From 17 to 19 November, the Achilles was tested by two Symbitron test pilots (group I) in two different experiments. In the first experiment different controllers for balancing with the Achilles were evaluated and in the second experiment the balancing performance of the subjects while receiving vibrotactile feedback about the Center of Mass or the ankle angle was evaluated. Balancing performancing was evaluated during standing with eyes open and eyes closed during perturbations that were performed with the Achilles. For all measurements, EMG and motion capture data was collected.