On September 28, 2015, about 0825 central daylight time, a kit-built Rans S-12 experimental light sport airplane, N98ES, collided with terrain while maneuvering to land at the Gardner Municipal Airport (K34), Gardner, Kansas. The private pilot was seriously injured and the airplane was substantially damaged. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. The local flight departed K34 shortly before the accident.A witness, who was a private rated pilot, saw the accident airplane taxi from its hanger to runway 8/26. The witness next heard a sound consistent with the airplane's engine increase in rpms followed by a decrease in rpms. He saw the airplane gliding towards runway 17 before the airplane began to slowly pitch up. The witness saw the airplane stall and roll into a left turning spin with the nose pointed towards the ground. The airplane impacted terrain in a near vertical attitude before coming to rest. The pilot stated that he departed from runway 26. Shortly after takeoff, the engine stopped producing power. He nosed the airplane down and maneuvered to avoid a ditch. During the descent, he leveled off to avoid impacting the ground at a steep angle. He recalled that after the crash he could not find the master switch, and could not turn off the right fuel shutoff, so he only closed the left fuel shutoff valve. The airplane was examined by inspectors from the Federal Aviation Administration. The forward portion of the fuselage and cockpit area was crushed and distorted. Both wings were twisted near their outboard ends. The flaps were retracted. The left fuel tank contained over 7.5 gallons of fuel and the right tank contained about 5 gallons of fuel. Both fuel lines appeared to contain fuel with no visible contaminants. The left fuel switch was off and the right fuel switch was on; both fuel filters were clear of debris. The "ignition 1" switch was off and the "ignition 2"switch was on, however there was damage to the switch housing near the "ignition 1" switch. The pilot reported that in May 2016, the engine was examined and started. During the test run, fuel delivery to the engine was restricted and the engine only produced about 50 percent power. When external fuel was fed to the engine, it ran normally. In June 2016, the wing was removed and the fuel tanks were examined. The right fuel tank and sump contained residue consistent with grass.