Sandra - A New Concept for Management of Fault Isolation in Aircraft Systems

Abstract

The embedded Fault Isolation functionality in the Saab JAS39 Gripen aircraft has been designed to accurately and reliably provide the technician with proposed maintenance procedures. A previously identified drawback and built in limitation has been the significant lead time for Fault Isolation functional changes based on aircraft operational statistics and line experience. With the Fault Isolation executing as compiled source code, changes and corrections require adaptation of the regular onboard systems computer software and careful planning of code and documentation releases, implying not only significant delays, but also high costs for necessary updates. The "Sandra" project aims at even further refine - and to introduce a state of the art - fault isolation maintenance concept for the Saab JAS39 Gripen aircraft. Based on an easy-to-use PC based graphical tool, Fault Isolation on dedicated aircraft monitoring and safety check result data is specified. Output in the form of design documentation artifacts, such as flowcharts and technical publications, is generated. The contained Fault Isolation object data is updated in parallel with the regular onboard computer software development process and the corresponding Loadable Data File will be delivered when convenient. The PC application constitutes the maintenance engineer's primary Fault Isolation design tool. The tool enables the maintenance engineer to select dedicated settings via a graphical user interface and use logical expressions to propose detailed and specific maintenance actions to be performed by the aircraft technician. The tool is capable of verifying a complete set of design documents towards the content of a generated loadable file. Thus, a generated output file with a minimum of additional verification can be delivered to be loaded into the aircraft. This new approach implies that the lead time for a Fault Isolation functional change can be reduced by as much as 80 %. The cost for the corresponding functional change will decrease by more than 50 %.