AIRCRAFT SYSTEMS - OUTSIDE AIR TEMPERATURE GAUGE AND FUEL INJECTION SYSTEMS

OUTSIDE AIR TEMPERATURE GAUGE
Most airplanes also are equipped with an outside air temperature (OAT) gauge calibrated in both degrees Celsius and Fahrenheit. It provides the outside or ambient air temperature for calculating true airspeed, and also is useful in detecting potential icing conditions.

AIRCRAFT SYSTEMS - CARBURETOR AIR TEMPERATURE GAUGE

Some airplanes are equipped with a carburetor air temperature gauge, which is useful in detecting potential icing conditions. Usually, the face of the gauge is calibrated in degrees Celsius (C), with a yellow arc indicating the carburetor air temperatures where icing may occur.

AIRCRAFT SYSTEMS - CARBURETOR HEAT

Carburetor heat is an anti-icing system that preheats the air before it reaches the carburetor. Carburetor heat is intended to keep the fuel/air mixture above the freezing temperature to prevent the formation of carburetor ice. Carburetor heat can be used to melt ice that has already formed in the carburetor provided that the accumulation is not too great. The emphasis, however, is on using carburetor heat as a preventative measure.

AIRCRAFT SYSTEMS - FUEL MIXTURE NEEDLE

The mixture needle controls fuel to the discharge nozzle. Mixture needle position can be adjusted using the mixture control.

AIRCRAFT SYSTEMS - OTHERS

CARBURETOR ICING
One disadvantage of the float-type carburetor is its icing tendency. Carburetor ice occurs due to the effect of fuel vaporization and the decrease in air pressure in the venturi, which causes a sharp temperature drop in the carburetor. If water vapor in the air condenses when the carburetor temperature is at or below freezing, ice may form on internal surfaces of the carburetor, including the throttle valve.

AIRCRAFT SYSTEMS - MIXTURE CONTROL

Carburetors are normally calibrated at sea-level pressure, where the correct fuel-to-air mixture ratio is established with the mixture control set in the FULL RICH position. However, as altitude increases, the density of air entering the carburetor decreases, while the density of the fuel remains the same.

AIRCRAFT SYSTEMS - CARBURETOR SYSTEMS

Carburetors are classified as either float-type or pressure-type. Pressure carburetors are usually not found on small airplanes. The basic difference between a pressure carburetor and a float-type is the pressure carburetor delivers fuel under pressure by a fuel pump.