F-20 versus Lavi: The Tigershark, the Young Lion and the Viper

This is a story about US foreign policy and its intersection with aerospace. The relevant period is the ‘80s, but the interweaving of US industrial, trade, defence and foreign policy settings can be observed essentially continuously from the Second World War to today. This interaction has a number of objectives, which might be expressed benignly as a desire to strengthen the military capability of the US and its Allies, or, less benignly, to ensure that foreign competitor systems are, as far as possible, contained, in order to protect the position of US Industry.

No doubt, some will disagree with this latter perspective, but others will note the very few co-development programmes which have led to advanced equipment sales into the US. Leaving the difficulties of collaboration on one side, the US has always adopted a quite hard-nosed approach to acquiring Defence equipment from third parties. The recent history of the KC-135 replacement program is a good example, where the outcome of the competition was overturned on appeal, and the contract awarded to the Boeing KC-46 rather than the Airbus MRTT, a lower risk product which is giving good service with many air arms while the USAF struggles to achieve operational capability with the KC-46.

While this may legitimately be perceived in the US as the acquisition process simply playing out, it could also be characterised as one of a number of instances of the US ‘running interference’ to protect its aerospace industry from competition. Another approach has been the offering of alternative solutions, either legitimately in the hope of winning business, or perhaps disingenuously as an attempt to disrupt a potential competitor. As a couple of examples, which might represent this sort of behaviour, I will offer the F-111K/TSR2 saga in the UK, and, as a delivered solution, the CF-101 Voodoo/BOMARC in place of the Avro Arrow.

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However, I am not going to focus on ‘running interference’ aspects here, but rather on the effects of differences of view within the US Government, and how changes in policy across Administrations, have affected two programs, the Northrop F-20 Tigershark and the Israeli Aircraft Industries Lavi (Young Lion).

This article provides a brief overview of the technical characteristics and programme histories of the Northrop F-20 Tigershark and the IAI Lavi, and also provides some comparative data for these aircraft and the contemporary General Dynamics F-16C, officially named the Fighting Falcon, but frequently referred to as the Viper. The F-16/79, a competitor for the F-20 Tigershark, is also briefly discussed. Through the stories of these aircraft, we shall see glimpses of the complex interaction between the US State Department, Department of Defense, and industry in their efforts to influence worldwide politics and Defence capabilities, while supporting US export sales and industry products.

The Tigershark

“..built at the administration’s suggestion as a so-called nonprovocative 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.” –– 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:
• Performance, cost & capabilities should be between those of the F-5E and F-16A
• Optimised for the air-to-air role, and with deliberately limited strike capabilities
• Payload/range performance had to be substantially inferior to that of contemporary fighters in the US inventory
• 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 People’s Republic of China. President Nixon’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 ‘no export of advanced weapons’ 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-5E’s two General Electric J85s. This improved the aircraft’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-20’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 2 30 mm 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. Comparative data on the Tigershark, Lavi , F-16/79 and F-16 C can be found towards the end of this article. 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 administration’s export policies. Nevertheless, there was some interest from Bahrain and Morocco, and also some interest from South Korea.

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F-16/79 technical characteristics

General Dynamics responded to the FX opportunity with a low-risk down-grading of the F-16A in which the Pratt & Whitney F100 engine of the F-16A was substituted by a General Electric J79. This represented a reduction in thrust of some 28%, and came along with other penalties, including additional fuel consumption and additional weight for heat shielding. The reduction in thrust could be alleviated for short periods through the use of a ‘Combat Plus’ power setting, giving a maximum thrust of 92.8 kN, compared to the maximum normal thrust of 80.1 kN, and the 112.2 kN of the F-16’s F100 engine.

The engine required somewhat less airflow than the F100, resulting in a limited redesign of the intake. The rear fuselage was increased slightly in length because the J79 was 0.45m longer than the F100, and a transfer gearbox was added to allow the J79 to drive the engine ancilliaries (generator, hydraulics etc) of the F-16 airframe that had previously been driven by the F100. Overall, the change in engine and the consequential other modifications to the airframe increased its empty weight by 817 kg.

Inevitably, with less thrust and higher weight, the performance of the F-16/79 was degraded compared to that of the F-16. Nevertheless, it was still sufficient to attract interest from a number of air arms, so long as they were excluded from acquiring the F-16, and the F-16/79 was demonstrated to at least 20 air arms.

Robert Kemp, San Diego Air and Space Museum

What went wrong?
The FX , and with it, the fate of the F-20 Tigershark and the F-16/79, was largely derailed by three factors. Firstly, the objectives of the FX were of more value to the State Department than the Defense Department. However, the State Department did not have the knowledge and expertise to run an aircraft development program, and the Defense Department had no intention itself of operating additional, somewhat second tier aircraft. As a consequence, the second problem became the lack of a US acquisition, resulting in an inability to use established Foreign Military Sales procedures to market the aircraft, and reluctance of third parties to procure an aircraft not in US service.

