Aviation Mechanic - General, Airframe, and Powerplant › III. Powerplant › Task I. Engine Fuel and Fuel Metering Systems

AM.III.I.K2

Knowledge

Float carburetor theory, components, operation, and adjustment.

Study note

Get a short, cited explanation of this element written from the FAA handbooks: the core idea, the numbers that matter, common test traps, and a quick self-check.

From the FAA library

Aviation Maintenance Technician Handbook - Powerplant p. 2-10
Chapter 2: Engine Fuel & Fuel Metering Systems › Float-Type Carburetors › Float Chamber Mechanism System
correct amount of fuel flow and to prevent fuel leakage from the nozzle when the engine is not operating. The level of fuel in the float chamber is kept nearly constant by means of a float-operated needle valve ... hardened steel, or it may have a synthetic rubber section which fits the seat. With no fuel in the float chamber, the float drops toward the bottom of the chamber and allows the needle valve to open wide. As fuel…
Pilot's Handbook of Aeronautical Knowledge p. 7-8
Chapter 7: Aircraft Systems › Propeller Overspeed in Piston Engine Aircraft › Carburetor Systems
Figure 7-10. Float-type carburetor. The fuel-air mixture is then drawn through the intake manifold and into the combustion chambers where it is ignited. The float-type carburetor acquires its name from a float that rests on fuel ... within the float chamber. A needle attached to the float opens and closes an opening at the bottom of the carburetor bowl. This meters the amount of fuel entering into the carburetor, depending upon the position of the float, which…
Aviation Maintenance Technician Handbook - Powerplant p. 2-2
Chapter 2: Engine Fuel & Fuel Metering Systems › Basic Fuel System
During starting, the boost pump forces fuel through a bypass in the engine-driven pump to the metering device. Once the engine-driven pump is rotating at sufficient speed, it takes over and delivers fuel to the metering device ... specified pressure. The airframe fuel system begins with the fuel tank and ends at the engine fuel system. The engine fuel system usually includes the engine-driven pumps and the fuel metering systems. In aircraft powered with a reciprocating engine…
Aviation Maintenance Technician Handbook - Powerplant p. 2-41
Chapter 2: Engine Fuel & Fuel Metering Systems › Engine Fuel System Components › Main Fuel Pumps (Engine Driven)
typical two-stage turbine engine driven pump is illustrated in Figure 2-60. The impeller, which is driven at a greater speed than the high pressure elements, increases the fuel pressure depending upon engine speed. The fuel is discharged from ... discharge port of the pump. This valve opens at a predetermined pressure and is capable of bypassing the total fuel flow. This allows fuel in excess of that required for engine operation at the time to be recirculated. The bypass…
Aviation Maintenance Technician Handbook - Powerplant p. 2-40
Chapter 2: Engine Fuel & Fuel Metering Systems › Fuel Control Maintenance › Fuel System Operation
Water Injection System Fuel Control Maintenance Fuel System Operation The fuel pump receives fuel from the airplane fuel system. The low pressure boost stage of the pump pressurizes the fuel and sends it to the fuel/oil cooler (FOC). The fuel ... flows from the FOC, through the fuel pump filter element, and then to the high pressure main stage of the pump. The high pressure main stage increases the fuel pressure and sends it to the fuel metering unit…