Occurrence
The float-equipped Cessna 185F, registration C-GAXK and serial number 18502673, departed from a remote fishing camp approximately 21 miles east of Orillia, Ontario, with two passengers and their belongings. The aircraft climbed to about 1000 feet above ground level and headed toward its home base at Orillia. A few minutes into the flight, the Teledyne Continental IO-520-D engine lost power. The pilot moved the mixture control to full rich and selected the auxiliary electric fuel pump on, which restored power. The flight continued with the auxiliary pump selected on. Shortly thereafter, the pilot switched off the auxiliary pump, and the engine immediately lost power again. The pilot applied full throttle, switched fuel tanks, and re-selected the auxiliary pump on, but the engine did not regain power.
An emergency landing was performed in a wetland area at 1308 eastern daylight time. After touchdown, the aircraft traveled a short distance over soft, wet ground, struck a tree, and came to a stop. One passenger sustained a minor injury, and all three occupants evacuated the aircraft safely. The aircraft was substantially damaged. The pilot maintained radio and cellular communications with another company aircraft and the home base. The occupants were evacuated by a search and rescue helicopter shortly after.
Weather conditions at the time included winds from the southwest at 5 to 10 knots, visibility six nautical miles or greater, an overcast sky, and a temperature of 30°C.
Investigation
Records indicated that the aircraft was maintained in accordance with existing regulations and procedures, and the pilot was qualified for the flight. The aircraft was moved from the accident site by helicopter to a hangar in Orillia. The engine had been rebuilt by Teledyne Continental in September 2001 and had accumulated about 480 hours since. The last maintenance, involving repair to a leaking propeller blade seal, occurred six weeks before the incident. There were 14 hours of flight time remaining until the next 50-hour inspection.
The lower side of the engine oil sump was damaged during the occurrence, and most of the engine oil drained. The oil filter was free of contamination, and the spark plugs tested serviceable. A fuel sample from the gascolator was consistent with 100LL fuel and free of contamination. The internal fuel screen contained a small amount of sediment but not enough to affect fuel flow. All fuel lines at the rear of the engine compartment were secure with no leakage.
The fuel feed line to the fuel distributor was disconnected, and the auxiliary fuel pump was selected on to verify fuel supply and pressure; fuel flow and pressure increased. When the auxiliary pump was selected off and the fuel selector switched to the other wing tank, then selected back on, the pump operation became intermittent and finally stopped. The auxiliary fuel pump wiring showed signs of corrosion at the solder connection to the resistor block, with minimal contact.
The engine, electrical wires, and auxiliary fuel pump switch were removed for further examination. Fuel components were tested at an approved shop; all except the engine-driven fuel pump (EDP) operated within specifications. When fuel flow to the EDP was raised to specifications, output pressure dropped below spec; when pressure was raised, flow dropped below spec. The pump was disassembled, revealing a piece of thread sealant lodged between the ball and seat in the bypass valve.
Findings
Engine power was restored when the pilot selected the auxiliary fuel pump on, as the additional fuel pressure was sufficient to overcome the deficiency caused by the foreign material in the EDP bypass valve. When the auxiliary pump was selected off, the engine immediately lost power. The pilot's re-selection of the auxiliary pump failed because the pump's operation had become intermittent due to a poor electrical connection at the resistor block, and it did not operate when selected a second time.
The piece of thread sealant in the EDP bypass valve resulted in inadequate fuel pressure for normal engine operation unless the auxiliary fuel pump was on. The poor electrical connection within the auxiliary fuel pump caused intermittent operation, and when the pilot re-selected the pump, it did not provide additional pressure.