In the early 1980s Bell helicopter Textron and boeing Vertol began collaboration to develop a larger derivative of the XV-15 tilt-rotor demonstrator for the Joint Services Advanced Vertical Lift Aircraft programme. Combining the vertical lift capabilities of a helicopter with the fast-cruise forward flight efficiencies of a fixed-wing turboprop aircraft, the resulting V-22 Osprey was awarded full-scale development in 1985.
Mounted in wingtip nacelles, the engines can be swivelled through 97.5° and drive three-bladed prop-rotors through interconnected drive shafts. For shipboard stowage, the main planes pivot centrally to rotate along the fuselage top, the prop-rotor blades also folding in parallel.
Initial requirements called for 913 Ospreys, comprising 52 MV-22A assault versions for the USMC and US Army; 80 USAF CV-22As for long-range special forces transport; and 50 US Navy also foresaw a need for up to 300 SV-22As for ASW.
Flight-testing started on 19 March 1989, but the programme suffered a serious setback on 21 July 1992 with the crash of the fourth prototype. Already under financial and political review, a serious reappraisal of the Osprey programme followed, with the ultimate conclusion that 300 (later 425) aircraft would be acquired for the USMC only.
The MV-22A can cary up to 24 troops, or 12 litters and medical attendants. In September 1994 production authorisation was granted for this batch, plus 48 Ospreys for the US Navy and 50 for the US Air Force. The loss of three V-22s during testing in 2000 cast a further shadow over the programme, but this most important of future combat aircraft reached IOC with the USMC during 2001/2002. Pre-production deliveries to the USAF and US Navy started in 2003.