An electronically controlled mechanical seal, in a configuration suitable for aerospace applications, has been built and tested in the laboratory. The thickness of the lubricating film between the seal faces is controlled by adjusting the coning of one of the faces, which is bonded to a piezoelectric crystal. An applied voltage causes the crystal to deform in the shear mode, thereby inducing coning of the seal face; the larger the voltage, the larger the coning. The coning affects the fluid mechanics of the film such that the larger the coning, the larger the average film thickness. Therefore the film thickness increases with increased applied voltage.Steady state tests have shown that the leakage rate (and therefore, the film thickness) can be adjusted over a substantial range, utilizing the available range of voltage. Transient tests have shown that either the leakage rate or the face temperature can be maintained near a set point during both gradual and abrupt changes in operating conditions, by utilizing a closed-loop control system.