The third major difficulty was that the US administration had changed, and with Republican Ronald Reagan as President, the US significantly relaxed the Democrat Jimmy Carter’s arms control policies, leading to numerous countries being allowed to procure the F-16. As if this was not enough, in 1983, Congress approved funding for the Israeli Lavi program, placing another sophisticated and capable combat aircraft on the table as a potential competitor to the FX aircraft.

In the end, after six years, no sales, and the expenditure of more than $1.2 billion of its own funds, Northrop bowed to the inevitable and cancelled its Tigershark program in late 1986. In the course of the program, two of the three aircraft had been lost in fatal accidents. Both accidents occurred in air display conditions, a demonstration flight in South Korea and an air display practice in Canada, and both were attributed to g-loc – loss of consciousness under high g conditions.

The F-16/79 had, by comparison, been a less risky project for General Dynamics. A key factor for General Dynamics was that the potential lost sales of the F-16/79 were being filled with orders for its ‘full-strength’ product, the F-16 Viper, due to the relaxation of export policies by the Reagan administration. The F-16/79 program seems to have eventually been seen as a distraction by General Dynamics, and efforts to market the aircraft had essentially ceased by 1985. Once it became clear that the US would sell you an F-16, no air arm was really interested in its less-capable brother, the F-16/79. The program is reported to have cost General Dynamics a total of $60 million.

The Young Lion
The Young Lion in this story is, of course, the Israeli Aircraft Industries Lavi. The Israeli Defence Force in the 60s had been a major user of French aircraft, notably the Dassault Mirage III. However, International reactions following the Six-Day War of 1967 had led to Israeli relations with the French cooling, exemplified by a refusal by France to deliver Mirage 5 aircraft to Israel, and the Israeli development of its own advanced Mirage derivative, the Kfir or Lion Cub.
In parallel, Israel successfully positioned itself with the US as a bastion of Western democracy in the Middle East, its existence threatened by its Arab neighbours, particularly the (then) Soviet-backed Syria, Libya and Egypt. This general pitch has continued today, with the position of chief threat being transferred to Iran, and its nuclear weapons program, and the now Russian-backed Syria. This has led to an on-going close Defence relationship with the US, leading to the supply of Defence equipment, weapons and aircraft, backed by strong political lobbying of, and by, the US Congress.

As a need to replace the Kfir emerged, Israel was successful in obtaining the supply of US F-15 and F-16 fighters, while looking to develop advanced technical capabilities of its own. This was partly to avoid a dependency on others, partly to ensure the availability of capabilities uniquely tailored to its geographic environment, and its seemingly unending state of tension and conflict with its neighbours, and partly to complement the capabilities available through the F-15 and F-16.

Israel’s aerospace capabilities had advanced significantly through the Kfir program, through the development of upgrades to other aircraft like the F-4 Phantom, and through the development of its own weapons and other defence systems.

In these circumstances, the time seemed ripe to embark on an Israeli-developed aircraft project to provide a multi-role fighter capable of strike missions, advanced training, and air defence. The scope of the requirements for the aircraft gradually grew, from a relatively simple and low-cost strike platform with some air defence capability, to a multi-role aircraft whose capability would be similar to, and in some areas perhaps exceed, that of the General Dynamics (now Lockheed-Martin) F-16 Viper.

Lavi technical characteristics
The aircraft developed between project launch in 1980 and project cancellation in 1987 turned out to be quite remarkable in its ambition and in its application of the latest ideas in aerodynamics, flight control and weapons systems. The embodied capability was a mix of US-developed and Israeli in origin, with some capabilities initially developed in the US to be transferred to Israel during the course of the programme. The programme was part- funded by the US.

The fundamental leap in technology was the use of an unstable canard-delta configuration, enabled through the use of a digital fly-by-wire flight control system. In addition the structure made extensive use of composite materials. In making these choices, the Lavi adopted a similar approach to the BAe EAP which was broadly contemporary in timescale, the two aircraft making their first flights within a few months of each other in 1986.

The benefits of the use of an unstable canard-delta configuration are the ability to obtain a highly responsive and manoeuvrable airframe, while also being able to minimise supersonic wave drag and lift dependent-drag. Today, the outcomes of fully-developed aircraft with this design approach can be seen in the highly capable Dassault Rafale and Eurofighter Typhoon aircraft, although both these aircraft benefit from a higher degree of instability than the Lavi, and greater combat thrust to weight ratios.

