ANC98LA102

The pilot taxied with carburetor heat on, and removed it just before takeoff from a lake. The engine ran rough at 300 feet above the water during takeoff. The pilot applied carburetor heat and the engine smoothed out. The pilot removed carburetor heat, and the engine lost total power. The airplane landed on a gravel road at the end of the lake, collapsing the struts. Inspection of the airplane, engine, and carburetor revealed no anomalies. The engine operated normally on a test stand. The temperature dew point combination falls within the 'moderate icing - cruise power' range of the Transport Canada carburetor icing chart.

On July 18, 1998, at 1554 Alaska daylight time, a float equipped Piper PA-18 airplane, N8162C, sustained substantial damage during a forced landing after takeoff from the Lily Lake Seaplane Base, Kodiak, Alaska. The airline transport pilot was not injured, and the sole passenger sustained minor injuries. The flight was operated under 14 CFR Part 91, as a personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed.

The pilot told the NTSB investigator-in-charge on July 18, that he taxied with carburetor heat applied, and had a normal run-up and magneto check prior to takeoff. He performed a takeoff with carburetor heat off, and at 300 feet above the surface during the initial climb, the engine "coughed." He said he applied carburetor heat and the engine smoothed out. He stated that he then removed carburetor heat and the engine lost total power. There was not enough room to land on the lake, so he landed straight ahead on a road at the departure end of the lake. During the landing roll, the floats contacted soft gravel, and the float struts and fuselage buckled.

The airplane's engine had been overhauled 167 hours prior to the accident. Inspection of the airplane by an FAA inspector revealed no anomalies. The engine was removed to Anchorage, Alaska, and operated normally on a test stand on August 24. The carburetor was disassembled and inspected on September 11, with no anomalies noted.

The Aviation Safety Bureau of Transport Canada chart "Conditions Known Favorable For Carburetor Icing" shows an outside air temperature of 57 degrees Fahrenheit combined with a dew point of 40. Fahrenheit falls in the "moderate icing - cruise power" range.