The US Navy could not be accused of being unwilling to try out new concepts. Even before the Skyray development was initiated, it had commissioned the construction of three prototype fighters from Chance Vought in June 1946. These were again based on German work and the result was a revolutionary tailless design with directional control achieved by twin fin and rudder assemblies at mid span on each wing. Like the Skyray, the new XF7U-1 Cutlass was intended as a deck-launched interceptor and to achieve the required performance a twin-engine configuration was adopted, two Westinghouse J34-WE-32 turbojets with afterburning being set side by side in the fuselage nacelle. The result was unlike anything flown before or since and, considering the unorthodox layout, performed better than might have been expected, although several serious problems were encountered. The prototype XF7U-1 flew on 29 September 1948 and was followed by the first of fourteen production F7U-1s in March 1950. These were eventually allocated to the Navy’s Advanced Training Command at Corpus Christi in 1952 as problems with the J34 engine as well as handling difficulties made the Cutlass unsuitable for carrier deployment. These caused the cancellation of the F7U-2 with more powerful J34s and development was centred on the F7U-3, which was re-engined with Westinghouse 4,660 lb thrust J46-WE-8A engines. The centre fuselage was entirely re-designed and the underwing section of the vertical tail surfaces was virtually eliminated. The F7U-3 was first flown in December 1951 and initially four Navy squadrons (VF-81, VF-83, VF-122, VF-124) were equipped with the Cutlass, although operational deployments did not commence until May 1954, the first being VF-81 aboard the USS Ticonderoga. A total of 290 F7U-3s were delivered, which included ninety-eight F7U-3Ms with provision to carry four Sparrow air-to-air missiles and twelve F7U-3P photo reconnaissance aircraft. However, the type’s record in service was very poor with serious maintenance problems and a frighteningly high accident rate so that production ceased in 1955 and it had been entirely replaced before the end of the decade. Originally intended as a pure interceptor, it was outclassed in this role by the Skyray and subsequently was more often utilised in the attack role, carrying two 1,000- or 2,000 lb bombs, and it could also be fitted with a centreline pod carrying forty-four 2.75 inch air-to-air unguided rockets.
Although the US Navy was never able to field a swept wing jet fighter in the Korean War, things might have been different if development of another design had progressed as hoped. This was the McDonnell F3H Demon, which was ordered in prototype form in September 1949 following the company’s response to an earlier request for proposals issued by the Bureau of Aeronautics in May 1948 for a swept-wing naval interceptor. For its time, the Demon was an advanced design with sharply swept flying surfaces, wide lateral air intakes and provision for afterburning with the tailplane and fin being set well above the jet efflux. The prototype XF3H-1 flew on 7 August 1951 but even by that time the programme was in deep trouble. Things were not helped by a BuAer requirement that the Demon should be redesigned as an all-weather fighter under the designation F3H-1N. This significantly delayed development, the first production examples not flying until December 1953. In the meantime a much more serious problem had arisen in the shape of the failure of the Westinghouse J40 engine programme. The afterburning 9,200 lb thrust J40-WE-8 had initially been selected as the powerplant for the Demon but the XF3H-1 prototype was only fitted with the unreheated 6,500 lb thrust J40-WE-6. Eventually the afterburning variants were fitted to both prototypes and initial carrier trials were carried out aboard the USS Coral Sea in October 1953. Even by that time the J40 was proving unreliable, resulting in damage to one aircraft, and both being grounded for various periods. When testing of production F3H-1Ns began, the results were even more disastrous with no fewer than five aircraft being destroyed in accidents, including three in which the pilot was killed. In most cases the root cause of the accident was a failure of the J40 engine and it was quite clear that the Demon was seriously underpowered. Matters were so bad that many of the fifty-eight F3H-1Ns completed were never even flown, but were shipped by barge down the Mississippi from St Louis to Memphis where they were used as instructional airframes.
