On February 24, 1996, at 1030 eastern standard time (est), a Piper PA-22-150, N6939B, piloted by a private pilot, was substantially damaged when it nosed over during a forced landing onto a muddy field. The pilot reported a total loss of power during cruise flight. The 14 CFR Part 91 flight was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The pilot and pilot rated passenger reported no injuries. The flight departed Rochester, Indiana, at 1015 est.

The pilot said the airplane had been flying about 7 minutes when he changed his fuel tank selector position from the "Right" to "Left." He said N6939B's engine abruptly stopped running about 7 minutes later. Following the power loss the pilot said he immediately switched back to the "Right" fuel tank. The pilot said the engine power surged once and then stopped. He said the engine would not start after he manipulated the engine controls and magnetos.

The passenger, according to the pilot, continued to prime the engine during the emergency descent. The engine did not regain power during this activity. The pilot said the airplane could not glide to the field he had originally chosen. He said he had to use a plowed field next to his chosen field. The pilot said he could not line up with the field's furrows due to his airplane's altitude and heading. The airplane landed cross-furrow, nosing over shortly after touchdown.

The passenger said the engine stopped running suddenly when the pilot switched fuel tanks. He said the pilot switched the fuel selector back to the "Right" fuel tank and the engine power surged briefly. The engine stopped running immediately after the power surge.

A Federal Aviation Administration Principal Maintenance Inspector (PMI) represented the NTSB during the on-scene investigation. The PMI said the field was very soft mud. He reported that N6939B's main landing gear tires were caked with mud. The tailwheel did not have any mud on it according to the PMI. The PMI said fuel was leaking out of both fuel tank caps. The PMI said he found "...several droplets of dirty water..." in the fuel strainer. No water was found when the fuel system sumps were drained.

The magnetos, sparkplug leads, and sparkplugs were tested on a testing unit. The PMI said the ignition components met the manufacturer's operating specifications during the test. According to the PMI, engine control continuity was established for the throttle, mixture, and carburetor heat.

The carburetor's finger screen was not contaminated. Inspection of the carburetor float bowl revealed 2, 1/2 diameter by 1/4 inch deep markings on either side of the bowl. These markings "...indicated there had been some water or other foreign mater that had dried and since flaked off..." according to the PMI.

Contaminants were not found in the carburetor's accelerator pump well. The carburetor's seals and gaskets did not show evidence of deterioration. The carburetor's metering valve and jet were free of contamination. The needle valve was not damaged and its set was not obstructed.

According to the PMI, the right fuel tank had about 1 quart of fuel in it. The left fuel tank had about 7 gallons of fuel in it. He said the airplane had been upside down in a wing's level position with a 10 degree nose down attitude. The PMI said the fuel caps were tightly installed and their respective gaskets were not damaged.

The FAA's Flight Training Handbook, AC 61-21A, states that a soft field landing in a tailwheel airplane should be done with the tailwheel "...touch[ing] down with or just before the main wheels... ." On-scene evidence showed N6939B landed on its right main gear tire, then its left main gear tire, followed by the right tire. Its landing roll was about 50 feet before it nosed over. The valleys between the furrows were about 6 inches below the rounded furrow crowns.

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