Disk drive determining operating fly height by detecting head disk contact from disk rotation time

A method of operating a disk drive, the disk drive comprising a disk comprising a plurality of tracks, wherein each track comprises a plurality of data sectors and a plurality of servo sectors, a spindle motor for rotating the disk, and a head actuated radially over the disk, wherein the head comprises a dynamic fly height (DFH) heater, the method comprising:

• positioning the head over one of the tracks;
• measuring a first rotation time of the disk in response to at least one of the servo sectors;
• adjusting the control setting for the DFH heater;
• measuring a second rotation time of the disk in response to at least one of the servo sectors;
• and
• detecting whether the head has contacted the disk in response to the first and second rotation times.

A disk drive comprising:

• a disk comprising a plurality of tracks, wherein each track comprises a plurality of data sectors and a plurality of servo sectors;
• a spindle motor for rotating the disk;
• a head actuated radially over the disk, wherein the head comprises a dynamic fly height (DFH) heater;
• and
• a means for positioning the head over one of the tracks;
• a means for measuring a first rotation time of the disk in response to at least one of the servo sectors;
• a means for adjusting the control setting for the DFH heater;
• a means for measuring a second rotation time of the disk in response to at least one of the servo sectors;
• and
• a means for detecting whether the head has contacted the disk in response to the first and second rotation times.