The Procrustean bed of 1750A and 1553

WASHINGTON - The MIL-STD 1750A computer and MIL-STD 1553 databus stand a good chance of surviving longer than Roger Maris`s 37-year-old single-season home run record.

by John Rhea

WASHINGTON - The MIL-STD 1750A computer and MIL-STD 1553 databus stand a good chance of surviving longer than Roger Maris`s 37-year-old single-season home run record.

Both technologies emerged from the U.S. Air Force`s Avionics Laboratory, Wright-Patterson Air Force Base, Ohio, in the early 1970s. This was the same time the microprocessor was independently making its appearance in Silicon Valley, and both standards have remained virtually unchanged while microprocessors have proceeded through a series of generations with apparently no end in sight.

The idea of creating new systems architectures out of standard building blocks of computers and databuses was revolutionary in its time. It still is. The problem is that systems designers today find themselves enmeshed in a 35-year-old Procrustean bed. Unlike the ancient Greek innkeeper Procrustes, however, who had a one-size-fits-all bed and chopped the legs off of people who were too tall and stretched the people who were too short on a rack , the systems designers must look to the rack and stretch the current architecture.

The amount of data traffic needed within military platforms to handle the ever more complex sensor inputs and to generate real-time situational information for the warfighter has been growing at a comparable rate to the vehicular traffic on the nation`s highways. Without the equivalent of an Interstate Highway System, convoys of 18-wheelers are clogging two-lane roads.

The underlying problem is that both military standards are final destinations and offer only limited growth paths. Designers can either add more computers and databuses, - a costly step - or try to scrap the architecture entirely and implement new technologies in more capable architectures, an even more costly step. The reality is that new architectures are likely to be introduced incrementally in clean-sheet-of-paper designs, such as the Joint Strike Fighter and Future Scout Cavalry System (FSCS), and then eventually retrofitted onto existing platforms as opportunities arise.

Even before the revolutionary innovations at the Avionics Lab, the U.S. Navy had implemented the same basic idea in its ships with the AN/UYK series of onboard computers and the Naval Tactical Data and soon specified its own all-purpose airborne computer, the AN/AYK-14. From the beginning there were multiple sources for all of these systems, and they are all still performing their tasks at sea. Since ships are larger than aircraft, it`s easier for the Navy to rip out old cabling and install modern architectures, but, like the Air Force, the Navy takes the sensible attitude that, if it ain`t broke, why fix it?

At the same time the Air Force was pressing ahead with the 1750A and the Navy was following suit with the AYK-14, the U.S. Army explored the possibility of creating a new family of computers of its own. The idea, known as the Modular Computer Series, or MCS, was even more Procrustean than those of the other services. The MCS was destined for every Army platform: tanks, helicopters, armored personnel carriers, missiles, and even the emerging technology of smart munitions. Based as it was on 1970s vintage component technology, MCS over the years would have required a Herculean task of chopping and stretching to meet all the users` needs.

In fact, that`s what killed MCS. Although a number of observers at the time (including me) thought this would be the last word in achieving interoperability and economies of scale, MCS failed because it could never find a champion within the Army. By trying to be all things to all people, it wound up being no things to no people. That lesson is worth remembering today.

The MCS failure may have been a blessing in disguise. Although a number of alternate sources would have built the computers to the MCS standards, this approach would have involved a proprietary architecture with severely constrained growth opportunities. Lacking a standard of its own, the Army was able to shop around and choose the best solutions from the other services and from eager hardware vendors.

An example of how this continues to work in practice is offered by retired U.S. Amy Col. Chris Cardine, the former program manager on the Abrams and Bradley upgrades at the Army`s Tank Automotive Command (TACOM), Warren, Mich. He`s perfectly happy with 1553 and says it`s good for at least another 10 years. Cardine praises General Dynamics Land Systems, Sterling Heights, Mich., for what he calls a "brilliant design" that gets the maximum performance out of the 1553.

The shopping around part represents the real payoff, according to Cardine. TACOM has multi-year contracts with some 250 contractors for the vetronics and other subsystems used in the Army`s tanks. These independently managed contracts represent 54 percent of the total value of the tank, he adds, and the subsystems are provided to General Dynamics Land Systems as government-furnished equipment, a method Cardine maintains has reduced tank prices by 20 percent.

Fiber-optic databuses will eventually be needed, according to Cardine, as the Army moves increasingly to battlefield video. He cites the FSCS and the Crusader artillery system as possibilities. However, despite the inherent advantages of optical fibers in reducing vulnerability to electromagnetic interference, it`s still cheaper and easier to encase the copper wires with protective cabling, he says.

That`s fine for ground vehicles and ships, where weight is not a pressing problem, but how about aircraft? Or spacecraft, where weight, volume, and power are even greater limitations? Also during the 1970s, the U.S. Marine Corps experimented with optical-fiber databuses in its AV-8B Improved Harrier and successfully demonstrated their utility in a non-mission-critical application involving some cockpit gauges. This was a useful exercise for the engineers at McDonnell Douglas in St. Louis (now part of the Boeing organization) since they had never worked with fiber-optic databuses before. That experience is still available to designers of all military platforms, as is Boeing`s own use of optical fibers in commercial aircraft.

The 1750A and 1553 standards still have the momentum, but designers will eventually want to move beyond the Procrustean approach and design new beds rather than trying to rearrange the sizes of their occupants. In engineering, as in athletics, records are expected to be broken.

More in Home