The objective of this project is to determine the effects of long-term subjection of an aircraft fuel system to ethanol based fuel. The fuel system investigated was manufactured by Teledyne Continental Motors, and included the fuel pump, flow controller, and auxiliary components such as a flow divider, hoses and fittings.;The project entailed the design and implementation of both an enclosed fuel system incorporating a TCM 646212-23A1 fuel pump and 639715A16 fuel flow controller, as well as supporting electronic devices capable of varying the fuel flow settings according to a simulated flight schedule, while monitoring the performance of the tested parts. Once the system was designed and constructed, the system was subjected to an automated test lasting over nine months, during which the system was monitored to observe performance as subjected to ethanol based fuel.;Finally, after nine months of operation, the test was concluded, the data was gathered and analyzed, and the performance of the fuel system was evaluated. The fuel system had logged over 3700 hours of simulated flight time, and another 1800 hours of fuel system soaking. Since the manufacturer recommended time before overhaul for this specific system was 1800 hours, under normal conditions, this fuel system would have undergone two overhauls during this period. The test was concluded because of a failure of the DC motor used to power the fuel pump. This motor was not part of the fuel system; its failure was a result of worn and corroded brushes.;With regard to the performance of the pump, the data revealed little change in fuel pressure throughout the test (5.8% decline, worst-case); though the torque required to circulate the fuel had fallen 6% after an initial break-in period. When the data were considered together, these changes likely revealed the deteriorating condition of the motor, not deterioration within the fuel pump.;Regarding the fuel servo, the data indicated the fuel pressure exiting the servo for the fuel flow divider had fallen approximately 12%. However, since the inlet pressure (pump pressure) had fallen 5.8% over the same period, the majority of this change most likely reflected the condition of the fuel pump and motor drive, not deterioration within the servo. Also, data indicated the torque required to adjust the mixture and throttle settings had increased approximately 7 and 27% respectively. Though these results may indicate some deterioration of the seals within the fuel servo, the results were not alarming, since neither leakage was observed nor did external testing indicate similar changes.;When all factors are considered together - the deterioration of the motor, the length of the test exceeding beyond two recommended overhauls - the data indicates ethanol-based fuel caused no abnormal wear to the fuel system.
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