PL-4 (missile)

PL-4 (Pi Li, 霹雳, Thunderbolt-4) is the first Chinese Semi-active radar homing (SARH) air-to-air missile (AAM), and it has an anti-radar derivative, which is also the first Chinese anti-radiation missile. However, neither entered Chinese service en masse, and both programs were eventually cancelled after very limited numbers had been built for evaluation purposes.

PL-4 program began in March 1966, as the primary weapon that would be used by the proposed Chengdu J-9. The primary contractor was the 612th Research Institute of Chinese Aeronautical Ministry, more commonly known as the Luoyang Electro-Optics Technology Development Center (洛阳光电技术发展中心) nowadays, which became the China Air-to-Air Guided Missile Research Institute (中国空空导弹研究院) in 2002. The primary subcontractor for the propulsion was the 331st Factory, which would later become Zhuzhou Aero-engine Factory (株洲航空发动机厂). PL-4 is based on the American AIM-7D Sparrow IIIa AAM North Vietnam provided to China, after obtaining samples from downed American fighters during Vietnam War. However, barely two month after the program begun, Cultural Revolution started and due to this political turmoil, PL-4 program was disrupted to a complete stop, and it would not be until more than a decade later, well after the end of Cultural Revolution, would the program restart again.

The rocket motor of PL-4 is designated as FG101, and is shared by another anti-radar derivative named Fenglei-7 (风雷7号). The revival of PL-4 was partially due to the decision to develop the anti-radar derivative in January 1979. The designer of the rocket motor was Harbin Ship Engineering Academy (哈尔滨船舶工程学院), the predecessor of Harbin Engineering University, 349th Factory was tasked to manufacture the propellant, 845th Factory was tasked for ground test, and 331st Factory was tasked for final integration. During the propulsion development, the contractor and subcontractors developed new manufacturing techniques, including improvements in installation, new rivet pins, graphite exhaust nozzle, and tolerance. A brand new heat processing method for integrated spin forming was adopted to achieve the high precision engine components, and this was achieved via the use of a special spin forming machinery set specially developed by the Beijing Nonferrous Metal Research Academy (北京有色金属研究院). Once the bottleneck of propulsion has been overcame, both programs went forward with ease, and but the conclusion of political turmoil, namely, the end of Cultural Revolution was an even more crucial contribution in the later development.