Accident Overview
On March 24, 2015, about 1915 eastern daylight time, a privately owned and operated Trick Trikes 582 Cyclone Storm weight-shift control aircraft, N993RA, was substantially damaged when it collided with trees during a forced landing near Live Oak, Florida. The sport pilot applicant (SPA) owner and sport pilot examiner (SPE) sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the instructional flight conducted under 14 Code of Federal Regulations Part 91. The flight originated about 1845 from a private airstrip near Live Oak, Florida.
Pre-Accident Activities
Earlier that day, the SPA flew the accident aircraft with his instructor for about 1 hour, with no engine discrepancies reported. Following that flight, the SPA drove to the SPE's location and passed the oral portion of the practical test for a sport pilot certificate. The SPA then drove to where the aircraft was located, fueled it, performed a preflight inspection, and flew to the SPE's location, landing uneventfully.
Before departure of the accident flight, a preflight inspection and engine run-up were performed; no discrepancies were reported. The flight departed with "at least" 5 gallons of fresh fuel onboard, mixed with a little more than a 50:1 ratio of fuel to two-cycle engine oil.
Accident Sequence
After takeoff, the SPA performed maneuvers. While flying about 1,000 feet above ground level (agl) with fields nearby, the SPE informed the SPA that they would be performing emergency power off procedures and asked him to reduce power. The SPA reduced power, selected a suitable landing field, and surveyed the field while in a spiral descent. He set up to land in the field, and when the aircraft was about 50 feet agl, the SPE terminated the maneuver and told him to add power and go around. The SPA immediately started turning, then added power, but the engine sputtered and did not respond to the throttle input. The aircraft subsequently impacted trees.
The SPA indicated that during the descent with power reduced, he did not add power to "clear" the engine, nor did he recall the SPE advising him to do so. He also indicated that he mistakenly turned before adding power and otherwise could have landed "OK" in the field he selected. In hindsight, he believed the sputtering was related to the lack of engine clearing during the descent at a reduced throttle setting.
The SPE stated that he instructed the SPA to turn to a heading of 090 degrees. As the right turn started, the SPE told the SPA to reduce the throttle to idle to simulate an engine failure and to designate an emergency landing field. The SPA indicated the field below was suitable—an open 1.5 square mile cattle farm with flat grassland, cows, and small isolated groves of trees. During the spiral descent, the SPE did not recall the SPA "clearing the engine" and thought in hindsight that he should have. At 200 feet agl, the SPE told the SPA to "throttle up go-around." When the SPA advanced the throttle, the engine did not regain power. The intended landing field was straight ahead, but the aircraft turned left and began to climb immediately. The SPE attempted to recover, but the aircraft entered a left descending turn and hit trees no taller than 15 to 20 feet. The aircraft impacted the ground at an estimated speed of 30 mph. The SPE and SPA evacuated and walked to a house to summon assistance. The SPE further stated that the engine's failure to respond could also have been due to the SPA's rapid throttle application, which he described as "a little fast."
Post-Accident Examination
According to the Federal Aviation Administration inspector-in-charge, the frame near the nose gear was slightly bent to the right, and the right side diagonal frame tube was significantly bent. One propeller blade of the three-bladed propeller was impact damaged, and approximately 5 gallons of uncontaminated fuel were recovered from the fuel tank. Examination of the Rotax 582 engine revealed no apparent damage. Both carburetor bowls were inspected; no contamination was noted. The aircraft was fueled with the recovered fuel, and the impact-damaged propeller was removed. The engine then started immediately and ran to idle with no issues.
Following recovery, the SPA/owner inspected the engine with the exhaust removed and reported no scuffing or scoring on the piston sides; honing marks in each cylinder were present. A replacement propeller was installed, and after setting blade angle, the engine started and achieved near full redline rpm with no discrepancies.
According to the engine operator's manual, the engine by design is subject to sudden stoppage, which can result in forced landings or no power landings. The manual also stated: "Do not idle for prolonged periods as normal rich condition present at this power setting can cause unnecessary carbon deposits and spark plug fouling." A representative of the engine manufacturer reported that during a long underpowered descent, a two-stroke engine such as the accident engine "loads up" because not all fuel is burned in the cylinders. With rapid throttle advance, the fuel/air ratio becomes too high, causing hesitation until the excess fuel is cleared out.
Maintenance History
The aircraft had been operated about 19 hours since its last condition inspection, which was performed on April 14, 2014. At that time, the aircraft total time was 180 hours.