The story of the F-20 Tigershark (including pilot interview)

The F-20 was the ultimate US F-5 derivative. However unlike the twin-engined Tiger II and Freedom Fighter, the F-20 was powered by a single engine. It was intended to serve the needs of US client nations not cleared for fighters as advanced as the F-16. The F-20 had similar performance to the F-16 but would have been easier to maintain and cheaper to operate. Flight trials went extremely well and Chuck Yeager became an enthusiastic advocate of the type. When restrictions on F-16 exports relaxed, the F-20 lost its raison dâ€™etre. An attempt to provide F-20s for the US aggressor fleet proved unsuccessful. In the end this privately funded fighter fell by the wayside.

Jim Smith

â€œ..built at the administrationâ€™s suggestion as a so-called non-provocative fighter, which meant one that was designed to be sold to friendly countries but designed to be vulnerable to our own state-of-the-art interceptors. Arming our friends was good business, but being able to shoot them down if they became our enemies was good strategy. To build this kind of airplane required the permission and cooperation of the administration, which could otherwise block such hardware sales.â€ â€“ Ben R. Rich & Leo Janos, Skunk Works

The key strand running behind the Tigershark story is the FX program. FX (Fighter eXport) was a result of a decision by the Carter Administration in 1977 that sales of US front-line equipment would be restricted to NATO allies, Australia and Japan. The intention was for the US to be seen as a force for peace in the world, rather than a promoter of conflict through the export of highly capable weapons of war. Part of the context for this decision would have been the decision by the preceding Ford Administration to sell F-14s to Iran and F-15s to Israel

While this noble aspiration to be a force for peace sounded good, there were a few immediately evident problems. The first of these was that many nations that fall loosely into a political category of West-leaning democracies felt threatened by peers and neighbours who were operating Soviet-built equipment. In order to support these nations it would be necessary to make available capable, but not absolutely top-end, aircraft that would be able to defend against exported Soviet systems, while not making use of the most sensitive US technologies. This was the driving objective behind the FX program. A secondary factor was that, in the absence of US aircraft being available for export, other countries were turning to alternatives, notably the Dassault Mirage 2000, and this was threatening to impact on US Industry.

As may be inferred from the short description above, the FX programme was really addressing State Department and industry objectives rather than US Defense Department needs, and as a result, the two departments had rather differing degrees of interest in the programme. Differences of emphasis between these Departments would later significantly affect FX programme outcomes.

The requirements for the FX programme were rather unusual. The aircraft to be supplied under the programme would have to meet the following requirements:
â€¢ Performance, cost & capabilities should be between those of the F-5E and F-16A
â€¢ Optimised for the air-to-air role, and with deliberately limited strike capabilities
â€¢ Payload/range performance had to be substantially inferior to that of contemporary fighters in the US inventory
â€¢ Deployment and maintenance had to be easier.
These requirements defined a second-class aircraft, with offensive (strike) roles limited, and emphasis given to air defence capability. In addition, the DoD took the view that such an aircraft was unlikely to be required by the USAF, and in consequence development of the aircraft would be the responsibility of the selected contractor, although the State Department and Department of Defense would assist with sales efforts.
This approach to the FX programme represented a considerable risk to Industry participants, who would have to carry much of the cost of developing and producing FX aircraft, and in the event, there were only two bidders, Northrop with the F-5G/F-20 Tigershark, and General Dynamics with the F-16/79.

F-5G/F-20 Tigershark technical characteristics

The F-5G was a development of the F-5E, originally intended for sale to the air force of Taiwan, intended as a higher-powered version of the F-5E, offering enhanced performance at a reasonable cost. The F-5G would be fitted with the GE-F404 engine in place of the 2 General Electric J85 engines of the F-5. The result of this engine change would be an additional 60% thrust in an airframe weighing only 17% more than the F-5E.

This aircraft would perhaps have been an attractive option for Taiwan, but for a change in US policy in regard to the Peopleâ€™s Republic of China. President Nixonâ€™s visit to China in 1972 had begun a process of rapprochement and dialogue, and in pursuing this, the State Department were made aware of Chinese concerns about US arms sale to Taiwan. As a result of these concerns, President Carter blocked the sale of the F-5G to Taiwan, which then developed its own light fighter, the AIDC Ching-Kuo.

In early 1981, there was a change in administration in the US, with Ronald Reagan replacing Jimmy Carter as US President. In consequence, the attitude of the US to Arms Control began to change, and additional exceptions to the â€˜no export of advanced weaponsâ€™ policy began to occur. Israel had already been allowed to purchase both the F-15 and F-16; following the change in US administration, a number of additional nations were authorised to procure the F-16A, including Pakistan, Egypt, Venezuela, Greece, Turkey, and South Korea. Other export sales to the Netherlands, Norway, Denmark, Belgium, Israel were allowed under the earlier Carter policy.

