NTSB Factual Report

History of Flight

On August 4, 1998, at 1925 central daylight time, a Piper PA-18-150, N9396D, was destroyed when it impacted the ground about 1/3 mile from the departure end of runway 27 at Jensen Airfield, Rosemount, Minnesota. The private pilot, pilot in command, and the second pilot received fatal injuries. The 14 CFR Part 91 flight was conducting touch and goes from the private grass airfield. Visual meteorological conditions prevailed at the time and no flight plan had been filed.

Witnesses reported that the pilot and second pilot were practicing touch and goes at Jensen Airfield for approximately 30 minutes prior to the accident. A witness reported that he observed the PA-18-150 climbing out from runway 27 at about 300 to 500 feet agl. He reported that the PA-18-150 appeared to do a wing rock to the right, and then the airplane's wings leveled momentarily. Then the left wing and nose dropped to the left and the airplane went straight down. The witness reported that airplane whipped over fast, like a snap roll. The witness reported that the airplane went straight down, although he did not see the impact due to trees.

Personnel Information

The pilot was a private pilot with a single engine land rating. He held a Third Class medical certificate. He had received his private pilot rating on January 19, 1998, and had a total of about 123 hours of flight time. He had about 35 hours of tailwheel airplane experience. The pilot had flown about 25 hours of flight time in the accident airplane in the 12 days prior to the accident.

The second pilot was a private pilot with a single engine land rating. He held a Second Class medical certificate. He had a total of about 500 hours of flight time. A majority of the flight time had been logged in tailwheel airplanes. He had flown about 21 hours in the accident airplane in the 12 days prior to the accident.

The pilot and second pilot both held Airframe and Powerplant mechanics ratings. Both were employed by a major airline as maintenance technicians.

Aircraft Information

The airplane was a Piper PA-18-150 Super Cub, serial number 18-6673. The engine was a 150 horsepower Lycoming O-360-A2A. The last annual inspection was conducted on October 1, 1997. According to the airplane's tachometer reading, the airplane had flown 22 hours since the last inspection and had a total time of 1,821 hours.

The airplane's logbook and the examination of the airplane indicated that all AD's had been complied with. There was no logbook entry for an Supplementary Type Certificate (STC) for autogas. A weight and balance was not obtained.

Wreckage and Impact Information

The airplane wreckage was located about 1/3 mile west of the departure end of runway 27 at Jensen Airfield. The location was North 38 degrees, 51.334 minutes, West 94 degrees, 47.941 minutes.

The airplane impacted the ground in a grassy ravine surrounded by farm fields. The airplane impacted the ground at about a 50 degree nose down attitude. The outboard 1/2 of the left wing indicated leading edge crush with corresponding buckling of the wing ribs. The broken glass lens of the left wing landing light was located in front of and under the left wing landing light. The ground sloped up to the left at the impact site. The left wing's crush and subsequent collapsing followed the contour of the slope. There was no apparent forward movement of the airplane after it impacted the ground.

The right wing had been removed by emergency personnel. There was no leading edge crush damage. Photographs of the right wing before it was moved indicated that the wing had collapsed forward and downward at impact, buckling the wing struts.

The empennage was largely intact. The empennage tubing located aft of the rear seat was buckled forward and upward at impact. The vertical and horizontal stabilizers exhibited no impact damage.

The engine and cockpit were pointed in a direction of about 090 degrees. The propeller flange was bent back on the crankshaft. The carburetor was broken at its base. The engine fire wall was pressed forward around the rear cylinders and accessory case of the engine. The exhaust had crush damage but the baffles were intact.

One blade of the propeller was visible at the accident site, and the other blade was underneath the engine. The visible propeller blade did not exhibit any scoring or leading edge damage. The blade underneath the engine exhibited leading edge damage and chordwise scratching on the front and back of the blade. The propeller blades did not exhibit forward twist. The propeller dome exhibited some rotational and torque signatures.

The examination of the engine revealed continuity through the drive train. The crankshaft was rotated and thumb compression was evident in all cylinders. The left and right magnetos had spark in all four towers. The spark plugs indicated normal wear. The top spark plugs exhibited some soot.

The inspection of the carburetor revealed that fuel was in the bowl and the accelerator pump was operational. The carburetor had a one piece venturi and metal floats. The fuel that remained in the bowl was clean except for two specks of dirt.

The on-site inspection of the airframe revealed continuity through the flight controls. The wing struts and the strut attach points were examined. The struts and attach points exhibited buckling and overload fractures as a result of impact forces.

The fuel selector was in the right tank position.

Fuel samples were taken from the left wing. The color of the fuel was pale yellow. Contamination was evident in one sample taken. No fuel sample was obtained from the right wing since it had been tipped over and emptied during the extraction of the pilots from the wreckage.

Fuel samples were taken from the fuel tank located in the bed of the pickup. The samples were dark golden in color and were free of contamination. The owner of the pickup reported that the autogas in the fuel tank was 92 octane gasoline and was free of alcohol.

