A-X and A/F-X designs from the Los Angeles area

After the cancellation of the A-12 Avenger II naval stealth bomber in January 1991, the US Navy still found itself in need of a replacement for the A-6 Intruder, and thus Secretary of Defense (and future vice president) Dick Cheney asked the Secretary of the Navy to initiate a new effort at shopping for an A-6 replacement, the A-X (not to be confused with the A-X ground attack aircraft competition won by the A-10). Like the ATA program for which the A-12 had been designed, the A-X program called for a stealthy, two-seat attack aircraft with all-weather/day/night capability and advanced, integrated avionics and countermeasures, but it also stipulated that the aircraft have greater operating range and multirole combat capabilities. A Request for Proposals (RFP) was issued for the A-X program on July 1991, with an October 29, 1991 deadline set for aircraft manufacturers to submit initial A-X designs, and the Navy planned to fund up to five A-X studies at a cost of $20 million each, with follow-on plans for separate demonstration, development, and production stages by late 1992. The US Air Force also took part in the A-X program, hoping to someday deploy a stealthy successor to the F-15E Strike Eagle, which was replacing the F-111 Aardvark as the USAF's frontline fighter-bomber, and also potentially the F-117 Nighthawk.

Northrop's flying wing (left) and blended wing (right) proposals for the Navy's A-X program. (courtesy of Tony Chong via the Secret Projects Forum)

Northrop responded to the A-X requirements with three subsonic designs (flying wing, a performance-driven aircraft, and a blended wing body) and a few supersonic designs in the first half of 1991. The flying wing proposal resembled Northrop's losing design for the ATA competition in seating the pilot and navigator/bombardier in tandem in the cockpit but differed in having a sawtooth trailing edge of the center wing section like that of the B-2 and the engine inlets placed near the wing leading edges and adjacent to the crew compartment, and it was 40 feet 9 in (12.4 meters) long with a wingspan of 76 feet (23 meters) and a speed of Mach 0.85. Power was provided by either two 24,164 lb (107.49 kN) thrust General Electric F404s or alternate engines from Pratt & Whitney. The blended wing body design also had a tandem-seat cockpit and engine inlets below the wings but featured a spearhead-shaped wing with a tail empennage incorporating backswept horizontal stabilizers with slight dihedral, and it was 57 feet 9 in (17.6 meters) long with a wingspan of 68 feet (20.7 meters) and a top speed of Mach 0.95. The powerplant (including potential options) for the blended wing body design was the same as that for the flying wing design. The performance-driven iteration had clipped diamond-shaped wings, all-moving trapezoidal canards, and a butterfly-shaped tail with two armpit inlets just aft of the wing leading edges, and it was  60 feet 8 in (18.5 meters) long with a wingspan of 54 feet 9 in (16.69 meters), a top speed of Mach 0.95, and two 27,322 lb (121.5 kN) thrust Pratt & Whitney PW7000 turbofans. The supersonic  design studies, which resembled Northrop's designs for the cancelled Naval Advanced Tactical Fighter (NATF) program, had speeds of up to Mach 1.8, and one proposal, the Advanced Strike Fighter, was 60 feet 5.4 in (18.42 meters) long with a wingspan of 54 feet (16.46 meters), featuring folding wings with an angled trailing, two outwardly canted vertical stabilizers, a pair of swept canards along the nose, and two supercruise turbofans (probably based on the Pratt & Whitney F119). Armament of the Northrop proposals consisted of AIM-120 air-to-air missiles and laser-guided bombs carried in internal weapons bays. Northrop judged the subsonic designs to have a better chance of fulfilling the A-X performance parameters, but it neglected to continue with its subsonic A-X proposals, presumably because of its preoccupation with the B-2 Spirit stealth bomber and AGM/MGM-137 TSSAM stealth cruise missile (which played a role in the company's YF-23 losing the ATF competition to the F-22), and in mid-October 1991 it joined an industry team formed by General Dynamics and McDonnell Douglas which in July had offered for the A-X program a derivative of the A-12 Avenger II with slightly higher aspect ratio wings whose outer wing sections had cranked leading edges.