Unlike the BAe EAP, which was a technology demonstrator, the Lavi was the prototype of what was intended to be a production weapons system with deliveries expected to begin in 1990. The aircraft was, to quote contemporary material (Janes All the World’s Aircraft 1986) “expected to become the workhorse of the of the Israeli Air Force, which has a requirement for at least 300, including about 60 combat-capable two-seat trainers”.

The requirement for the aircraft was focussed an interdiction and strike, with a secondary air defence role. With these requirements, the Lavi can be seen as complementary to the early F-16 and F-15 fighter aircraft which were in service with the IDF, filling a role close to that of later-model F-16s, which are widely used as strike platforms rather than interceptors. It was intended to replace the A-4 Skyhawk, F-4 Phantom and the Kfir in Israeli service.
The aircraft was powered by the Pratt & Whitney PW1120 engine with 92 kN (20680 lb) thrust. This engine was specifically developed for the Lavi, and offered about 10% less thrust than the F100 engine of the F-16C. Overall performance included a maximum speed of Mach 1.85, and the ability to carry a wide range of weapons.
Comparative performance data for the Lavi, Tigershark, F-16 and F-16/79 are presented after discussion of the aircraft programmes.

The equipment for the Lavi represented the state-of-the art of the time, and included:

• Carbon fibre wing and fin structure
• 4 underwing hardpoints
• Lear-Siegler/MBT quadruplex digital fly-by-wire flight control system
• Elta EW, ECM and IFF systems, computer-based with active and passive countermeasures
• Hughes holographic head up display and 3 multi-function displays, integrated by Elbit
• Lear-Siegler/MBT quadruplex digital fly-by-wire flight control system
• Elta pulse-Doppler radar
• Elbit mission computer and stores management system with Mil-Std 1553 databus
• 30-mm cannon plus Python 3 Air-to-Air missiles.

As a minor sidenote, the PW1120 engine was tested in an Israeli Phantom. IAI showed a developed version of the Phantom at the Paris Air Show in 1987, complete with PW1120 engines, and an advanced avionic suite and cockpit displays. With a thrust increase of 17% over the F-4E, the modified Phantom could supercruise (maintain supersonic flight in dry thrust) and had a combat thrust to weight ratio of greater than 1.0. The potential of this project was not to come to fruition, however, as McDonnell-Douglas refused to sanction the modifications due to its performance being too close to that of the F-18.

Credit: Burkhard Domke

A teething lion cub
The Lavi programme was launched in February 1980, with full-scale development beginning in October 1982. Due to the technologies involved, and the selected propulsion system, there was considerable US industry involvement in the programme, with the involvement of at least 80 Companies. In some ways, the Israeli engagement with the US was the boldest and most innovative aspect of the program. In essence, Israel was launching a cutting-edge fighter program with neither the money nor the technology to do so. Both would be sought from the US.

Quite early in the programme, a problem emerged over the issue of licences to transfer critical US technologies for the Lavi project to Israel, and in the Spring of 1983, this led to a concerted lobbying effort to persuade Congress to provide funding to Israel through the foreign aid program and FMS credits to enable the development of the Lavi. This lobbying activity did not involve the Department of Defense, who had concerns about both the transfer of technology to Israel and the use of FMS funds to support overseas programs. In parallel with a separate effort to get the necessary technology transfer licenses agreed, the lobbying of Congress was successful, and significant US funding became available to the Lavi program.
Between 1983 and its cancellation in 1987, a total of about $2Bn is reported to have been provided by the US to fund the Lavi programme, the bulk of which was spent in Israel. During the development programme, increasing doubts began to be voiced in the US, focused on a number of issues:

• A perception by the DoD that support to Lavi was a mis-use of FMS funding, which was seen as intended to support US Industry;
• A perception by the DoD that advanced and sensitive technologies would be transferred from the US to Israel;
• A perception by the State Department that the programme was absorbing too much of the foreign aid budget, and moreover was seen by many as evidence of a US bias toward Israel in the Middle East;
• A perception that the programme was incompatible with the Gramm-Rudman-Hollings deficit reduction Act;
• A perception by Northrop that the US was unfairly subsidising an Israeli product that would compete with the F-20 Tigershark;
• Similar perceptions by McDonnell-Douglas and General Dynamics in regard of Lavi competing for the export markets of the F/A-18 and F-16; and finally
• A perception by the GAO (General Accounting Office) and OMB (Office of Management and Budget) that Israeli costings were unrealistic, and that the US would have to pay yet more to co-fund the production of the aircraft.
As a result of these concerns, the US withdrew funding from the programme, resulting in its cancellation by Israel in August 1987.

