AUSTIN, NV, USA
N4872A
Piper PA-18-150
The pilot reported that he had been monitoring an increase in the fuel burn rate over a period of time. His normal leaning procedure for best power operating from 5,800 feet mean sea level required more mixture control travel. On the day of the accident, it was the second time that the engine had failed to respond to throttle input. The subsequent loss of engine power occurred low to the terrain. Post accident examination of the carburetor revealed a black composite float that felt heavier than normal. One pontoon exhibited light damage to the smooth shell. The engine spark plugs were lightly fuel sooted. According to Precision Airmotive Corporation "mandatory" Service Bulletin MSA-1(replacement of composite floats with metal floats), the type certificate holder of the carburetor, states that; "field reports indicate that composite floats may be absorbing fluid and sinking," replace the existing composite float with a metal float. A sinking float may result in disruption of fuel flow to the engine, Precision Airmotive therefore considers the replacement of composite floats with metal floats mandatory. Compliance is optional for 14 CFR Part 91 operators.
On June 1, 2000, at 0615 hours Pacific daylight time, a PA-18-150, N4872A, collided with terrain while maneuvering near Austin, Nevada. The aircraft sustained substantial damage and the certificated commercial pilot and his passenger received minor injuries. The aircraft was being operated as a public-use flight by the United States Department of Agriculture, Office of Wildlife Services, when the accident occurred. The flight originated from the Austin airport at 0600. Visual meteorological conditions prevailed at the time and a VFR company flight plan was filed. The pilot reported that he had been monitoring an increase in the fuel burn rate over a period of time. His normal leaning procedure for best power operating from 5,800 feet mean sea level required more mixture control travel. On the day of the accident, it was the second time that the engine had failed to respond to throttle input. The subsequent loss of engine power occurred low to the terrain. Post accident examination of the carburetor revealed a black composite float that felt heavier than normal. One pontoon exhibited light damage to the smooth shell. The engine spark plugs were lightly fuel sooted. According to Precision Airmotive Corporation "mandatory" Service Bulletin MSA-1 (replacement of composite floats with metal floats), the type certificate holder of the carburetor, states that; "field reports indicate that composite floats may be absorbing fluid and sinking," replace the existing composite float with a metal float. A sinking float may result in disruption of fuel flow to the engine, Precision Airmotive therefore considers the replacement of composite floats with metal floats mandatory. Compliance is optional for 14 CFR Part 91 operators.
Loss of engine power caused by a fuel soaked float pontoon causing an over rich fuel/air mixture, in a critical phase of flight.
Source: NTSB Aviation Accident Database
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