NTSB Factual Report

On July 16, 2013, about 0805 central daylight time, an experimental amateur-built Thompson Sonerai II, N788T, was destroyed during collision with terrain and a post-crash fire following an uncontrolled descent after takeoff from Abernathy Field Airport (GZS), Pulaski, Tennessee. The certificated private pilot/owner was fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight, which was operated under the provisions of Title 14 Code of Federal Regulations Part 91.

Witnesses reported to a Federal Aviation Administration (FAA) inspector that they watched as the airplane came to a stop on Runway 34, with the propeller stopped, after having taxied out from the parking area. They watched the pilot deplane, walk to the front of the airplane, restart the engine, then climb back into the cockpit. According to the witnesses, the airplane began its takeoff roll from that point, where approximately 2,500 feet of the 5,310-foot-long runway remained. The airplane departed downwind, and used the entire up-sloping runway that remained before it rotated "steeply."

The airplane travelled 2,900 feet beyond the departure end of the runway before it descended "vertically," impacted a state highway in a nose-down attitude, and subsequently caught fire.

A witness who was travelling on the state highway noticed the airplane because it was lower than typical departing traffic. Just prior to the airplane crossing over the roadway, it "pulled straight up…like a crop duster…about 70 –75-degree angle" before it rolled to the left and descended straight down to ground contact.

Witnesses stated that they heard the engine "sputtering" and running roughly during taxi and takeoff.

Examination of photographs revealed the engine compartment, cockpit, left wing, and empennage were completely consumed by fire. The right wing was largely intact, and the leading edge was crushed uniformly across the leading edge, consistent with a near-vertical, nose-down impact. Control continuity was established from the cockpit to all flight control surfaces. The right-side engine cylinder heads were separated from the engine by impact, and the internal components were exposed. An examination of the engine was not completed due to extensive impact and fire damage.

The pilot held a private pilot certificate with a rating for airplane single-engine land. His most recent FAA third-class medical certificate was issued February 10, 2012. A review of the pilot's logbook revealed that he had logged 120 total hours of flight experience, of which 9 hours were in the accident airplane. He had logged 3 hours in the 90 days prior to the accident, and 28 hours in the year previous to the accident.

The airplane was manufactured in 1982, and was purchased by the pilot/owner on March 31, 2013. The maintenance logbooks were not recovered, but according to the FAA inspector, an annual inspection was completed in May 2012. The inspector added that the engine was not equipped with an electric starter.

In an interview with an FAA inspector, the previous owner explained the flight characteristics of the accident airplane. He detailed the inherent instability of the airplane's design, the speeds necessary to maintain stable takeoffs and landing approaches, and the airplane's stall characteristics. The previous owner stated that the airplane required "lots of airspeed" to be stable. He stated 100 mph was his preferred airspeed in the airport traffic pattern, as well as in a climb to facilitate engine cooling. He stated that the airplane had no dihedral in the wing, which lessened its lateral stability, and added that the wing would dip very quickly in a stall. He indicated that a 1,000-foot altitude loss would be normal for a recovery from the resultant spin. The airplane also exhibited adverse yaw tendencies, which required "lots of rudder attention." The previous owner stated he had entered an inadvertent spin on several occasions while practicing aerodynamic stalls.

At 1621, the weather reported at GZS included clear skies and wind from 140 degrees at 3 knots. The temperature was 26 degrees C, the dew point was 23 degrees C, and the altimeter setting was 30.31 inches of mercury. The computed density altitude was 2,040 feet.

NTSB Probable Cause

The pilot's failure to maintain airspeed during a near-vertical climb after takeoff, which resulted in an aerodynamic stall and subsequent collision with terrain.