Through the Lavi programme, Israel succeeded in using largely US money and US technology to construct prototypes of a very advanced aircraft, which might have become a very effective weapons system. In addition, Israel gained insights on numerous advanced US technologies and manufacturing capabilities.

As an immediate consequence of the cancellation of Lavi, Israel was able to procure 40 F-16C Block 30, and 30 F-16D Block 40. In 1994 these purchases were followed by the F-15I, a version of the F-15E Strike Eagle. Procurement of advanced US aircraft has continued, including more than 100 F-16I, a version of the F-16C Block 52 in which much of the avionics suite is provided by Israel. With the release of all this defence capability to Israel, the Lavi programme was perhaps more successful in its failure than it would have been had it succeeded in developing a production aircraft.

How do the Lavi, the Tigershark, the F-16/79 and the F-16C stack up?

Comparison between aircraft using published performance data is often extremely difficult. Partly due to the limited data generally provided, and partly due to understandable inconsistencies, as the data is normally presented so as to show the product in the best light. For example, while the Maximum Mach number achievable will be a definite number, defined either by the drag of the airframe and the thrust available from the engine, nozzle and intake system, or by some structural or temperature limit, manufacturers are likely to present this figure at light weight, and with no external stores or fuel tanks. Similarly, range is likely to be presented for an aircraft with maximum fuel, possibly including oversized external ferry tanks, and in a clean configuration. No standard definition appears to exist of a combat configuration which might be used as a comparator

While one does sometimes see 50% internal fuel plus two AAM used, for example, detailed examination sometimes shows that the AAM are only short-range, or the gun ammunition, or the pilot or both have been omitted. Even were a standard combat weight to be defined, and data available, many other aspects of performance, such as radar range, signature, weapons capability and so on simply cannot be encapsulated in a few numbers. Inevitable, what follows is a simple snapshot, rather than a valuable comparison.

A further complication with these aircraft is that the F-20 and F-16/79 had deliberately limited strike performance, whereas the Lavi was intended to maximise strike performance, with a secondary air defence role. For the F-16, the original Light Fighter concept has developed over time from the lightweight air defence fighter of the F-16A, to the multi-role, versatile, and much heavier F-16C Block 50. Comparison of true multi-role aircraft would need to include consideration of mission performance as well, and would be well beyond the scope that can be achieved in unclassified material.

Lavi Tigershark F-16/79 F-16C Performance Wing Loading (Wref/S) 294.6 429.0 390.8 409.0 ITR

Performance Wing Loading (Wref/S)
(lower loading aids instantaneous turn rate)
294.6429.0 390.8409.0
Aspect Ratio (Span2/S) (higher number aids subsonic sustained turn rate) 2.33 3.55 3.03.00
Thrust/Weight (higher number aids Energy Manoeuvrability)0.960.990.87 1.16
Fuel Fraction (higher number aids combat peristence)0.28 0.280.29 0.28
ConfigurationUnstable canard-deltaConventional aft-tail, small strakeRelaxed stability, aft-tail, large strakeRelaxed stability, aft-tail, large strake

The data in this table is relatively firm. The reference weight is the empty weight of the aircraft, plus the maximum internal fuel weight. The same approach is used for all aircraft. As we have seen, the maximum turn rate depends on the lift available from the wing or structural limit (ITR), and the wing aspect ratio, lift, airframe drag and engine thrust (STR). A low wing loading, a high aspect ratio, and high thrust to weight ratio will increase sustained turn performance. A high Clmax will increase ITR, as will a reduced stability or unstable configuration.

On this basis, we might expect the unstable Lavi, with its much lower wing loading and unstable aerodynamics to have great ITR, while the Tigershark ITR would be reduced compared to the Lavi and the F-16. Both the F-16 and the Tigershark benefit from wing leading edge strakes, and, notably, all aircraft claim to be able to operate up to a 9g structural limit. The real issue here is for how much of the flight envelope is this capability available, and how much energy will be lost in such a manoeuvre.

