NTSB Factual Report

On July 15, 2017, about 1700 Alaska daylight time, a float-equipped Cessna A185F airplane, N401WC, sustained substantial damage during a forced landing following a loss of engine power about 5 miles southwest of the Wasilla Airport (IYS), Wasilla, Alaska. The private pilot, the sole occupant, sustained no injuries. The airplane was registered to and operated by the pilot as a 14 Code of Federal Regulations Part 91 visual flight rules flight. Visual meteorological conditions prevailed and no flight plan was filed. The flight departed the Lake Louise Seaplane Base, Lake Louise, Alaska, about 1600, destined for Campbell Lake Seaplane Base, Anchorage, Alaska.

During an interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot stated that the purpose of the flight was to reposition the airplane from a cabin on Lake Louise to his home on Campbell Lake. On the day of the accident, about 1 hour into the 1.3-hour flight, he noticed that the digital fuel flow indicator was showing a fuel flow of 11 gallons per hour (gph) before it rapidly decreased to 4 gph. When the decrease occurred, the left fuel tank quantity gauge indicated zero and the right fuel tank quantity gauge indicated about ½ full. He said he verified that the fuel selector valve was in the "both" position and he advanced the throttle to full open. The fuel flow increased to 15.6 gph and then the engine sputtered and lost all power. The pilot maneuvered to perform a forced landing on the mudflats north of the Knik Arm inlet. During the forced landing touchdown in an area of tall grass, the left float contacted a log, and the airplane nosed over. The airplane came to rest inverted and the pilot safely egressed.

The pilot stated that he last fueled the airplane on July 11, prior to flying north to Lake Louise, and at that time, the airplane had about 62 gallons of fuel on board. During his preflight inspection, he sumped all the fuel tanks and visually checked the fuel levels in both wing tanks. The flight to Lake Louise was uneventful.

On the day of the accident, just before departure, the fuel quantity indicators each read 3/4 full and he verified that by visual inspection of the fuel tank quantities. He then sumped the fuel tanks and gascolator, he noted no water or particle contamination was present.

The pilot reported that the airplane flew about 2.3 hours since the fueling on July 11.

On the day of the accident, a Federal Aviation Administration (FAA) aviation safety inspector witnessed the airplane flying low over the Wasilla mudflats just prior to the accident. He stated that as he watched the airplane descend towards the mud-covered beach, he heard the engine sputtering for about 45 seconds. He said that just before the airplane's floats touched down, he momentarily heard the engine power increase, which was followed by silence. The FAA inspector then responded to the scene of the accident and noted that the airplane was inverted and that there was no fuel leaking from the airplane. The airplane sustained substantial damage to the wings, left lift strut and vertical stabilizer.

Following recovery of the airplane to a secure storage facility, the NTSB IIC and FAA inspector conducted an examination and documentation. The left fuel quantity gauge indicated empty and the right tank indicated about ½ full. The four fuel tank caps were in place and secure and the tanks were visually inspected. The tanks were drained and fuel from the left tank measured about 1 3/4 gallons and the right tank measured about 8 gallons. The fuel quantity indicators both read empty after draining the tanks.

The airplane was outfitted with extended range fuel tanks. The Cessna A185F owner's manual lists the maximum fuel capacity as 84 gallons, with 6 gallons unusable. The fuel tank caps were a vented design. An Electronics International FP-5L digital fuel flow monitor was installed and operable.

The airplane was equipped with a Continental Motors IO-520 series engine. A detailed engine examination is pending.