 In part to answer these doubts, a three-dimensional model was produced and subjected to wind tunnel tests, which revealed extreme instability.A 'stop design' order was promptly issued on the cushion system while further tests were performed, which determined that the addition of single peripheral jets remained inadequate for the original design.As the use of transverse jets, as used on the original model, was impractical, an extended planform was adopted along with an additional peripheral jet along the outside to address the stability issue.