1984 F-16 lineup. From the top F-16C , F-16A , F-16XL , F-16/79 and AFTI/F-16

On sustained turn rate, the trade-offs are more complex, but it is apparent that the F-16/79 is likely to be handicapped by its lower thrust to weight ratio. Note that the thrust used is a short-term power plus mode. At normal thrust, the F-16/79 has a thrust to weight ratio of around 0.75. The low aspect ratio of the Lavi, and its slightly lower thrust-to-weight ratio are likely to reduce STR, but the much lower wing loading will counter this to some extent.
Thrust to weight ratio is particularly important, as a high thrust to weight ratio will enable high energy manoeuvrability. This will allow a turning fight to be readily taken into the vertical, and, in BVR combat will allow rapid cycling between engagement, missile release, disengagement, acceleration and re-engagement. Of these four aircraft, the F-16C has a definite advantage in energy manoeuvrability, and the F-16/79 will be at a disadvantage.
The Table below presents some limited data for the four aircraft. The data reflect what could be gleaned from the web, and is not fully defined, in that aircraft configuration, altitude and Mach number are not generally available to fully define the quoted figures. As all aircraft claim to be capable of generating 9g, the small variation in ITR figures probably reflects differing altitude or speed conditions, although the higher value for the Lavi may reflect both its low wing loading and its unstable aerodynamics. The ITR for the F-16/79 is based on the assumption that the aircraft can reach the same CLmax, and has the same structural limits as the F-16. The F-16/79 would lose energy much faster than the F-16 due to its much lower thrust.

LaviTigershark F-16/79F-16C
Mach max 1.852.002.002.00
ITR max deg/s 24.3 20(24.9)24.9
STR max deg/s13.211.5 11.822.0

Maximum Mach number claimed for the F-20 and the F-16 is Mach 2.0, and this was also reported to be achievable in the F-16/79, which seems slightly surprising, but may be a result of better intake performance. The maximum Mach claimed for the Lavi is Mach 1.85.

It is notable that the higher thrust to weight ratio of the F-16C gives a significant benefit in Sustained Turn Rate – the figure noted comes from a dataset that suggests the F-16 is structurally limited in STR as well as ITR. The slightly higher ITR figure is at a lower speed, where the aircraft is lift-limited rather than g-limited. The impact of the low thrust of the F-16/79 is evident in comparison of its sustained turn performance with the F-16, and the F-20 Tigershark achieves similar STR, the higher thrust to weight ratio somewhat offsetting its higher wing loading. It should not be forgotten that the Lavi was really well ahead of its time in aerodynamics, control system and mission system design. Its nearest equivalent would probably be the Gripen, which made its first flight in December 1988, some 2 years after the Lavi.

In WVR combat, for example when used in dissimilar air combat training, the Tigershark might well have been a real handful because of its small size and relatively good thrust to weight ratio. Otherwise, the Lavi configuration should have high subsonic agility (through its good ITR), but would perhaps be susceptible to losing energy in turning combat. It should have low supersonic wave drag and could perhaps have developed into a good BVR platform.
From this analysis, we can see that both the Lavi and the Tigershark were very effective designs in terms of achieving their desired performance characteristics. The Lavi had great potential as a multi-role platform, and would have been effective against the threat aircraft of the time. The Tigershark was a small, fast and manoeuvrable light fighter, but was deliberately limited in strike capability.

Neither the Lavi, nor the Tigershark would have been able to match an air-combat-configured Viper, but the Lavi might have been a pretty close match in the strike role, and was certainly a big step forward from the Skyhawk and Phantom it was intended to replace. The F-16/79 was broadly comparable to the Tigershark, but only when able to access its short-term ‘Combat Plus’ engine mode. At the normal thrust setting which offered a maximum thrust of 80.1 kN compared to the short-term setting of 92.8 kN, it would simply not have been competitive.

Policy Considerations
In thinking about the sorry tale of the Tigershark, the Young Lion and the Viper, it is important to realise that, in the period concerned, there were five major players involved, each with somewhat different objectives.
The State Department seem to have had a fairly consistent view that armed conflict between nations was undesirable, and should be avoided. To ensure this, it seemed reasonable that ‘friendly’ Nations (I use the term loosely in view of a number of US misjudgements in this regard) should be enabled to protect themselves, but only to a level which would deter their competitors, and not to a degree which would encourage aggression. This was also desirable from a domestic economic perspective. Business would be generated for US industry, and nations would be able to deter aggression without involving US armed forces. Israel might have to be a special case given its difficult relationship with pretty much all of its neighbours, and the fact that some of those neighbours were receiving support from the USSR (or Russia in contemporary times).

The Defence Department was generally OK with the desirability of not getting dragged into other people’s conflicts, but had reservations about developing aircraft which were only going to be of interest to third parties. It had particular concerns about the potential for the transfer of sensitive technology overseas and the possible use of export fighters in aggressive rather than defensive operations. As the DoD and the Services had no intention of ordering any of these aircraft for USAF use, there was tension between DoD and State, because this would decrease the likelihood of orders. Finally, DoD was opposed to the use of FMS (foreign military sales) funding to develop the Lavi programme, as the funding would largely be spent in Israel rather than in the US. However, participation in Lavi was pushed through Congress, quite deliberately by-passing the DoD.

