Saturday, February 25, 2017

Japan's F-2 and the Lavi: The Road Not Taken

I was recently asked in an email if I might draw a comparison between the Lavi, and Japan's F-2 fighter.

As was pointed out in my book on the Lavi, prior to launching the Lavi program, Israel's government had twice asked for permission to set up a local assembly line for the F-16 in Israel, similar to what had already been granted for NATO partners in Europe, as well as to the local assembly lines that would later be granted for the F-16 in Turkey and South Korea. Israel was denied this option on both occasions, once in 1977 and again in 1980. Had the F-16 gone into production in Israel, it would have afforded Israeli developers an opportunity to modify the aircraft - which had originally been envisioned as a lightweight air-to-air day fighter - into the more versatile, multirole platform that the IDF required.

There were two, highly evolved versions of the F-16 which would later be developed, which provide some insight into the options that a local, Israeli assembly line might have afforded the IDF. The first was the F-16XL, a radically different, cranked-arrow delta-winged derivative of the F-16, which first flew in 1982. The second was the Mitsubishi F-2 which first flew in 1995. Both aircraft provide insight into what an evolved F-16 platform could accomplish.

The Mitsubishi F-2 was developed out of General Dynamics' conceptual proposals to the U.S. Air Force for the "Agile Falcon" program, which was intended to recover some of the air-to-air performance that had been eroded as the F-16 had been tasked with ever expanding air-to-ground roles. Between the Block 10 and the Block 40 editions of the F-16, the airplane had evolved from an empty weight of 15,140-lb (6,870-kg), to an empty weight of 19,020-lb (8,630-kg), as additional structural weight was added to increase its maximum payload capacity. New engine technologies had allowed the F-16 to effectively maintain its thrust-to-weight ratio, but they could not restore the effects of the added weight on wing loading. The Agile Falcon was intended to correct this, producing a derivative fighter with an expanded range and payload capacity, that also mirrored the earlier, intended wing loading of the Block 10 F-16A.
The F-2 was intended to recover the erosion in wing loading that had accompanied later models of the F-16.

Although the U.S. Air Force elected not to fund the Agile Falcon program, it was later proposed as a contendor for Japan's FS-X domestic fighter development effort. The F-2 fighter that resulted from this program, features a stretched fuselage, with an added center-plug section, but with an all-new wing that adds 25-percent to the wing area, as well as an enlarged horizontal tail. As a direct derivative of the F-16, the F-2 shared over 20% of its components with its U.S.-built predecessor - in contrast to the Lavi which, despite superficial similarities, bore no parts commonality with the earlier F-16. The added wing area allowed the F-2 to increase the available weapons stations from nine to eleven. Like the Lavi, the F-2 featured additional fuel capacity and external weapons load.

The F-2 features an empty weight of some 21,000-lb (9530 kg), with a maximum take-off weight of some 48,700-lb (22,100-kg). This compares to a Lavi empty weight of some 15,310-lb (6,940-kg), with a maximum take-off weight of some 42,500-lb (19,280-kg). Despite its larger size and greater take-off weight, it should therefore come as no surprise that the F-2 would offer slightly poorer range performance than the Lavi - as it also had to carry the additional empty weight that made its higher take-off weight possible. The F-2 also included a Japanese-developed avionics suite, including the first AESA (active electronically scanned array) radar to enter service on a production fighter, as well as a modernized cockpit. To afford a wider field-of-view for the head-up display (HUD), the F-2 replaced the single-piece F-16 canopy with a two-piece canopy, much like the Lavi had done, to protect the pilot from a fragmented HUD in the event of an ejection.

A Mitsubishi F-2 takes off for a training sortie, its F-16 lineage clearly evident.
The composite wing for the F-2, developed locally by Mitsubishi, was one of the more radical features to appear on the Japanese F-16 derivative. It featured a co-cured, all-composite structure, unlike the composite wing of the Lavi which featured a composite skin secured by fasteners to conventional metal spars. The Lavi developers had actually explored the option for developing an all-composite wing structure for the Lavi, but had backed away from it as too costly and ambitious at the time - after an initial co-cured test article had failed during test. The Japanese developers, however, continued to pursue this concept, to take the maximum benefit possible from composite weight savings. This remained, however, a relatively new and immature technology, with the F-2 static structures prototype developing cracks in its wing structure as the design continued to be learned out.

Among the most striking differences between the Lavi and the F-2 program, however, was cost. Japan's government originally envisioned a requirement for 141 F-2 fighters, a total which would eventually be reduced to a mere 94 aircraft. This represented a very small production run indeed. Japan's consitution forbade Japan from seeking export customers for the fighter, something which had also helped to persuade the U.S. government to permit Japan to develop the F-2 with extensive U.S. assistance. With such a small production run, it was no surprise that the unit cost would be considerably higher than for a similar, Block 52+ F-16, or even higher than the projected cost for the Lavi as envisioned under its original 300-aircraft production program. What was more surprising, however, was the high development price associated with the F-2. The entire Lavi development program, including flight testing, had been estimated by the U.S. General Accounting Office to total no more than $1.90 billion, in Fiscal 1985 dollars. Normalized against the same Fiscal Year currency, the F-2 would cost Japan a total of $2.31 billion to develop - a considerable amount for what had been sold as a relatively low-cost, derivative fighter program. The costs associated with developing the all-new, composite wing, as well as the all-new, Japanese avionics suite, eventually overshadowed the cost savings from utilizing an existing U.S. design as a starting point for the airframe.

The F-2 has of course gone on to serve the Japan Air Self-Defense Force well, and has provided an important technology development and learning milestone for the Japanese aerospace industry. It was not, however, an inexpensive alternative.

Thanks again to William Zhou for suggesting this topic.

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