Vertical stabilizer and dorsal fin are the yaw control surface of the aircraft. To satisfy the low radar observability design requirement, stealth aircraft usually use canted twin vertical stabilizer and/or twin dorsal fins. The canted surfaces not only shield the high temperature components in the aft fuselage and hot exhausts to a certain degree, they also enhance the mixing of exhaust jet with air. Fig. 4-44 show the effects of inward- and outward-canted vertical stabilizers have on the exhaust jet. In the outward-canted configuration, the shear layer of the jet is smooth. In the inward-canted one, the jet is twisted and the shear layer become rough; the mixing between jet and the surrounding flow is significantly enhanced; the decay of the high temperature region is increased.