Magnetic disk drive systems and associated methods are described for
precisely detecting contact of read/write elements of a recording head
with a magnetic disk due to increasing a heating power applied to heating
elements in the recording head. Contact is detected based on adjusted
timing signals which are generated by measuring the current applied to a
spindle motor, and generating an estimated timing signal from the
measured motor current for increments of the heating power. An actual
servo timing signal is simultaneously measured from servo fields on the
magnetic disk, and the adjusted timing signals are calculated based on
the difference between the estimated timing signal and the servo timing
signal. Multivariate statistical analysis may also be performed on the
adjusted timing signals and other contact indicative variables (such as
off-track and slider vertical bouncing) to generate a likelihood of
contact at the increments of the heating power.