The United States Navy in the 1950s deployed a array of outstanding jet fighters for air-t-air combat in the daylight, including the Grumman F9F Cougar/Panther series, Vought F7U Cutlass and F8U Crusader, and McDonnell F3H Demon, not to mention that it acquired a navalized version of the North American F-86 Sabre as the FJ-2/3/4 Fury (which almost shared nothing in common with the earlier straight-wing FJ-1 Fury). However, somewhat lost in talk of US naval fighter aviation in the 1950s is the fact that a few naval jet fighter designs were conceived in the Los Angeles basin in southern California during the early Cold War, the Douglas F4D (F-6) Skyray and F5D Skylancer interceptors as well as the Douglas F6D Missileer fleet defense fighter project. This post will be the first of a two-post series concerning the 1950s jet fighter designs of the El Segundo Division of Douglas, mostly centering upon the development and operational service of the F4D and F5D.
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| Models of the Douglas F4D Skyray and its supersonic derivative, the F5D Skylancer, photographed by me at the Lyon Air Museum in December 2021 |
In late December 1946, the chief designer at Douglas Aircraft's El Segundo, Ed Heinemann (famous for designing the SBD Dauntless, A-1 Skyraider, A-3 Skywarrior, and A-4 Skyhawk), proposed a tailless delta-wing jet interceptor under the company design D-571, capitalizing on captured wartime German aeronautical research regarding the benefits of delta wings. The initial D-571 design was a tailless flying wing with a single vertical stabilizer, two Westinghouse 24C turbojets, and four 20 mm cannons in the nose. Although the US Navy's Bureau of Aeronautics (BuAer) was delighted with the layout of the airframe, it was concerned about developmental problems with the Westinghouse engines and suggested that Douglas consider fitting the D-571 with the Rolls-Royce Nene instead. On February 14, 1947, the Navy gave Douglas an engineering contract for development for the D-571, including constructing a full-scale mock-up, and two new D-571 designs were worked out, the D-571-1 with two Westinghouse 24Cs and the D-571-2 with one Rolls-Royce Nene. Both proposals differed from the initial D-571 design in having the cockpit moved forward to give better visibility, greater space in the nose for alternative armament including spin-stabilized rockets, and utilizing the afterburner for climb to altitude rather than supersonic speeds. Although specifications for the D-571-1 and D-571-2 are given in Buttler (2013) and need not be discussed in depth, the two proposals had the same length but differed in wingspan, wing area, and gross weight.
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| The first Douglas XF4D-1 prototype (BuNo 124586) on the deck of the USS Coral Sea carrier in October 1953 |
On June 17, 1947, Douglas was awarded a preliminary contract to construct two D-571-1 prototypes (BuNos 124586/124587) under the designation XF4D-1. In March 1948, Douglas made adjustments to the XF4D-1 design to create the D-571-4, including rounded delta wing edges and the replacement of the Westinghouse engines with a single Westinghouse J40 turbojet, and these changes were tailored to allow the XF4D-1 design to meet the parameters of the OS-113 specification issued by the Navy in May for a high-performance interceptor to climb rapidly to altitude to intercept enemy bombers, thus leading to the XF4D-1 prototype contract being emended on December 16, 1948 to cover the D-571-4 rather than the D-571-1. The XF4D-1 was officially christened Skyray by the Navy, and although the first XF4D-1 prototype was completed in 1950, the J40 was not yet available and Douglas decided to power the two prototypes with one Allison J35 turbojet, clearing the way for the first flight of the Skyray on January 23, 1951. The next month, the Navy ordered an initial production batch of twelve F4D-1s (BuNos 130740/130751), and when the Westinghouse J40 finally became available in 1952, the two Skyray prototypes were re-engined with the J40. On October 3, 1953, the second XF4D-1 became the first carrier-based aircraft in history to break the sound barrier when it attained a speed of 753 mph (1,212 km/h) while flying over the Salton Sea in California. The F4D Skyray was 45 feet 4 in (13.82 meters) long, with a wingspan of 33 feet 5 in (10.18 meters), a height of 13 feet (3.96 meters), a wing area of 557 square feet (51.8 m²), a top speed of 722 mph (1,162 km/h), and armament comprising four 20 mm cannons or 76 unguided air-to-air rockets. In the spring of 1952, the Navy placed an additional production order for F4D Skyray when it ordered 230 F4D-1s (BuNos 134744/134973).
