Detection of fly height change in a disk drive

1. A method of initiating head cleaning in a disk drive comprising:

establishing a baseline position error signal (PES);

measuring the transient PES at a plurality of different radii of the disk drive, wherein at least one of the plurality of different radii includes an outer diameter of the disk drive;

calculating a change in average absolute PES; and

performing a responsive action including generating an error condition when the change in average absolute PES exceeds a threshold at two or more of the plurality of different radii.

2. The method of claim 1 , further comprising canceling the performance of a responsive action.

3. A method of detecting a change in fly-height comprising:

measuring a first baseline position error signal (PES) representing an initial PES at a first diameter on a disk;

measuring a second baseline PES representing an initial PES at a second diameter on the disk;

measuring a first transient PES at the first diameter subsequently to the first baseline PES;

measuring a second transient PES at the second diameter subsequently to the second baseline PES;

determining a first change in PES by comparing the first transient PES to the first baseline PES;

determining a second change in PES by comparing the second transient PES to the second baseline PES;

performing at least one responsive action when one of the first change in PES exceeds a first threshold and the second change in PES exceeds a second threshold; and

generating a general error condition when both the first change in PES exceeds the first threshold and the second change in PES exceeds the second threshold.

4. The method of claim 3 , wherein the first diameter includes an inner-diameter of the disk.

5. The method of claim 3 , wherein the second predetermined diameter includes an outer-diameter of the disk.

6. The method of claim 3 , wherein the at least one responsive action includes generating a decreasing fly height condition.

7. The method of claim 3 , wherein the at least one responsive action includes initiating a head cleaning procedure.

8. The method of claim 3 , further comprising determining a corresponding first change in PES and a corresponding second change in PES for each head of the disk.

9. The method of claim 8 , further comprising:

performing the at least one responsive action when one of the first corresponding change in PES exceeds the first threshold and the second corresponding change in PES exceeds the second threshold; and

generating a general error condition when both the first corresponding change in PES exceeds the first threshold and the second corresponding change in PES exceeds the second threshold.

10. An apparatus for detecting a change in fly-height comprising:

means for measuring a first baseline position error signal (PES) representing an initial PES at a first diameter on a disk;

means for measuring a second baseline PES representing an initial PES at a second diameter on the disk;

means for measuring a first transient PES at the first diameter subsequently to the first baseline PES;

means for measuring a second transient PES at the second diameter subsequently to the second baseline PES;

means for determining a first change in PES by comparing the first transient PES to the first baseline PES;

means for determining a second change in PES by comparing the second transient PES to the second baseline PES;

means for performing at least one responsive action when one of the first change in PES exceeds a first threshold and the second change in PES exceeds a second threshold; and

means for generating a general error condition when both the first change in PES exceeds the first threshold and the second change in PES exceeds the second threshold.

11. The apparatus of claim 10 , wherein the first diameter where a measurement is made by the means for measuring a first transient PES and the means for measuring a first baseline position error signal (PES) includes an inner-diameter of the disk.

12. The apparatus of claim 10 , wherein the second predetermined diameter where a measurement is made by the means for measuring a second transient PES and the means for measuring a second baseline position error signal (PES) includes an outer-diameter of the disk.

13. The apparatus of claim 10 , wherein the at least one responsive action of the means for performing at least one responsive action includes generating a decreasing fly height condition.

14. The apparatus of claim 10 , wherein the at least one responsive action of the means for performing at least one responsive action includes initiating a head cleaning procedure.

15. The apparatus of claim 10 , further comprising means for determining a corresponding first change in PES and a corresponding second change in PES for each head of the disk.

16. The apparatus of claim 15 , further comprising:

means for performing the responsive action when one of the first corresponding change in PES exceeds the first threshold and the second corresponding change in PES exceeds the second threshold; and

means for generating a general error condition when both the first corresponding change in PES exceeds the first threshold and the second corresponding change in PES exceeds the second threshold.

17. The apparatus of claim 10 , further comprising means for canceling a performance of the at least one responsive action when a general error condition is generated.