Electronic fuel control for a gas turbine engine

An electronic fuel control for a gas turbine engine, comprising:

• means for generating an engine speed error signal, limiter means sensitive to engine operating conditions to limit said speed error signal, an integrator for integrating said error signal, a first difference amplifier for comparing the output signal of the integrator with an engine actual speed signal to produce a fuel error signal, and a fuel flow control actuated by said fuel error signal controlling fuel flow to the engine, surge detection means comprising means for producing a signal corresponding to the rate of change of the output of the difference amplifier, a comparator means connected to produce a surge indication signal when said rate of change signal exceeds a predetermined level for a predetermined period, said comparator means comprising a first voltage comparator connected to said means for producing a signal corresponding to the rate of change of the output of the difference amplifier and to a reference signal source and a delay circuit connected to the output of said first voltage comparator for preventing the output of the first voltage comparator producing a surge indication signal until said predetermined period has elapsed, and a surge indicating signal muting arrangement for preventing a surge indicating signal being produced at the commencement of acceleration following a sudden change in the speed demand, said muting arrangement including a second voltage comparator connected to the means for generating an engine speed error signal and arranged to produce an output when that error signal exceeds a predetermined value, a logic gate connected to the outputs of said first and second voltage comparators and to a monostable circuit connected to be triggered by said second comparator, said monostable circuit blocking the logic gate for a predetermined period after the second comparator starts to produce said output.