System Software Safety Assessment Process for Certification of Commercial and Military Aircraft

Abstract

For the next 10 years new world-wide communication, navigation, and surveillance (CNS) requirements are being incrementally imposed upon military aircraft avionics, and upon the Air Traffic Control community, by the Aviation Administrations of most nations, including the FAA and the JAA. These requirements are the result of a decade of study by the United Nations' International Civil Aviation Organization (ICAO) to improve aviation safety and efficiency. In 2001 the USAF mandated compliance to the CNS requirements for its military aircraft, which is called Navigation Safety (NS) GATM by the USAF. By complying with these requirements, the military aircraft can maintain their ability to fly internationally without CNS restrictions. The FAA requires that flight software be assessed, developed and/or verified (proven) with a methodology recommended by the RTCA document called DO-178B for software based systems. This has posed a big challenge to the stakeholders of the military aircraft since typically all legacy software for the military aircraft has been developed using military software standards like MIL-STD-498 and MIL-STD-2167. Although there are similarities in the software processes and documentation among the commercial and military standards, military standards typically lack structured software safety related processes. This paper presents the software safety assurance (SSA) process utilized in commercial aircraft certification of digital systems and recommends an approach to the certification of military aircraft systems based on the strategic process objectives derived from the same.