Airborne electronic hardware design assurance : a practitioners guide to RTCA DO 254 Preface This book was inspired by and evolved from the experience we gained while teaching the DO 254 class at RTCA in Washington D.C. and at numerous companies throughout the United States and abroad. In some respects it is the logical extension of our DO 254 class and in fact some of the material in this book shares common origins. Most of this book however is a testimony of the lessons learned and wisdom gained from many years of first hand experience in the design verification and approval of airborne electronics and software including some of the very first projects in which DO 254 was applied and also including the very first projects where DO 254 was applied at the LRU level. The early years of DO 254 were seminal to us for revealing not only the difficulties inherent in applying a comprehensive document like DO 254 to a very narrow target but also for the labor pains endemic throughout the industry as it struggled to understand let alone comply with this new way of doing business. Pain is a hard but effective teacher so by any measure those of us who experienced those years should be geniuses by now. As we and the rest of the industry adjusted and eventually mastered both the document and its ramifications we were able to discern the practices and techniques that complemented the processes in DO 254 and therefore worked best in this new environment. This book documents the practices and techniques that we have identified and witnessed as being compatible with the intent of DO 254 and which thus make the road to compliance and eventual approval as direct efficient and effective as possible