A disk drive includes a rotatable data storage disk and a vane positioned
adjacent to the disk that receives airflow generated during rotation of
the disk. A sensor is operably coupled to the vane and measures airflow
force on the vane. Because of a known relationship between altitude and
airflow force, the amount of airflow force on the vane is indicative of
altitude of the disk drive. The sensor provides an output signal that is
indicative of measured airflow force on the vane. The vane surface may be
oriented substantially orthogonal to a plane of the disk or substantially
parallel with a plane of the disk.