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| Left: A Douglas F4D-1 Skyray (BuNo 139097) over San Diego Bay, 1960 Right: An F4D-1 Skyray landing aboard the aircraft carrier USS Bon Homme Richard on August 30, 1957 |
Even before the XF4D-1 broke the sound barrier, however, it was clear to Douglas and the Navy that the J40 turbojet was becoming prone to inflight fires and explosions as well as its inability to produce the expected thrust output. Therefore, in March 1953, the US Navy decided to have production F4Ds fitted with the Pratt & Whitney J57 turbojet, which was more reliable and powerful than the J40, but the J57 was so large and heavy that 80 percent of the F4D airframe had to be redesigned to accommodate this powerplant. As developmental of the production F4D-1 got underway, the XF4D-1 was used for carrier qualification trials aboard the USS Coral Sea, with tests performed by Lieutenant Commander James Verdin in fairly poor weather, and these conditions made it possible to test the aircraft's low-speed stability on approach with its leading-edge slats. On June 5, 1954, the first production F4D took to the skies, going supersonic in a brief dive, but flight testing revealed frequent engine stalls at high speeds above 40,000 feet (12,192 meters), prompting modification of the geometry of the air intakes and addition of an airflow baffle plate ahead of each air intake to alleviate this problem. Changes were also made to the fairing around the afterburner exhaust to make the airflow smoother, eliminating a high-speed turbulence problem that had been encountered during early flight tests of the F4D-1. The F4D began reaching US Navy squadrons in April 1956, and it entered service with the US Marine Corps in early 1957; Navy pilots nicknamed the Skyray the "Ford" in reference to its designation. An additional 408 F4D-1s were ordered (BuNos 136163/136392 and 139030/139207), but only BuNos 139030/139207 were completed, while BuNos 136163/136392 were canceled, and deliveries of the F4D Skyray continued until December 22, 1958, by which a total of 422 examples had been completed (two prototypes and 420 production aircraft). Late production F4Ds were fitted with the more powerful J57-P-8 and had seven hardpoints for external weapons loads, three under each wing and one on the ventral fuselage centerline. Underwing loads could consist of six pods, each containing seven 2.75-inch unguided rockets, four pods each containing nineteen 2.75-inch rockets each, two 2,000 lb (907 kg) bombs, or two Sidewinder air-to-air missiles. A proposal to fit the F4D-1 with one J57-P-14, designated F4D-2, did not progress beyond the design phase. On May 22 on 23, 1958, US Marine Corps Major Edward N. LeFaivre set five time-to-height records in F4D-1 BuNo 130745: 9,842.5 feet (3,000 meters) in 44.39 seconds, 19,685 feet (6,000 meters) in 1 minute 6.13 seconds, 29,527.5 feet (9,000 meters) in 1 minute 29.81 seconds, 39,370 feet (12,000 meters) in 1 minute 51.23 seconds, and 49,212.5 feet (15,000 meters) in 2 minutes 36.05 seconds.
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| A Douglas F4D/F-6A Skyray of the US Marine Corps operating from Leeward Point Field, Guantanamo Bay, Cuba, in early 1963 |
Despite having a good climb rate, high service ceiling, high speed, and powerful interception radar, the F4D Skyray had a brief operational career because it was only designed for high-altitude interception and lacked the multi-mission capabilities of newly developed US Navy fighters like the F8U Crusader and F4H Phantom II. Indeed, a 1957 Navy evaluation report found the F4D-1 only marginally effective as an all-weather fighter, identifying deficiencies like a modest top speed capability, poor transonic flying qualities, and armament control system limitations. Moreover, the Skyray had not been built for supersonic flight and could only exceed Mach 1 in brief dives. The F4D was deployed to Taiwan in late 1958 in response to China's air war over the Taiwan Straits, and to the Guantanamo Bay Naval Base in southeastern Cuba in October 1962 in response to the USSR's deployment of medium-range ballistic missiles in Cuba the same month, but never saw any combat. One F4D-1 (BuNo 134759) was loaned to the NACA Ames Aeronautical Laboratory (now NASA Ames Research Center) at NAS Moffett Field, California, for aerodynamic research beginning on April 4, 1956, and it was used for flying qualities, stability and control, and performance evaluations until October 16, 1959. When the Department of Defense introduced the Tri-Service designation system in September 1962, the F4D was redesignated F-6A. After eight years of operational service, the Skyray was retired from operational Navy service on February 29, 1964.
