A new chapter 8 has been added to report KD 409: “Development of an ecliptic safety system with a torsion spring”. In chapter 8 an alternative is described for which the spring moment is constant. This results in lower maximum values for the rotational speed, the thrust, the torque and the power than for the original option for which the spring moment increases by a factor 1.5 at the maximum angle of rotation of the vane arm. I think that a constant or only little increase of the spring moment gives the best result but to realise this might be technically more difficult.