Dear Simon,
A similar question was discussed in the following forum topic: Geometric Properties of the NREL 5-MW baseline blade - #3 by Paul.Schunemann.
Relating the AeroDyn v15 variables to your figure:
BlCrvAC = X
BlSwpAC = Y
BlCrvAng = not shown in your figure; see Figure 3 in the draft AeroDyn User’s Guide and Theory Manual for more information: nwtc.nrel.gov/system/files/Aero … 15.04a.pdf.
BlTwist = Aerodynamic Twist
BlCrvAC and BlSwpAC are related to AeroCent and AeroTwist from FAST v7.02 as follows:
BlCrvAC = -(0.25-AeroCent)ChordSIN(AeroTwst)
BlSwpAC = -(0.25-AeroCent)ChordCOS(AeroTwst)
I hope that helps,
Best regards,