Today the U.S. Air Force, Navy, and Marine Corps operate more than 400 V-22 Osprey tilt-rotor aircraft of several variants, with more on the way. The V-22 configuration permits vertical takeoff and landing—like a helicopter—coupled with the ability for high-speed, long-range flight.
The first such aircraft was developed by Transcendental, a small company formed by former Piasecki Helicopter employees in 1945 to investigate tilting rotor technology. The firm completed an aircraft designed and built by Mario A. Guerrieri known as the “Model 1G.” It was a single-seat, convertible helicopter with two contrarotating rotors located at the end of its wings.1
Subsequently, Bell Helicopter developed the XV-3 in the early 1950s. That single aircraft, although underpowered, demonstrated that rotors could be used for both lift and propulsion on a practical basis by tilting the rotors.
The XV-3 was followed by the Bell XV-15 tilt-rotor prototype that first flew on 3 May 1977. The XV-15 development was funded by the Defense Advanced Research Projects Agency and National Aeronautics and Space Administration (NASA). The aircraft had two helicopter-like rotors fitted in nacelles that were mounted on the wingtips. The nacelles pointed upward for takeoff, landing, and flight like a helicopter; they rotated forward for flight like a conventional aircraft. The cockpit control layout was identical to a helicopter, with a control stick, pedals, and power lever. Pilot controls had the same function regardless of nacelle angle or flight mode, with pitch and role commands through the control stick. Yaw control was by pedals, and rotor thrust changes were controlled by the power lever.
Two XV-15s were built as technology demonstrators. They achieved their flight demonstration goals during extensive testing by NASA and the military services. One was flown in a C-5A Galaxy transport to the 1982 Paris air show, where it performed well and received international attention. In a key XV-15 evaluation, one of the aircraft made 54 landings and takeoffs from the helicopter carrier Tripoli (LPH-10) in August 1982. Although the XV-15 configuration was not intended for shipboard operation, the test was successful, with only minor difficulties encountered.
The Marine Corps expressed special interest in the concept for the amphibious assault role. It envisioned an operational version of a tilt-rotor aircraft that could replace the CH-46 Sea Knight and CH-53 Sea Stallion helicopters. The Air Force soon began considering such an aircraft for its special operations requirements, then being performed by helicopters and C-130 Hercules transports. And there were industry proposals for tilt-rotor aircraft for the Navy’s carrier-based antisubmarine and airborne early warning requirements.
Interestingly, the Army had withdrawn from the program because of financial issues, including the ongoing procurement of large numbers of UH-60 Black Hawk and AH-64 Apache helicopters and development of an advanced lightweight helicopter (LHX program).
Overall, U.S. military interest in the tilt-rotor concept was limited until the ill-fated Iranian hostage rescue mission in 1980—Operation Eagle Claw. That action indicated the need for an aircraft that could combine the basic features of a helicopter and conventional aircraft in an operational environment. To meet that requirement the JVX aircraft program was initiated in 1981 under Army leadership (JVX = joint vertical takeoff/landing experimental).
Although the Army and Marine Corps initially supported the JVX program, there was opposition from the Office of the Secretary of Defense and from the Navy. But members of Congress supported the program, and its management was shifted to the Marine Corps and Navy, the latter managing Marine aviation development programs. A request for proposals was issued to industry in December 1982.
Several aircraft firms declared an interest in the program: Aérospatiale, Bell Helicopter, Boeing Vertol, Grumman, Lockheed, and Westland. Subsequently, Bell partnered with Boeing Vertol and on 17 February 1983 submitted a proposal for an enlarged version of the Bell XV-15. (Grumman had proposed a tilt-nacelle turbojet aircraft.)
A preliminary design contract was awarded to the Bell–Boeing team on 26 April 1983. As the program developed, the JVX aircraft was designated V-22 and given the name Osprey on 15 January 1985. Six prototypes were ordered, leading to the most successful tilt-rotor program, with the MV-22 variant procured for the Marine Corps, CV-22 for the Air Force, and CMV-22 for the Navy.
1. Tommy H. Thomason, “The Promise of Tilt Rotor,” Professional Pilot (December 1977), 40–46. This was a comprehensive discussion of tilt-rotor development to that time.