NTSB Factual Report

HISTORY OF FLIGHT

On June 12, 2008, about 0805 eastern daylight time, an amateur-built Pitts S-1, N347MM, was substantially damaged when it struck the runway during an attempted takeoff from St. Petersburg-Clearwater International Airport (PIE), Clearwater, Florida. The certificated private pilot received minor injuries. The personal flight was operated under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the flight, and no flight plan was filed.

According to the pilot/owner, who was also the builder of the airplane, the accident flight was to be the first flight for the airplane. On the morning of the accident, the pilot taxied from his hangar to the approach end of runway 9, in order to conduct the engine run-up and other pre-flight checks prior to the first flight. The pilot stated that he encountered some engine roughness during the magneto check, but that the roughness was successfully eliminated after he conducted a "lean burn-out" and a second magneto check.

The pilot contacted the PIE air traffic control tower (ATCT) for takeoff clearance and permission to remain in the traffic pattern for runway 9. ATCT personnel approved his request, and cleared him for takeoff. The pilot stated that he taxied into position on the runway, applied full power, and was satisfied with what he "saw, heard, and felt." He stated that since it was the initial flight of the airplane, he planned to hold the airplane in ground effect after liftoff, in order to accelerate to an airspeed above the prescribed normal climbout speed.

The pilot stated that the airplane had climbed to approximately 20 feet above ground level when he felt something "let go." The pilot stated that he felt as though the engine had lost "some power." He knew that the airplane was slow at this point, and that he was going to abort the takeoff, even though the airplane was already airborne. The airplane then stalled, and rolled "very hard" to the right. The pilot added that the roll onset was so sudden, and at such a low altitude, that he did not have time to react. By the time the airplane was nearly inverted, it descended so that the upper right wingtip struck the runway. The airplane then slid inverted to a stop. The pilot extricated himself from the airplane. His injuries consisted of lacerations, bruises, and scrapes.

PERSONNEL INFORMATION

According to information provided by the pilot and the Federal Aviation Administration (FAA), the pilot had approximately 1,800 total hours of flight experience, with approximately 340 hours in the accident airplane make and model. The pilot reported 4 hours of flight experience in the 90 days preceding the accident. His most recent third-class medical certificate was issued on December 26, 2006.

AIRPLANE INFORMATION

The airplane was newly-constructed by the pilot using plans and some components from one vendor, and components from several other vendors. The airplane was a biplane with conventional landing gear, and was equipped with a new Lycoming IO-360 engine.

METEOROLOGICAL INFORMATION

The 0813 surface weather observation at PIE recorded winds from 120 degrees at 4 knots, visibility 10 miles, clear skies, temperature 26 degrees Celsius (C), dew point 22 degrees C, and an altimeter setting of 30.05 inches of mercury.

AIRPORT INFORMATION

According to FAA information, runway 9-27 was asphalt, and measured 5,165 feet long, and 150 feet wide. Taxiway A intersected runway 9-27 approximately 1,780 feet from the threshold of runway 9, and runway 17L-35R intersected runway 9-27 approximately 2,280 feet from the threshold of runway 9. Airport elevation was 11 feet above mean sea level.

WRECKAGE AND IMPACT INFORMATION

Examination of the airplane and the accident site was conducted by an FAA inspector and law enforcement personnel. The airplane came to rest on the south side of runway 9, just beyond taxiway A. The surface of runway 9 exhibited propeller strike marks and other impact scars. The distance from the first ground contact, to where the airplane came to rest, measured approximately 250 feet. The majority of the damage to the airplane was confined to the right wing. The upper right wing exhibited chordwise fractures at three separate span locations, and the lower right wing was twisted about the spar axis. The propeller and other components were also damaged.

ADDITIONAL INFORMATION

According to the pilot, in the days just prior to the first flight attempt, he spent a significant amount of time trying to resolve a low static rpm issue with the engine. He believed that the issue was a result of a problem with the fuel lines that he had fabricated. The fuel lines were "Aeroquip 303" series, which consisted of a flexible line, and a fitting on each end. Aeroquip procedures specified the use of a special tool called a mandrel to install the end fittings on the lines. The pilot did not use the mandrel, because he deemed its use to be difficult and time consuming. Instead, he used a self-developed shortcut procedure, which he initially believed to produce satisfactory results. Subsequent to the low rpm problems, the pilot examined the fuel lines, and observed that some of the lines exhibited internal "chafing," which he concluded might have interfered with the fuel flow. He determined that his shortcut procedure was the cause of the chafing, and he then

re-fabricated all but two of the lines using a mandrel. He replaced the previous lines with the new lines, and after engine testing, he believed that he had resolved the issue satisfactorily.

Subsequent to the accident, the engine fuel distribution system was tested on a flow bench; the system did not pass the test. Post-test examination of the components revealed that the fuel servo was contaminated with fragments of material similar to the fuel line material, and that the screens on some of the fuel injector nozzles were partially occluded by paint. The pilot concluded that the servo contamination was a result of his self-developed shortcut for fabricating the fuel lines, and that the paint was inadvertently and unknowingly deposited on the injector screens when he painted the engine.

NTSB Probable Cause

The pilot's failure to maintain adequate airspeed following a partial loss of engine power, which resulted in an aerodynamic stall. Contributing to the accident was improper maintenance practices during the construction of the airplane, which resulted in contaminants being accidently introduced into the fuel system.