The Douglas F4D Skyray (later redesignated F-6) was the result of a 1947 Navy design competition for a new aircraft based on delta wing planforms. Analysis of the studies carried out by Dr. Alexander Lippisch on delta winged aircraft in Germany during the war attracted a considerable amount of interest on the part of both the US Army Air Forces and the US Navy, since such aircraft offered particular promise in the design of fast-climbing interceptors.
Several manufacturers submitted proposals for interceptor aircraft to the Navy that embodied a delta-winged format. On June 17, 1947, the US Navy Bureau of Aeronautics (BuAer) selected the Douglas proposal as being the best of the lot, and a contract was awarded for a preliminary design study.
Douglas engineers E. H. Heinemann and C. S. Kennedy directed the preliminary design study. Very early on, the pure delta planform was abandoned in favor of a tailless aircraft with a pair of mid-mounted, low aspect-ratio, highly-sweptback wings with round tips. The single turbojet was fed by a set of lateral air intakes located in the wing roots. The tricycle undercarriage had to be supplemented by a small retractable tailwheel mounted under the rear fuselage because of the aircraft's high angle of incidence during takeoff and landing. The tailhook extended from the base of the tailwheel assembly. The armament was to be four 20-mm cannon, the guns being mounted in the wing roots just outboard of the main wheels, their muzzles being located slightly below and behind the wing leading edges. The cockpit was situated well forward in the lose and was equipped with an ejector seat.
The engine was to be the afterburning Westinghouse J40 turbojet, which was the powerplant of choice for the next generation of high-performance Navy aircraft such as the McDonnell F3H-1 Demon, the Grumman F10F Jaguar, and the Douglas A3D Skywarrior. With this engine, it was estimated that the Douglas design should be able to achieve a maximum speed in level flight slightly greater than Mach 1, and would have an initial climb rate exceeding that of all other contemporary fighters.
On December 16, 1948, Douglas was awarded a contract for the construction and testing of two prototypes. The designation XF4D-1 was assigned. The BuAer serials were 124586 and 124587.
The airframe was completed in 1950, but the 7000 lb.s.t. Westinghouse XJ40-WE-6 engine that was intended for the XF4D-1 had experienced serious development delays and was not yet ready for flight. Rather than wait until the J40 was completed, Douglas decided to install a 5000 lb.s.t. Allison J35-A-17 turbojet in the two XF4D-1 airframes for the initial testing. XF4D-1 BuNo 124586 took off on its maiden flight on January 23, 1951, test pilot Robert Rahn being at the controls. The similarly-powered second prototype flew shortly thereafter. The first prototype had a clamshell- type canopy, whereas the second had a rearward-sliding canopy. The clamshell canopy was adopted for the production version. The Navy ordered an initial production batch of 12 F4D-1s in February of 1951.
With the J35, the XF4D-1 was seriously underpowered. The XF4D-1 prototypes were both re-engined with the 7000 lb.s.t. non- afterburning XJ40-WE-6 when it finally became available. This was later replaced with a 11,600 lb.s.t. afterburning XJ40-WE-8 turbojet.
The XJ40 turbojet was highly temperamental and was prone to sudden inflight failures, but it did enable the high-speed performance profile of the XF4D-1 to be explored. On October 3, 1953, BuNo 124587 flown by Navy Lt-Cdr James B. Verdin set a new world's air speed record of 752.944 mph over a three-kilometer course above the Salton Sea in California. This was the first time in history that the world air speed record had been captured by a carrier-based aircraft. On October 16 of that year, Douglas test pilot Bob Rahn used the same aircraft to set a 100-km closed course speed record of 728.11 mph over Muroc Dry Lake.
In the meantime, the problems with the J40 were beginning to get very serious. The engine would not deliver the expected thrust output, and was notoriously unreliable, being subject to sudden inflight failures, fires, and explosions. By March of 1953, the J40's problems were beginning to make the Navy very nervous, and in that month the decision was made to adapt the Skyray to the Pratt & Whitney J57 axial flow turbojet as insurance in case the J40 project should fail. The J57 was not only more reliable than the J40, it was also more powerful. However, it was also quite a bit larger and heavier than the J40, requiring that up to 80 percent of the airframe be modified in order to accommodate it.
