anchor.diff:     END IF
      
      
  -      ! index for u_AD%BladeMotion(1)%translationDisp field
  -   AD_Start_td = y_FAST%Lin%Modules(MODULE_AD)%Instance(1)%LinStartIndx(LIN_INPUT_COL) &
  -               + u_AD%TowerMotion%NNodes * 9  & ! 3 fields (MASKID_TRANSLATIONDISP,MASKID_Orientation,MASKID_TRANSLATIONVel) with 3 components
  -               + u_AD%HubMotion%NNodes   * 9    ! 3 fields (MASKID_TRANSLATIONDISP,MASKID_Orientation,MASKID_RotationVel) with 3 components
  -   
  -   do k = 1,size(u_AD%BladeRootMotion)
  -      AD_Start_td = AD_Start_td + u_AD%BladeRootMotion(k)%NNodes * 3 ! 1 field (MASKID_Orientation) with 3 components
  -   end do
      
      DO k=1,size(u_AD%BladeMotion)
  +      AD_Start_td = Indx_u_AD_Blade_Start(u_AD, y_FAST, k) ! index for u_AD%BladeMotion(k)%translationDisp field
   
            !AD is the destination here, so we need tv_ud
         if (allocated( MeshMapData%BDED_L_2_AD_L_B(k)%dM%tv_ud)) then
  
positive.code: 
           call SetBlockMatrix( dUdu, MeshMapData%BDED_L_2_AD_L_B(k)%dM%tv_ud, AD_Start_tv, AD_Start_td )
        end if
  
           ! index for u_AD%BladeMotion(k+1)%translationDisp field
        AD_Start_td = AD_Start_td + u_AD%BladeMotion(k)%NNodes * 9 ! 3 fields (TranslationDisp, Orientation, TranslationVel) with 3 components
  
     END DO
        
  
negative.code:          MAP_Out_Start = y_FAST%Lin%Modules(MODULE_MAP)%Instance(1)%LinStartIndx(LIN_OUTPUT_COL)
           ED_Start      = Indx_u_ED_Platform_Start(u_ED, y_FAST) ! start of u_ED%PlatformPtMesh%TranslationDisp field
           call Assemble_dUdy_Loads(MAPp%y%ptFairLeadLoad, u_ED%PlatformPtMesh, MeshMapData%Mooring_P_2_ED_P, ED_Start, MAP_Out_Start, dUdy)
        
           ! ED translation displacement-to-ED moment transfer (dU^{ED}/dy^{ED}):
           ED_Start = Indx_u_ED_Platform_Start(u_ED, y_FAST) + u_ED%PlatformPtMesh%NNodes*3   ! start of u_ED%PlatformPtMesh%Moment field (skip the ED forces)
           ED_Out_Start = Indx_y_ED_Platform_Start(y_ED, y_FAST) ! start of y_ED%PlatformPtMesh%TranslationDisp field
           call SumBlockMatrix( dUdy, MeshMapData%Mooring_P_2_ED_P%dM%m_uD, ED_Start, ED_Out_Start )
        end if
           
     end if
     
  