Left: Artist's conception of three Lockheed/Boeing/General Dynamics AFX-653s in flight near a carrier task force
Right: The Rockwell International/Lockheed proposal for the A-X/A/F-X program

About the same time that Northrop was fleshing out its A-X concept studies, Lockheed and Boeing put forward a design for a two-seat aircraft which had delta wings with backswept trailing edges, a pair of outwardly canted triangular vertical stabilizers, and two supercruise turbofan engines. When the RFP for the A-X program was issued in July 1991, this proposal gave way to a joint proposal by Lockheed, Boeing, and General Dynamics for a derivative of Lockheed's F-22 derived swing-wing proposal for the cancelled NATF program. The Lockheed/Boeing/General Dynamics proposal was 61 feet 8 in (18.80 meters) long with the wings spanning 67 feet 8 in (20.62 meters) when in forward position or 37 feet 2 in (11.33 meters) when full swept, and it differed from the navalized F-22 in having a slightly shorter nose, straight leading edges of the wing roots, slab-shaped horizontal stabilizers, and two 27,322 lb (121.5 kN) thrust Pratt & Whitney PW7000 turbofans. The pilot and bombardier/navigator were seated in tandem in the cockpit, and armament consisted of AIM-120s and laser-guided bombs housed in four internal weapons bays. In the same month that they jointly conceived their swing-wing A-x proposal, Lockheed and Boeing co-partnered with Grumman to develop a clean-sheet A-X proposal, for which few details are known. In late October 1991, Rockwell International and Lockheed jointly proposed an an A-X design which seated the pilot and bombardier/navigator in tandem and had swing wings like the Lockheed/Boeing/General Dynamics concept but featured a platform shaped like an isosceles triangle. The Rockwell International/Lockheed design was powered by two PW7000 turbofans fed by inlets below the fuselage near the leading edges of the center section and situated at the rear of the fuselage between two outwardly canted vertical stabilizers. 

On December 30, 1991, the Navy awarded $20 million Concept Demonstration/Evaluation contracts to the McDonnell Douglas/LTV, Lockheed/Boeing/General Dynamics, Grumman/Boeing/Lockheed, Rockwell International/Lockheed, and Northrop/McDonnell Douglas/General Dynamics industry teams for their A-X proposals. The Demonstration/Validation (Dem/Val) proposals were to be offered by September 1992, and one of the industry consortium designs would be selected for prototyping in 1994, after which the first flight of the whichever A-X proposal was selected was to take place by 1996, with plans to deploy the A-X in 2005. However, in September 1992, several people in Congress demanded that the A-X Dem/Val phase also involve prototype aircraft to be evaluated in a fly-off contest, and the Navy delayed the Dem/Val phase by two years and planned A-X deployment to 2007, but it rejected the idea of a fly-off competition as too expensive. The cancellation of the NATF program in the spring of 1991 also meant that the Navy and Air Force added an air-to-air capability to the A-X requirements in late 1992, leading to the A-X program being renamed A/F-X to fully reflect its combined attack/fighter capabilities. To reflect this change, the Lockheed/Boeing/General Dynamics A-X design was refined to have cranked chines like those of the F-22 and thus became known as AFX-653 or "A/F-22X", even though it still shared only 20 percent parts and 50 percent technology commonality with the F-22. 

The F/A-18E/F Super Hornet, which ended up becoming the Navy's successor to the F-14 and A-6 after the A/F-X program was canceled.  

In early 1993, before the Navy could prepare to evaluate the design submissions for the A/F-X program, the Pentagon initiated a Bottom Up Review of existing military aircraft programs in early stages of development, including the A/F-X, amid defense budget cuts after the end of the Cold War that came to be known as the "peace dividend". On September 1, the A/F-X program was cancelled along with the Grumman ASF-14 derivative of the veteran F-14 Tomcat and the F/A-18E/F Super Hornet derivative of the F-18 Hornet proposed in 1991 as a low-cost alternative to the A-X program was instead selected for full-scale development as an interim replacement for the F-14 and A-6, carrying out its first flight on November 29, 1995.

For more on the design studies for the A-X and A/F-X programs from southern California, see the following link:

https://www.secretprojects.co.uk/threads/navy-ax-and-a-f-x-projects.2150/

References:

Chong, T., 2016. Flying Wings & Radical Things: Northrop's Secret Aerospace Projects & Concepts 1939-1994. Forest Lake, MN: Specialty Press.

Friedmann, N., 2022. U.S. Navy Attack Aircraft 1920-2020. Annapolis, MD: Naval Institute Press.

Taylor, J.W.R., 1995. Jane's All the World's Aircraft 1995-1996. Coulsdon, UK: Jane's Information Group.

Thomason, T., 2009. Strike From the Sea: U.S. Navy Attack Aircraft from Skyraider to Super Hornet 1948-Present. Forest Lake, MN: Specialty Press.