Dear Ruchit,
Figure 18 from the old FAST User’s Guide (drive.google.com/file/d/1d_-vRR … sp=sharing) shows a picture of an upwind furling wind turbine. When looking downwind, if the shaft is to the left of the yaw axis, Yaw2Shft is positive, if the shaft is the right of the yaw axis (as in Figure 18), Yaw2Shft is negative.
Best regards,