McDonnell Aircraft Corporation’s F-4 Phantom was quickly becoming the do-all fighter by the mid 1960s, able to lug thousands of pounds of bombs on one mission and then strictly air-to-air missiles the next. The potential for evolving the already successful Phantom became especially attractive as high-end combat aircraft programs of the ‘60s began to sputter, namely the Navy’s F-111B. Enter the F-4(FV)S variable-geometry wing Phantom concept.

The F-4(FV)S concept took the F-4 fuselage and omitted its low, bent-wing configuration. In its place was a redesigned highly-mounted swing-wing mated to large wing-root extensions. Within these extensions were the pivot points for the swing-wings. The result was a design that looked more like what would become the Soviet MiG-23 Flogger than anything else ().

Like the in development at the time, the F-4(FV)S’ variable geometry wing, able to sweep between 23 and 75.5 degrees, would have given the F-4 blistering high-speed performance, while also allowing for improved low-speed handling.

The F-111 Aardvaark, also known as the "The Pig," served for thirty years in USAF service, and with

This configuration could have solved what was a a trade-off in the Phantom’s evolving wing design. Up until the F-4E and the F-4S, the F-4 had a “hard wing” with no leading-edge maneuvering slats to enhance its agility and slow-speed handling. This configuration was fine for pure interceptor or reconnaissance missions as it offered a wing that was optimized for high-speed flight, but for dogfighting, hard maneuvering trying to avoid enemy ground fire and surface-to-air missiles, and flying around the carrier, it was far from ideal.

By employing a variable geometry wing, the Phantom could be more aerodynamic than ever before at high speed and more responsive at low speed. This could all be had without the F-4E and F-4J’s “improved wing” that did induce a high-speed performance penalty.

In addition to a new high, swing-wing arrangement, other changes were made on F-4(FV)S concept, including improved fuel capacity, a modified tail and a new main landing gear arrangement. Even updated engines were discussed as part of the new configuration — ones with better fuel efficiency than the standardstill found in Phantoms flying today.

Although the Navy did not bite at the swing-wing Phantom idea, McDonnell, which became McDonnell Douglas in 1967, kept revamping the concept. The main problem was that the Navy was looking for a Fleet Defender aircraft capable of lugging the massive AWG-9 radar and AIM-54 Phoenix missiles, something the Phantom just couldn’t be adapted to do. Instead, it would be restricted to the less capable AWG-10 radar and the latest version of the AIM-7 Sparrow, both which had a fraction of the range of the AWG-9 and Phoenix combination. The upside was it would be far less expensive than larger, more complex options.

A swing-wing fighter-interceptor solution eventually would be found for the Navy’s Fleet Defender dreams, developed under the VFX program. That aircraft being Grumman’s outgrowth production version of their McDonnell Douglas also put forward their model 225, of which a swing-wing variant was possible although it was passed over for the Grumman design.

Even though the swing-wing Phantom may not have been right for the U.S. Navy’s needs, the Royal Navy and Royal Air Force was another possible suitor. For the Royal Navy, McDonnell proposed the F-4J(FV)S. It would feature increased fuel, a new tail design, the AWG-10 radar and AIM-7F Sparrows with simultaneous multi-engagement capability, and a variable geometry wing with a sweep of 19 degrees to 70 degrees and full-span flaps and spoilers along its trailing edge. It would also have a pair of

The Royal Air Force was offered a similar aircraft under the designation F-4M(FV)S that would work for their land-based strike-fighter needs. Both designs kept high commonality with the original Phantom design for ease of transition and maintenance.

In the end, the updated swing-wing Phantom did not represent a large enough leap in capability for the UK to take the risk on procuring it. Additionally, the, and proceeding with a swing-wing Phantom would have endangered it. With the Navy also going in a more advanced direction, the variable geometry F-4 Phantom would never take flight.

Credit: DoD for photos, concept art and line drawings McDonnell/Industry

Sources: Hushkit.net, Aerospaceprojectsreview.com

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