Pumped

This aircraft was equipped with a turbonormalizing system, which requires a fuel pump with an aneroid compensator to regulate the mixture replaces the original pump. On this installation, the fuel mixture cam profile was erroneous. Fuel flow rate increased normally from idle cutoff to approx 80 percent of mixture-lever range of motion where fuel flow is at maximum. Then the fuel ratio decreases as lever continues toward maximum position: 80 percent mixture provides 37.5 gph; 100 percent provides 35.5 gph.

Key Takeaways:

• Several aircraft experienced fuel pump malfunctions, including an erroneous fuel mixture profile, fuel system contamination from a leaking pump, abnormally high fuel pressure, and external fuel leaks.
• A hydraulic pump failure on a Piaggio P.180 Avanti resulted in partial landing gear retraction and impaired directional control and braking during landing.

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