Industry found itself in a somewhat awkward position. Of course, any programme is a good programme if it maintains employment and a high-quality knowledge base in the US. In some ways, FX was an attractive programme, a bit like Marshall Aid following WW2, where US Sabres (and some other aircraft) were provided under FMS to pretty much every European air force. Good business for US industry, and an equally good means of slowing the development of European competitors.

However, there was much more risk in the FX programme, as the USAF would not operate the product. General Dynamics were OK – they could afford an each-way bet. Development of the F-16/79 was very low risk, and who knows, someone might buy it. Northrop were, however, much more exposed. The F-20 was a much bigger departure from the F-5E than the F-16/79 from the F-16. Much more risk was involved, and a much greater degree of systems development and integration was needed. Then along came ‘exceptionalism’, with many overseas F-16 sales, and to cap it all the Lavi project. Not only as a direct competitor, but as a source of technology improvements for a Super-Phantom which might also win sales. To cap it all, the programme was being lavishly funded using resources intended for US Industry.

What about the Politics? Well, Jimmy Carter’s policy of seeking to minimise conflict by providing friendly Nations carefully controlled capabilities to deter aggressors, while limiting their own ability to take aggressive action themselves, seemed like a good idea at the time. Particularly since there was a prospect of business for US Industry as well. And it might have proven to be a good idea, had the US been able to resist the opportunity to indulge in ‘exceptionalism’ – rewarding some Nations for perceived good behaviour, or exceptional need by provided them the advanced capabilities anyway. Under the Reagan Administration, the export controls were gradually wound back. Pakistan, Egypt, Venezuela, South Korea, Turkey and Greece could all buy F-16s, and Israel could buy the F-15C. And Israel could have US funding to support the Lavi.

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The Lavi story, and the reasons for US withdrawal from the programme have been detailed above. Unlike Jimmy Carter’s approach, which might have been ‘a good idea at the time’ had it been seen through, the decision to fund Lavi and expend some $2Bn of US resources earmarked for US Industry on an overseas program still looks like a ‘What were they thinking?’ moment. The Lavi program remains a lasting tribute to the power of advocacy and lobbying, and the skill with which the Department of Defense was by-passed so that a compliant Congress would pass the required legislation.

Concluding Observations
What were the outcomes? Northrop lost $750M of its own money on F-20, as well as losing 2 pilots in fatal accidents. No aircraft were sold. General Dynamics did OK, only dropping some $60M on F-16/79, and compensating that with increased sales of the F-16 worldwide. Israeli Aircraft Industries (IAI) took a short-term hit, but in the end had been exposed to significant US advanced technology. Israel lost the Lavi and the ‘Super Phantom’, but gained the F-15 Strike Eagle, Apache Helicopter, and greater numbers of more advanced F-16 aircraft. The US policy of supporting Israel appears fixed in concrete and immutable, assisted by Russia providing support to Syria, and Iran developing towards nuclear capability. IAI and other Israeli companies have become adept not only in manufacturing their own Defence solutions, but also in providing significant capability upgrades to equipment obtained mainly from the US.
Ideally, Nations should follow a path of ‘Joined-up Government’, where Foreign Policy, Defence, Overseas Trade, Employment and Industry Policies are all coherent, enduring and non-Partisan. Such a policy has never been achieved by a Western Democratic Nation, and it looks increasingly unlikely that it ever will. The FX and Lavi programmes are great examples of the consequences of a failure to achieve joined-up government.

In the past, the USSR tried its own variant of a coherent approach, but failed, largely because its economy proved unable to compete with the West in accessing advanced technologies and building the necessary industrial, economic and social infrastructure.

On the other hand, China seems to be giving such an approach a fair go at present, and appears to possess the resources, the technologies, and the will to achieve its aims of becoming a dominant world power.
Joe Biden may well respond “Not on my watch” – the rest of us will have to wait and see.