It was a good thing that this decision to replace the J40 was made, because the J40's problems proved to be insoluble, and the entire J40 program had to be cancelled. The J40 episode was a sorry experience for all concerned, especially for Westinghouse, which was driven out of the jet engine manufacturing business altogether.
In October of 1953, while work on the J57-powered production F4D-1 was getting underway, the XJ40-WE-8-powered XF4D-1 was used for carrier qualification trials aboard the USS Coral Sea.
The second XF4D-1 (BuNo 124587) was loaned to General Electric in 1956 for use as a test bed for the J79 turbojet and later for the CJ805-3 turbojet which was intended for the Convair 880 commercial jet transport.
Serials:
BuNo 124586 and 124587 Douglas XF4D-1 Skyray
The first production F4D-1 (BuNo 130740) took off on its maiden flight on June 5, 1954. It exceeded the speed of sound in level flight during its first flight. During flight test, frequent engine stalls were encountered at high speeds above 40,000 feet, and it was found necessary to modify the geometry of the air intakes and to add an airflow baffle plate ahead of each air intake in order to alleviate this problem. Changes also had to be made to the fairing around the afterburner exhaust in order to make the airflow smoother.
It was not until early 1956 that the first production F4D-1s could be delivered to Navy service units. The first Navy unit to receive Skyrays was Composite Squadron 3 (VC-3) based at NAS Moffett in California, which got its first planes on April 16, 1956. This outfit performed the initial service evaluation of the type. The first truly operational unit was VF-74 at NAS Oceana in Virginia, which came on line in mid 1956. In early 1957, Skyrays were issued to the Marine Corps, the first unit to receive the type being VMF-115 based at MCAS Cherry Point in North Carolina.
A total of 419 production F4D-1s were built, the last example being delivered on December 22, 1958. At least 230 others were cancelled.
On May 22 and 23, 1958, Major Edward N. LeFaivre of the Marine Corps set five time-to-height records in F4D-1 BuNo 130745. These were 3000 meters (9842.5 feet) in 44.39 seconds, 6000 meters (19,685 feet) in 1 min 6.13 seconds, 9000 meters (29,527.5 feet) in 1 minute 29.81 seconds, 12,000 meters (39,370 feet) in 1 minute 51.23 seconds, and 15,000 meters (49,212.5 feet) in 2 minutes 36.05 seconds.
Late production F4D-1s were powered by the J57-P-8,P-8A, or P-8B turbojet which offered 10,200 lb.s.t. dry and 16,000 lb.s.t. with afterburning. The F4D-1 was equipped with an APQ-50A radar mounted in the nose. This radar was interfaced with an Aero 13F fire control system. Underwing loads could consist of six pods each containing seven 2.75-inch unguided rockets, four pods containing 19 2.75-inch rockets each, two 2000-pound bombs, or two Sidewinder air-to-air missiles.
VC-3 was later redesignated VFAW-3, and was attached for a time to the Air Defense Command. Its Skyray interceptors participated in the aerial defense of the United States, and carried an electronics package on the fuselage centerline pylon, a pair of 300-gallon underwing drop tanks, two packs of 12 2.75-inch unguided rockets, and two Sidewinder air-to-missiles on the outer underwing pylons.
F4D-1s were used by a total of eleven Navy squadrons and six Marine Corps fighter squadrons, as well as by three reserve squadrons and by several specialized units. The Navy squadrons using the Skyray were VFAW-3, VF-13, VF-23, VF-51, VF-74, VF-101, VF-102, VF-141, VF-162, VF-213, VF-881, VF-882. The Marine Corps units using the Skyray were VMF-113, VMF-114, VMF-115, VMF-215, VMF-314, VMF-513, VMF-531, VMF-542. Both carrier- and land-based units were equipped with the Skyray.
