12th August 2021Mitsubishi F-X user+1@localho Thu, 08/12/2021 - 21:17
The Mitsubishi Heavy Industries (MHI) Next Fighter ( ), abbreviated as F-X in English, is a prospective fighter which will be developed in partnership with Lockheed Martin (LM). The program was originally referred to as the Future Fighter ( ). The aircraft is expected to feature a large, very low observable airframe optimized for endurance and beyond-visual-range (BVR) air-to-air engagements. It will feature a suite of wide field of regard sensors, advanced power and thermal management capabilities and manned-unmanned teaming. The first F-X is planned to enter operational service in 2035. Approximately 90 fighters will be procured for the Japan Air Self Defense Force (JASDF) at a total program cost of at least 5 trillion ($45 billion).
The F-X s history can loosely be categorized into three eras: the development of the preceding F-2, early conceptual studies and technology demonstration efforts and contemporary efforts to launch the F-X program.
FS-X (F-2) Program (1982-2011)
Even before production of the F-2 ended in 2011, Japan had begun efforts to develop a successor. Perceived deficiencies in the F-2 program shaped the F-X s ambitions and requirements, with the MoD essentially seeking to avoid a repeat of the F-2. In 1982, the Japanese Government began the Fighter Support Experimental (FS-X) program to replace the indigenously designed Mitsubishi Heavy Industries (MHI) F-1 fighter. The U.S. lobbied Japan to develop the FS-X from an existing U.S. design in 1985. This U.S. effort sough to promote greater U.S.-Japan interoperability and mitigate the possibility of an independent Japanese national security policy. A key piece of the U.S. leverage was its engine technology which Japan would have required even under an indigenous development program.
Japan eventually acceded to U.S. demands and selected the F-16C Block 40/42 as the basis of further FS-X development in October 1987. The program was quickly hampered by American reticence to transfer key technologies and disagreement over the scope of Japanese industry participation. Lockheed Martin was awarded $75 million ($123 million in 2020 dollars) to support the development of the F-2 in October 1996. The company would be responsible for 40% of the program s workshare by value including the avionics support equipment, the data entry electronic units and the stores management system.
In the end, the F-2 program produced a fighter featuring novel technologies such as the first fighter mounted active electronically scanned array (AESA) radar, but at an unacceptable cost and with no roadmap to keep the type technologically relevant. The F-2 had a flyway cost of $122.6 million in adjusted 2020 dollars and only 98 airframes (including four test articles) were produced between 1996 and 2011.
Japanese sources maintain that the F-2 s intellectual property agreements with the U.S. severely constrained its ability to upgrade the type. In many respects, current configuration F-2s remain less capable than contemporary F-16 Block 70s such as in stores compatibility, avionics, data links, and self-protection equipment. Some Japanese sources have derided the FS-X limited opportunities for Japanese industry and have expressed frustration against the U.S.' technology and export policies. These grievances later influenced Japan s decision to reject LM s F-22/F-35 hybrid proposal.
Genesis of F-X (2005-2018)
According to Lt. Gen. (Ret.) Takayoshi Yamazaki, the genesis of F-X did not begin with a statement of need or requirements process from the MoD or JASDF. Rather, the program began from a 2007 industry assessment which concluded Japanese companies were withdrawing from the aerospace market. A similar study published in 2009 by the MoD ( ) stated the number of aerospace engineers was expected to decline by 70% after F-2 production ended in 2011. To ameliorate further attrition of the industrial base, the MoD s Technical Research and Development Institute (TRDI) and MHI began work on the Advanced Technology Demonstrator X (ATD-X) Shinshin (Spirt of the Heart) in 2007. At the time, the MoD remarked, A quick start [of the program] is essential to sustain the domestic military technological base and to obtain bargaining power. The comment followed an unsuccessful campaign to import the Lockheed Martin F-22A Raptor.
The resulting ATD-X design has an empty weight of 29,000 lb. and features caret inlets, canted vertical stabilizers and planform alignment to reduce its radar cross-section (RCS). The design is powered by a pair of IHI XF5-1 turbofans producing 11,000 lbf. of thrust and which are fitted with thrust vectoring nozzles. The ATD-X airframe underwent static fatigue life testing in 2013 and was rolled out a year later. It first flew in April 2016 following a year-long delay prompted by unspecified issues with the aircraft s low observable (LO) features. As of November 2017, the ATD-X had flown 34 of the planned 50 test fights and was scheduled to be withdrawn from service in March 2018.
