Everyone is familiar with the F-15 Eagle, F-16 Fighting Falcon, and F-22 Raptor jet fighters for the US Air Force and the F-18 Hornet strike fighter for the US Navy. (The Lockheed F-35 Lightning II was given an out-of-sequence designation after winning the Joint Strike fighter contest in October 2001 because the X-35 was Lockheed Martin's technology demonstrator for the JSF competition, but that's another story.) But whatever happened to the F-17 slot between F-16 and F-18? While Northrop aced a couple of success stories in combat jet development with the F-89 Scorpion all-weather fighter and F-5 lightweight fighter to make up for the cancellation of its flying wing bomber programs, it also produced a handful of jet fighter designs that are less well-known to most people, the YF-17 Cobra and F-20 Tigershark lightweight jet fighters and the YF-23 Black Widow II/Grey Ghost prototype stealth fighter jet. Therefore, I thought it'd be convenient to give an overview of all three "lost" jet fighters created by the Northrop Corporation in the 1970s and 1980s, because these designs remained at the prototype stage only.
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Left: Desktop model of the Northrop YF-17 at the Western Museum of Flight
Right: Northrop YF-17 during flight testing, 1974 |
The first "lost" Northrop jet fighter design that is worth discussing is the Northrop YF-17 Cobra. In the late 1960s, the US Air Force initiated the Lightweight Fighter (LWF) competition for a lightweight jet fighter to replace the F-5 Freedom Fighter/Tiger II, at the behest of the so-called "Fighter Mafia" led by Pierre Sprey, Everest Riccioni, and John Boyd. Boeing, General Dynamics, Lockheed, Northrop, and Vought responded with proposals for the LWF competition. Since 1965 Northrop had initiated design studies for advanced versions of the F-5E Tiger II, including the N-300 proposal with a longer fuselage, two General Electric GE15-J1A1 turbojets each delivering 9,000 pounds (40 kN) of thrust, small leading-edge root extensions (LERXs), and a slightly elevated wing. and the N-530 proposal with a greater wing area, two GE 15-J1A5 turbojets delivering 13,000 pounds (58 kN) of thrust, a trapezoidal wing planform and nose section, and LERXs that tapered into the fuselage under the cockpit and enabled maneuvering at angles of attack exceeding 50° by providing about 50% additional lift. By January 1971, Northrop conceived a revised version of the P-530 design with cannons mounted on the upper part of the fuselage, designated P-600, to meet the LWF requirement parameters. The P-600 had two General Electric YJ101 turbojets each delivering 14,400 pounds (64 kN) of thrust, two rudders with a 45° cant, and a fly-by-wire electronic control augmentation system (ECAS) that utilized ailerons, rudders, and stabilators for primary flight control. The General Dynamics and Northrop designs were selected for prototyping by the Defense Department and designated YF-16 and YF-17 respectively. The design of the P-600's LERXs resembled a cobra, hence the YF-17's unofficial name, Cobra. The YF-17 made its first flight on June 9, 1974, nearly five months after the F-16, and two prototypes were built (serial numbers 72-1569/1570). After a fly-off contest between the F-16 and YF-17, on January 13, 1975, Air Force Secretary John L. McLucas declared the F-16 the winner of the LWF competition, citing low operating costs, greater range, and higher maneuver performance in the supersonic flight regime. Despite losing the LWF competition, Northrop would later team with the St. Louis division of McDonnell Douglas to use the YF-17 Cobra design as the basis for a new-generation lightweight jet fighter for the US Navy, the F-18 Hornet, which flew in 1978, and the first prototype YF-17 was sent to NASA Dryden Research Center (now Neil Armstrong Flight Research Center) for base drag studies in May-July 1976. The first and second YF-17 prototypes are now preserved at the Western Museum of Flight in Torrance, California, and Battleship Memorial Park in Mobile, Alabama, respectively.
