Certification of an operating system as a reusable component

VxWorks/sup /spl reg// has been available as a Commercial Off-The-Shelf (COTS) Real Time Operating System (RTOS) for many years. It was not developed specifically for safety critical applications, but the expectation was that through careful "subsetting" of its functionality, the RTOS could be made suitable for safety critical systems. A project was undertaken to adapt the RTOS and to re-engineer certification evidence for it to be compliant with DO-178B objectives for Level A. This certification work was started in late 1999. There were no specific system requirements at this point in time because this was a COTS system. As the RTOS certification project was coming to an end, the Wide Area Augmentation System (WAAS) program selected VxWorks/Cert to become the COTS operating system that supported the application. A Board Support Package (BSP) for a PowerPC based single board computer was identified; some extensions to the RTOS libraries were also identified; and the combination was subjected to the rigors of certification (or in the case of this ground based system the rigors of approval).