Pressure carburetor
A pressure carburetor is a type of fuel metering system manufactured by the Bendix Corporation for piston aircraft engines, starting in the 1940s.
The problem was keenly felt by the RAF during the first years of World War II, because the Rolls-Royce Merlin engines fitted to Hurricanes and Spitfires suffered from the problem, unlike the direct fuel injection engines of their German counterparts.
It was largely solved by installing a flow-restricting washer that allowed just enough fuel into the carburetor for the engine to develop maximum power (the R.A.E.
Many have an accelerator pump, an automatic mixture control, and models on turbocharged engines feature a temperature compensator.
The discharge valve acts as a variable restriction which holds the pressure in chamber C constant despite varying fuel flow rates.
The needle valve is controlled by an aneroid bellows, causing a leaning of the mixture as altitude increases.
The cockpit lever has either three or four detent positions that causes a cloverleaf shaped plate to rotate in the mixture control chamber.
Pressure carburetors were used on many piston engines of 1940s vintage used in World War II aircraft.
After the war, Bendix made the smaller PS series which was found on Lycoming and Continental engines on general aviation aircraft.
These small pressure carburetors eventually evolved into the Bendix RSA series multi-point continuous-flow fuel injection system which is still sold on new aircraft.
The RSA injection system sprays fuel into the ports just outside the intake valves in each cylinder, thus eliminating the chilling effect of evaporating fuel as a source of carburetor ice—since the temperature in the intake ports is too high for ice to form.
