Expanding the trade space: an analysis of requirements tradeoffs affecting system design - Tutorial

Acquisition Review Quarterly, Wntr, 2002 by Mark W. Brantley, Willie J. McFadden, Mark J. Davis

A final example regards the parts commonality among FMTV variants. Ideally, we do not want to maximize the commonality of a system but instead maximize the benefits of the system and minimize the costs through repair parts commonality. The potential benefits of commonality include reduced costs associated with purchasing and stocking repair parts, reduced training on different variants for mechanics, and reduced costs associated with developing and producing maintenance manuals. These are all monetary cost benefits.

However, the ability to achieve the monetary benefits of commonality is offset by other systems. For instance, these monetary costs are impacted by the reliability of each subsystem or component; the supply system and its associated costs of purchasing, stocking, and replacing these subsystems and components; the production system for the vehicle; and the fielding plan (system) for the vehicle. Ultimately, any benefits gained through commonality may be lost due to monetary cost increases in other systems in the FMTV's life cycle.

Parts that are readily available on the commercial market, have a high reliability, or are not mission critical (and hence may not be important to stock in large quantities) could also dilute the anticipated monetary benefits of commonality. We also will not achieve many benefits unless the vehicles are produced and fielded in a manner requiring commonality. Again the interplay of system-to-system interaction is a critical aspect to effective analysis of the FMTV program. Trade space analysis of these critical systems would help decision makers understand whether commonality would truly yield substantive cost savings to warrant its inclusion in the FMTV program. The benefits associated with solving this complex problem justify an extensive M&S effort to answer this critical question for this program.

TIMELY DECISIONS

In a perfect world, all of our decisions would be as easy as the process we used to narrow the range of values for the width of the vehicle. In reality, as we analyze the trade space interactions and determine the decision criteria, we are constructing what can be referred to as a core methodology for the system. This is a representation of "all logical and physical relations between variables representing the decision problem being examined. It defines a set of feasible solutions but does not contain any preferential structure" (Granat & Makowski, 1999, p. 2). Decision makers provide this preferential structure by defining the importance of the trade space elements. The sheer complexity of most problems will not permit a brute force check of all possible combinations and degrees of importance of the trade space elements. The challenge is identifying, refining, and analyzing the critical set of trade space elements from which to select a robust solution. This is predicated on timely decisions on performance and mission criteria and metrics. It also requires clearly designated decision makers, determining the times to make decisions, and establishing methods to help make the decisions.