HORSESHOE BEND, AR, USA
N800C
Stinson 108-3
After refueling an empty right fuel tank, the airplane commenced a takeoff roll, and about 400 feet down the runway, the engine 'quit', and the takeoff was aborted. Afterwards, the pilot made several engine run ups and high speed taxis to diagnose the problem. With no problems detected, he attempted another takeoff, and climbing through 75 feet AGL the 'engine lost power' again. The pilot made a 'hard left turn' to avoid electrical wires, trees, and houses. The airplane then impacted down sloping terrain. Fuel samples were found to be clear and free of contaminants. After the accident, the pilot said that it was common to find mud wasp nests throughout the airframe, and that the right fuel tank had been empty for 3-4 weeks. He stated that he thinks that the fuel vent was blocked by a mud wasp nest. This would result in a vacuum effect because of the unoccupied space between the fuel and top of the tank. The vacuum effect would prevent fuel from entering the fuel lines and result in fuel starvation to the engine.
On September 11, 1997, at 1016 central daylight time, a Stinson 108-3 airplane, N800C, registered to and operated by the pilot, was substantially damaged following a forced landing immediately after take-off, from Horseshoe Bend Airport, Horseshoe Bend, Arkansas. Of the 2 occupants, the commercial pilot received serious injuries and the one passenger received minor injuries. Visual meteorological conditions prevailed, and a VFR flight plan was filed for the Title 14 CFR Part 91, personal cross country flight. The flight originated from Horseshoe Bend Airport at 1015. The following information was obtained from NTSB Form 6120.1/2 (Pilot/Operator Report), and a telephone interview with the pilot conducted by the Safety Board. The pilot flew the airplane from his property located in Ash Flat, Arkansas, to the Horseshoe Bend Airport earlier that morning, which is approximately a 10 minute flight. During that flight, the left fuel tank was selected because the right tank was empty, and had been empty for the previous three to four weeks. Upon arrival at Horseshoe Bend, the airplane was refueled with automotive fuel to prepare for a planned cross country flight to Westosha, Wisconsin. During the refueling the pilot was distracted, which resulted in overflowing the right fuel tank. The pilot took samples from the fuel drains after refueling and found no water or debris. After his static preflight, the pilot performed an engine run-up at 1500 RPM, which included a magneto and carburetor heat check, which yielded no discrepancies. He selected the right fuel tank for take-off because it was "too full." The winds were light and variable when he initiated a take off roll on runway 13. Approximately 400 feet down the runway, the engine "quit", and the take off was aborted. The pilot restarted the engine and performed a "normal" run-up, which included pulling "the mixture control out far enough to over-lean the engine to make sure there were no mixture problems." He then executed a high speed taxi down the runway. After successfully completing the first high speed taxi, he completed a second run-up and high speed taxi, during which he became airborne "...for a short distance." Upon completion of this last check, he taxied back to runway 13 to attempt another departure. The 3,000 hour commercial pilot added that, the airplane became airborne and was climbing through an altitude approximately 75 feet above ground level, when he retracted the flaps. As the flaps retracted, the "engine lost power and the prop[eller] wind milled." Unable to land on the runway, the pilot was forced to make a "hard left turn" to avoid electrical wires, trees, and houses. Subsequently, the airplane contacted the ground with the left wing, and turned approximately 120 degrees to the left while sliding down sloping terrain. The airplane came to rest upright resting on the right wing tip, approximately 75 feet from the departure end of the runway. A few minutes after moving away from the airplane, the pilot heard someone yell, "Get away from the airplane, gas is spurting out!" The pilot stated the he looked towards the airplane and observed fuel spurting out, 2-3 feet forward of the right wing fuel vent. Another witness also observed fuel coming from the "vent on top of the [right] wing." The fuel vent is located on the outboard end of the tank. Examination of the wreckage by an FAA inspector revealed that the left main gear folded under the airframe and the right main gear separated from the aircraft. The firewall was structurally damaged, and the passenger door separated from the aircraft. Significant damage was sustained by both wing tips, the propeller, engine, engine mounts and forward fuselage frame. Samples of fuel obtained by a FAA inspector were found to be clear and free of contaminants. After the accident, the pilot reported that during annual inspections it was common to find mud wasps, commonly referred to as "dirt daubers," throughout the airframe. He said that he had never experienced plugged fuel vents (from mud wasps) because the tanks were never empty and fuel fumes were so strong in the top vents, they kept the wasps away. However, in his opinion, since the right fuel tank had been empty so long (3 weeks), their were no fumes to keep them out of the vent. The pilot further explained that the mud wasps frequently built nests inside his airplane and were a "constant problem." The pilot indicated that he did not blow into the fuel vent during the pre-flight inspection and thinks that the fuel vent was blocked by mud wasps. This would result in a vacuum effect because of the unoccupied space between the fuel and top of the tank. The vacuum effect would prevent fuel from entering the fuel lines and result in fuel starvation to the engine and consequently a loss of engine power. He relayed that, "a plugged vent explains why no fuel was spurting out the vent at first; the fuel flowed slowly until it loosened the mud nest, then it blew all at once. Mud nests quickly dissolve when exposed to any liquid."
Fuel starvation due to partially blocked fuel vents. Factors were: the pilot's inadequate preflight inspection of the airplane; the pilot's improper decision to continue operation of the airplane with known deficiencies; and the lack of suitable terrain for the forced landing.
Source: NTSB Aviation Accident Database
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