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The Douglas F4D Skyray (later redesignated F-6 Skyray) is an American carrier-based supersonic fighter/interceptor designed and produced by the Douglas Aircraft Company. It was the last fighter produced by the Douglas Aircraft Company before the company merged with McDonnell Aircraft to become McDonnell Douglas.

In the late 1940s, Douglas and the U.S. Navy launched the D-571-1 design study, which called for delta wing interceptor that could climb quickly enough to intercept approaching bombers. Chosen by the Navy to fulfill a formal requirement issued in 1948, the plane was initially designed around the Westinghouse J40 turbojet engine, but required a redesign for the Pratt & Whitney J57 after the J40 was cancelled. Aerodynamic problems prolonged development; considerable design changes were made after the maiden flight of the first production-standard Skyray in June 1954. The Skyray was declared ready for fleet introduction in April 1956 and entered service with both the United States Navy (USN) and United States Marine Corps (USMC) shortly thereafter.

The Skyray had a relatively brief service life and never saw combat. It was the first carrier-launched aircraft to hold the world's absolute speed record: 752.943&nbsp;mph, (1,211.487&nbsp;km/h). It is widely reported as the first naval fighter to break the speed of sound in level flight rather than in a dive. The D-571-1 had a relatively thick wing with no conventional fuselage save for a pod-like cockpit in a forward position. A total of four 20mm cannons extended forward of the leading edge of the wing; alternative armaments consisted of spin-stabilized rockets. In June 1947, the Navy issued a contract to Douglas to proceed with preliminary investigation and engineering works on the concept up to the mockup stage.

As the design was refined, the wing's thickness was substantially reduced to increase its high speed capabilities. The twin J34 engine arrangement was also swapped out for a single Westinghouse J40 engine. Only a single hydraulic system was incorporated and measures to permit manual reversion in the event of hydraulic failure were included. At the time, Navy planners were particularly concerned by the threat posed to its carrier battle groups by high altitude Soviet bomber aircraft; as early jet aircraft were fuel-hungry and had limited endurance, it was necessary for an interceptor to climb very quickly to its operational altitude to attain the time on station the Navy desired.

thumb|The XF4D-1 prototype aboard , in October 1953.

On account of the numerous design changes, the mockup review was delayed by almost one year, taking place in March 1949. One criticism produced at this stage was that the nose-up attitude was greater than had been anticipated, necessitating changes to the aircraft's nose and radome to improve the pilot's external visibility. this approach proved to be quite fortunate as the J40 had a particularly troubled development and was eventually cancelled with no production units delivered. As a temporary measure, the prototype had to be outfitted with an Allison J35 engine instead. The ensuing delays to the program led to several other aircraft, such as the North American F-100 Super Sabre and the Mikoyan-Gurevich MiG-19, beating it into operational service. An intense period of flight testing and remedial design work followed, as there had been inadequate time to evaluate the J57 during the prototype stage. To address an engine stalling problem at near-supersonic speeds above of altitude, the air intake geometry had to be changed, and an airflow baffle plate added in front of each intake. The aft section of the fuselage was reprofiled to eliminate undesirable buffeting and reduce drag. The thick wing roots contained the air intakes that fed its single turbojet engine. Fuel was contained both in the wings and the deep fuselage. Leading edge slats were fitted for increased lift during takeoff and landing while the trailing edges comprised mostly elevon control surfaces. Additional pitch trimmers were fitted inboard near the jet exhaust, and were locked upwards on takeoff and landing. It had a relatively unique design for the era, which was a key factor in the Skyray becoming one of the best-known early jet fighters. It was affectionately known as the "Ford" (after the "Four" and "D" of its designation). During 1953, Edward H. Heinemann was awarded the Collier Trophy in recognition of his design work on the F4D.

