NTSB Factual Report

HISTORY OF FLIGHT

On April 3, 2011, about 1253 Pacific daylight time, an experimental amateur built Tomei Rans S12 XL airplane, N8113N, collided with the ground shortly after takeoff from a private airstrip near Pleasant Grove, California. The certificated sport pilot was fatally injured. The airplane sustained substantial damage to the forward fuselage, empennage and wing assembly. The airplane was registered to the pilot, and operated under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and no flight plan was filed for the local flight.

A pilot rated witness, who was an acquaintance of the pilot, stated that the airplane landed at the private airstrip about 1150. The witness reported that he and the pilot talked for 30-45 minutes and among other things, discussed flying to another airstrip south of their location as a flight of two. The witness reported that while he was doing a run-up, he watched the accident airplane depart to the northwest. Shortly after takeoff, as the accident airplane reached an altitude between 200 to 300 feet above ground level, it appeared to slow down, bank to the left, and subsequently spiraled to the ground. During a separate conversation, the witness reported that the accident airplane was airborne “a couple of minutes” after the engine was started.

TESTS AND RESEARCH

The airplane was equipped with a 2-stroke Rotax 582 liquid cooled, 2-cylinder piston engine; serial number 4656067. Engine total time since new was 318.6 hours. Post accident examination of the engine revealed evidence of abnormal piston wear. Mechanical scoring and vertical grooves were noted along the forward (mag) cylinder walls and forward piston skirt. Both piston rings were intact; however, were seized within their ring lands. The associated piston wrist pin, wrist pin bearings and connecting rod were in place with no damage noted. Detailed exam notes are contained in the public docket.

A representative of the engine manufacturer reported that the observed cylinder and piston wear and damage signatures was indicative of an in-flight “cold seizure” of the piston; a condition where the piston seizes within the cylinder. The manufacturer’s representative stated that this occurs when there is a thermo-imbalance of the piston and cylinder caused by a lack of engine warm-up or excessive temperature coolant difference inlet to outlet on the engine.

ADDITIONAL INFORMATION

In a manufacturer issued Service Information Letter (SIL) dated July 1994, Rotax addressed, in part, the potential for piston seizure. The letter stated in part “...Putting a cold engine to hard work without uniform and correct warm up will cause the piston to expand quicker than the cylinder, minimizing clearance and creating piston scuffing and seizure.”

NTSB Probable Cause

The pilot’s failure to allow the airplane’s engine to properly warm up before applying takeoff power, which resulted in the forward cylinder's piston seizing and a subsequent loss of engine power. Also causal was the pilot's failure to maintain an adequate airspeed after the loss of engine power, which resulted in a stall-spin.