The report presents the results of an experimental and, in some cases, analytical investigation into the stability characteristics of the herringbone-grooved rotor supported in self-acting and hybrid gas-lubricated journal bearings. The analytical investigation was accomplished using previously developed theory. Measurements of threshold of instability speeds (half-frequency whirl) were made for four different rotors. Two of the rotors were fully grooved and two were partially grooved. Variables investigated were bearing radial load, radial clearance, and bearing supply pressure. Also, the effects on stability of rotating the herringbone-groove geometry so as to be both inward pumping (toward the bearing center) and outward pumping(away from the bearing center) and of axially misaligning the groove geometry were investigated. (Author).

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