The US Navy had a major commitment to the J40 engine, which was the prime powerplant for several projected aircraft (including the F4D Skyray and twin-engined A3D bomber), and was reluctant to abandon development despite the evidence of flight tests. However, the McDonnell team was determined to salvage the Demon programme and persuaded the US Navy to allow two F3H-1N airframes to be converted to accommodate an Allison J71-A-2E rated at 9,700 lb thrust (14,400 lb with afterburning). Thus powered, the first F3H-2N flew on 23 April 1955 and proved to be a much better performer, although the Demon would have benefited further if an even more powerful engine could have been fitted but this was not possible without a major redesign. Eventually the F3H-2N began to reach squadrons in late 1956, subsequently embarking in the USS Forrestal for a Mediterranean deployment in January 1957. The standard F3H-2N was armed with fuselage-mounted 20 mm cannon but in August 1955 the missile-armed F3H-2M made its first flight. This could carry four AAM-N-2 Sparrow 1 semiactive homing guided missiles, which relied on the target being illuminated by the aircraft’s AN/APG-51B radar. In this guise the Demon became the US Navy’s first all-weather missile armed interceptor and remained in service until replaced by more capable fighters in the early 1960s. Thus the Demon was too late to see service in the Korean War and had been phased out of service by the time the United States became involved in Vietnam.
Despite the fact that the Demon had a relatively inauspicious career, it did provide the springboard for another project that was to become not just a first-class naval fighter, but one of the most successful all-round combat aircraft ever flown – the Mach 2 capable McDonnell F4H Phantom II. Although the first flight and subsequent development of this superb aircraft lie outside the period covered by this book, its initial development can actually be traced back as far as 1953 when McDonnell began a series of studies aimed at offering a substantial improvement in capability and performance of the F3H Demon. Under the designation Model 98, a series of single- and two-seat, single and twin-engined proposals were made. Of these, and after discussions with the US Navy, the Model 98B powered by either two Wright J67s or two General Electric J79s was taken as the basis for a new single-seat aircraft initially designated AH-1 in recognition of its planned attack role. However, by May 1955 when the construction of two prototypes was authorised, it was decided that they would be completed as two-seat, missile armed, all-weather fighters under the designation YF4H-1. Subsequently the prototype flew on 27 May 1958 and its startling performance led to substantial US Navy orders and, in a remarkable achievement, it was also ordered in quantity for the USAF – the first time that a naval fighter had achieved this distinction.
In fact, successful as the Phantom was to prove, it would not be the US Navy’s first fully supersonic fighter as it was preceded by two other types, both of which were easily capable of exceeding Mach 1 in level flight. The first of these to enter service was the Grumman F11F-1 Tiger, which had first flown on 30 July 1954 and subsequently entered operational service in early 1957. Development of the F11F had commenced in December 1952 when the possibility of applying the area rule principle to the swept wing F9F was investigated. It quickly became apparent that a fresh design would be required and this evolved as a slim-fuselaged, swept wing jet fighter with an empty weight of around 13,000 lb. The incorporation of area rule led to distinctive narrowing of the fuselage where the wings were mounted in order to eliminate rapid changes in the total cross-sectional area presented to the airflow. The slim fuselage was achieved by using an axial flow jet engine, in this case an afterburning Wright J65, which was actually a licence-built version of the British Armstrong Siddeley Sapphire. Considerable attempts were made to reduce weight and one unusual feature was that the wingtips were folded down manually, saving the complexity of the more conventional power-actuated upward-folding wings. The first prototype was lost in an accident in October 1954 due to an engine flameout – a recurrent problem with the J65. However, the second prototype had flown by then and was able to carry on the test programme, exceeding Mach 1 for the first time before the end of the year. A third prototype flew in December 1954 and incorporated various modifications, including redesigned tail surfaces, a longer nose, air intake splitter plates, a new clear-view canopy and had provision for an air-to-air refuelling probe to be fitted. A standard armament of four 20 mm cannon was fitted and the F11F-1 could carry four Sidewinder missiles or two missiles and two drop tanks of 150 US gallons.
Carrier trials aboard the USS Forrestal in April 1956 highlighted the need for further modifications, notably increasing the fuel capacity to make good shortfalls in range and endurance. As already related, service entry followed in 1957 but the Tiger’s operational career was relatively short and it was withdrawn from frontline units by 1961, although it enjoyed a longer career with second line training units and was adopted as the mount for the famous Blue Angels naval demonstration team. When the Tiger passed out of frontline service, it was the end of an era for Grumman who had provided naval fighters continuously from 1933 and it was not until the 1970s that another Grumman jet fighter (the F14 Tomcat) was to serve aboard US carriers. The reasons for the Tiger’s premature withdrawal were varied but included poor handling, which made it an unsteady gun platform, and the unreliability of the J65 engine. However, the main reason was that it was totally eclipsed by another fighter that had entered service at the same time.
