A brief method is presented for estimating the speed response of turbojet and turbine-propeller engines to a step change in fuel flow. The method approximates the dynamic-equilibrium in the gas-turbine engine with a first-order linear differential equation, the time constant of which varies inversely with the equilibrium speed.nFor the application of the method to the turbojet engine, the data required are (l) the variation with engine speed of the steady-state engine air flow and the steady-state compressor temperature rise;and (2) the polar moment of inertia of the engine. For the turbine-propeller engine, the variation with engine speed of the steady-state propeller torque is required in addition to the data required for the turbojet engine.
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