Abstract: The present invention comprises a system for detecting windshear and associated downdraft effects when they are encountered in flight by an aircraft. The system includes an input unit (12), a first processing unit (14), a second processing unit (16), an output unit (18), and a pilot warning device (20). The input unit receives aircraft performance data from the instruments and/or flight systems on the aircraft and preconditions this data to produce a set of signals corresponding to various aerodynamic and inertial input parameters. The first processing unit differences signals representing the aerodynamically derived and inertially derived accelerations of the aircraft in order to generate windshear signals. These windshear signals are then corrected for pitch rate induced coriolis acceleration effects. The corrected signals are used to form a signals representing longitudinal windshear along the horizontal heading axis of the aircraft and the change in aircraft climb gradient due to longitudinal windshear.