According to program manager Hirofumi Doi, the ATD-X program gave F-2 engineers the opportunity to pass skills to the next generation of Japanese aerospace engineers . The Society of Japanese Engineers found that just 20% of the 270 engineers across the main Japanese primes involved in the F-2 program remained in the workforce as of November 2017. Another critical element of the program was the development of associated test infrastructure which would later be needed in a full scale developmental program such as RCS measurement and ranging equipment. A total of $664 million was spent on the advanced technology demonstrator between 2009 and 2017.
Trade Studies & Concept of Operations
While Japanese industry gained experience in basic LO design and shaping under ATD-X, the MoD began the i3 program which was first disclosed in 2010. The i3 sought to develop technologies not covered under the ATD-X program such as slim engines capable of supercruise, electroconductive canopy materials, metamaterials for controlling radio waves passing through the radome, data integration for counter-stealth applications and cooperative sensor and weapons employment.
TRDI examined scenarios in which Japan would have to combat a larger adversary in a close or distance geographical context. Results from these studies indicated the need for high survivability via LO, deep magazine capability for air-to-air missiles (AAMs) and cooperative engagement capability. Speed was shown to not greatly improve mission performance. More important to aircraft survivability is the range of angles at which the aircraft can paint targets with its radar and guide missiles toward them. TRDI found that increasing a fighter s radar sweep from about 140 deg. (that is, 70 deg. either side of the centerline) to about 220 deg. gave the pilot more time in which to fire missiles and reduced the enemy s opportunity by around 40%. If the range of available guidance command directions is increased from about 200 deg. to 360 deg., the time available for the pilot to fire is almost doubled and the enemy s is almost halved.
TRDI (likely with support from MHI) produced concepts in 2011, 2012, 2013 and 2014 which were successively designated 23DMU, 24DMU, 25DMU and 26DMU. (Note that the number in each designation corresponds to the regnal year of then Emperor Akihito. DMU stands for digital mock-up.)
The series of designs shows a progressively stronger emphasis on LO design illustrated by the flattening of the aircraft, moving the engines outboard and changing from straight intakes with radar blockers to S-shaped ducts. Earlier emphasis on maneuverability and speed gave way to focus on endurance, loiter time and weapons load. A detailed explanation of each concept design follows.
- 23DMU This concept shared the planform of the ATD-X. Its overall design prioritized maneuverability and incorporated carriage of four BVR air-to-air missiles (AAMs) as well as a pair of within-visual-range (WVR) weapons. TRDI found the 23DMU s deep fuselage contained significant radar-reflecting side area.
- 24DMU The next design was a refinement of the 23DMU intended to reduce side reflecting area by flattening the aircraft. The engines were moved outboard and fed with straighter ducts, relying on blockers to reduce the RCS. The BVR AAMs were carried in tandem pairs. A V-tail combines both rudder and elevator functions as on the Northrop YF-23. Simulations with the new design found a pilot flying a 24DMU instead of a 23DMU would be able to fire about 10% more missiles and the enemy about a third fewer. The time available for taking shots was shorter for both, but the enemy s firing interval suffered more.
- 25DMU This design has a greater emphasis on LO when compared to the preceding concepts. In place of the straight, blocked inlets, 25DMU has S-ducted intakes with inboard engines to create a broad space for side-by-side stowage of six BVR AAMs under the ducts, which twist upwards and inwards. The four tail surfaces reappeared but the fins remained highly canted and were kept shorter than those of the 23DMU. Wingspan and aspect ratio increased by almost 20% compared to the 24DMU. These wing changes were expected to increase range through an improved lift to drag ratio and greater fuel volume. TRDI confirmed range increased with the 25DMU, though it gave no figures. Speed and acceleration likely suffered, especially since 25DMU appears at least 10% larger than its predecessors. All of TRDI s published designs show a modest 40-deg leading-edge sweep of the main plane, suggesting none were designed to supercruise, but rather for range and loiter time.
- 26DMU The final design preserves the concept of long-endurance and moderate flight performance. 26DMU represents the final attempt by the ministry s engineers to evaluate the trade-offs in the performance and acquisition of the new fighter. Implying the formation of more stable program requirements or key performance parameters.