Experimental warplanes from the Los Angeles basin, part 3: Lockheed and North American penetration fighter designs

The early years of the Cold War saw the US develop a wide variety of jet fighters for a plethora of officially delineated combat missions, including air superiority, long-range interception, escort, and all-weather/night operations. Some, like the F-84, F-86, F-89, and F-94, entered production and operational service, but others remained at the prototype stage only. During my recent visit to the Planes of Fame Museum, I surprisingly happened to notice desktop models of two seldom-known US jet fighter designs of the early Cold War, the Lockheed XF-90 and North American F-93 penetration fighters. Therefore, I have devoted the third post of my multi-post series on prototype warplanes created in the Los Angeles to discussing in detail the XF-90 and F-93.

On August 28, 1945, a few days before the Japanese surrender aboard the USS Missouri, the US Army Air Force issued a requirement for a new-generation penetration fighter able to escort heavy bombers to enemy targets. Intended as a successor to escort versions of the P-51 Mustang that were used to escort B-17s and B-24s over Nazi Germany in World War II, the new jet-powered penetration fighter was to have a combat radius of 900 miles (1,450 km) and high combat performance. Several companies submitted bids to the jet penetration fighter contest, including Convair, Curtiss, Goodyear, Lockheed, McDonnell, Northrop, and North American. Technical details regarding the Convair and Northrop penetration fighter designs are discussed Buttler (2013) and will not be replicated here, although it should be stressed that the Northrop design was a derivative of the XP-79B flying wing fighter. The USAAF selected the McDonnell Model 36 and Lockheed L-167/Model 90, and North American NA-167 designs for prototyping, designating them XP-88, XP-90, and P-86C respectively. After the Air Force became independent of the US Army in September 1947 and adopted the policy of classifying fighter planes as fighters rather than pursuit planes, these designs were redesignated XF-88, XF-90, and F-86C (later YF-93A) in June 1948.

Left: Desktop model of the Lockheed XF-90 at the Planes of Fame Museum

Right: First XF-90 prototype (serial number 46-687) in flight over Edwards Air Force Base, California

Now this brings me to describing the two US penetration jet fighter designs from the Los Angeles basin, of which I will discuss the XF-90 first. The Lockheed XP-90/XF-90 was a sleek jet fighter with a pointed nose and engine intakes similar to that of Lockheed's earlier P-80/F-80 Shooting Star, as well as two 3,000 lb (13.3 kN) thrust Westinghouse J34 turbojets. Armament provisions included six 0.79 inch cannons, eight 5 in (127 mm) HVAR rockets, and 2,000 lb (907 kg) of bombs. The original design of the XP-90 featured a delta-wing, T-tailed configuration, but the US Air Material Command judged the delta wing configuration to produce high drag at lower speeds, so Lockheed reworked its fighter design into a backswept wing machine with a tail empennage like that of the F-86 Sabre. After a mock-up inspection in December 1947, two XF-90 prototypes (serial numbers 46-687/688) were ordered and the first of these flew on June 3, 1949, with the second prototype following suit on April 12, 1950. The XF-90 broke the speed of sound in a dive on May 17, 1950, reaching a speed of Mach 1.2. However, the XF-90 was too big and heavy for the available thrust generated by the Westinghouse turbojets, and RATO boosters were used for most of the takeoffs.

Left: Desktop models of the North American YF-93 at the Planes of Fame Museum

Right: First YF-93 prototype (serial number 48-317) in flight over Edwards Air Force Base, California

The other penetration jet fighter from the Los Angeles area that took flight was the North American YF-93. It was a derivative of the F-86 Sabre that had the air intakes moved to the fuselage sides to  allow the nose to accommodate the radar scanner. Due to its size difference compared to the F-86, the F-93 was powered by one Pratt & Whitney J48 turbojet delivering 6,000 lb (27 kN) of thrust, and it featured a dual-wheel main landing gear and increased wing area. Although originally designated P-86C/F-86C, in September 1948 the Air Force judged the NA-157 design sufficiently distinct to be allocated the new designation YF-93A. Two prototypes (serial numbers 48-317/318) were ordered in June 1948, along with 118 production F-93As (serial numbers 49-001/048, 49-059/068, 49-392/421, 49-1966/1995). The production order was cancelled in February 1949 due to budget cuts, work on the two prototypes continued apace, with the first aircraft flying on January 25, 1950.

The USAF staged a fly-off of the XF-88, XF-90, and YF-93A in June-July 1950, and the XF-88 was declared the winner of the penetration fighter contest in late July. The McDonnell design was judged superior to the Lockheed and North American designs in terms of handling, maneuverability, and high-speed characteristics, as well as armament stability and ability to operate from existing runways (see Buttler 2013, pp. 75-76). However, the euphoria at the McDonnell Aircraft Corporation over the outcome of the penetration fighter competition was all for naught. On August 22, 1950, just as the XF-88 was about to be cleared for production, the US Air Force gave up on the penetration fighter concept due to changing priorities and a tight defense budget. However, experience gained during the Korean War prompted the USAF to revive the notion of the penetration fighter, leading to General Operational Requirement (GOR) 101 being issued in February 1951 for a long-range escort fighter. McDonnell eventually developed an enlarged version of the XF-88, the F-101 Voodoo, which made its first flight in late September 1954.

References:

Buttler, T., 2013. Early US Jet Fighters: Proposals, Projects, and Prototypes. Manchester, UK: Hikoki Publications.