The Fire Chief reported that no water or foam had been used at the accident site.

Medical and Pathological Information

Autopsies were performed on the pilot and copilot at the Regina Medical Center, Hastings, Minnesota.

Forensic Toxicology Fatal Accident Reports were prepared by the FAA Civil Aeromedical Institute. The reports indicated negative results for both pilots.

Tests and Research

Two fuel samples taken from the left wing were examined. The laboratory report indicated that the sample #0898-0010 contained "water which will extract the ethanol and change the octane value of the fuel."

Additional Information

The airplane had recently been purchased by the pilot. The pilot's logbook indicated that he had first flown the airplane on July 24, 1998, for 3.5 hours when he departed Hector, Minnestoa, and landed it at Airlake Airport, Lakeville, Minnesota, where he hangared the airplane.

The pilot's logbook indicated that he flew N9396D on July 25, 1998, for 4.5 hours, and on July 30, 1998, for 2.0 hours. There were no further entries in the pilot's logbook.

The second pilot's logbook indicated that he had flown with the pilot for about 21 hours in N9396D from the time the pilot had purchased the airplane until the day of the accident.

The second pilot's father, a Certified Flight Instructor (CFI), reported that he had given the pilot flight instruction in N9396D on four separate occasions, for a total of about 4.5 flight hours. He reported that he had not entered the flights into the pilot's logbook because the pilot did not have the logbook with him during the instructional flights.

The CFI reported the pilot was a "...fairly low time pilot..." who was "...building confidence in tailwheel aircraft... ." He reported that the pilot, "...did a pretty good job..." of flying and landing the airplane. He reported that the pilot did not need further instruction in tailwheel airplane. He reported that the pilot was building time in tailwheel aircraft.

The CFI reported that he had flown the airplane "quite a bit." He reported that it was "a smooth running airplane." He reported that it was running fine 40 minutes prior to the accident.

A witness reported that the second pilot preferred flying the airplane from the rear seat. The witness reported that he had flown the airplane since it was purchased by the pilot, and that it "...was a good flying airplane."

A witness reported that the pilot and second pilot had departed Airlake Airport, Lakeville, Minnesota, earlier in the day and had landed and shut the aircraft down at Jensen Airfield. The witness reported that at approximately 1630 the pilot went flying with the accident's second pilot's father, a Certified Flight Instructor, for about 30 to 45 minutes. The witness reported that the pilot practiced about 10 to 12 touch and goes. Shortly after 1715, the airplane landed and was shut down.

The witness reported that the pilot and accident second pilot went flying again and did some touch and goes and practiced slow flight maneuvers. The witness reported that the pilot landed about 1830 to 1840 and shut the airplane down. The witness reported that the second pilot fueled the airplane with 20 gallons of autogas, putting 10 gallons of fuel in each wing tank. The fuel was pumped from a tank located in the bed of a pickup. The witness reported that the wing tanks were about 3/4 full (27 gallons) after the airplane had been fueled.

The witness reported that the pilot and second pilot went flying again at approximately 1850 and continued to practice touch and goes in the local pattern at Jensen Field.

The witness left Jensen Airfield in his vehicle and drove to Airlake Airport in order to fly back to Jensen Airfield in a Cessna 152. The witness reported that once he returned to Jensen Field with the Cessna 152, the plan was that both aircraft would depart Jensen Airfield and land at a private airstrip not far from Jensen Field.

The witness reported that he departed Airlake Airport in the Cessna 152 at about 1915. He departed to the north and climbed to about 1,500 to 1,600 feet agl. The witness reported that when he neared Jensen Airfield, he flashed his landing lights two different times to alert the pilot and second pilot who were flying the PA-18-150.

The witness reported that when he was about 1/4 mile south of the Jensen Airfield about 750 feet agl, and in a position to enter a left downwind for runway 27, he flashed the landing lights a second time. He reported that he observed the PA-18-150 climbing out from runway 27 at about 300 to 500 feet agl. He reported that the PA-18-150 was at his 12 o'clock position traveling to the west and perpendicular to his route of flight. He reported that the PA-18-150 appeared to do a wing rock to the right, and then the airplane's wings leveled. The witness reported that the left wing and nose dropped to the left and the airplane went straight down. The witness reported that airplane whipped over fast, like a snap roll. The witness reported that the airplane went straight down, although he did not see the impact due to trees.

The witness circled the accident site once and then landed at Jensen Airfield. The witness and others arrived at the accident site to render assistance, but both pilot's had received fatal injuries. The witness reported smelling fuel at the site, but no fire or explosion occurred.

The aircraft wreckage was released to Aviation Accident Investigation and Management.

Parties to the investigation included the Federal Aviation Administration, the New Piper Aircraft Company, and Textron Lycoming.

NTSB Probable Cause

The loss of engine power due to water-contaminated fuel and the pilot's failure to maintain adequate airspeed which resulted in a stall.