anchor.diff:  
            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
         
  
positive.code:    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 is the destination here, so we need tv_ud
        if (allocated( MeshMapData%BDED_L_2_AD_L_B(k)%dM%tv_ud)) then
  
negative.code:             HD_Out_Start = Indx_y_HD_AllHdro_Start(HD%y, y_FAST)
              ED_Start     = Indx_u_ED_Platform_Start(u_ED, y_FAST) ! start of u_ED%PlatformPtMesh%TranslationDisp field
              call Assemble_dUdy_Loads(HD%y%AllHdroOrigin, u_ED%PlatformPtMesh, MeshMapData%HD_W_P_2_ED_P, ED_Start, HD_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 SetBlockMatrix( dUdy, MeshMapData%HD_W_P_2_ED_P%dM%m_uD, ED_Start, ED_Out_Start )
  ! maybe this should be SumBlockMatrix with future changes to linearized modules???            
           end if
  
              
     end if
  