Narrative:

I departed from lake hood seaplane base in a C180 using a standard west departure. I had performed a thorough preflight, which included pumping the floats, checking all float attachments, added 1 quart of oil, and filling the tanks with gas. I taxied toward the west and did a run-up and everything was normal. I contacted lake hood tower and was cleared for departure. Their sky was clear and the wind was negligible. Takeoff was normal in all ways. Upon reaching a safe airspeed and altitude, I retracted the flaps and began a climbing right turn to the north. After traveling about 1/2 mi, I began to reduce power and when I did so the engine began to run extremely rough. A small amount of smoke came from the right cowl, so I reduced power. It appeared to me that the engine was going to fail and that I needed to land immediately. I was at 300 or 400 ft and was not certain that I could turn around and land on lake hood if I lost total power, so I advised lake hood tower that I had an engine problem and was landing in cook inlet. I saw no other aircraft nearby. The inlet was almost calm and the wind was negligible. I saw no boats or objects in the water or any people on the mudflats nearby. The landing was normal with no damage to the aircraft. I landed about 75 yards from the shore and was able to taxi but the engine was still running very rough. I called lake hood tower and told them I did not require emergency assistance. After some discussion with lake hood tower and anchorage ground control, it was decided that I should taxi to the anchorage small boat harbor which I did without incident. I beached the aircraft in the mudflats to the north of the public boat launch, shut the engine down and waited for assistance. I examined the engine and saw oil leaking from the #3 cylinder and assume the engine problem was the result of cylinder failure. I do not believe there is anything that can be done to prevent such occurrences.

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Original NASA ASRS Text

Title: A C180 FLOAT PLANE PVT PLT MAKES AN EMER OFF ARPT LNDG IN COOK INLET WITH A ROUGH RUNNING ENG AFTER A NORMAL DEP FROM LHD, AK.

Narrative: I DEPARTED FROM LAKE HOOD SEAPLANE BASE IN A C180 USING A STANDARD W DEP. I HAD PERFORMED A THOROUGH PREFLT, WHICH INCLUDED PUMPING THE FLOATS, CHKING ALL FLOAT ATTACHMENTS, ADDED 1 QUART OF OIL, AND FILLING THE TANKS WITH GAS. I TAXIED TOWARD THE W AND DID A RUN-UP AND EVERYTHING WAS NORMAL. I CONTACTED LAKE HOOD TWR AND WAS CLRED FOR DEP. THEIR SKY WAS CLR AND THE WIND WAS NEGLIGIBLE. TKOF WAS NORMAL IN ALL WAYS. UPON REACHING A SAFE AIRSPD AND ALT, I RETRACTED THE FLAPS AND BEGAN A CLBING R TURN TO THE N. AFTER TRAVELING ABOUT 1/2 MI, I BEGAN TO REDUCE PWR AND WHEN I DID SO THE ENG BEGAN TO RUN EXTREMELY ROUGH. A SMALL AMOUNT OF SMOKE CAME FROM THE R COWL, SO I REDUCED PWR. IT APPEARED TO ME THAT THE ENG WAS GOING TO FAIL AND THAT I NEEDED TO LAND IMMEDIATELY. I WAS AT 300 OR 400 FT AND WAS NOT CERTAIN THAT I COULD TURN AROUND AND LAND ON LAKE HOOD IF I LOST TOTAL PWR, SO I ADVISED LAKE HOOD TWR THAT I HAD AN ENG PROB AND WAS LNDG IN COOK INLET. I SAW NO OTHER ACFT NEARBY. THE INLET WAS ALMOST CALM AND THE WIND WAS NEGLIGIBLE. I SAW NO BOATS OR OBJECTS IN THE WATER OR ANY PEOPLE ON THE MUDFLATS NEARBY. THE LNDG WAS NORMAL WITH NO DAMAGE TO THE ACFT. I LANDED ABOUT 75 YARDS FROM THE SHORE AND WAS ABLE TO TAXI BUT THE ENG WAS STILL RUNNING VERY ROUGH. I CALLED LAKE HOOD TWR AND TOLD THEM I DID NOT REQUIRE EMER ASSISTANCE. AFTER SOME DISCUSSION WITH LAKE HOOD TWR AND ANCHORAGE GND CTL, IT WAS DECIDED THAT I SHOULD TAXI TO THE ANCHORAGE SMALL BOAT HARBOR WHICH I DID WITHOUT INCIDENT. I BEACHED THE ACFT IN THE MUDFLATS TO THE N OF THE PUBLIC BOAT LAUNCH, SHUT THE ENG DOWN AND WAITED FOR ASSISTANCE. I EXAMINED THE ENG AND SAW OIL LEAKING FROM THE #3 CYLINDER AND ASSUME THE ENG PROB WAS THE RESULT OF CYLINDER FAILURE. I DO NOT BELIEVE THERE IS ANYTHING THAT CAN BE DONE TO PREVENT SUCH OCCURRENCES.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.