F-4X PHANTOM III: The Swing-wing Phantom

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 General Dynamics F-111 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.

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 standard General Electric J79 axial-flow turbojet still 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 303E concept, the F-14A Tomcat. 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 more powerful and fuel efficient Rolls-Royce Spey turbofans.

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 Anglo-French AFVG project in its early stages, 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, foxtrotalpha.jalopnik.com