In the mid 1960s, the JapanAir Self-Defense Force commenced studies into an advanced jet trainer which could also be modified to serve in the ground attack and anti-shipping roles. After considering license production of the T-38 Talon and SEPECAT Jaguar, Japan decided to develop its own trainer, the supersonic Mitsubishi T-2, this first flying on 20 July 1971. Cost over-runs in the T-2 program led to the proposed single seat attack version almost being abandoned, but the cancellation of the Kawasaki P-XL, the planned replacement for Japan's Kawasaki P-2Jmaritime patrol aircraft freed-up funds, while making it important to keep Japan's aviation industry employed, and contracts were awarded for the development of the attack version as the FS-T2kai in 1973. The new aircraft was a minimum change derivative of the T-2, with the rear cockpit being converted to an avionics bay by removing the rear seat, and replacing the canopy with a simple unglazed access hatch. Two additional hardpoints were fitted under the wing to allow carriage of a heavier weapon load, and the avionics were improved, with a new J/AWG-12 radar set, similar to that fitted in British Royal Air ForceF-4M Phantom fighter jets. This set provides ranging information. Aside from the avionics changes, deletion of the rear seat, and new one-piece canopy, the only other major change from the T-2 was the strengthening of the airframe to enable it to carry a larger weapons load than the T-2. The F-1 is fitted with an internally mounted 20 mm JM61A1 Vulcan cannon with 750 rounds of ammunition. The aircraft also has seven external hardpoints for the carriage of a wide variety of stores. The fuselagehardpoint and inboard pair of underwing hardpoints are plumbed for external fuel tanks to increase the aircraft's range. The primary weapon of the F-1 is the ASM-1 and the newer ASM-2 long-range anti-ship missile. This weapon is roughly in the class of the AmericanAGM-84 Harpoon or French AM.39 Exocet. Other weapons carried include the all-aspect short-range heat-seeking AIM-9 Sidewinder air-to-air missile for air-to-air combat. This weapon is carried on the wingtip rails usually, but it can also be carried on the outboard underwing hardpoints for the F-1's secondary air defense role. Other air-to-ground weapons carried include rocket pods of 70 mm size as well as bombs of 227 kg and 340 kg in size. In addition, the Mk-82 and M117 bombs can be fitted with infrared guidance kits, turning them into precision-guided weapons that home in on heat radiation emitted from seaborne targets such as ships or other ground-based targets. When fitted with this kit, the bomb becomes known as GCS-1. The F-1 was replaced by the F-2, as well as upgraded F-4EJ Kai Phantom IIs. The last six active F-1s, based at Tsuiki in Fukuoka Prefecture, were retired on 9 March 2006, having reached the 4,000 hour limit of their airframes.
