A controller for a gas turbine engine comprises a fuel flow sensor interface for receiving input signals indicative of a fuel flow into a combustor, a power output sensor interface for receiving input signals indicative of power output of an electrical generator driven via the gas turbine engine, a bleed valve interface for providing an output signal to a bleed valve that controls bleed air to vent a compressor of the gas turbine engine, and memory having stored therein instructions for determining functionality of the bleed valve based on evaluating efficiency of the gas turbine engine when the output signal is issued. A method comprises sensing efficiency of a gas turbine engine in response to actuation of a compressor bleed valve, comparing the efficiency to baseline efficiency, and outputting indicia of a differential between the efficiency and the baseline efficiency as an indication of operability of the first bleed valve.