Mitsubishi F-2 “Viper Zero”: Japan’s Fighter Derived From The F-16

Viper Zero 546 during early morning take off. (All images: Author)

JASDF Fighter carries a name that is a combination of the unofficial nickname of the F-16 (“Viper”) and the well-known Mitsubishi A6M Zero.

At the beginning of the 1980s, the Japanese Air Self-Defence Force (JASDF) began to consider a successor to the Mitsubishi F-1, the first combat aircraft developed and built by Japan independently. A feasibility study was carried out in 1985. Decisive requirements for the future aircraft were the ability to carry four ASM-1/ASM-2 sea target missiles (with no limitation of the load factor of -3 to +9 G) and to achieve a combat radius of at least 450 nautical miles.

Since neither of these requirements could be met by any existing weapon system, the only option was to develop a completely new system (“clean-sheet”) or to adapt an existing design. The Japanese aviation industry could have further expanded and consolidated its own capabilities with a new development. The alternative was an adapted F-16 Block 40 from the American manufacturer General Dynamics.

Due to the high costs and pressure from the US, the idea of a new development was abandoned and in 1988 a memorandum of understanding (MoU) was signed between Japan and the USA for the Fighter Support Experimental (FS-X) program, which was renegotiated in 1989 under the term of George H. W. Bush. The work packages were distributed in a 60:40 ratio in favour of Japanese companies. The main contractor was Mitsubishi Heavy Industries (MHI). In addition to General Dynamics, subcontractors included Kawasaki and Fuji Heavy Industries. The new fighter was given the designation Mitsubishi F-2 Viper Zero. This name is a combination of the unofficial nickname of the F-16 (Viper) and the well-known Mitsubishi A6M Zero.

Different size and shape of F-2A and F-15J.

Among the externally visible changes of the F-2 compared to the F-16 are:

  • An adapted wing (larger wingspan, longer root chord, less leading edge sweep angle, modified leading edge root extensions (LERX), more underwing stations) with a 25% increased wing area
  • Adapted fuselage (radome, front and rear fuselage extended, two-piece canopy frame for better resistance against bird strike)
  • 20% larger elevators
  • Installation of a brake parachute housing in the foot of the vertical tail.
Full afterburner take off from this 3 Hikotai F-2A.

Not directly visible is the 18% increase in the proportion of composite materials used in wings, rudder, tailplane, landing gear doors and some other components. A weight saving of around 250 kilograms was achieved by this measure. The radar signature was also improved. The engine (a licensed production of the F110-GE-129 from IHI), ejection seat (ACES II) and machine gun (licensed copy of the M61) remained identical. However, the biggest difference to the F-16 is in the avionics. Here almost exclusively Japanese components were used.

These include:

  • J/APG-1 AESA radar and an electronic warfare suite from Mitsubishi Electric
  • Head-up display (HUD) from Shimadzu
  • Multi-function displays (MFDs) from the company Yokogawa
  • Navigation system (inertial navigation and gyro) of Japan Aviation

The armament includes the Japanese MHI ASM-1/2 and AAM-3 as well as the American air-to-air missiles of the type AIM-7F/M Sparrow and AIM-9L Sidewinder. Since the Americans refused to disclose the source code for the flight control of the F-16, the Japanese used data from tests with a modified Mitsubishi T-2 CCV (Control Configuration Vehicle). The modified flight control system had to take into account, among other things, the 7,000 pounds higher takeoff mass (MTOM), the larger wing area, the changed aerodynamics and center of gravity (C.G.) position. Problems with flutter and delamination in parts of the wing led to an extension of the flight tests (originally planned until 1998) until December 1999.

Data from this T-2 CCV was used for development of flight control system for the F-2.

The first prototype of the F-2 (XF-2A 63-0001) left the MHI assembly line in Nagoya on Jan. 12, 1995 and flew for the first time on Oct. 7. The second XF-2A (63-0002) took off for its maiden flight on Dec. 13, 1995. A total of four flying (two single and two two-seater) prototypes and two cells were produced for fatigue tests on the ground. The static and dynamic load tests of the cells took place from April 1995 to April 2000 and revealed some weak points, especially in the newly designed wings made of fiber composite materials. These findings were directly incorporated into the modification of the series production. The project was also a challenge for the Japanese aviation industry, as this was the first time that fibre composite materials had been used in the primary structure of an aircraft. In 1997, the registration of flying prototypes was changed to the format of the series machines:

  • XF-2A 63-0001 became F-2A 63-8501
  • XF-2A 63-0002 became F-2A 63-8502
  • XF-2B 63-0003 became F-2B 63-8101
  • XF-2B 63-0004 became F-2B 63-8102
Second single seat prototype of F-2 63-8502.
First double seater prototype 63-8101.
The second F-2B prototype (63-8102) has equipment installed in the back instead of an ejection seat.

Of the originally 141 ordered aircraft, the 11 F-2Bs planned for the Blue Impulse were the first to be cancelled. This was followed by further cutbacks so that finally in 2008 the end of production was set after the 94th serial aircraft. Serial production ran between 1999 and 2011 and ended with the delivery of the last aircraft (F-2A 13-8564) to JASDF on Sept. 27, 2011.

During the devastating tsunami on Mar. 11, 2011, 18 F-2Bs of the 21st Hikotai from Matsushima were damaged by the tidal wave of salt water. Five of them (23-8107, 23-8110, 23-8114, 33-8120 and 53-8131) were so badly damaged that they had to be scrapped. The 13 remaining airframes were brought back to service with an approximately repair cost of 13 Billion Yen per aircraft, which is more than the price of a new build Viper Zero. F-2B 43-8126 crashed during a test flight in Nagoya because the cables of the sensors for pitch and roll rate gyro of the flight control system were mixed up. Another two-seater (73-8132) was lost due to a pilot error over the Sea of Japan. So there are currently only 25 two-seater available for the JASDF.

The distinctive shape of the Viper Zero during a late afternoon mission.

During our visit to Hyakuri in February 2020 we could already meet half the squadron of the 3rd Hikotai from Misawa. Their complete transfer was completed on Mar. 25, 2020 with the F-2A 13-8562. The 3rd Hikotai was then subordinated to the 7th Wing (Kokuudan). Thus, besides the 301 Hikotai with F-4EJ Kai Phantom II, there is now also a squadron of F-2 Viper Zero based in Hyakuri.

Sorties were mainly done with four aircraft per wave.

Sources: (Military Database, Orbats), (F-16 FSX/F-2),, Wikipedia (Mitsubishi F-2),, (Mitsubishi F-2), Development Of XF-2 Fighter Composite Structures (AIAA Meeting Paper April 2000)