Cyclic hotline,
Some background on the Helistat is that Frank Piasecki did little dynamic analysis of the big airframe, a factor which perhaps contributed to the mishap. The chief pilot he had during the development told me that virtually no computer analysis was done to study the low frequency modes of the structure, which is a big problem area on all larger machines (and a major contributer to the problems with the largest helicopter that ever flew, the V-12).