Replacing an obsolete test system with modern, PXI-based hardware without incurring a costly recertification process.
Ontic supports more than 6000 legacy avionic, electrical and hydromechanical products across civil and military aircraft the world over. Its business model is not to develop new products; instead, it purchases or licenses ageing product lines from a multitude of OEMs. Each product adoption typically comes with associated test systems which have been developed according to that company’s test strategy at that particular time. This results in a huge range of test architectures which in turn use an even larger range of bespoke and COTS components, much of which are obsolete and with a very limited source of available spares or support. In parallel with this, the test systems that Ontic adopts are typically provided with little or no information about their provenance, their function or how they should be maintained leading to the situation that, when failures occur, it can be a costly and time-consuming process to get the test system back on line.
Recognising the risk that test equipment failure poses to its ability to meet business objectives such as production and repair demands, Ontic called on Spherea to investigate the options available to it. We began by auditing all major test systems at the Bishops Cleeve (UK) site, looking at technical aspects such as general architecture, instrumentation, known issues, documentation and spares status but also project and commercial aspects, such as project duration, life expectancy of the current system, risk of failure, perceived criticality and product throughput. On a technical level we found common issues across the board with controllers, instrumentation and a wealth of bespoke, mostly undocumented, PCBs together with a large number of test cables that were typically one-offs. Our survey report contained recommendations for quick fixes alongside a proposal to introduce test platform commonality (to ease long-term support costs), refurbishment of some items and the implementation of a common core test system based on a hybrid PXI solution.
Six platforms were identified as having sufficient throughput, complexity and commonality to be candidates for the development of a new common core platform. Of these, the Typhoon Fuel Probe was selected to launch the development, the existing system suffering from reliability and obsolescence issues whilst being critical to the delivery of a high volume of units for many years to come. In all, four test sets were built – three to provide test means for both sensor characterisation and final ATP test of probe assemblies, with the fourth being used as a development platform to prove the design and to develop future upgrades and modifications both of the Typhoon systems and other of other future core platforms.
The first task was to identify the test needs of each Test Programme Set (TPS) in the absence of any clear documentation or source code. We achieved this by attaching sniffer devices to the existing test system whilst in operation to understand which instrument command sets were being used. Our colleagues at NI reviewed the command sets and TPS accuracies to determine which PXI instruments were best suited to meet test requirement needs, all the while cross-referencing data with other expected common core candidates for the future.
Rehosting the existing software with a modern version was deemed impossible due to a strong desire to avoid the costs and duration of recertification. Lack of known source code, and undocumented changes since the system had been initially fielded were also major risks to this approach. To resolve this, we used our proprietary TIMS and TILS products to emulate the older instrumentation utilising the new resources allowing the older software to fully run onto the new hardware without affecting performance.
