CHI97LA302

The pilot, who worked as an aviation mechanic for the aircraft manufacturer, installed vortex generators on the wings and fuselage of a Rans S-11. He then flew the S-11, while a chase plane followed. The S-11 pilot slowed the airplane to let the chase plane catch up. The pilot of the chase plane reported that the S-11's altitude was about 1,500 feet AGL, but the airspeed was slow. He observed the airplane doing slight Dutch rolls and '...just mushing along.' The S-11's nose pitched down and started a 1/4 spin to the left. The aircraft started to pull up from the nose down spin attitude, and then made a shallow arc before impacting the ground. The pilot of the S-11 was not a test pilot. He had a total of 3 hours in the S-11. The S-11 pilot reported the flight was a personal flight. The company did not have a policy for test flying airplanes. The engine and flight controls exhibited continuity.

History of Flight

On September 28, 1997, at 1921 central daylight time, a RANS S-11 Pursuit, N4299Y, operated by RANS, Inc., sustained substantial damage when it impacted terrain after a loss of control. The airplane was observed flying at a low airspeed at 700 feet above the ground when the nose dropped and the airplane entered a spiral. A recovery was attempted but the airplane impacted the ground in about a 30 degree nose down attitude. The private pilot was seriously injured. The 14 CFR Part 91 flight had departed the company airstrip at Hays, Kansas, on a local flight. Visual meteorological conditions prevailed and no flight plan was on file.

The pilot, who worked as an aviation mechanic for the aircraft's manufacturer, had installed vortex generators on the airplane's wings and fuselage on the day of the accident. After the work had been accomplished, the pilot decided to fly the S-11 for pleasure. A chase airplane piloted by the owner of the company followed the S-11 after it departed.

Both aircraft climbed to altitude. The pilot reported that the S-11 was faster and started to out distance the chase plane. He reported that pilot of the chase airplane said, "Come back. You're outrunning me."

The pilot of the chase plane reported that the S-11's altitude was about 1,500 feet above ground level (AGL), but the airspeed was slow. He recognized that the airplane was getting too slow and low. He observed the airplane doing slight Dutch rolls. He described the airplane as "...just mushing along." He reported that the airplane was in a rapid descent when the nose pitched down and started a 1/4 spin to the left. He reported that the "aircraft then started to pull up from the nose down spin attitude. [The] aircraft then made a shallow arc toward [the] ground and contacted the ground at an oblique angle sliding to a stop, fairly intact." He reported that the airplane impacted the ground in about a 30 degree nose down attitude. He reported that the pilot of the S-11 exited the airplane within 15 seconds after impact.

Personnel Information

The pilot of the S-11 was a private pilot with single engine land rating. He had logged a total of 376 flight hours. He had a total of 3 hours in the S-11.

He reported that he had flown and performed maintenance on almost all the aircraft produced by the aircraft manufacturer. He was a member of the company's flying club and was able to fly many of the airplanes manufactured by the company. He reported he was very familiar with the S-11 and was, "...excited about the aircraft since the prototype."

He reported the accident flight was not "on company time," and that he considered it a personal flight. He reported that he did not remember anything about the flight, and the information he knew had been supplied to him by others.

Aircraft Information

The aircraft was the second S-11 produced. It had a total of 259 flight hours on the airframe. The engine was a Rotax 912 which produced 80 horsepower. The airplane was certified under the Experimental category and was used for Research and Development.

Company Information

The owner of the company reported that the vortex generators were installed to lower the stall speed of the airplane. He reported that the airplane cruised between 140 to 160 mph. He reported the stall speed was about 69 mph, but he wanted to get the stall speed down to 50 to 55 mph. He reported that the S-11 flew like a Piper J-3 Cub, and that it was very stable in pitch.

The owner reported that on the day of the accident the weather was beautiful and it was Saturday so they decided to go flying. The flight was considered a personal flight because the S-11 had already been flown 259 total hours and would not require a test flight.

The owner reported there were only two test pilots used by the company. He was the primary test pilot and a contract test pilot also flew test flights. He reported that the accident pilot was not a test pilot, but a member of the flying club. He reported that the company did not have a written down policy concerning test flights.

The owner reported that since the accident occurred, the company changed its policies governing the flying club. The flying club became a separate entity and the members could only fly aircraft belonging to the club, and no longer had privileges of flying non-production or company aircraft.

Wreckage and Impact Information

An examination of the accident site by the company owner and the Federal Aviation Administration indicated that the airplane impacted the ground and slid on its fuselage on about a 250 degree heading. A 1 to 1.5 foot deep by 30 foot impact mark was created as the airplane traveled about 180 feet before coming to a stop. Both of the wooden propeller blades were sheared and bent back about 12 inches from the propeller hub. The landing gear had sheared off. The composite fuselage was largely intact. A 8 to 12 inch section of the elevator had separated from the rest of the elevator.

The engine and flight controls exhibited continuity.

Additional Information

The Federal Aviation Administration was a party to the investigation.