In September of 1962, the F4D-1 was redesignated F-6A under the new tri-service designation system. By this time, the Skyray was in service with only three front-line squadrons (VFAW-3, VMF-114, and VMF-531) and with three reserve units (VF-881, VF-882, and VMF-215).
The service life of the Skyray with the Navy and USMC was relatively brief, since the aircraft was specialized to the high-altitude interception role and lacked the multi-mission capability that was becoming increasingly important. The Skyray had a good climb rate, a high ceiling, a relatively high speed, and a good radar, all features which made it a good interceptor. However, it had a reputation of being a difficult plane to fly. The last Skyray left service on February 29, 1964. The Skyray never saw any combat, although it was deployed to Taiwan in 1958 and to Guantanamo in 1962 in response to crises.
In 1956, F4D-1 BuNo 134759 was transferred to NACA at Ames for various research and development tasks. It was retired in 1959.
BuAer serials of Douglas F4D-1 Skyray:
130740/130750 Douglas F4D-1 Skyray 134744/134973 Douglas F4D-1 Skyray 136163/136392 Douglas F4D-1 Skyray - contract cancelled 139030/139207 Douglas F4D-1 SkyraySpecification of Douglas F4D-1 Skyray:
One Pratt & Whitney J57-P-8, 8A, or 8B turbojet, 10,200 lb.s.t. dry and 16,000 lb.s.t. with afterburning. Maximum speed 722 mph at sea level, 695 mph at 36,000 feet. Cruising speed 520 mph. Initial climb rate 18,300 feet per minute. Service ceiling 55,000 feet. Combat ceiling 51,000 feet. Landing speed 134 mph. Normal range 700 miles, maximum range 1200 miles. Weights: 16,024 pounds empty, 22,648 pounds combat, 25,000 pounds gross, 27,116 pounds maximum. Dimensions: wingspan 33 feet 6 inches, length 45 feet 3 inches, height 13 feet 0 inches, wing area 557 square feet. Internal fuel capacity was 640 US gallons. Two 150-US gallon or 300-US gallon drop tanks could be carried underwing, bringing total maximum fuel capacity to 1240 US gallons. Armed with four 20-mm cannon in the wings. External stores of up to 4000 pounds in weight could be carried on seven wing and fuselage hardpoints (Four underneath the wings, two underneath the wing roots, and one on the fuselage centerline). Underwing loads could consist of six pods each containing seven 2.75-inch unguided rockets, four pods containing 19 2.75-inch rockets each, two 2000-pound bombs, or two Sidewinder air-to-air missiles.
Two prototypes were ordered under the designation F4D-2N. Serials were BuNo 139208 and 139209. However, as engineering work progressed, the F4D-2N became progressively more and more different from the F4D-1, and the new design was redesignated F5D-1 and named Skylancer.
The F5D-1 retained the general wing planform of the F4D-1, but the wings were much thinner and the fuselage was longer. The internal fuel capacity was increased from 640 US gallons for the F4D-1 to 1333 US gallons. The fuselage of the F5D-1 adopted the Area Rule, being deliberately slimmed down in the region of the wing roots to improve the transonic flight characteristics. The air intakes were redesigned, and a new V-edged cockpit windshield and canopy replaced the rectangular, flat-topped units of the F4D-1. A taller fin and rudder was fitted. The armament of four 20-mm cannon in the wings was retained, but the primary armament was to be a missile suite consisting of four Sidewinder or two Sparror air-to-air guided missiles and/or a battery of spin-stabilized unguided 2-inch rockets. An advanced X-24A radar fire-control system was to have been used.
Nine service test machines (BuNos 142349/142357) and fifty-one production machines (BuNos 143393/143400 and 145159/145201) were ordered. The prototypes and the service test machines were to be powered by the Pratt & Whitney J57-P-8, rated at 10,200 lb.s.t. dry and 16,000 lb.s.t. with afterburning. Production machines were to have been powered by the J57-P-14 engine rated at 10,700 lb.s.t dry and 16,900 lb.s.t. with afterburning. It was planned that the Skylancer would ultimately be powered by the General Electric J79 turbojet.
