Squawk Box

August 2015 Issue


The following information is derived from the FAA’s Service Difficulty Reports and Aviation Maintenance Alerts.

Cirrus SR22TN
Bad Fuel Mixture Profile

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.

Part total time: Unknown

Diamond DA20-C1
Contaminating Fuel Pump

Engine shutdown in flight. Inspection revealed a fine dark particulate contaminating fuel system. Airframe boost pump appeared to be source of contamination. The airframe boost pump was leaking fuel from isolation chamber between pump and motor sections of boost pump and from the seam where the pump section attaches to the isolation chamber.

Part total time: Unknown

Piper PA-44-180 Seminole
Redlined Fuel Pressure

During climbout, pilots noted the right engine’s fuel pressure was at redline, eight psi. Turning off the electric fuel pump reduced pressure into the green arc. The aircraft returned to the airport. Using a secondary, calibrated pressure gauge, maintenance found the gauge was indicating correctly, and the electric fuel pump was producing abnormally high pressure. The electric fuel pump was replaced and no further defects were noted.

Part total time: 520.0 hours

Piper PA-46-350P Malibu Mirage
Leaking Fuel Pump

During annual inspection, the engine-driven fuel pump was found to be leaking fuel from the relief valve gasket. Fuel also was found in the upper deck pressure lines at the pump. An existing service bulletin references the same problem and includes the model number of this pump but not this serial number.

Part total time: 932.0 hours

Piaggio P.180 Avanti
Landing Gear Hydraulic Pump Failure

After departure, landing gear only partially retracted and hydraulic pump failed. Crew ran the emergency checklist, which requires the gear to be pumped down. Three green lights were obtained and the aircraft landed at the departure airport. Hydraulic pump failure contributed to the inability to maintain directional control and braking at the end of the roll out. Hydraulic system circuit breaker reset and system operation was normal.

Part total time: Unknown