CEN16LA230

The private pilot stated that a preflight inspection of his experimental, amateur-built airplane revealed no discrepancies. After takeoff, the pilot completed two circuits around the airport traffic pattern with "no problems." During the upwind leg of the third circuit, he "noticed some vibration" and saw that the horizontal stabilizer was shaking/vibrating. The pilot began an approach for a precautionary landing, but during the base-to-final turn of the approach, the airplane experienced an aerodynamic stall. The pilot stated that he did not lose elevator control authority during the last legs of the flight but that he was "distracted" by a fear that parts may be separating from the airplane. The airplane, which was built from plans based upon a 100-year old design, was not equipped with a stall warning system. The pilot further reported that the flight control vibration was likely the result of the control cable that linked the two elevators in a "Y" configuration. He stated that the single control cable was not supported for "a number of feet" through guides/fairleads, which can make the elevators "flutter."

On June 17, 2016, at 2040 central daylight time, an experimental amateur-built Nieuport 11, N124TG, experienced a hard landing and an impact with terrain during a precautionary landing at Gardner Municipal Airport (K34), Gardner City, Kansas. The pilot performed the precautionary landing after he felt a vibration from the horizontal stabilizer while in the airport traffic pattern. The airplane sustained substantial damage. The pilot was uninjured. The airplane was registered to and operated by the pilot under 14 Code of Federal Regulations Part 91 as a personal flight that was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The local flight originated from K34 at 2015. On June 16, 2016, the pilot trailered the airplane to K34 for an upcoming weekend event. On the day of the accident, the airplane was untrailered and reassembled mid-day. The pilot then preflighted the airplane and taxied it to a parking area at the airport for an evening flight. The pilot stated that before takeoff he performed an engine run-up and checked the flight controls for a takeoff using runway 17. After takeoff, the pilot flew the airplane in a left-hand airport traffic pattern and completed two circuits over the airport with "no problems." He said that during the upwind leg, parallel to runway 17, he "noticed some vibration," and saw the horizontal stabilizer shaking/vibrating. He varied the engine throttle setting while the airplane was near the departure end of runway 17 to cease the vibration, but the vibration continued. The pilot then heard, but did not see, an inbound aircraft that made a radio transmission referencing runway 26. Due to the inbound aircraft, the pilot thought that it was "unsafe to land" on runway 26, so he flew a left base to runway 17 for landing. As the airplane neared the left side of runway 17, the pilot initiated a "shallow" left turn for a "modified" final over runway 17, and the airplane "quickly began to sink." The said that the airplane experienced an "aerodynamic stall." The pilot added full engine power, which induced a yaw and a roll. The airplane descended and impacted the ground coming to rest short and on the left side of runway 17. The pilot stated that he did not lose elevator control authority during the flight and his attention to flying the airplane was "distracted" by a fear that parts/empennage may be separating from the airplane, which led to his stalling the airplane. He said that the airplane model was "super draggy" and "super light" and without engine power, the airplane slows down rapidly. The pilot stated that the airplane was built from plans that were based upon a 100-year old airplane. The plans depicted and the airplane was manufactured without the left and right elevators connected to each other. A single control cable linked the two elevators via a Y-connection. The single control cable was not supported for "a number of feet" through guides/fairleads,which can make the elevators "flutter." The pilot said that following the accident several other airplane owners with the same model of airplane have modified the elevator control system by either installing a bellcrank in the elevator control system or by connecting the left and right elevators together. The pilot said that neither the plans nor any subsequent modification to those plans in the building of the accident airplane resulted in the installation of a stall warning system in the airplane.