anchor.diff:  
       F = Ftip * Fhub
   
  +    if ( EqualRealNos(F, 0.0_ReKi) ) then
  +      fzero =  0.0_ReKi
  +      a     =  1.0_ReKi
  +      ap    =  -1.0_ReKi
  +      chi   =  0.0_ReKi
  +      return
  +    end if
       
       ! bem parameters
       
  
positive.code:    
      
      if ( EqualRealNos(phi, 0.0_ReKi) ) then
        fzero =  0.0
        a     =  0.0
        ap    =  0.0
        return
      end if
      
  
negative.code:       yawCorr = (15.0_ReKi*pi/64.0_ReKi*tan(chi/2.0_ReKi) * (r/Rtip) * saz)
        a = a * (1.0 +  yawCorr) ! *(-yawCorr/0.785 + 1) )
          !a = min(a, 0.9)
     !else if ( skewWakeMod == SkewMod_Coupled ) then
     !   chi = (0.6_ReKi*a + 1.0_ReKi)*chi0
     !   a = a * ( 1.0_ReKi + 0.63_ReKi*(r/Rtip)**2 )*(c1 + c2*lambda + c3*lambda**2 + c4*lambda**3 )*( chi*180.0_ReKi/pi )*saz   ! chi needs to be in degrees here.
     end if
     
      ! compute tangential induction factor
  