The present invention relates to a flow control device and more particularly to reactive self-contained modular flow control device with deployable flow effectors. The present invention further relates to a method of operating the flow control device.One embodiment of the present invention includes a method of controlling air flow across a surface of an aircraft under certain flight conditions comprising the steps of sensing fluid separation from the surface by measuring the pressure on the surface; determining a standard deviation of the pressure measurements over a period of time; and deploying a flow effector in response to the standard deviation of the pressure measurements exceeding a predetermined threshold number.