There are many design decisions and compromises to be made in the course of developing a new piece of avionic equipment. The specifications prescribed by the contractual requirements leave room for a wide range of engineering practices to meet not only the performance, cost and schedule, but also the reliability and maintainability requirements. Only with an understanding of the ultimate fleet environment and its effects on avionic equipment can these engineering practices include design characteristics that will result in equipment that will best survive and operate in that "real world" environment. Throughout the developmental period, the materials specialist, the metallurgist, the reliability and maintainability engineers, and the electronic design engineers must all understand the environmental implications and interact fully among these disciplines. The design techniques discussed in this section are a summary of recommended "DO's" and "DON'Ts" based on features that have displayed significant impact on the durability and reliability of avionic equipment in fleet service.