Major F-20 versions and their designations:
Configurations and Designations over Time
The F-5 series of aircraft had their origin in 1953 with a design called by Northrop the N-102 Fang. By 1957 this had evolved into the N-156. The N-156 became the T-38 in a trainer version, and the F-5A in a fighter version. The F-5E was an improved version of the F-5A with an Emerson Electric fire-control radar and uprated engines. Further improvements were made to the F-5E models built for Saudi Arabia and Switzerland in the mid-1970's, including a Litton inertial navigation system and other avionics that allowed the fighter to carry Maverick and other advanced weapons. This configuration was the baseline for any further improvements on the F-5.
Northrop had an Advanced Design Group, which, like all such groups, spent its time not only imagining new aircraft, but dreaming up and evaluating all possible modifications of existing designs.
Early work on major improvements to the F-5E were referred to within the company as F-5X (such designations were unofficial and not allocated by the US government). This included an F-5E equipped with AIM-7 Sparrow capability, as desired by Taiwan. This would require a new radar, and deletion of one M39 gun to make room for the extra radar avionics. But carriage of the big Sparrow missiles so degraded the performance of the basic F-5E that it was clear a new-technology engine would be required.
Advanced design had already looked at such possibilities over the years. One possibility was replacing the two J85 engines of the F-5E with a single F404 engine from the F-18 (the F-5/404 concept of May 1975). This had been studied as soon as the F-18 contract had been awarded. It certainly provided the needed performance improvement, and engine reliability had improved so much between the 1950's and 1970's that a fighter with a single F404 would (theoretically) have the same safety as a twin-engine aircraft with J85's. Preliminary aerodynamic studies showed the F-5E wings and forward fuselage could be kept unchanged. The aft fuselage would turn from the flat lifting body of the F-5E to a cylindrical barrel section to accommodate the F404 and its intakes, but the aerodynamic characteristics would be maintained by building a kind of shelf between the barrel fuselage and the F-5E wings.
But Northrop had for years advocated the safety features of two engines. A twin engine aircraft was not just safer in flight operations, but also in sustaining battle damage in combat and being able to return to base. So a faction within Advanced Design looked at re-engining the F-5E with two improved engines. Garret built a modern turbofan engine for business jets in the correct thrust class, the TFE-731. For a fighter a version of this engine with afterburners would have to be developed, but this was not seen as a major risk area.
A sharp debate within Northrop developed. Northrop had a traditional relationship with engine manufacturer General Electric, going back to the development of the radical Turbodyne engines for the B-49 flying wing in the 1940's. Northrop sincerely believed that GE engines were better engineered, more reliable, and had lower life-cycle costs than the equivalent engines from Pratt and Whitney. Garrett had no experience in building engines for high-performance fighter aircraft, which were abused like no other engines in the air.
Furthermore, Northrop was expecting big sales of the F-18L land-based version of the Navy F/A-18. This was nearly an entirely different aircraft, with Northrop having the lead design responsibility, and was more akin to the F-17 that was rejected by the USAF than the Navy F-18. The F-18L would be powered by two F404's. This meant that Northrop engineering, logistics, and contracting would already have developed intimate relationships and understandings with General Electric concerning the F404. Furthermore, an F404-powered version of the F-5E would allow Northrop to market a high/low F-18L/F-5X fighter mix using a common engine. This would mirror the F-15/F-16 high/low fighter mix using the Pratt and Whitney F100 engine.
All of these arguments, but in particular the 'special relationship' between Northrop and General Electric at the highest corporate levels, led to the decision in June 1978 to use the F404 engine in the Taiwan aircraft and other future F-5 developments.
At this time the Carter administration had promulgated a fighter export policy that sought to reduce military spending by developing countries and dictatorships. This policy prohibited American companies from marketing or selling front-line American fighters to foreign countries. In particular the F-14, F-15, F-16, and F-18 were not to be marketed or sold to countries outside American's primary allies (NATO, Australia, New Zealand, Japan; and after the Camp David accords, Egypt and Israel). Any fighters exported could only be modifications of existing fighters and 'not as good as' American front-line fighters.