Supersonic capability

Thomason disputes the commonly accepted claims that the Skyray achieved supersonic speed in level flight and was the first naval aircraft to do so. He notes that the formal Navy report from the F4D-1 acceptance trials explicitly states that the aircraft "does not have level flight supersonic capability", and that Heinemann and Rahn never mention this capability in their memoirs, with Rahn mentioning only that the Skyray was supersonic in a dive. Thomason further notes that the Skyray's speed-record flight was conducted when the ambient temperature was unusually high at , delaying the onset of transonic drag; although the speed of sound is at standard temperature and pressure, it rises to at 37°C, so the Skyray's speed during the record-setting flight was equal to only 0.95 Mach. Thomason writes that, according to U.S. Navy records, the first naval aircraft to exceed the speed of sound in level flight was a Grumman F11F Tiger prototype.

Operational history

thumb|APQ-50A radar of an F4D-1

thumb|F4D-1 of VF(AW)-3 in flight over San Diego.

During April 1956, VC-3 became the first squadron to attain operational status with the F4D-1.

The Skyray was designed exclusively for the high-altitude interception role, with a high rate and angle of climb. It set a new time-to-altitude record, flying from a standing start to in two minutes and 36 seconds, all while flying at a 70° pitch angle.

F5D Skylancer

The F5D Skylancer was derived from the F4D and intended to be a Mach 2 capable successor to the Skyray. Although four prototypes were built and flown, the project was cancelled as being too similar in mission parameters to the F8U Crusader and also to reduce dependence upon Douglas Aircraft, which was also producing several other aircraft for the U.S. Navy. This decision effectively removed Douglas from active fighter development.

Variants

thumb|F4D-1 Skyray

;XF4D-1

:Prototypes; redesignated YF-6A in 1962, two built.

;F4D-1

:Single-seat fighter aircraft, production model; redesignated F-6A in 1962, 420 built.

;F4D-2

:Re-engined F4D-1 with the J57-F-14, 100 on order cancelled.

;F4D-2N

:F4D-2 version with extended nose housing twin radar scanners, project only evolved into the F5D Skylancer.

Operators

thumb|Formation of two VF-102 F4D-1 Skyrays

thumb|F4D-1 of VMF-542

;

  • United States Navy
  • VFAW-3
  • VF-13
  • VF-21
  • VF-23
  • VF-51
  • VF-74
  • VF-101
  • VF-102
  • VF-141
  • VF-162
  • VF-213
  • VF-881
  • VF-882
  • United States Marine Corps
  • VMF-113
  • VMF-114
  • VMF-115
  • VMF-215
  • VMF-314
  • VMF-513
  • VMFA-531
  • VMF(AW)-542
  • VX-3
  • NACA/NASA

Aircraft on display

thumb|USMC F4D-1 BuNo 139177 from the Flying Leatherneck Aviation Museum

;XF4D-1

  • 124587 – In front of the main gate of Naval Air Weapons Station China Lake, California. It is on loan from the National Naval Aviation Museum, Naval Air Station Pensacola, Florida.

;F4D-1 (F-6A)

  • 134748 – Pima Air and Space Museum adjacent to Davis–Monthan Air Force Base in Tucson, Arizona. It is on loan from the National Naval Aviation Museum.
  • 134764 – Naval Air Station Patuxent River in St. Mary's County, Maryland. It is on loan from the National Naval Aviation Museum.
  • 134806 – National Naval Aviation Museum at Naval Air Station Pensacola, Florida.
  • 134836 – Intrepid Sea, Air & Space Museum in New York City. Originally on display at the New England Air Museum before relocating to Intrepid in 2021.
  • 134936 – Pueblo Weisbrod Aircraft Museum at Pueblo Memorial Airport, Colorado.
  • 134950 – Aviation Heritage Park at Naval Air Station Oceana in Virginia Beach, Virginia. It is on loan from the National Naval Aviation Museum.
  • 139177 – Flying Leatherneck Aviation Museum at Marine Corps Air Station Miramar in San Diego, California. It is on loan from the National Naval Aviation Museum.

Specifications (F4D-1)

frameless|right|3-view line drawing of the Douglas F-6A Skyray

See also

References

Citations

Bibliography

Further reading

  • Boeing history, F4D
  • VFAW-3 photos and history