Douglas F4D / F-6 Skyray High-Altitude Carrier-borne Interceptor Aircraft
The Douglas F4D Skyray was the quintessential jet fighter of the 1950's, appearing in limited service though possessing an impressive rate-of-climb.
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The F4D Skyray (affectionately nicknamed the "Ford" for its "F", "Four" and "D" used in the designation) stemmed from a 1947 United States Navy requirement to field a competitive Mach 1-capable, high-altitude interceptor. Not to be outdone by their Air Force counterparts developing their North American F-100 Super Sabre program and the competing Soviets and their Mikoyan-Gurevich MiG-19 "Farmer" design, the USN set about to find an equal force for in defense of their carrier battle groups.
The design of the Skyray indirectly had its origins in German World War 2 delta-wing research and, in particular, the work of one German engineer, Alexander Lippisch. Lippisch had relocated to the United States after the end of the war in 1946 and his work did not go unnoticed by the United States Navy. Douglas Aircraft Company's legendary designer Ed Heinemann was an astute admirer of Lippisch's work centering on the concept of a tailless delta-wing aircraft. Lippisch's work produced the well-known, single-seat, rocket-powered Me 163 Komet interceptor for the German Messerschmitt firm in the latter years of the war. His ground-breaking research furthered the envelop of aircraft design, especially as turbojet technology began to evolve into more capable powerplants with sufficient output for new and better airframe types. The tailless delta wing concept was one of Lippisch's revolutionary forays that sought to contain the violent reactions encountered by objects traveling past the speed of sound. The stability and aerodynamic capabilities inherent with a high amount of surface area held some innate benefits for any design regardless of the chosen powerplant. In theory, this would play well into the burgeoning world of jet-powered aircraft design, considering the field of jet technology was still essentially in its infancy.
On June 17th, 1947, the Douglas Aircraft Corporation was ready with its proposal for the delta wing concept, a unique concept which the US Navy began to favor. The initial Douglas D-571-1 plan was selected for further development, producing the D-571-4. The D-571-1 featured a more straight wing delta while the D-571-4 differed in featuring the rounded delta wing edges consistent with production Skyrays. The USN granted a contract to Douglas for two XF4F-1 prototypes on December 16th, 1949 - by this time the designation of "Skyray" was affixed to the aircraft based on its resemblance to the ocean-going manta ray. The prototype first flew on January23rd, 1951 and proved a promising endeavor.
The XF4D-1 was initially designed around the temperamental Westinghouse J40 series engine though engineering foresight on the part of Douglas engineers made sure that the airframe could accept a variety of powerplants as needed. Though development of the XF4D-1 airframe progressed nicely, the Westinghouse J40 proved a whole other matter. The Westinghouse J40 eventually floundered (leading to accidents surrounding it and the F3H Demon series) despite a good amount of support from the US Navy forcing the Skyray to accept the now USN-approved Pratt & Whitney J57 turbojet for the aircraft - an individual decision that most likely saved the aircraft from becoming a forgettable - and possibly cancelled - Cold War design. Though the Pratt & Whitney J57 proved a larger powerplant than the intended Westinghouse, the extra space afforded by Douglas designers from the beginning ensured that the J57 was a proper fit for the airframe and the Skyray program progressed without much delay.
Performance for the Douglas product eventually yielded a top speed of 722 miles per hour. As sustained Mach 1 speeds were part of the USN requirement, the Skyray excelled. Throughout its service life, the Skyray was fitted with several Pratt & Whitney engines including the J57-P-8, J57-P-8A and the J57-P-8B models. Dry thrust from these engines was reported at 10,200lbf and this rose to an impressive 16,000lbf with the use of afterburner. A range of 700 miles was possible with a ferry range of 1,200 miles. A service ceiling of 55,000 feet was reported, falling well in line with the early USN requirements. Most important, however, was in the Skyray's impressive 18,300 feet-per-minute rate-of-climb. The concept of a slow-climbing interceptor was not a consideration in the jet-age (or any age for that matter) and the Skyray did not disappoint in this performance category.
The Skyray itself was constructed with a semi-stressed skin incorporating aluminum alloy. Despite its large wing area, every effort was made to rid the design of excess weight. This is the area where Douglas designer Ed Heinemann shined. The delta wing concept as applied to the Skyray proved most efficient in both construction methodology and in high speed performance. In the center of the design was the sleek fuselage, integrated into two thick wingroots each containing a split triangular air inlet for the single Pratt & Whitney J57 series afterburning engine. The wings extended out from the roots and, as a whole, provided for a very solid structural base. The wings gave the aircraft its identifiable and definitive shape with its sharply swept leading edges that rounded out nicely at the wing tips. Being a tailless delta wing concept, the Skyray made no use of rear-mounted tailplanes consistent with conventional aircraft designs (as these were essentially absorbed as part of the large delta wing surface) and featured a single large vertical tail surface extending out over the engine and rearward portion of the fuselage.
The pilot was afforded the best seat in the house, with the cockpit placed well ahead of the main body. The cockpit featured relatively heavy framing but still allowed for good views outside. The canopy was contoured as such that the cockpit was seamlessly integrated into the aircraft's aft fuselage. The nose extended out just a bit forward of the cockpit. Cockpit avionics included the APQ-50A series radar system. The undercarriage was of a conventional tricycle design with the two main gears recessing under the wings and a nose wheel gear retracting under the forward fuselage.