The 'tip jet' technology was used on the XV-1. The other two aircraft in the XV series, the McDonnell XV-1 compound autogyro and Bell XV-3 tiltrotor, were actually built with two prototypes of each being produced. (The Sikorsky XV-2 was not built as mentioned in the textual description; the 'picture' shown of the XV-2 in a hangar on the linked site is a model that was super-imposed on a photo.) The XVs were all designed for competitive comparison in a program sponsored by the US Army Transportation Command with NASA involvement. The XV-1 and XV-3 prototypes were flown successfully and had flight programs lasting several years. Although a lot of good research material was gathered, neither was a viable option for production due to obvious limitations (too heavy, not enough power, etc., and resultant performance/payload inadequacies).
Last edited by 21st Century; 28th Mar 2007 at 17:48.