Flight Crew Commercial; Flight Crew Instrument; Flight Crew Sea
Flight Crew Last 90 Days 100; Flight Crew Total 10000; Flight Crew Type 4000
Confusion; Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Flight Crew Landed in Emergency Condition; General Maintenance Action
Aircraft
While operating a seaplane in conjunction with a private yacht the engine quit while in level flight. The seaplane was over calm water and landed without damage. The yacht dispatched a tow boat and recovered the airplane on board.Subsequent investigation found that fuel was not being delivered to the engine (Total Time Aircraft and Engine was 59.25 hours). Fuel present on board was 4.0 gallons as indicated on the EFIS (Electronic Flight Instrument System) and visual sighting of the tank. The Pilot Operating Handbook lists unusable fuel as 1 gallon. Subtracting the listed unusable fuel leaves 3.0 gallons providing over 30 minutes of fuel at cruise settings with the indicated fuel quantity (for 5 GPH). The fuel filter was checked for blockage and found to be partially obscured (estimated blockage less than 50%); but still capable of fuel flow. The threaded fuel filter cover was found to be snug; but not requiring significant wrench torque to open (an O-ring provides the primary seal for the cover). Fuel was added and the engine started and ran normally. Further investigation found the inlet head for the fuel pumps exceeds the maximum specified in the Rotax engine installation manual. The measured distance from the bottom of the tank to the inlet fuel filter was found to be 14 inches (310 mm); exceeding the maximum of 10 inches (250 mm) specified in the Rotax document. The problem is easily avoided by allowing for a greater margin of unusable fuel. Unfortunately in an airplane with limited useful load the additional weight is a consideration. A modification of the fuel system to meet Rotax engine specifications is the real solution. It would also help to have a factory specification for torque to secure the fuel filter housing cover.
A 2014 Searey LSA Elite pilot reported an engine failure followed by a successful calm water landing. Troubleshooting revealed fuel starvation because the fuel line from the tank to the fuel pump filter inlet was too long resulting in low head pressure when the fuel quantity got low.