Development of the Skyray was started by Douglas during the late 1940s as the D-571-1 design study. It was a delta wing interceptor capable of a high rate of climb as to permit the rapid interception of approaching hostile bombers. Douglas' proposal was selected by Navy officials to fulfill a formal requirement issued in 1948. The decision to adopt the Westinghouse J40turbojet engine led to considerable difficulties, as this engine would be cancelled prior to entering production, and the aircraft was redesigned to accept the Pratt & Whitney J57 instead. Aerodynamic issues led to a protracted development cycle; 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. Despite this, it was the first carrier-launched aircraft to hold the world's absolute speed record, having attained a top speed of 752.943mph,[1][2] (1,211.487km/h).[3] The Skyray also set a new time-to-altitude record, flying from a standing start to 49,221 feet (15,003m) in two minutes and 36 seconds, all while flying at a 70° pitch angle. The last Skyrays were withdrawn from service in February 1964, although a handful continued to be flown for experimental purposes by National Advisory Committee for Aeronautics (NACA) up to the end of the decade. The F5D Skylancer was an advanced development of the F4D Skyray that ultimately did not enter service.
Design and development
The Skyray originated within a design study, the D-571-1, performed by Douglas and funded by the United States Navy (USN). It was a fast-climbing pure interceptor aircraft with a delta wing, powered by a pair of Westinghouse J34turbojet engines, which were equipped with afterburners for bursts of additional acceleration.[4] 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.[5] The design study had harnessed the designs and research of the German aerodynamicistAlexander Lippisch, who moved to the United States following the end of World War II, and whose work had been examined by several of Douglas's design team.[6] 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.[5]
As the design was refined, the wing's thickness was substantially reduced to increase its high speed capabilities.[7] 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.[8] Rockets would be the primary armament, housed in pylon-mounted pods underneath the wing. A formal operational requirement was issued by the Navy in 1948; however, according to aviation author Tommy H. Thomason, it was a foregone conclusion from the outset that Douglas would win the contract.[8] Specifics of this requirement included the ability to intercept and destroy an enemy aircraft at an altitude of 50,000ft (15,240m) within five minutes of the alarm being sounded.[9] 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.[10]
The XF4D-1 prototype aboard Coral Sea, in October 1953.
On account of the numerous design changes, the mockup review was delayed by almost one year, taking place in March 1949.[11] 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.[11] A more pressing issue would be the J40 engine. Douglas' design team made accommodations for other engines as a contingency measure;[12] this approach proved to be quite fortunate as the J40 had a particularly troubled development and was eventually cancelled with no production units delivered.[13] As a temporary measure, the prototype had to be outfitted with an Allison J35 engine instead.[6]
The long-term replacement for the J40 on production aircraft was the Pratt & Whitney J57, a more powerful but considerably larger engine.[14] 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.[6]
On 5 June 1954, during its maiden flight, the first production F4D-1, bureau number (BuNo) 130740, became the first naval fighter to exceed the speed of sound in level flight.[15] 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 40,000ft (12,000m) 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.[14][16] In September 1955, initial carrier suitability trials were performed onboard USS Ticonderoga.[12] No production aircraft were delivered until early 1956 when the F4D was declared ready for fleet introduction in April.[12][17] A total of 419 F4D-1 (later designated F-6 under the unified designation system) aircraft would be produced prior to the end of production in 1958.
The Skyray was a wide delta wing design with long, sharply swept, rounded wings. It was named for its resemblance to the manta ray.[18] 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.[8] Additional pitchtrimmers 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).[19] During 1953, Edward H. Heinemann was awarded the Collier Trophy in recognition of his design work on the F4D.[20]
Operational history
APQ-50A radar of an F4D-1F4D-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.[1] This unit was later redesignated VFAW-3 and assigned to NORAD, becoming the only United States Navy fighter squadron in what was predominantly a United States Air Force (USAF) and Royal Canadian Air Force (RCAF) organization. VFAW-3 was permanently based at NAS North Island in San Diego.
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 49,221 feet (15,003m) in two minutes and 36 seconds, all while flying at a 70° pitch angle.[1] As a dedicated interceptor, the F4D was unsuited to the multi-mission capabilities that became increasingly in demand, thus the type had a relatively short career in both USN and USMC service. In addition to multiple Navy and Marine Corps squadrons, Naval Air Reserve and Marine Air Reserve squadrons VF-881, VF-882 and VMF-215 also flew the Skyray. The last operational squadron was VMF(AW)-115, which flew the Skyray until February 1964. A total of four aircraft were used for experimental purposes by the National Advisory Committee for Aeronautics (NACA) (which was later renamed NASA) until 1969.[22]
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.[22][23] This decision effectively removed Douglas from active fighter development.[24]
Variants
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
Formation of two VF-102 F4D-1 SkyraysF4D-1 of VMF-542
Francillon, René J. (1988). McDonnell Douglas Aircraft since 1920. Vol.I. Annapolis, Maryland: Naval Institute Press. ISBN0 87021-428-4.
Frankel, Mark (2010). Killer Rays: The Story of the Douglas F4D Skyray and F5D Skylancer. North Branch, Minnesota, US: Specialty Press. ISBN978-1-58007-155-0.
Green, William; Pollinger, Gerald (1955). The Aircraft of the World. London, UK: Macdonald.
Williams, Nicholas M. (2021). Douglas F4D-1/F-6A Skyray. Naval Fighters. Vol.113. Ginter Books. ISBN978-1-7349727-7-1.
Winchester, Jim, ed. (2006). "Douglas F4D Skyray". Military Aircraft of the Cold War (The Aviation Factfile). London, UK: Grange Books. ISBN1-84013-929-3.
Winchester, Jim (2006). Fighter: The World's Finest Combat Aircraft, 1913 to the Present Day. New York, US: Barnes & Noble Publishing and Parragon Publishing. ISBN0-7607-7957-0.
Encyclopédie illustrée de l'aviation n°196 - Editions Atlas
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
