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N925KM accident description

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Crash location 41.550000°N, 70.483333°W
Nearest city Mashpee, MA
41.616776°N, 70.499472°W
4.7 miles away
Tail number N925KM
Accident date 02 Aug 2010
Aircraft type Cessna 177B
Additional details: None

NTSB Factual Report

On August 2, 2010, about 1205 eastern daylight time, a Cessna 177B, N925KM, registered to Rocky Wings, Inc., sustained substantial damage while ditching after a loss of engine power near the southern coastline of Mashpee, Massachusetts. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight conducted under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The private pilot and one passenger were not injured. The flight originated from Fairmouth Airpark, Fairmouth, Massachusetts, about 1000.

The pilot stated that he conducted a thorough preflight inspection and engine run-up before departure, with no discrepancies noted. The flight departed with full fuel tanks and flew locally at 1,000 feet with the power set to 20 inches manifold pressure and 2,300 rpm for most of the flight. While south of Mashpee, preparing to return to the departure airpark, the pilot moved the propeller control to the low pitch position and applied carburetor heat, but the engine lost power. He immediately removed carburetor heat which did not restore engine power, and trimmed to maintain 70 knots while attempting to restore engine power by the application of carburetor heat, and switching the fuel selector to the left and right positions. The engine responded for a few seconds then lost power again. The pilot then concentrated his efforts at flying the airplane and elected to ditch the airplane away from the beach area. The airplane remained upright after water contact and both occupants exited from the co-pilot's door and swam to shore.

Examination of the engine by a Federal Aviation Administration (FAA) airworthiness inspector revealed crankshaft, camshaft, and valve train continuity. Inspection of the ignition system components consisting of the magnetos, spark plugs, and ignition leads revealed no evidence of preaccident failures or malfunctions. Inspection of the air induction and exhaust systems revealed some impact damage but there was no evidence of preaccident failures or malfunctions. Inspection of the oil filter revealed no ferrous contamination, and the fuel system components consisting of the carburetor, engine-driven fuel pump, auxiliary fuel pump and flexible fuel lines revealed no evidence of preaccident failures or malfunctions. No mechanical reasons for the reported loss of engine power could be determined.

Review of FAA Special Airworthiness Information Bulletin CE-09-35, titled Carburetor Icing Prevention revealed that, based on the temperature and dew point about the time of the accident, 75 and 52 degrees Fahrenheit respectively, the atmospheric conditions were favorable for serious icing at glide power.

NTSB Probable Cause

The pilot’s delayed use of carburetor heat while flying at reduced power settings in conditions that were favorable for carburetor icing resulting in the partial loss of engine power.

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