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| The first Douglas XF5D-1 Skylancer prototype (BuNo 139208) during its first flight on April 21, 1956 |
While the Skyray was just beginning to enter production, Douglas proposed an all-weather variant of the F4D-1 for supersonic flight, also designated F4D-2. This design retained the delta wing shape and fuselage of the production Skyray but differed in having thinner wings with reinforced skins to reduce transonic drag following the Whitcomb area rule, redesigned air intakes, and a taller vertical stabilizer, and it had an empty weight of 17,444 lb (7,912 kg), a gross weight of 28,739 lb (13,036 kg), and a top speed of 789 mph (1,270 km/h) at an altitude of 35,000 feet (11,000 meters). Armament consisted of four 20 mm cannons in the wing roots, 72 spin-stabilized unguided 2 inch (51 mm) rockets, and either four AAM-N-7 Sidewinder or two AAM-N-3 Sparrow II air-to-air missiles. The Navy decided that the F4D-2 was sufficiently distinct from the F4D to be given a new designation, XF5D-1, and two XF5D-1 prototypes (BuNos 139208/139209) were ordered in October 1953. Nine YF5D-1 service test aircraft (BuNos 142349/142357) and 51 production F5D-1s (BuNos 143393/143400 and 145159/145201) were ordered in 1955, and the prototypes and service test aircraft were powered by one Pratt & Whitney J57-P-8, while the production version was to be powered by one J57-P-14. The first Skylancer prototype made its first flight on April 21, 1956, piloted by Robert Rhan, and it was engineered well enough to break the sound barrier on its maiden flight. Compared to the F4D Skyray, the F5D was capable of flying supersonically at maximum altitude and had twice the operating range of the Skyray, and Douglas also proposed to fit later production F5Ds with the General Electric J79 turbojet, but that scheme did not win orders from the Navy. Despite the stellar performance of the Skylancer, the Navy terminated the F5D program in 1957 because the supersonic day fighter role for which the Skylancer was fulfilled by the Vought F8U Crusader, which had just entered deployment in March 1957, and by then the first two service test F5Ds had been completed, leaving the Navy to cancel the remaining YF5D-1s on order as well as contracts for the production aircraft. Moreover, the US Navy saw to it that Douglas was preoccupied with production of the AD Skyraider, A3D Skywarrior, A4D Skyhawk, and F4D Skyray, finding it to be against its conscience to give Douglas a monopoly on Navy combat plane production.
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| Left: The second YF5D-1 (BuNo 142350) in flight with tail code NASA 802 Right: The first F5D Skylancer prototype on the tarmac at an airfield in Ontario, Oregon, with tail code NASA 708, seen here in April 2004 |
After the Skylancer program was shelved, the F5Ds were given to NACA at Moffett Federal Airfield in Mountain View, northern California, on August 20, 1957, for flight research-related activities. The first XF5D and second YF5D-1 received the tail codes NACA 212 (later changed to NASA 212 in 1958, then NASA 708) and NACA 213 (later changed to NASA 213 in 1958, then NASA 802) respectively, operating at Moffett Federal Airfield until 1961 when they were assigned to Edwards AFB for tests of new radar systems, instruments and armament. While the second XF5D and first YF5D were grounded in 1961 to provide spare parts, the other two F5Ds were transferred to the NASA Ames Research Center in 1963 for testing the ogival delta wing for some American supersonic airliner designs and training pilots for the canceled Boeing X-20 Dyna-Soar military spaceplane program. The first F5D prototype was retired in April 1968, and the the second YF5D was used as a chase plane for lifting body aircraft and in support of SST design studies following the cancellation of the X-20 program, flying until 1970, when it was retired in 1970. The first F5D prototype subsequently became part of Merle Maine's private collection in Ontario, Oregon, until 2014, when it was transferred to the Evergreen Aviation Museum in McMinnville, Oregon, while the second YF5D is now on static display outside of the Armstrong Air & Space Museum in Wapakoneta, Ohio (the hometown of Neil Armstrong, the first man to set foot on the Moon).
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| A three view drawing of the Douglas D-652-1 variant of the D-652 submission to the OS-130 competition won by the Vought F8U Crusader |
As a side note, in early 1953 Douglas proposed a supersonic jet fighter derived from the F4D Skyray for the Navy's OS-130 requirement under the company designation D-652. Four D-652 designs were worked out, the D-652 sans suffixe with a longer fuselage and thin wings to reduce transonic drag as well as a Pratt & Whitney J57 turbojet, the slightly scaled down D-652A with a shorter nose and one Rolls-Royce Avon turbojet, the D-652-1 with the cockpit moved forward to allow more space for fuel in the fuselage, and the D-652-2 with the same airframe as the F4D but largely differing in electronics and external fuel tanks. Both the D-652-1, and D-652-2 proposals would have used either the J57 or Avon, and these designs along with the D-652A differed from the baseline D-652 in having a shorter nose. However, in May 1953, the competing Vought V-383 proposal was declared the winner of the OS-130 competition and became the F8U Crusader, making its first flight in May 1955.
References:
Buttler, T., 2013. Early US Jet Fighters: Proposals, Projects, and Prototypes. Manchester, UK: Hikoki Publications.
Frankel, M., 2010. Killer Rays: Story of the Douglas F4D Skyray & F5D Skylancer. North Branch, MN: Specialty Press.
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