Taiwan had been the main focus of the F-5G development, but sales to that nation had been blocked. In an effort to make the aircraft attractive to a broader customer base, Northrop approached the USAF and sought approval to re-badge the aircraft as the F-20 Tigershark, while at the same time introducing avionics and sensor upgrades to make the aircraft more competitive with the F-16.

Compared to the Northrop F-5E Tiger II, the most significant design changes for the Tigershark were the avionics upgrade, and the use of a single General Electric F404 engine, which was originally designed for the F/A-18 Hornet. The new engine provided 60% more thrust than the combined output of the F-5Eâ€™s two General Electric J85s. This improved the aircraftâ€™s thrust-to-weight ratio substantially, and enabled an increase in maximum Mach to 2.0, with a ceiling over 55,000 ft (16,800 m).

The wing was similar to the F-5E, but had modified leading edge extensions (LEX), which improved the maximum lift coefficient of the wing by about 12% with an increase in wing area of only 1.6% and also reduced pitch stability. A larger tailplane was fitted to improve manoeuvrability, along with a new fly-by-wire control system.
The F-20â€™s avionics suite was significantly enhanced, adopting the General Electric AN/APG-67 multi-mode radar as the principal sensor, offering a wide range of air-to-air and air-to-ground modes. A large number of weapons, including Sidewinder and Sparrow air-to-air missiles, could be integrated on the aircraft, which was also armed with two 20-mm Pontiac cannon. Cockpit instrumentation and layout was brought up to the then-current state of the art, with a head-up display supplemented by two flat screen multi-function displays.

The small size of the F-20 meant that payload range was somewhat limited compared to larger contemporary fighters. The F-20 was fast, agile and hard to spot visually due to its small size, but was perhaps less well armed and equipped than some of its competitors, at least partially as a result of the constraints imposed by the Carter administrationâ€™s export policies. Nevertheless, there was some interest from Bahrain and Morocco, and also some interest from South Korea.

We spoke to test pilot Paul Metz, author of a brilliant new book on the F-20 to find out more:

Best thing? State of the art avionics and reliable.

Worst thing? It did not sell

How did it compare with the F-16? One thing we did not cover in our interview was the Fighter For Export (FX) concept as defined by the U.S. government. In late1977, President Carter decreed that the FX had to have performance better than the F-5E but less than the USAF front line fighter, the F-16. Two companies responded to this opportunity to build the next FX. Northrop offered its F-20A and General Dynamics offered the F-16 re-engined with a General Electric J79, the so-called F-16J79. The F-20 significantly out-performed this export version of an FX. In 1981, President Reagan offered production F-16As to Venezuela, Pakistan and S. Korea. This was a fundamental change in the U.S. FX program. It authorized front line U.S. equipment, the F-16A/B, to traditional FX countries. Northrop countered with changes to the F-20 which would equal and exceed the F-16. There simply was not enough time to make those changes. National policy for the FX changed instantly. Changing an airplane takes years.

How do you rate it in the following areas

A. Sustained turn
B. Instantaneous turn
C. Acceleration
D. Climb rate

Again, an apples to apples comparison would be the F-20A versus the F-16J79 as an FX fighter. I will answer with an apples to strawberry comparison of the F-20A to the F-16A (with the F100 engine). My reference library of F-20 technical data has been donated to the Western Museum of Flight in Torrance, CA so I cannot provide the engineering details. In any event there are no one-sentence answers to your questions. There are areas where each airplane has a slight advantage over the other. For example, at slow speeds the F-16 flight control computers limit angle of attack to 26Â°. The F-20 has unlimited angle of attack maneuver capability. At the same time, at slower speeds, the F-16 has a lower wing loading and thus a better sustained turn rate than the F-20 until the F-16 hits its angle of attack limiter. In general the F-20 has better fuel specifics (analogous to miles per gallon).

Pleasure of flying The F-20 had a spacious cockpit and was a fighter pilotâ€™s airplane-easy to fly, easy to operate, reliable with intuitive flying qualities, a legacy of the F-5 family.

Cockpit roominess Excellent.

Ease of take-off and landing Piece of cake.

Why was it cancelled? Should it have been? The Tigershark project was terminated by Northop who funded all project costs. It was cancelled after the U.S. government changed the standing policy on sales of fighter aircraft to foreign allies. Policy can be changed at the discretion of the President of the U.S. A â€œpolicyâ€ is not a law nor is it a contract between the government and the company providing the product. A contractor assumes the risk of cancelation under these circumstances. Northrop assumed those risks. The government acted within their rights. There was no business case for an intermediate fighter for export (FX) after the President offered front line U.S. aircraft (F-16s) to all .

Biggest myth? That the Tigershark was as reliable as Northrop claimed. It exceeded all frontline fighters by a wide (and some termed â€œIncredibleâ€) margin.

What should I have asked? Nothing to add. Good job.

Were you sad about its demise? Disappointed is probably more accurate. The loss of the Tigershark occurred with the win of the Advanced Tactical Fighter program that produced the YF-23. So Halloween of 1986 was a bittersweet day at Northrop.