| F4D (F-6) Skyray | |
|---|---|
 | |
| General information | |
| Type | Fighter aircraft |
| Manufacturer | Douglas Aircraft Company |
| Status | Retired |
| Primary users | United States Navy |
| Number built | 422 |
| History | |
| Manufactured | 1950–1958 |
| Introduction date | April 1956 |
| First flight | 23 January 1951 |
| Retired | February 1964 |
| Developed into | Douglas F5D Skylancer |
TheDouglas F4D Skyray (later redesignatedF-6 Skyray) is an Americancarrier-based supersonicfighter/interceptor designed and produced by theDouglas Aircraft Company. It was the last fighter produced by theDouglas Aircraft Company before the company merged withMcDonnell Aircraft to becomeMcDonnell Douglas.
In the late 1940s, Douglas and the U.S. Navy launched the D-571-1 design study, which called fordelta 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 theWestinghouse J40turbojet engine, but required a redesign for thePratt & Whitney J57 after the J40 was cancelled. Aerodynamic problems prolonged development; considerable design changes were made after themaiden 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 theUnited States Navy (USN) andUnited States Marine Corps (USMC) shortly thereafter.
The Skyray had a relatively brief service life and never saw combat. It was the firstcarrier-launched aircraft to hold the world's absolute speed record: 752.943 mph,[1][2] (1,211.487 km/h).[3] It is widely reported as the first naval fighter to break thespeed of sound in level flight rather than in a dive.[4] The Skyray also set a new time-to-altitude record, flying from a standing start to 49,221 feet (15,003 m) in two minutes and 36 seconds at a 70° pitch angle. The last Skyrays were withdrawn from service in February 1964, although a handful were flown for experimental purposes byNational Advisory Committee for Aeronautics (NACA) up to the end of the decade. TheF5D Skylancer was an advanced development of the F4D Skyray that did not enter service.
The Skyray originated within a design study, theD-571-1, performed by Douglas and funded by theUnited States Navy (USN). It was a fast-climbing pureinterceptor aircraft with adelta wing, powered by a pair ofWestinghouse J34turbojet engines, which were equipped withafterburners for bursts of additional acceleration.[5] 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 theleading edge of the wing; alternative armaments consisted of spin-stabilized rockets.[6] The design study had harnessed the designs and research of the GermanaerodynamicistAlexander Lippisch, who moved to the United States following the end ofWorld War II, and whose work had been examined by several of Douglas's design team.[7] 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.[6]
As the design was refined, the wing's thickness was substantially reduced to increase its high speed capabilities.[8] The twin J34 engine arrangement was also swapped out for a singleWestinghouse J40 engine. Only a singlehydraulic system was incorporated and measures to permit manual reversion in the event of hydraulic failure were included.[9] 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.[9] Specifics of this requirement included the ability to intercept and destroy an enemy aircraft at an altitude of 50,000 ft (15,240 m) within five minutes of the alarm being sounded.[10] At the time, Navy planners were particularly concerned by the threat posed to itscarrier battle groups by high altitudeSoviet 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.[11]
%2c_in_October_1953.jpg)
On account of the numerous design changes, the mockup review was delayed by almost one year, taking place in March 1949.[12] 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 andradome to improve the pilot's external visibility.[12] A more pressing issue would be the J40 engine. Douglas' design team made accommodations for other engines as a contingency measure;[13] this approach proved to be quite fortunate as the J40 had a particularly troubled development and was eventually cancelled with no production units delivered.[14] As a temporary measure, the prototype had to be outfitted with anAllison J35 engine instead.[7]
The long-term replacement for the J40 on production aircraft was thePratt & Whitney J57, a more powerful but considerably larger engine.[15] The ensuing delays to the program led to several other aircraft, such as theNorth American F-100 Super Sabre and theMikoyan-Gurevich MiG-19, beating it into operational service.[7]
On 5 June 1954, during its maiden flight, the first production F4D-1,bureau number (BuNo)130740, reportedly became the first naval fighter to exceed thespeed of sound in level flight.[16] According toFlight, this was achieved during the aircraft's acceptance flight between the Douglas plant inEl Segundo, California, andEdwards Air Force Base, flown by test pilot Bob Rahn.[17] 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 40,000 ft (12,000 m) 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 reducedrag.[15][18] In September 1955, initial carrier suitability trials were performed onboardUSSTiconderoga.[13] No production aircraft were delivered until early 1956 when the F4D was declared ready for fleet introduction in April.[13][19] A total of 419F4D-1 (later designatedF-6 under theunified 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 themanta ray.[20] The thick wing roots contained the air intakes that fed its singleturbojet 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 thetrailing edges comprised mostlyelevon control surfaces.[9] Additionalpitchtrimmers 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 earlyjet fighters. It was affectionately known as the "Ford" (after the "Four" and "D" of its designation).[21] During 1953,Edward H. Heinemann was awarded theCollier Trophy in recognition of his design work on the F4D.[22]
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 37 °C (99 °F), delaying the onset oftransonic drag; although the speed of sound is 761 mph (1,225 km/h) atstandard temperature and pressure, it rises to 790 mph (1,270 km/h) at 37 °C, so the Skyray's speed during the record-setting flight was equal to only 0.95Mach. Thomason writes that, according to U.S. Navy records, the first naval aircraft to exceed the speed of sound in level flight was aGrumman F11F Tiger prototype.[4]
-3_in_flight_over_San_Diego.jpg)
During April 1956, VC-3 became the first squadron to attain operational status with the F4D-1.[1] This unit was later redesignatedVFAW-3 and assigned toNORAD, becoming the onlyUnited States Navy fighter squadron in what was predominantly aUnited States Air Force (USAF) andRoyal Canadian Air Force (RCAF) organization. VFAW-3 was permanently based atNAS North Island in San Diego.
TheUnited States Marine Corps (USMC) also operated the Skyray. When theDepartment of Defense adopted auniform aircraft designation system patterned on the USAF's aircraft designation system during September 1962, the F4D was redesignated as theF-6A Skyray. TheF4D (old designation) should not be confused with theF-4D (new designation) – the latter being the "D" variant of theMcDonnell Douglas F-4 Phantom II operated by the USAF.[23]
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 (15,003 m) 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 andVMF-215 also flew the Skyray. The last operational squadron wasVMF(AW)-115, which flew the Skyray until February 1964. A total of four aircraft were used for experimental purposes by theNational Advisory Committee for Aeronautics (NACA) (which was later renamedNASA) until 1969.[24]
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 theF8U Crusader and also to reduce dependence upon Douglas Aircraft, which was also producing several other aircraft for the U.S. Navy.[24][25] This decision effectively removed Douglas from active fighter development.[26]
.jpg)
Data fromThe American Fighter[1]
General characteristics
Performance
Armament
Avionics
Related development
Aircraft of comparable role, configuration, and era
Related lists
