MIA93FA183

The pilot was deviating around weather during descent when he noted the fuel flow and manifold pressure on the left engine oscillating. Because the propeller was still turning he elected not to feather the left propeller. The airplane would not maintain altitude so he lowered the landing gear and ditched the airplane in a swamp. Examination of the left fuel tank revealed the fuel float valve actuators and float arms excessively worn. This condition would allow unmetered air into the fuel lines. Also noted was the condition of one of the left fuel valves that could jam open allowing the fuel pickup to unport and induce excessive air into the fuel lines.

History of flight

On August 25, 1993, about 0855 eastern daylight time N206RH, a Cessna 402C, operated by Air Sunshine Inc. ditched in the Everglades near Andytown, Florida, while on a 14 CFR Part 135 commuter, scheduled, domestic, passenger flight. Visual meteorological conditions prevailed at the time and a VFR flight plan was filed. The airplane was substantially damaged and the pilot and three passengers received minor injuries, and one passenger received serious injuries. The flight was operating as flight No. 1721 and originated from Sarasota, Florida, about 35 minutes earlier.

The pilot stated that he lost power on the left engine and did not feather the propeller because he thought the engine was still producing partial power. The airplane was not able to maintain altitude, so he lowered the landing gear and ditched the airplane in swampy water. The pilot stated later that he remembered the manifold pressure on the left engine was about 15 inHg and the fuel pressure was oscillating before and during the loss of power.

Personnel information

Pilot information is located in the crew information section of this report.

Aircraft information

Historical airplane and engine information is located in this report and attachments.

Wreckage and impact information

The wreckage was documented on scene and the wreckage was removed from the swamp and subsequently examined at multiple locations. The fuel float valves in both the left and right wing tanks were marked and removed. All the floats were found not damaged but the plunger actuators were found excessively worn and would stick in the open position. The valves were forwarded to the FAA EMDO in Wichita, Kansas, for further examination. Both the left and right engines were dried out and water was drained from the engine interiors. Both engines were mounted on a test stand with run up "club" propellers. Both engines started and ran to full power with no other discrepancies noted.

Tests and research

The fuel valves were examined and tested both in a laboratory and on a static wing at various fuel quantities and various bank angles. At the lower fuel quantities and higher bank angles it was determined that air could enter the fuel lines and be pumped to the engines. This would give a leaner than scheduled air/fuel flow to the engines and could produce a partial loss of power. The fact that some of the actuators could jam open was also noted. In flight this could in combination with turbulence cause an unported fuel line pumping unscheduled air to an engine.

Additional information

The wreckage of N206RH was released to Mr. Richard Deickhoff, of Air Claims, representing the owner, on September 1, 1993, and the six floats were released to Mr. Richard Deickhoff on November 2, 1994.