This was the Chance Vought F8U Crusader, which originated from a US Navy requirement for a supersonic air superiority fighter issued in 1952. This company had, of course, made its name as the builder of the famous Corsair piston-engined fighter but had experienced less success with its subsequent jet designs. Awarded a contract in May 1953 for further development of its proposals, Chance Vought produced a fairly conventional design based around a single Pratt & Whitney J57-P-11 turbojet, which could produce 18,900 lb thrust with afterburning and was positioned towards the rear of the long fuselage. A pointed radome with a semi-circular chin air intake below gave the Crusader a distinct profile but its most unusual feature was the high-mounted swept wing with noticeable anhedral. This was unusual in a jet fighter but was accounted for by a unique feature intended to make the task of landing this hot ship aboard a carrier easier than it might otherwise have been. In normal flight the top surface of the wing centre section lay flush with the top of the fuselage but at slower speeds the leading edge could be raised by means of screw jacks, so increasing the angle of incidence of the whole wing relative to the fuselage. This in turn effectively reduced the nose-up attitude of the whole aircraft, improving the pilot’s view of the deck while also increasing lift. The high wing layout did mean that the main undercarriage legs had to retract in the fuselage, which resulted in a relatively narrow wheel track.
In service the F8U Crusader offered a substantial increase in performance over previous naval fighters. The top speed was around Mach 1.7 at altitude, although the initial rate of climb was only 12,000 feet/min, still very good but well below that achievable with the Skyray. This difference was accounted for by the weight of the Crusader, which grossed at 34,000 lb compared with the 25,000 lb MAUW of the Skyray. However, the Crusader had a much better endurance and was capable of carrying a wide variety of weapons apart from the internal four 20 mm cannon. The standard fit was either two (later four) Sidewinder infra-red homing homing missiles, or up to 5,000 lb of bombs or rockets, or any combination of these. Given the advanced performance of the Crusader, its development and entry into service was completed in an amazingly short time, especially when compared with earlier jets such as the Skyray and Demon. The prototype XF8U-1 flew in March 1955 and production standard aircraft were coming off the assembly lines by the end of 1956 with the first squadron (VF32) forming in March 1957. By the end of the year the squadron was deployed aboard the USS Saratoga and subsequently various versions of the Crusader flew with no fewer than seventy US Navy and USMC squadrons in a career that lasted until the mid 1980s. A total of 1,261 Crusaders were produced, which included forty-two for the French Navy, one of the few cases where US Navy fighters were exported. One of the most important variants was the RF-8 in which a battery of five cameras replaced the 20 mm cannon and provision was made for additional fuel. Both fighter photo reconnaissance versions saw considerable action during the Vietnam War, some units serving right through to the end in 1973.
The variable incidence wing of the Crusader was one example of altering wing characteristics to overcome the problem of landing high-performance swept wing aircraft on a carrier deck. A more ambitious solution dated as far back as 1946 when Grumman were asked to build a research aircraft to test swept wings with an eye to their later application to the XF9F-2 Panther. The initial proposal was for a single-engined, high-mounted, modified delta-wing aircraft with a T-tail and a contract was issued in April 1948 for two prototypes. However, by 1950 a new specification was issued calling for a fighter that would have good low-speed handling qualities and be capable of transonic speeds. At the same time a heavy armament and long range was required so that the final Grumman design increased in weight from around 18,000 lb MTOW to over 31,000 lb. After investigating the possibility of using variable incidence, the Grumman team went a step further and proposed a variable sweep wing with full-span leading edge slats and flaps along 80 per cent of the trailing edge.
The prototype XF10F-1 Jaguar eventually flew on 19 May 1952 but almost immediately severe problems were manifest. These were both technical failures and stability problems, although the wing sweep mechanism itself caused no trouble and turned out to be very reliable. The Achilles’ heel of the project was the use of the ill-fated Westinghouse J40 engine. The cancellation of this engine in 1953 and the subsequent grounding of all aircraft fitted with it effectively ended the Jaguar programme. Nevertheless it should be recognised as a pioneering attempt at what was actually a viable proposition and the concept of variable sweep was incorporated in the American F-111 and B-1 bombers, and the European Tornado.
