Vought F-8 Crusader
The supersonic Vought Crusader was one of the first supersonic fighters, but earned the nickname ‘Last of the Gunfighters’, because when it retired it represented the end of an era. It was an accomplished dog-fighter and was equipped with four 20mm cannon and 32 folding-fin aircraft rockets.
A pair of AIM-9 Sidewinders could also be mounted on rails on each side of the fuselage. Later models had four missiles, two on either side. Underwing pylons were fitted early in the production phase, allowing the carriage of air to surface weapons, such as the AGM-12 Bullpup missile.
Original production ran from 1956 until 1965, and it is a tribute to the soundness and utility of the design that surviving airframes were rebuilt and upgraded from 1960 right through until the end of the 70’s. An often-heard slogan in the Vietnam War was ‘When you’re out of Crusaders, you’re out of fighters!’
In 1952, as the Korean War was well under way, the US Navy announced that they needed a new, supersonic, cannon-equipped carrier-based fighter that could reach Mach 1.2 at 30,000′, climb at 25,000 fpm but land at not more than 100mph. The last requirement was difficult to achieve and resulted in some very unusual configurations being put forward.
Eight different manufacturers submitted twenty-two proposals, reflecting the strength of the US aircraft industry at that time. In September 1952 design work began at Chance Vought Aircraft on their contender for the competition – the Crusader.
Design & development
In May 1953 Vought was declared the winner and was awarded a contract for full-scale development, including three prototypes. Many of the competing designs had unusual features, leaving the Crusader relatively conventional but for one feature – it had a variable incidence wing.
The amount of lift a wing generates depends on the speed of the airflow around the wing and the angle of incidence, or attack, of the wing. Therefore the slower that aircraft fly, the higher the angle of attack that is required – all things being equal – to maintain the same amount of lift.
That is why when aircraft slow down for landing their bodies, and therefore wings, are at a higher than usual angle. At high angles this can make it more difficult to see the runway ahead when landing.
The Vought engineers and designers reasoned that while the wing certainly did need to be at a higher angle of attack at slow speeds, the rest of the plane did not have to be. Another benefit of the plane landing in a flatter attitude was that there was less chance of a tail-strike, and landing gear could therefore be shorter and smaller.
The wing was highly swept and tapered, with a dogtooth two-thirds of the way out from the root, which generated vortexes that discouraged the separation of boundary layer airflow. The wing itself was able to increased it’s incidence to +7 degrees using two hydraulic jacks.
The rest of the airframe was conventional with low-set rear horizontal stabilisers, and a tall vertical stabiliser at the rear. The single engine Pratt and Whitney J-57 took half of the length of the fuselage. A single inlet was position in the chin position, under the nose.
The wing tips folded to assist storage below the carrier deck. Catapults were not in service when the Crusader was on the drawing board, so it was designed to use the older ‘bridle’ harness/launching system. The air brake was located in an unusual position below the fuselage.
The image above shows off many of the Crusader’s design features, including the chin mounted air intake, two of the four 20mm cannon, side rail-mounted Sidewinders, under-belly airbrake, short landing gear, wing incidence of 7 degrees and folding wing-tips.
The fuselage was designed in accordance with the new ‘Area Rule’ developed by Richard Whitcomb to minimise transonic and supersonic drag. Whitcomb would go on to pioneer supercritical wing designs and the development of drag-reducing winglets.
The first prototype took to the air on the 25th March 1955 and comfortably went supersonic on its first flight. During testing throughout the remainder of 1955 the design firmed up into the initial production standard, which was approved the following year.
The initial production version of the Crusader appeared in 1956 and could reach Mach 1.53. The first combat squadron went to sea in late 1957 and the second a few months later. Although it was the faster US Navy fighter it did not to operate from the largest aircraft carriers.
The airframe was found to be quite versatile, and over the course of its life the Crusader grew in weight by around five tons, as avionics and weapons upgrades were regularly applied. These upgrades kept the Crusader competitive for many years longer that might have been originally envisaged.
Cuban Missile Crisis and Vietnam War
Along with the McDonnell RF-101A Voodoo, the Vought RF-8A Crusader featured in the Cuban Missile Crisis in the low level reconnaissance role. The Crusaders confirmed the erection of Soviet missiles and both types later confirmed their dismantling.
