Abstract : Pneumatic hammer instability of an inherently compensated thrust gas bearing was analyzed theoretically. Vohr's experimental correlation between pressure loss coefficient and Reynolds' number was used to calculate flow through the restrictor instead of using the nozzle equations. The time dependent Reynolds' equation was solved by a perturbation analysis for small axial oscillation. Based on the perturbation analysis, dynamic stiffness and damping coefficient were calculated. Utilizing these and Pan's stability criteria stability maps were constructed.