11. It is not to be confused with directional stability , as experienced by aircraft in flight. 12. It suffered from a lack of directional stability and the engines were unreliable and vibrated above. 13. The forces which result in directional stability , propulsion and braking may all be traced to creep. 14. The Swift has no vertical stabilizer and so faces the need for directional stability in yaw. 15. The horizontal tailplane mounts end-fins for directional stability . 16. In contrast to shell gave it directional stability . 17. These tests also revealed a lack of directional stability : Mitchell accordingly enlarged the fin area. 18. It also added more vertical surface to the aircraft to maintain directional stability at high speeds. 19. Patients also exhibited a greater variability in the postural oscillation, evaluated by the directional stability index. 20. Additional directional stability was achieved in the Rotachute Mark IV, that introduced endplates onto the rigid tailplanes.
