Harmonizing ARINC 653 and Realtime POSIX for Conformance to the FACE Technical Standard

The avionics industry is converging toward the next generation of software standards produced by The Open Group via the Future Airborne Capability Environment (FACE) consortium and related FACE Technical Standard. The standard combines ARINC 653, a previous avionics standard, with subsets of POSIX 1003.1 that are closely aligned with the POSIX realtime profiles PSE52, PSE53, and PSE54. In this paper, we describe our approach to design, implement, and certify a system with FACE Conformance to the FACE Operating System Segment Safety Base profile. Our approach integrates the ARINC 653-compliant Deos with RTEMS, an open-source real-time operating system (RTOS). Our goal in combining Deos/RTEMS was to achieve certification of FACE Conformance in a low-cost manner by relying on existing, mature software that already provides the majority of the functionality required by the FACE Technical Standard. We reached our goal with under 10,000 source lines of code (SLOC) written to integrate RTEMS into Deos and implement any additional POSIX application programming interfaces (APIs) and tests needed for certification.