Explicate '78: Uncovering the Implicit Assurance Case in DO-178C

For about two decades, compliance with Software Considerations in Airborne Systems and Equipment Certification (DO-178B/ED-12B) has been the primary means for receiving regulatory approval for using software on commercial airplanes. A new edition of the standard, DO-178C/ED-12C, was published in December 2011, and recognized by regulatory bodies in 2013. The purpose remains unchanged: to provide guidance 'for the production of software for airborne systems and equipment that performs its intended function with a level of confidence in safety that complies with airworthiness requirements.' The text of the guidance does not directly explain how its collection of objectives contributes to achieving this purpose; thus, the assurance case for the document is implicit. This paper presents an explicit assurance case developed as part of research jointly sponsored by the Federal Aviation Administration and the National Aeronautics and Space Administration.