You may have noticed we’re generally a fan of evolutionary versus revolutionary development of weapons. The M247 SGT York Divisional Air Defense System or DIVADS should have been a prime example of this evolutionary approach, but was instead a poster child for failed weapons development programs.
By the late 1960s and early 1970s the M163 Vulcan was increasingly obsolescent as the Short Range Air Defense platform for the protection of the maneuver forces of a heavy division. With an effective range of only about 1200 meters, the Vulcan couldn’t be relied upon to engage Soviet attack helicopters attacking with wire guided anti-tank missiles from up to 3000 meters. The Army had the MIM-72 Chapparal missile system to overcome this range deficit, but the Sidewinder based missile had a much longer reaction time than any gun based system, too long to effectively engage helicopters in the 20 to 30 seconds a Sagger missile attack might take. The Chapparal, with its early generation seeker head, also had trouble locking on to head on attacks. Finally, both the Chapparal and the Vulcan, based on the M113 hull, had trouble keeping up with the new M1 and M2/M3 vehicles on the battlefield.
The Army requested proposals for a radar directed gun system in the 30mm to 40mm range. The Army had already prioritized its spending to support acquisition of “The Big Five” programs*, so money for development of any other systems would be tight. The RFP urged contractors to use as many off-the-shelf components as possible. About half a dozen contractors submitted proposals, and eventually General Dynamics and Ford Aerospace were awarded development contracts to build prototype systems. After a controversial shoot-off, Ford Aerospace’s entry was selected.
Ford’s entry, named the M247 Sgt. York, used a surplus M48 Patton tank hull, a newly designed turret mounting twin Bofors 40mm L/70 cannons, and a search and track radars. The track radar was derived from the APG-66 radar of the F-16.
The choice of a derivative of the APG-66 proved problematical almost immediately. Remember, the APG-66 had been designed for the air to air environment. At ground level, it suffered greatly from ground clutter, making it very difficult for it to distinguish targets against the back ground of trees, rocks, buildings, powerlines and moving vehicles. This was the early days of digital radar signal processing and fire control. Programmers had little experience in designing software to work in such a difficult environment, and further, there were very real limits on the computational power in early digital radar signal processors. The General Electric proposal had used a radar system derived from the Navy’s Phalanx guns system, which was designed to work in a cluttered surface environment. Whether it would have been easier to adapt is an open question.
Further, the while mounting an aircraft radar on a tracked vehicle exposes it to stresses far different from on an aircraft. Vibration and dust are killers to delicate electronics, and the radar system suffered from reliability issues.
The Army was pretty much forced by fiscal restraints to use the M48 hull, but that had its own costs. The M48 was never as fast as the M1 and M2/M3 vehicles it was supposed to protect. The new 20 ton turret actually weighed more than the original tank turret is replaced, placing further strain on its performance. Apparently, hydraulic leaks in in the turret were a fairly common occurrence as well.
Initial production began, and work to alleviate the problems continued, but it eventually became clear that no (reasonable) amount of money would overcome the flaws in the design. The gun/radar combination never achieved any great success in destroying targets, even under the most benign testing.
Eventually, in 1985, the program was cancelled. About 50 systems had been built. Most were eventually used as targets on Air Force bombing ranges, but some were donated as museum pieces.
The need for a short range air defense system hadn’t disappeared, but given the other needs of the Army, funding for a replacement program was still a low priority. After an aborted attempt to procure the ADATS (Air Defense/Anti-Tank System) missile mounted on an M113 chassis, the Army eventually settled on mounting Stinger missiles on a Humvee chassis as the Avenger system, and on the Bradley as the M6 Linebacker system. The collapse of the Soviet Union meant by the mid 1990s, the perceived need for short range air defense had lessened, and the M6 Linebackers were withdrawn from service, many to be rebuilt as B-FIST fire support team vehicles. Current short range air defense for heavy brigade combat teams rely on Avenger systems and shoulder fired Stinger missile teams.
The Army realized it was taking a higher risk approach to the DIVADS problem by trying to adapt components designed for one purpose to a new mission, and compressing the development timeline. They failed, however, to conduct a realistic risk assessment, and when the program showed obvious shortcomings, the threw good money after bad in an effort to save the program. They could have learned a lesson aviators have been relearning since the Wright brothers- don’t attempt to salvage a bad approach. Go around.
*The Big Five were the M1 Abrams, the M2/M3 Bradley, the UH-60 Blackhawk, the AH-64 Apache, and the MIM-104 Patriot.