Abstract: A method for evaluating head flight characteristics in a disc drive includes accelerating a disc to an initial rotational velocity sufficient to aerodynamically support a head over the disc at a nominal flying height. A read bias current is applied to the head to generate a readback signal determined in relation to the voltage drop across the head. A thermal asperity threshold level is applied which the readback signal exceeds in response to contact between the head and the disc as the disc rotates. A head touchdown velocity is determined by decelerating the disc to decrease the flying height of the head and detecting subsequent contact between the head and the disc when the readback signal exceeds the thermal asperity threshold level. A head take off velocity is similarly determined by monitoring the head readback signal as the disc is accelerated and lifts off the disc.