The Crusader also served in the Vietnam War, first engaging with MiG-17s in April 1965. Over the next few years, despite the introduction of Phantoms with long range Sparrow missiles, it became apparent that the era of the dog-fighter was not over yet.
The land-based US Marine Corps Crusaders flew mainly in the south and the Carrier-borne Navy aircraft flew mainly in the north. Both were equipped to carry ‘iron’ bombs, and they used them to good effect up and down the country. In air to air combat the Crusader went on to claim nineteen MiGs downed for the loss of three of their own, to MiG-17 cannon fire.
During the Vietnam conflict a total of 170 F-8 Crusaders were lost to all causes. Most of these were to ground fire and accidents.
The model that had the longest service life was the unarmed photo-reconnaissance model, of which 144 were built, with 73 of those later being re-manufactured and re-designated RF-8G. They were finally replaced in the early 1980s by Grumman Tomcats equipped with an external multi-sensor pallet.
The fastest Crusader
The fastest of all the Crusaders was the F8U-2N, which was an all-weather (and night) interceptor, with a powerful radar, and provision for a special long range version of the Sidewinder missile. The aircraft has the rocket box removed, a revised air-brake and space for additional fuel. It could reach Mach 1.86, due to the more powerful version of the J-57 engine.
This model was also notable in that it was the first that came with a rudimentary autopilot, and an associated revision of the cockpit layout. 152 of this version were produced.
After having produced 1,261 single seat Crusaders, Vought offered the US Navy and UK Navies a two seat design, but there was little interest. More interest was shown by the French however, and a special variant was built for them, with even greater variable camber and a boundary-layer control bleed air system to prevent separation.
Between 1966 and 1970 Vought gave a second lease of life to 551 surviving airframes. They were completely rebuilt and equipped with new avionics and a range of other updates. Each airframe was cleared for a further 4,000 hours of flight time.
A number of refurbished Crusaders saw service with the Philippines Air Force.
Two initial prototypes. A third was ordered, but subsequently cancelled.
F8U-1 (later re-designated F-8A)
Initial production fighter version. 318 built.
F8U-1E (later re-designated F-8B)
All weather fighter with improved radar. 130 built.
F8U-1P (later re-designated RF-8A)
Unarmed photo-reconnaissance version. 144 built.
F8U-2 (later re-designated F-8C)
Upgraded air superiority fighter with more powerful engine, better cooling, ventral fins, carriage for four Sidewinders rather than two. 187 built.
F8U-2N (later re-designated F-8D)
The fastest of all Crusaders, with upgraded, more powerful engine, extra fuel and new radar. 152 built.
F8U-2NE (later re-designated F-8E)
Final US production model. Same engine as the F-8D, upgraded avionics, air to surface weapons on pylons. 286 built.
A version for the French Aeronavale with a high lift BLC wing, different avionics, pylons suitable for Matra missiles and other small changes. 42 built.
A rebuild of the RF-8A with more powerful engine, stronger structure, new equipment and ventral fins. 73 (re)built.
A rebuild of the F-8D with stronger structure, high lift BLC wings, and new avionics. 89 (re)built.
A rebuild of the F-8E to F-8H standard. 136 (re)built.
A rebuild of the F-8C to F-8H standard. 87 (re)built.
A rebuild of the F-8B to F-8H standard. 61 (re)built.
A totally different, faster and more powerful aircraft. Three were built and flown. The type lost out to the F-4 Phantom. The US Navy called it “by far the best airplane we ever cancelled.”
|Aircraft Type||Single engine, carrier-based, supersonic fighter|
|Crew complement||Single pilot|
|First flight||25 March 1955|
|Last flight||French Crusaders operated until 2000|
|Maximum weight||34,000 lb (15,000 kg)|
|Powerplant(s)||One J-57 Pratt & Whitney turbojet|
|Armament||4x20mm cannon, up to 4 Sidewinder missiles, 32 Mk 4/40 folding fin rockets, 2xLAU-10 rocket pods, 2xAGM-12 Bullpup air to surface missiles, 12x250lb bombs, 8×500 lb bombs, 4×1,000 lb bombs or 2×2,000 lb bombs.|
|Combat radius||450 miles|
|Cruise speed||495 knots|
|Maximum speed||Mach 1.86|
|Claim to fame||Had the only variable-incidence wing in operational use.|