McDonnell XV-1

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XV-1
Type Compound helicopter
Manufacturer McDonnell Aircraft
Maiden flight 14 July 1954
Number built 2
Developed from Model M-28
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The McDonnell XV-1 was an experimental compound helicopter, developed for a joint research program with the United States Air Force and the United States Army. It was designated a "convertiplane" and explored technologies to develop an aircraft that could take off and land like a helicopter but fly at faster airspeeds, similar to a conventional airplane. The XV-1 would reach a speed of 200 mph (322 km/h), faster than any previous rotorcraft, but the program was terminated due to the complexity of the technology which gave only a modest gain in performance.

Contents

[edit] Development

In 1951, the Air Force announced a competition to develop a compound helicopter, an aircraft that could take off and land vertically, like a helicopter, but could cruise at higher airspeeds than conventional helicopters.[1] The joint research program was being conducted by the Air Force's Research and Development Command and the Army's Transportation Corps.[2] Bell Aircraft submitted the design for the XV-3, Sikorsky Aircraft submitted the S-57, a retracting rotor design, and McDonnell submitted a design modified from its Model M-28 design.[3]

On 20 June 1951, the Air Force and Army signed a Letter of Intent with McDonnell to award a contract to develop an aircraft based on their design.[4] McDonnell benefited from the previous design work on the Model M-28 and had a complete mock-up ready for inspection by the Army and Air Force by November 1951. McDonnell was given approval to begin fabrication of what was then designated the XL-25 ("L" for Liaison). The basic airframe came from an early post-World War II commercial airplane program for a four-place airplane in the Bonanza and Navion class.[5]

McDonnell enlisted Friedrich von Doblhoff, the Austrian helicopter designer of the WNF 342, to provide technical direction on developing the rotor system.[4] As the aircraft was being constructed, the designation was changed to a helicopter designation, the XH-35. Finally, the aircraft became the first vehicle in the convertiplane series as the XV-1. After 22 months of fabrication, the first aircraft (serial 53-4016) was ready for flight testing by early 1954.[2]

After a flight testing program, the XV-1 was canceled in 1957 because it was deemed too complex for the speed gained.[2] Afterwards, McDonnell developed a small crane helicopter, designated Model 120, that used the XV-1's rotor. The first of two Model 120 prototypes flew for the first time on 13 November 1957. The Model 120 was successfully tested, but it did not find a market and development ceased.[6]

[edit] Design

Built mostly from aluminum, the XV-1 fuselage consisted of a streamlined tube mounted on skid landing gear, with a rear-mounted engine and a pusher propeller. It also had high aspect ratio, tapered, stub wings mounted high on the fuselage. In turn, twin tailbooms and twin vertical surfaces, inter-connected by a horizontal stabilizer elevator, were mounted to the wings. A three-bladed main rotor powered by blade tip pressure jets was mounted on top of the fuselage, above the wing roots.[1]

The cabin was covered almost entirely with Plexiglas windows providing visibility in all directions, except directly underneath the aircraft. The cockpit consisted of tandem pilot and copilot stations, or the aircraft could accommodate a pilot and three passengers, or a pilot and two stretchers.[1]

[edit] Operational History

The XV-1 began "tethered" hovering flight tests on 11 February 1954, with test pilot John R. Noll. The "tether" was lead weights intended to keep the aircraft in ground effect until issues with the rotor's tip-jet propulsion system were solved. On 14 July 1954, the lead weights were removed and the XV-1 conducted its first free hovering flight.[1]

As Noll continued flight testing, McDonnell completed the second machine (53-4017). Ship number two was modified from the original XV-1 in an attempt to reduce parasitic drag during high-speed forward flight. To achieve this end, the rotor pylon was reduced and the undercarriage was streamlined as well as strengthened.[4] The second XV-1 also featured two small tail rotors mounted on the outboard side, at the end of each tailboom. These were a result of the hover test flights by Noll who remarked on the lack of yaw authority. The original XV-1 would later be modified with the tail rotors. [1]

By the spring of 1955, the second XV-1 was ready to join the flight program.[2] On 29 April 1955, the XV-1 made its first transition from vertical to horizontal flight, and on 10 October 1955, the second XV-1 became the first rotorcraft to exceed 200 mph (322 km/h), nearly 45 mph (72 km/h) faster than the helicopter speed record at the time.[1] After three years and nearly 600 hours between the two aircraft, the XV-1 contract was canceled in 1957.[4]

[edit] Specifications (XV-1)

General characteristics

  • Crew: 1 pilot
  • Capacity: 3 passengers or 2 litters
  • Length: 50 ft 5 in (15.37 m)
  • Wingspan: 26 ft 0 in (7.92 m)
  • Main rotor diameter: × 31 ft 0 in (9.45 m)
  • Height: 10 ft 9 in (3.28 m)
  • Powerplant: 1 × Continental R-975-19 radial piston engine, 525 hp (410 kW)

Performance

  • Maximum speed: 200 mph (327 km/h)
  • Rate of climb: 1,300 ft/min (6.6 m/s)

[edit] See also

Comparable aircraft

[edit] References

Notes
  1. ^ a b c d e f (Connor & Lee, 2001)
  2. ^ a b c d (Harding, 1997)
  3. ^ (Markman, 2000)
  4. ^ a b c d (Francillon, 1997)
  5. ^ XV-1 (XL-25 / XH-35) page, GlobalSecurity.org. Retrieved December 30, 2007.
  6. ^ (Donald, 1997)
Bibliography
  • Connor, R. and R. E. Lee. McDonnell XV-1 Convertiplane. 24 September 2001. Smithsonian National Air and Space Museum, Washington, DC. Accessed 4 December 2007.
  • Donald, David. The Complete Encyclopedia of World Aircraft. New York: Barnes & Noble Books, 1997. ISBN 0-7607-0592-5.
  • Francillon, René J. McDonnell Douglas Aircraft since 1920: Volume II. London: Putnam, 1997. ISBN 0851778275.
  • Harding, Stephen. U.S. Army Aircraft Since 1947 An Illustrated Reference. Schiffer military/aviation history. Atglen, PA: Schiffer Pub, 1997. ISBN 076430190X.
  • Markman, Steve, and William G. Holder. Straight Up A History of Vertical Flight. Schiffer military/aviation history. Atglen, PA: Schiffer Pub, 2000. ISBN 0764312049.

[edit] External links

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