In order to make clear that the F-5/F404 was merely a 'modification' of the F-5E Tiger II, it was given the official F-5G designation by the US government. Northrop had developed a radome for the F-5E that improved the aerodynamics compared to the F-5G, and this had the same shape as a shark's head. So the appearance combined with the name of the F-5E suggested the name Tigershark for the aircraft.
Carter's strict export policy would seemingly prohibit Northrop from marketing radically-improved avionics. So Northrop conceived a two-phase program, whereby Taiwan and other customers would first build 'Engine Change Only' (ECO) aircraft. These would use the F404 engine but still be equipped with F-5E avionics. However under an 'F-5G Phased Improvement Program' improved avionics would be developed and phased in later when the policy (or administration) changed.
By the time the first contracts were let for the new avionics systems, the Carter administration was indeed out of office and the Tigershark was now in direct competition with the F-16A front-line fighter. So the avionics version of the aircraft was already superior in most ways to the F-16A when it started development.
The F-5G-1 was the designation given for the 'Engine Change Only' version of the aircraft. This would be the first put into production, and would retain the entire old F-5E fuselage and avionics.
The F-5G-2 was the designation given for the version with the engine change and completely new digital avionics. To accommodate these avionics a new fuselage forward of frame 138 was required. This allowed the avionics bays to be rearranged, and provide a more bulbous nose with a much larger radome for the new radar. The opportunity was given to provide the F-5E with a new 'panoramic canopy' and a modern zero-zero ejection seat.
Engineering designations given to Northrop aircraft had begun anew with the N-156F series in 1957. The numbers applied to all internal engineering drawings consisted of a first number indicating the aircraft model on which the part had first appeared. The second five-digit sequence indicated the type and location of the part within the airframe. A final one to three digit dash number indicated versions of the same basic part. Under this scheme, 2-13002-1 was the T-38 canopy. The same canopy was used on the F-5B and F-5F two-place aircraft, so that part was used on those aircraft with the same designation. Parts new for the F-5E received 14- designations, such as 14-13002-1 for the F-5E canopy. F-5F parts received 18- designations. F-5G-1 parts had 40- designations, and F-5G-2 50- designations.
Once the F-5G was in direct competition with the F-16A, the F-5G designation became a hindrance to marketing efforts. The F-5G-1 version had been dropped, and Northrop concentrated on marketing the better-than-an-F-16A F-5G-2 version. But the F-5G designation, used to imply to the Carter administration that this was just a modification of an existing aircraft, provided the same connotation to potential customers. Northrop needed a new fighter designation to ensure customers that the aircraft was all-new. Furthermore any number assigned would be 'higher' than F-16, also providing the connotation that the aircraft was newer and more advanced than the competition. So Northrop requested, and obtained, the official designation of F-20 for the aircraft.
This resulted in a lot of speculation over the years as to what happened to the F-19 designation. At the time speculation about development of the still-secret stealth fighter was rife, and it was assumed that the F-19 designation had been given to this aircraft. Articles in reference books authoritatively used the designation, and model kits of the 'F-19 Stealth Fighter' were released. Andreas Parsch , using the Freedom of Information Act, finally uncovered the real story:
The F-19 designation was never assigned. The official explanation by DOD was "to avoid confusion with MiG-19", which was generally regarded as very implausible (because so far no numbers had been skipped to avoid clashes with foreign designators). Therefore, it was much speculated whether F-19 was really skipped, and if so, for what real reason. One viable theory was that F-19 was originally allocated to (or at least reserved for) the F-117A Nighthawk, but eventually not usedů The other main line of reasoning was that Northrop specifically requested the F-20 designator for its then new Tigershark (originally designated F-5G) to make it look as "the first of a new fighter generation" (i.e., the "20" series).
Back to the F-20A Tigershark Home Page
© Mark Wade, 1997 - 2006 except where otherwise noted.
Please contact us with any corrections, additions, or comments.