Data are presented showing the flight characteristics of a large airplane having a control-surface booster and mechanical feel device in the elevator-control system. The tests were made with various force gradients provided by the adjustable feel device. The booster was set to operate at a very high boost ratio throughout the tests so that the measured or apparent stick-free stability would be influenced only slightly by the aerodynamic hinge moments. The results show the effect of the feel device on the handling qualities of the test airplane and also the design features which should be incorporated in such feel devices.