Dieudonné’s direct spiral maneuver identifies the directional stability characteristics of a ship. The numerical measures, obtained from this spiral maneuver, are the steady yawing rates as a function of rudder angle. A plot of these values is indicative of the stability characteristics of a ship. For example, if the plot is a single line going from starboard rudder to port rudder and back again - as shown for Ship A in figure 4.20 - the ship possesses controls-fixed straight-line stability. If, however, the plot consists of two branches joined together to form a ”hysteresis” loop - as shown for Ships B and C in figure 4.20 - the ship is unstable. The solid line curves show the steady turning rates.