Taiwan had developed its own mobile air defense system to replace the updated Chaparral systems it bought from the U.S. in the 1980s. Increasingly effective Chinese threats of economic retaliation against nations that sell weapons has forced Taiwan to develop its own. This is more expensive but Taiwan is quite capable and is currently a major source of electronic components for other nations.
The new Taiwan air defense system is called Arrow Crossbow and is a mobile system equipped with a radar, a 40mm autocannon and a ground launched version of the Taiwanese Sky Sword radar guided air-to-air missile. The version is comparable to the American AMRAAM missile, which has been used for an air defense system since the 1990s.
The ground launched AMRAAM was first used by NASAMS, a novel air defense system developed by a Norwegian defense firm (Kongsberg) in the 1990s, of using the combat-proven American AMRAAM air-to-air missiles as a SAM (surface to air missile). This was not a new idea, but using AMRAAM was the most ambitious use of air-to-air missiles as SAMs to date. One reason for using AMRAAM was that the United States was constantly updating the AMRAAM to improve performance and reliability. Norway bought and deployed the first NASAMS in 1998. While other systems have been developed using AMRAAM, the Norwegian version is seen as the best of the lot. Norway has six NASAMS batteries for its own defense and over a dozen other nations have purchased them as well. NASAMS is a cost-effective defense against all forms of aerial attack, including cruise missiles and terrorists trying to use UAVs or small commercial aircraft for suicide attacks.
The ground-based AMRAAM missile weighs 159 kg (350 pounds) and, when used from the ground, has a range of 30 kilometers while its radar can see out 50-70 kilometers. The ground version can hit targets as high as 21 kilometers (65,000 feet). What makes AMRAMM effective as a SAM (surface-to-air missile) is the capabilities of its guidance system, which is about two-thirds of the $400,000 missile's cost and constantly updated.
The NASAMS has a uniquely flexible open architecture that now handles more than 25 different target acquisition radar systems and can fire just about any air-to-air missile that can be fired from NATO aircraft. All that is required is modifications to the size and electrical connections in the NASAMS launcher cells and software modification of the FDC. NATO has long established standards for “NATO weapons” and NASAMS takes full advantage of this.
So far NASAMS has been configured with AIM-120 AMRAAM (together with ER variant), AIM-9X Sidewinder, ESSM (Evolved Sea Sparrow Missile) and European IRIS-T. The last one is an interesting story. Norway has a big stock of them for their F-16 but the new F-35 is not compatible with IRIS-T so they have decided to use this very modern European missile as an anti-aircraft one in the NASAMS system. This example clearly shows how flexible this system is while the competitor systems are “tied” to a limited number of missiles and radar.
Taiwan adapted the NASAMs concept to use its most modern air-to-air missile, which is very similar to AMRAAM. Chinese threats towards Norway prevent Kongsberg from selling to Taiwan. At the same time Kongsberg is not going to sue Taiwan for using the NSAMS concept when Taiwan would prefer to buy it rather than spend more time and money to develop their own.
Arrow Crossbow replaces the much less capable American Chaparral system. In 2017 the United States agreed to spend $23 million to provide new components for many of the several hundred MIM-72 SAMs (surface to air missiles) Taiwan bought from the Americans in the 1980s. These missiles were used on the 90 Chaparral air-defense missile systems Taiwan purchased. Chaparral was basically an M113 armored vehicle with the top and side armor removed and a launcher holding four early model Sidewinder air-to-air missiles in the rear. These Sidewinders were reconfigured for use from the ground and called MIM-72. The U.S. Army bought 600 Chaparral vehicles from 1969 to 1997. Also mounted on the vehicle were an optical sight for helping to find and aim (in the general direction of) the target aircraft.
The original MIM-72 had a range of 8,000 meters and was still a heat seeking missile. Later versions of the Sidewinder were used and the final version had a range of 10,000 meters and a much more effective heat seeker that was able to detect the target from any angle, not just the rear where the hot exhaust was. Chaparral never got much use and was replaced in 1993 by the Avenger. This was a hummer vehicle armed with Stinger surface-to-air missiles, a .12.7mm (50 caliber) machinegun, radar and laser range finder. The hummer has a turret mounted on the back that contains two missile pods (each containing four Stinger anti-aircraft missiles). Under one pod there is an M3P .50 caliber machine gun. The weapons operator has use of a FLIR (night vision) and a laser range finder. The Avenger machine-gun can't be depressed sufficiently to fire at ground targets towards the front of the vehicle. The Stinger has a range of 4.5 kilometers. Effective range of the .50 caliber machine-gun is more like two kilometers.
Taiwan could not afford to replace its Chaparrals with Avengers and preferred the longer range of the MIM-72 missile, especially one upgraded to perform like more modern heat seekers. Several years later Taiwan realized that the growing Chinese military threat made the updated Chaparrals much less useful and NASAMS seemed like a more useful and affordable approach for a replacement system.