On April 20, 2018, at 1830 eastern daylight time, an experimental amateur-built Kolb Mark III, N9123R, was destroyed when it collided with terrain shortly after takeoff from Collegedale Municipal Airport (FGU), Collegedale, Tennessee. The private pilot was fatally injured. Visual meteorological conditions prevailed near the accident site, and no flight plan was filed for the local personal flight conducted under the provisions of Title 14 Code of Federal Regulations Part 91.The airplane's owner reported that the pilot was supposed to be performing high-speed taxi testing of the airplane and that he did not know the pilot intended to take off. He stated that the pilot completed two high-speed taxis and "crow-hops" in the airplane (that is, he would "taxi, lift off, climb the airplane to about 10 ft above ground level [agl], and then land"). During the third taxi, the owner heard the pilot apply "full power," and the airplane then took off from the runway, turned right "above the trees" adjacent to the runway, and entered the traffic pattern. The airplane then "leveled, banked left, and dove into the ground." The owner added that it did not appear that the pilot attempted to correct the dive. Another witness, who was located on the northeast end of the runway, reported seeing the airplane above the departure end of the runway about 500 ft agl when it "turned left…and dove straight" into the side of a hill. He said that it sounded as though the pilot reduced power before the turn but increased power during the descent and that the engine was "screaming" as the airplane descended to ground impact. The owner provided a video recording of the airplane that was oriented in the direction of flight and which captured the ground taxi and takeoff and ended before the airplane's descent into terrain. A review of the video revealed that the takeoff roll was about 400 ft long. The engine sound was smooth, continuous, and remained unchanged throughout the takeoff roll and the 45 seconds of the climb that was recorded. The video showed that, after takeoff, the airplane had a high angle of attack and a steep angle of climb, and the tops of each wing were visible. The airplane drifted right of the runway centerline but remained flat in the roll axis. The pilot held a private pilot certificate with airplane single-engine land and instrument airplane ratings. His most recent Federal Aviation Administration (FAA) second-class medical certificate was issued on November 1, 1999, at which time, he reported 71 total hours of flight experience. The Office of the Hamilton County Medical Examiner, Chattanooga, Tennessee, performed the autopsy on the pilot and determined the cause of death as multiple blunt force injuries. The FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing on the pilot and the test yielded results for the presence of a sedating over-the-counter antihistamine cetirizine in blood (0.012 (ug/ml, ug/g) and liver samples. According to the NTSB Medical Officer, the levels detected were below the therapeutic range, and assuming normal dosage at the time of ingestion, the levels suggested the pilot was within the FAA's recommended period for the performance of airman duties. A review of photographs of the pilot's logbook revealed that the pilot had accrued about 248 total hours of flight experience. The low number and poor quality of the photographs prevented a determination of the total, type, and recency of his flight experience; however, the most recent entry and endorsement indicated that the pilot flew a tail-wheel equipped ultralight airplane on July 9, 2016, and an unidentified aircraft on September 10, 2016. The airplane was manufactured in 1995 and registered to the owner on January 4, 2017. It was powered by a Suzuki 1.3 liter, 4-cylinder automobile engine. According to the owner, he purchased the airplane disassembled and "half restored" from what appeared to be accident damage. He and the pilot completed the repairs and assembly of the airplane using a "build manual" and a set of plans. The owner did not have airframe or engine logbooks for the airplane, and a condition inspection had not been completed. The owner said the condition inspection was supposed to have been completed "before the first flight." At 1853, the weather reported at Chattanooga Lovell Field, located 9 miles from the accident site, included few clouds at 25,000 ft, 10 miles visibility, winds from 010° at 10 knots, temperature 20°C, dewpoint -4°C, and an altimeter setting of 30.28 inches of mercury. Examination of photographs of the wreckage provided by the FAA revealed that the airplane came to rest uphill of the initial ground scar, and the wreckage path was oriented along a magnetic heading of about 300°. Impressions in the grass on either side of the scar were of the same approximate dimensions as the leading edge and span of each wing. Both wings were uniformly crushed aft in compression, and the fabric covering of each wing was shredded. The empennage remained largely intact. Control continuity could not be established due to the extent of the damage to the remainder of the airframe and the entanglement of structure and control cables. Examination of breaks and fractures in the cables and bellcranks revealed that they were consistent with overload failure. The cockpit area was destroyed, and the instrument panel was separated. The engine cradle was separated and only remained attached by wires and cables. A nylon cargo strap was found entangled with the wreckage. According to the owner, the strap secured sand bags and a board used for ballast. According to the Kolb Aircraft website, "Although Kolb aircraft are easy to fly and have gentle flight characteristics, they are also high-performance aircraft. We recommend training or some transition training before attempting flight in our aircraft." FAA Advisory Circular (AC) 90-89B, "Amateur-Built Aircraft and Ultralight Flight Testing Handbook," was issued to make amateur-built aircraft pilots aware that "test flying an aircraft is a critical undertaking," which should be approached with "thorough planning, skill, and common sense" and to provide recommendations and suggestions that could be combined with other sources on test flying (such as, the aircraft plan/kit manufacturer's flight testing instructions, other flight testing data) that would assist amateur owners to "develop a detailed flight test plan, tailored for their aircraft and resources." The AC also provided guidance on developing a plan for each phase of an amateur-built airplane's production, including preparing for the airworthiness inspection, determining weight and balance, conducting taxi and flight testing, and developing emergency procedures. The suggested flight-testing regimen was separated into 10-hour segments for the 40-plus-hour flight testing requirement. The AC also included guidelines for the experience level of the test pilot, which included, in part, the following: The test pilot should be experienced and competent. He/she should have made a minimum of 100 solo flights in similar make, model, and type of ultralight and must follow the FLIGHT-TEST PLAN exactly. The FLIGHT-TEST PLAN should examine the ultralight and its performance capability, beginning with the pre-flight inspection and ending only after the test pilot has explored the ultralight's published flight envelope as described in the flight manual. The owner reported that he was not familiar with FAA AC 90-89B.