A common problem in weapon system acquisition programs is the definition of Special Test Equipment (STE) requirements too late to incorporate an efficient interface between the system, STE, and subcontractor-supplied subsystems. When the STE considerations are ignored until the design is well-established, efficient module and test point partitioning, and a well-thought out tradeoff between automation and BIT is not incorporated into the product design. The acquisition manager then is faced with one of two alternatives: (1) proceed with the design "as is," ignoring well-founded test requirements; or (2) undertake a redesign effort that alters a proven system configuration to accommodate STE requirements that should have been addressed during FSD. Either choice leads to increased cost, schedule slippage, and risk of degradation of system performance in production hardware.
An STE approach should consider tradeoffs between the use of "off-the-shelf" test equipment and STE. These tradeoffs most efficiently can be assessed when the product design remains fluid. STE development should include a tradeoff analysis to determine what test functions only can be accomplished using STE. "Off-the-shelf" test equipment that can accommodate any necessary test functions also should be identified in the tradeoff analysis. Optimum use of "off-the-shelf" test equipment optimizes the balance between contractor's capital investment and the government's investment in STE development. Failure to consider these tradeoffs results in needless increases in system acquisition cost.
A thorough factory test plan should be developed before the design of the system is completed. In addition, a realistic production-rate analysis need to be completed to avoid test equipment shortages (or overbuying). Such an analysis should include yield estimates that can be expected in various phases of product development and production including potential field returns. The factory test plan and the production-rate analysis should be major inputs in the test requirements definition. Design engineering should concur on the test requirements and test approach before the design configuration is frozen.
Specific engineering tasks that are conducted during STE development include a test tolerance funneling scheme that reveals problems at the lowest functional level, but does not cause excessive rejection at final acceptance. STE engineering should also (1) use design strategies that simplify modification to tolerance limits and enable tests to be readily added and deleted, (2) provide for a manual intervention capability in automated test equipment so that manual test equipment can be used if software problems do occur, and (3) provide for adequate test equipment engineering and maintainability engineering input to the system design and include optimum functional partitioning for ease of test.
Today's state-of-the-art test equipment requires software programming. Adequate time should be afforded for test equipment software debugging and compatibility verification. The use of a "proof of design" model to assist in software debugging, test equipment compatibility, and accuracy is encouraged. A collocated engineering team (STE engineering and system engineering) enhances tradeoff analysis, facilitates analysis of the test approaches for completeness, and improves the efficiency of communication necessary to correct any test escapes inadvertently generated from performance-oriented design changes.
Management decisions will be needed to determine the capital investment needed to accommodate these new requirements. In batch manufacturing operations, the test equipment hardware already exists on the factory floor. The use of such test equipment, therefore, requires a minimum investment; only costs for software programming peculiar to the item being tested are normally incurred. When the test operation on the factory floor is made efficient, production costs are lowered and rapid return on the investment in test equipment (STE or "off-the-shelf") is realized. Therefore, the maximum use of test equipment available on the factory floor should be used. When test requirements are determined, a list of "off-the-shelf" equipment that can meet those requirements should be developed. That list, when compared to the inventory of test equipment on the factory floor, will identify areas where capital investment by the contractor, or the development of STE (requiring additional investment by the government) is warranted. The same list of test equipment also is useful to the government in planning for logistic support requirements. Test requirement definition and STE tradeoff analysis should be completed early while the design is fluid and compatibility between the system and STE can be optimized. An STE plan should be established that allows for integration of STE activities, with both the design and manufacturing planning activities (particularly tooling design activities) being executed concurrently.
Just as the weapon system requires attention to design discipline, so does the development of STE. The definition of sound test requirements is essential. Requirements for STE development should be addressed in the contract statement of work for both the prime contractor and all subcontractors. Just as weapon system development requires careful attention to a discipline design process, so does the development of special test equipment. STE should be designed, qualified, and used as early as possible to ensure a uniform final test from development through production transition. STE development should commence concurrent with weapon system development, and qualified STE should be used during the final product test on all deliverable hardware.