Left: Sole remaining F-20 prototype (serial number 82-0064) at the California Science Center, Los Angeles
Right: F-20 prototype (serial number 82-0062) in flight
Years after losing the LWF competition to General Dynamics, Northrop began work on an advanced version of the F-5E Tiger II with one General Electric F404 turbofan engine under the designation F-5G in response to the FX program initiated in the late 1970s for a new fighter jet for export that could outperform the F-5E. After a series of back-and-forth moves by the Defense Department to support and then defer the FX program, the F-5G was cleared for full-scale development and four prototypes (serial numbers 82-0062/0065) were ordered. The first F-5G prototype made its first flight on August 30, 1982, and recognizing the advanced nature of the F-5G compared to past F-5 variants, Northrop requested that the F-5G be redesignated F-20, and this request was approved by the Defense Department in late 1982 (Northrop initially wanted the F-5G to be redesignated F-19, but it later changed its mind and requested that F-19 be skipped in favor of F-20 due to possible confusion with the Mikoyan-Gurevich MiG-19 fighter). In March 1983, the F-20 was officially named Tigershark and a number of countries, including Bahrain and South Korea, expressed customer interest in the F-20. With Northrop looking at incorporating avionics upgrades, an expanded fuel tank, and fiberglass composite materials into the planned production F-20, plans were made to have the fourth Tigershark prototype built to include fully operational equipment. Although the Tigershark performed well during test flights, Northrop's hopes for securing production orders for the F-20 from foreign customers were stymied by several US allies in Europe, East Asia, and the Middle East buying the F-16 but also a Congressional investigation in 1984 on the merits of the F-20 compared to the F-16, and the fact that European countries were offering combat jet designs of their own to foreign customers. Meanwhile, the first and second F-20 prototypes crashed during flight testing, with the first aircraft being lost during a demonstration flight in South Korea on October 10, 1984, and the second prototype crashing at Goose Bay in Labrador, Canada, in May 1985; both crashes were found to have been caused by the pilots losing consciousness due to excessive g-forces. By late 1986, Northrop canceled the F-20 program without any orders from foreign customers, and the fourth F-20 prototype (serial number 82-0065) was only half-complete when the Tigershark program was terminated. The third F-20 prototype (the only one to survive the flight test program) is now on display at the California Science Center at Exposition Park in Los Angeles.
Left: Second YF-23 prototype (serial number 87-8701) at the Western Museum of Flight in Torrance, California
Right: The first YF-23 prototype (serial number 87-8700) in flight over the Mojave Desert, California
The third and final "lost" Northrop jet fighter to be discussed is the Northrop/McDonnell Douglas YF-23 stealth air superiority fighter. In 1981, the US Air Force initiated the Advanced Tactical Fighter program for a stealthy air superiority fighter to replace the F-15 Eagle in response to the Soviet Union's new MiG-29 and Su-27 jet fighters. The ATF requirement called for supercruise capability (sustained supersonic flight without the need for afterburners), survivability, and ease of maintenance, and several aerospace companies, including Lockheed, Boeing, General Dynamics, McDonnell Douglas, Northrop, Grumman and Rockwell International, submitted bids for the new aircraft by July 1986. Lockheed later decided to form a team with Boeing and General Dynamics to develop whichever of their proposed designs was selected, while Northrop followed suit by forming a team with McDonnell Douglas should its design be chosen. In October 1986, under the "fly-before-buy" principle, the USAF selected the Lockheed/Boeing/General Dynamics and Northrop/McDonnell Douglas designs for prototyping, and these designs were designated YF-22 and YF-23 respectively. The YF-23, like the F-22, had chines along the nose, but utilized diamond-shaped wings as well as vertical stabilizers angled 50 degrees from vertical position. S-duct engine air intakes were provided to allow air to flow into the jet engines. The two YF-23 prototypes were painted in different colors, the first prototype (serial number 87-8700) being painted in charcoal gray and nicknamed "Black Widow II" in honor of the Northrop P-61 Black Widow night fighter of World War II, while the second prototype (serial number 87-8701) was painted in two shades of gray and nicknamed "Spider" and "Grey Ghost".