A fan air modulating valve (FAMV) employs a pair of doors rotatably attached at the fan bypass air exit of a precooler. An actuator engages the doors for simultaneous rotation through a range of motion from a first closed position to a second open position, wherein trailing edges of said doors sealingly engage an exit plenum extending from the precooler in the first closed position and fan bypass air flow is modulated by positioning the doors within the range of motion between the first and second positions.