![]() ![]() ![]() The last is FADEC where most of the mechanical regulating devices are discarded and the entire management is by software controlling the entire metering system. When the electronics are turned off in this type of system, the engine reverts to its baseline hydromech fuel schedule. Most non-FADEC engines built after the 70s have this electronic fuel control, better thought of as electronically supplemented fuel control. There is still the old fashioned hydromech fuel controller and a baseline fuel schedule, but this is bypassed by an overlaid electronic fuel schedule, controlled by the ECU through its torque motor. This is done by software (an Electronic Control Unit or ECU) that drives a metering device through a torque motor (a torque motor is like a rotary actuator that moves in proportion to a voltage applied and springs back to zero if the voltage is removed). This takes the traditional hydromechanical fuel controller and fine tunes the final fuel schedule in a way that can't be done mechanically. In the 70s, the idea of adding electronic control to fine tune fuel management got started and you could call this the second generation. This allowed things like "slam acceleration" where the engine could take sudden throttle changes smoothly, which was a no-no on the very early jet engines. The first modern hydromechanical fuel control systems in the early 50s used mechanical regulating and governing devices so that when the throttle was moved it more or less commanded a power setting and the regulating devices would manage the amount of fuel admitted. The pilot's eyes and brain using data from the gauges was all that prevented stalling/surging, overtemps, etc, needing very careful throttle movement and monitoring. The very first systems like on the Junkers Jumo and other early engines was not much more than a needle valve connected to the throttle. First was pure hyrdomechanical, which used mechanical devices to regulate power setting and acceleration. You can think of it as 3 broad categories or generations of engine fuel control. I can give you a generalized answer and most of the details you are looking for are hopefully buried here. ![]()
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