* The first YF-23 had two Pratt & Whitney F119s, while the second YF-23 used two General Electric F120s. The first flight of the YF-23 took place on August 27, 1990, piloted by Alfred "Paul" Metz (who later became the test pilot for the first service test F-22 Raptor in 1997), while the second prototype flew on October 1990. A fly-off contest between the YF-22 and YF-23 continued into late 1990, and on April 23, 1991, the Air Force declared the YF-22 the winner of the ATF competition. The YF-23 was faster and stealthier, while the YF-22 was more maneuverable, but development experience played the final role in the outcome of the ATF contest; the Northrop company was busy with development of B-2 Spirit stealth bomber, and McDonnell Douglas was reeling from the cancellation of the A-12 Avenger II carrier-based stealth attack aircraft. Lockheed, by contrast, had built the F-117 Nighthawk under budget and on time, so the USAF must have decided that the YF-22 offered lower technical risks (Jenkins and Landis 2008; Miller 2005). The YF-23 prototypes were transferred to NASA Dryden Flight Research Center (now NASA Armstrong Flight Research Center) at Edwards AFB with their engines removed. One of the aircraft was to be used by NASA for studying techniques for the calibration of predicted loads to measured flight results, but those plans never materialized, and the first YF-23 prototype is now on display at the US Air Force Museum in Dayton, Ohio, while the second YF-23 is now displayed at the Western Museum of Flight in Torrance, California.
*The different names applied to the YF-23 prototypes reflected the different naming conventions by the YF-23 manufacturers for their jet fighters. Northrop named its fighters after arachnids and other deadly animals, while the St. Louis division of McDonnell Douglas named its fighters after evil spirits.
In an interesting footnote, McDonnell Douglas submitted a design for a lightweight stealth fighter based on the YF-23 for the Joint Strike Fighter competition of the 1990s. It was similar to the YF-23 in the tail empennage design but differed in a having wings reminiscent of the McDonnell F-101 Voodoo escort fighter, and utilized a reheated turbofan, with a remote gas-driven fan to augment lift in STOVL mode. However, the McDonnell Douglas proposal was rejected in favor of the Boeing and Lockheed Martin designs for JSF prototyping by the Pentagon in late 1996, and the Boeing and Lockheed Martin technology demonstrators for the JSF became X-32 and X-35 respectively, flying in late 2000 (the Lockheed Martin design won the JSF contest on October 26, 2001, and subsequently developed into the F-35 Lightning II, but that's another story). Northrop Grumman in the early 2000s conceived a long-range fighter-bomber version of the YF-23 (internally known as "FB-23") as an interim stopgap design pending the arrival of a planned replacement for the B-52H and B-1B (now called the B-21 Raider), but this design remained on the drawing board.
Although Northrop had accomplished something to make up for the cancellation of its jet flying wing bomber programs in the late 1940s by producing the F-89 Scorpion and F-5 Freedom Fighter/Tiger II, the 1970s to early 1990s sapped away Northrop's fortunes in the fighter jet business, either because of technical and aerodynamic considerations or fierce competition from other aircraft for the export market. Nevertheless, the YF-17, F-20, and YF-23 constitute Northrop's willingness to adapt to leaps and bounds in aviation technology during the late Cold War as well as geopolitical circumstances, and the design philosophy of the YF-17 is still prevalent in the F-18 Hornet naval strike fighter. References:
Chong, T., 2016. Flying Wings & Radical Things: Northrop's Secret Aerospace Projects & Concepts 1939-1994. Forest Lake, MN: Specialty Press.
Jenkins, D.R. and Landis, T.R., 2008. Experimental & Prototype U.S. Air Force Jet Fighters. North Branch, Minnesota: Specialty Press.
Miller, J., 2005. Lockheed Martin F/A-22 Raptor, Stealth Fighter. Hinckley, UK: Midland Publishing.
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