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Turning Performance – Sustained Turn Rate
To show some of the difficulties in simply accepting published data. Let’s consider sustained turn rate – a performance parameter of much interest, particularly to those who regard WVR air combat as important, rather than something to avoid. The key factors in determining sustained turning performance are drag and thrust, because the maximum sustained turn rate, STR, occurs when the aircraft drag is equal to the maximum thrust available from the engine. However, drag and thrust can be very sensitive to weight, altitude, aircraft configuration and Mach number.
The drag depends on the configuration and Mach number, through the zero lift drag element, Cd0 – carriage of external stores and tanks will increase Cd0, as will zero-lift wave drag if supersonic flows are present. The drag due to lift depends on weight, through the Lift Coefficient, Cl, squared (Cl2), and weight will depend on the stores carried and the fuel state of the aircraft, including whether tanks are carried. Subsonic lift dependent drag is inversely proportional to Aspect Ratio (the slenderness of the wing planform), so having a higher aspect ratio reduces subsonic lift dependent drag. However, a higher aspect ratio will increase supersonic wave drag. In addition, wave drag also varies with lift, and hence weight and configuration. The propulsion side of this balance also depends on Mach number, which affects intake and nozzle efficiency, and altitude, which affects both air density and temperature. Altitude also affects the drag, as the lift coefficient required increases as air density decreases. It is worth noting that maximum sustained turn rates will generally occur in subsonic flight, because of the absence of wave drag. Turning Performance – Instantaneous Turn Rate The Instantaneous turn rate (ITR) is the absolute maximum turn rate achieved by an aircraft, and, typically, is defined by either a structural or a lift limit. At given conditions, the ITR is reached when the pilot rolls the aircraft to wings vertical and pulls to achieve the maximum lift available from the wing, or reaches the structural design limit of the aircraft (maximum permitted ‘g’). Note that there is no requirement for this to be a balanced turn, and even at maximum thrust, most aircraft will be either losing speed or height when the maximum ITR condition is reached. At lower speeds or higher altitudes, the ITR is generally limited by the amount of lift that the wing can generate. At higher speeds and moderate altitude, pretty much all fighter aircraft will be structurally limited, generally to 9g, which currently represents a physiological limit for pilots. The speed and altitude combination where the aircraft reaches its structural limit and lift limit at the same time is known as the manoeuvre point, and for most fighter aircraft, this will generally be at medium altitude and a subsonic Mach number. From the discussion of turn rates, we can see why performance data is rarely presented for the professional in the form of simple data points. Instead, aerodynamic, propulsion and weights data is prepared, and will be validated through flight test. This data can then be used to predict performance, or to build validated performance models once flight-test proven data is available. These performance models will then show how differing performance measures vary with configuration, weight, altitude and Mach number. This then provides a mechanism to demonstrate that specified point and mission performance requirements can be met. An example of a point performance requirement might be to demonstrate a sustained turn rate of 12 deg/sec at 11 km altitude and Mach 1.4, in a defined air combat configuration. A mission requirement might be to take-off, climb to 11km, accelerate to Mach 1.6, jettisoning external tanks at Mach 0.95, fly out to an air combat, represented by performing 4 360 deg turns in full afterburner and the release of 4 AAM, and return to base at most economical cruise speed and altitude, descend to land, with a 30 minutes fuel reserve remaining. The specification would detail the mission profile, and the distance from base at which the air combat is to take place. None of this sort of data is available for the aircraft under discussion here at a level of detail to make robust comparisons. But this is not the end of the story. Key Parameters We can examine the key data on size, shape and weight of the aircraft and their engines, and consider how this might impact on performance. And we can report the limited performance data that is available, and see whether this is consistent with our analysis. Hard data (i.e. definite figures) is available for parameters such as the aircraft wing area, the aspect ratio of the wing, the planform, the type of intake, and the maximum thrust of the engine. Slightly softer data is available on aircraft empty weight and on internal fuel capacity, as well as information on weapons carried and some (very soft) data on claimed performance. From this data, we can assemble some key parameters, and use these to develop a view of how the aircraft compare with each other. In the absence of any form of mission modelling tool, I am going to look at point performance characteristics relevant to fighter aircraft, rather than considering strike roles, as these would be heavily dependent on the weight and drag of external fuel tanks, stores, targeting, electronic warfare pods and so on. To derive these parameters, I am going to make some consistent assumptions for the aircraft, particularly about their weight. The Table below provides some data which I will then discuss in terms of its anticipated impact on performance. All F-16/79 data assumes the use of the ‘Combat Plus’ engine setting.


  1. Jay

    Good article. Two small corrections: Reagan took office in early 1981, not 1982. Also, the country is spelled Bahrain (no e).

  2. Duker

    “the expenditure of more than $1.2 billion of its own funds “, this is a common claim about Northrop F-20. Its based on the companys accounts when the F-20 program was abandoned of a ‘writeoff’ of that amount. Of course Northrop didnt spend $1.2 bill or anything near that for what werent major mods for an existing aircraft. What did happen was the program accounting for the entire T-38/F-5 ended with the F-20 demise. Program accounting allowed some costs to be written off over the life of the program or even held till its end. Watch Boeing write off considerable sums when the B747 finally ends later this year or next, ( it also has been making writeoffs for the 747 in last 5 years because it was tax efficent to do so) Its the same thing for Northrop but in a different way the accounting rules allow a ‘continuing’ program of money spent long ago to be kept in the books rather than written against revenue from that time. The existence of program accounting and its misunderstanding is common grief for aviation enthusiasts
    Remember the F-20 ( developed from 1975) was only a few years after the the YF16 prototype development as the LWF ( first flight 1974) was done with USAF contracts in the region of $40 mill ( which wasnt the full cost, but this is what that sort of money could get in that era), productionising would cost much more but we are only talking about a few hand built prototypes , which was the same for the F-20. ( from 1975

