PDAS home > Contents > SNEAK
Public Domain Aeronautical Software (PDAS)  

Input to this program consists of data representing the circuit to be analyzed. The data is prepared by converting the schematic of the circuit into a "wire list". In this wire list all switches are assumed closed with special circumstances, e.g. double throw switches, being noted as switchable continuity. The output consists of any paths that meet the criteria for sneak circuits. These areas of suspicion must then be submitted to manual analysis, but the number of paths to be analyzed is greatly reduced by the criterion of opposing power and ground. Post-analysis consists of checking switch logic to sift out paths that cannot be switched on and then determining any systems effects of the remaining possible sneak circuits. The computer output is designed to present the path tracing information in a format that readily assists manual analysis of the suspected sneak circuits.

The automated sneak circuit analysis is accomplished in three processing phases. The first phase is the data reduction phase. In this phase the "wire list" is generated. Input may be in several different formats and even segmented such that separate groups or contractors may prepare "wire lists" covering subsystems with discontinuities at interfaces. The "wire list" is merged with an in-line disconnect table establishing continuity at the interface between any subsystems. This "wire list" is then reduced to an ISAM file containing a branch cross-reference table, in which each to-node/from-node branch is uniquely identified and stored with its associated characteristics. The second phase is the path derivation phase. In this process the data in the branch cross-reference table is used to examine all possible paths to see which meet the above mentioned two-fold criteria for a possible sneak circuit. The third phase is the path regeneration phase. The paths flagged are listed in branch sequence number and then in to-from connector sequence. The output report generated is in a highly usable format that allows the engineer to verify the suspected sneak circuit path by locating the wire segments on the circuit schematic drawings.

Potential users of this package are informed that this is not a ready-to-use system. Although the documentation is massive, certain aspects of the system such as preparation of input data from schematics are not explained in a convenient, detailed format. Users will have to intensively review the manual and the code itself to gain full knowledge of the operation of the sneak program. Neither training nor technical assistance in the use of this program can be provided by COSMIC or NASA. (Boeing Co.)

This program was released by NASA through COSMIC as HQN-10517. The italicized text above is from the official NASA release.

PDAS home > Contents > SNEAK
Public Domain Aeronautical Software (PDAS)