At this point brief mention should be made of two significant aircraft that were built in prototype form to explore the concept of a VTOL combat aircraft. These were the Convair XFY-1 and the Lockheed XFV-1. Both came about as a result of studies made by both the US Navy and Air Force in the late 1940s and with the outbreak of the Korean War development funds became available. The two designs were very similar in concept, power for take-off and conventional flight being provided by turboprops driving a pair of three-bladed contra-rotating propellers. With broad chord blades these acted as helicopter rotors to lift the aircraft from the ground, the transition to horizontal flight being made gradually as speed and altitude increased. The Lockheed XFV-1 had short stubby wings with wingtip tanks, and a cruciform tail assembly that incorporated four wheels on which the aircraft rested when on the ground. The pilot was provided with an ejector seat. For initial flight trials a 5,850 hp Allison XT40-A-6 turboprop was installed with a more powerful YT40-A-14 scheduled for later tests, although this never actually became available. The production FV-2 would have had an even more powerful T54-A-16. The prototype was fitted with a temporary fixed undercarriage to permit conventional take-off and landings for the initial test flights and officially flew on 16 June 1954, although it had previously become airborne in high-speed taxi trials. Although transitions from horizontal to vertical flight modes and back again were made in the air, vertical take-offs and landings from the ground were never attempted as the trials engine did not produce enough power. The programme was cancelled in mid 1955 when it was realised that even if full transitions could be achieved, the performance of the turboprop fighter would lag well behind that of contemporary jets.
The Convair XFY-1 was much more successful and featured a broad delta wing, together with upper and lower vertical fins. This made a much more stable base (an important consideration aboard ship) but in other respects the design was similar to that of the Lockheed aircraft with the same powerplant and a tilting ejector seat for the pilot. Initial tethered flights commenced in April 1954 and these culminated in the first free flight in which transition to horizontal mode was successfully accomplished and was then followed by a vertical landing. This occurred in November 1954 and subsequently the XFY-1 recorded a maximum speed of 610 mph at 15,000 feet and had an excellent rate of climb, reaching 30,000 feet in 4.6 minutes. Despite the apparent success of the programme the project was cancelled in 1956, one possible reason being that the widespread adoption of VTOL combat aircraft might result in a reduction in the size of the US Navy’s carrier fleet – something that many Admirals did not wish to see. A similar attitude prevailed in Britain in the 1960s when aircraft such as the P1127 and Kestrel (forerunners of the Harrier) were seen by some as a possible threat to the Royal Navy’s carriers.
Convair were to achieve considerable success with the production of delta-winged jet fighters for the USAF (F-102 and F-106) and applied some of their experience to produce a jet-powered water borne fighter, the XF2Y-1 Sea Dart. Powered by two 3,400 lb thrust J34-WE-32 engines, the Sea Dart was very similar in outline to the F-102 Delta Dagger except that the engine intakes were on the top of the fuselage to prevent spray ingestion on take-off. Instead of a conventional flying boat hull, the XF2Y-1 was fitted with retractable hydro skis, which offered less drag in the air and permitted higher speeds on the water. The official first flight was on 9 April 1953, although the aircraft had previously been briefly airborne during taxi trials. There were problems both with the engines, which failed to develop the expected thrust, and with controlling the aircraft on take-off while running on the skis. Consequently only three development YF2Y-1s were built and one of these crashed in November 1954. Although the US Navy continued test and evaluation trials, the project was finally halted in 1956.
By the mid 1950s, the development of jet combat aircraft for naval use had advanced considerably in the decade following the end of World War II. By 1955 high-performance swept wing aircraft, some with supersonic capability, were either in service or under active development in both Britain and America. However, it was almost inevitable, given the strength of their industrial base, that the Americans should forge ahead. Thus in 1955, while the Royal Navy was still operating straight-winged Seahawks and Sea Venoms, the US Navy had swept wing Furies and Cougars and was about to introduce the fast-climbing Skyray, while the supersonic Crusader (capable of speeds in excess of 1,000 mph) had already flown in prototype form.