    • James Smith

      I think it is entirely reasonable, if the company wrote off that amount in their accounts against the F-20, to report that fact. My source was A Case Study of the F-20 Tigershark by Martin and Schmidt 1987, but in any case you are confirming the information. If it is advantageous to the Company to report a larger loss than they actually made, that is a matter between them, their tax lawyers and their accountants.
      I do think the F-20 was a non-trivial modification – not only was the propulsion system changed, the wing was modified, the tailplane was enlarged, and the flight control system was modified. In addition, new weapons were integrated, along with a new radar and a state-of-the-art cockpit. The changes in propulsion system, aerodynamics and flight control systems changed the flight envelope and performance characteristics of the aircraft markedly which would necessitate a flight test program comparable with that of a new aircraft. Coupled with the weapon system requirements of integrating the Sparrow missile, a new radar, and new cockpit environment, this program was definitely not just making a few mods to an existing aircraft. Moreover, apart from the first aircraft, which was a propulsion-only change, Northrop’s stated intent was that the Tigershark aircraft be representative of production examples. Not all this was achieved within the program, as the fourth aircraft would have incorporated further changes to the avionics, radar and control systems.
      With distance and time, and Northrop’s own reporting as well as a contemporary study, I’m not going to argue the merits of differing perspectives on the loss. It would have been substantial, given the development and integration effort required, and the flight test effort needed to validate the design, certify the aircraft and demonstrate the integration of the weapon system.

      • Duker

        The report by Martin and Schmidt also says 3 pre production airframes were completed and that Northrop used its ‘Production Development Centre’ , PDC, for this version. None of that says it was production ready development merely ‘production quality’ and they do say it would require ‘ongoing development of production process’ when they had an order. This confirms my claim of ‘hand built’ in the PDC for the 3 airframes completed ( plus 1 part complete at cancellation). The systems apart from flight control seem to have been ‘proposed’ from existing hardware available rather than ‘installed and working’ in the flying examples.
        As well the report says that Northrop did not provide cost data to the authors, there is a graph of spending but that was from LA Times not Northrop. This is a significant omission as it doesnt provide an original source for the developments costs part of the whole T-38/F-5/F-20 program accounting cost.
        I appreciate your story covers much more than the ‘costs’ and is well worth reading. However getting original sources is an ongoing process. Just last year I bought some old aviation magazines from the late 50s and into the 1960s from a reputable title. Included in a story on the RR Spey engined UK Phantom was the information that the maximum speed of the airframe was limited by the ‘turbine inlet temperature’ ( the air was heated by the compression stages). Which was a development issue for the then civil developed Spey. This information was now available to refute a common claim the maximum speed of the F-4 (UK) was lower than the GE J79 version because the ‘drag from the bigger engine inlet’.

  3. Rick G

    Really enjoyed this article! Reading it reminded me of all the aircraft magazines I read in my younger years, so many of which had advertisements where Northrop were pitching the tigershark. Some slick advertising, great pictures of the F-20, and catchy slogans but despite Chuck’s best efforts, no sale! I always wondered, does advertising in a publication for general consumption actually influence the sales prospects of a complex system such as a jet fighter?

    • James Smith

      Always wondered this myself. It’s not plausible that acquisition decision makers would be swayed by an advert in the popular press, but the adverts will place the company name in the public eye. Why do this? Perhaps there are other products where name recognition will help. For example, in thin times, Westland used to build garage doors, and maybe that Wessex ad put their name in your mind. Otherwise, who can influence the decision makers? Politicians. So the ads might be targeted at local constituents, lobbyists etc. Overall, not a strong case, though.

  4. Brian

    With all the discussion about the F35 being too expensive, not just the purchase price but also running costs it shows there is still a need for a lower tier aircraft. Unfortunately the F20’s range with a full load out would be too small to make it a viable strike/ground attack plane. If the aircraft was marketed less of the hot rod air to air fighter but more of a bomb truck they may have sold some. Just need to figure out where to tack on some more fuel cells.

    • James Smith

      Of course the FX requirement, against which the Tigershark was designed, intentionally de-emphasised Strike roles. One comment in the literature notes that, with a low wing and relatively short undercarriage, the scope for heavily loaded underwing pylons was limited.

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  6. anon

    so long story short, the israeli lobby siphoned US money and tech to a foreign project with no benefits to the american people. after it was cancelled, they double dipped by selling their work to china (j-10). really makes you wonder how israel developed the rest of their high-tech industry

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