The first F5D-1 (BuNo 139208) took off from Edwards AFB on its maiden flight on April 21, 1956, with test pilot Robert Rahn at the controls. It easily exceeded the speed of sound on its first flight.
The performance of the F5D-1 proved to be excellent. The new larger fuel tanks endowed the F5D-1 with twice the range of the F4D-1. A maximum speed of nearly 1000 mph could be attained at altitude. However, after two prototypes and two production examples had been constructed, the Navy decided to cancel its order for the Skylancer. The reason given was that the Navy had already decided to purchase the Vought F8U Crusader, and that they just really didn't need to have on their rolls another fighter with essentially the same performance characteristics. Politics might also have played a role, since Douglas was already heavily involved in the production of the A3D Skywarrior, the A4D Skyhawk, the F4D Skyray, and the AD Skyraider and that it would not be a good idea for Douglas to be given a virtual monopoly on Navy combat aircraft construction.
At the time of the cancellation of the Navy contract, two prototypes (139208 and 139209) and two service-test aircraft (142349 and 142350) had been constructed. Following the termination of the Navy Skylancer contract, these four planes participated in various military test programs throughout the late 1950s and early 1960s. 139209 and 142349 were grounded in 1961, but the other two were transferred to NASA's Dryden Flight Research Center at Edwards AFB. 139208 was renumbered as NASA 212 and was used in support of the US supersonic transport program. For a while, it was fitted with wings of modified ogee planform. It was transferred to the Ames Laboratory in 1963. While there, it was renumbered 708. 708 was retired in April of 1968. 142350 was renumbered as NASA 213 and was used for the simulation of abort procedures for the Boeing X-20A Dyna-Soar orbital spaceplane. Following the cancellation of the Dyna-Soar program, NASA 213 continued to fly in support of lifting-body projects and SST studies. It was finally retired in 1970. Both NASA F5D-1s were retired in 1970.
Serials of Douglas F5D-1 Skylancer:
139208,139209 Douglas F5D-1 Skylancer
- originally designated F4D-2N
142349/142357 Douglas F5D-1 Skylancer
- 141351/142357 cancelled
143393/143400 Douglas F5D-1 Skylancer
- all cancelled.
145159/145201 Douglas F5D-1 Skylancer
- all cancelled.
Specification
of Douglas F5D-1 Skylancer: One Pratt & Whitney J57-P-8 turbojet, 10,200 lb.s.t. dry and 16,000 lb.s.t. with afterburning. Maximum speed: 953 mph at 35,000 feet, 990 mph at 44,000 feet, 749 mph at sea level. Cruising speed 637 mph. Initial climb rate 20,790 feet per minute. An altitude of 30,000 feet could be attained in 7.9 minutes. Service ceiling 57,500 feet. Combat ceiling 49,200 feet. Landing speed 155 mph. Stalling speed 112.7 mph. Combat range 1335 miles. Weights: 17,444 pounds empty, 24,445 pounds combat, 25,000 pounds gross, 28,072 pounds maximum takeoff. Dimensions: wingspan 33 feet 6 inches, length 53 feet 9 3/4 inches, height 14 feet 10 inches, wing area 557 square feet. Internal fuel capacity was 1333 US gallons. Two 150-US gallon drop tanks could be carried underwing, bringing total maximum fuel capacity to 1633 US gallons. Armed with four 20-mm cannon in the wings.
The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.
United States Navy Aircraft Since 1911, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.
Flying the Frontiers--NACA and NASA Experimental Aircraft, Arthur Pearcy, Naval Institute Press, 1993.
McDonnell Douglas Aircraft Since 1920: Volume 1, Rene J. Francillon, Naval Institute Press, 1988.
American Combat Planes, Ray Wagner, Third Enlarged Edition, Doubleday, 1982.
Joe Baugher