent personal exchange occurred between the pilot and the local controller.
Post-Crash Investigation
The aircraft was almost completely consumed in the post-crash fire. Extensive investigation of the remains found no preimpact mechanical malfunction or failure in the engine or airframe systems. Pistons, cylinder interiors, and spark plugs from all six cylinders were clean without combustion deposits. The cockpit fuel selector lever, intermediate linkages, and valve were found in the OFF position; however, engineering analysis established that insufficient fuel was available in the lines forward of the selector to start, taxi, and perform a takeoff with the selector in the OFF position.