ARINC Report 847: Product Development Guidance for Maintainability and Testability (PDMaT) is intended to be used as guidance to enhance the design of avionic equipment, with a focus on maintainability and testability characteristics. It is a separate and parallel standard to ARINC Report 607: Design Guidance for Avionic Equipment. This document does not represent the complete formula for successfully designing and manufacturing avionics equipment or system. It does present the vision of the airline community based on extensive experience gained through the use of such equipment. It is intended to provide information that would be useful in devising the necessary foundation to develop superior products through design philosophy as well as recommended practices in the design and conception of systems that should be beneficial not only to the equipment manufacturer designing avionic equipment, but also for the airframe manufacturers in incorporating avionic equipment into aircraft systems.