HISTORY OF FLIGHTOn April 19, 2021, about 1346 central daylight time, a Cessna 340A airplane, N801EC, was destroyed when it was involved in an accident near Tatum, Texas. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight. According to information provided by a fixed-base operator (FBO) at the East Texas Regional Airport (GGG), Longview, Texas, the pilot intended to perform a functional test of a newly upgraded autopilot system. On the day of the accident, a mechanic at the FBO reported that he pulled out the airplane from the hangar, and that the pilot planned to get fuel and have the propellers balanced before the flight. According to the mechanic, he explained to the pilot that the autopilot should not be engaged until the airplane was at an altitude of at least 5,000 ft above ground level or higher, which was a standard procedure that the mechanic provided to all pilots who were testing an autopilot. The pilot started the engines, and the airplane sat on the ramp for about 15 minutes. The pilot then shut down the engines and told the mechanic that he could not get the autopilot to work. The mechanic showed the pilot where the main autopilot and trim master switches were located and showed him that the autopilot passed a self-test. The mechanic then told the pilot to try another autopilot self-test with engines running and, if the autopilot did not pass another self-test, to shut down. The pilot ran the engines for about 5 to 10 minutes and then departed. According to air traffic control (ATC) information, the controller cleared the pilot to operate under visual flight rules to the east of the airport. Communications between ground control, tower control, and the pilot were normal during the taxi, takeoff, and climb. Automatic dependent surveillance–broadcast (ADS-B) data showed that the airplane took off from runway 13 at GGG about 1340. The data also showed that, after takeoff, the airplane was in a steady climb to the east of GGG. The airplane climbed to an altitude of 2,750 ft mean sea level (msl) and then descended to 2,675 ft msl. The last recorded data point, at 1346, showed that the airplane was heading east at an altitude of 2,675 ft msl and a groundspeed of 152 knots. The airplane impacted wooded terrain about 3/4 mile east of the last recorded data point. Groundspeeds and headings were consistent throughout the flight with no abrupt deviations (see figures 1, 2, and 3). Radio and radar communications were lost 6 minutes after takeoff. No radio distress calls were received from the pilot. Figure 1. Airplane flightpath. Figure 2. Flightpath elevation view. Figure 3. Flight track with final data points. A local resident about 1 mile from the accident site reported that, while inside his residence, he heard and felt a “boom” that shook the windows. His wife then saw black smoke rising immediately. WRECKAGE AND IMPACT INFORMATIONThe accident site was located at an elevation of 361 ft msl. The airplane impacted wooded terrain in a nose-down, near-vertical flight attitude. The forward fuselage and cabin were embedded into the ground and were mostly consumed from a postimpact fire. The empennage and aft fuselage were folded forward over the cabin area and were charred and consumed by fire. Both left and right wings showed leading-edge aft crushing along their respective spans. Portions of both wings were charred, melted, and consumed by the fire (see figure 4). Figure 4. Airplane wreckage. Both the left and right engine nacelles were separated from the wings, and the engine and propeller assemblies were embedded in 3-ft-deep craters forward of the main airplane wreckage. The engines sustained heavy impact damage, and the propellers were fractured and separated at their crankshafts immediately aft of the flanges. All three blades on the left and right propellers were bent aft and showed leading-edge polishing and chordwise rubs and scratches. Flight control continuity was confirmed. The elevator trim cables stop blocks were secured to the cables and undamaged. They were found against the forward stop meaning the trim tab was at full down travel (elevator leading edge full down) which indicated that the airplane was trimmed full nose up at impact. The airplane’s instrument panel, avionics, autopilot, and engine controls were broken out, fragmented, melted, and consumed by the postimpact fire. Avionics and instrument tubing and wiring behind the panel were melted and consumed by the fire. A functional test of the autopilot system could not be performed due to the damage that it sustained in the accident. Examination of the engines revealed no preaccident failures or malfunctions that would have precluded normal operation.