MANPAD (MAN-Portable Air-Defense) systems provide infantry-level units with a useful short-ranged aircraft deterrent. In the West, the primary weapon fulfilling this role is the American-originated FIM-92 "Stinger" shoulder-fired missile, introduced in 1981 during the Cold War period (1947-1991). Operators of this system proved plenty (mainly U.S. allies) and the series was eventually taken on by the Japanese Self-Defense Force (JSDF) .
In time, the country sought to upgrade its MANPAD capability over that of the Stinger with a more indigenous effort. Thus began a new venture in 1982 with development eventually headed by Toshiba which went on to last over a decade. The resulting weapon, the all-modern Type 91 "Hand Arrow", fits the same form and battlefield function as that of the Stinger system but features improvements, mainly to its guidance system. The Type 91 was formally introduced for service in 1994.
The complete weapon system, weighing 11.5 kilograms, includes the launcher itself made up of the launch tube, optics set, battery pack and Identification Friend or Foe (IFF) components. The tube is essentially the full-length of the weapon with open ends and the optics set/battery pack is fitted to the business end. The weapon is rested on the shoulder of the operator prior to firing and requires only a single person. The missile itself makes use of twin rocket motors consisting of an initial "booster" unit and a flight path "sustainer" unit. The former is activated upon launch and expended soon after, allowing the sustainer (the latter) to take over for the duration of the missile's flight. The guidance system involves a seeker-type combination UV/IR homing pairing which improves on the Stinger's targeting, tracking and ultimate kill-probability. When launched, the missile can record speeds up to nearly twice the speed of sound, giving the target little time to react.
Production of the Type 91 began in 1991 and first-batch units were delivered into 1993. A second run, begun in 2007, is ongoing as of this writing (December 2017) and has produced the Type 91 "Kai" improved variant. The Type 91 Kai has since superseded the original Type 91 models in service. The Type 91 is also featured on the Kawasaki OH-1 "Ninja" light attack helicopter as its primary close-in air-defense weapon and makes up the basis for the Type 93 SAM launcher - both instances showcasing the weapon's versatility in vehicle-mounted form.