<div class="htmlview paragraph">The civil aircraft market frequently employs propulsion systems originally developed and qualified for military aircraft applications. When this occurs, the civil sector benefits greatly from the lessons learned during the military engine development and qualification process. This paper presents the unique test experiences and lessons learned during development of the T406-AD-400 turboshaft engine that the GMA2100 turboprop, GMA3007 turbofan, and GMA1107 turboshaft engines will profit from for years to come.</div> <div class="htmlview paragraph">Some of these valuable T406 test experiences include: 1) development of engine attitude capabilities, 2) integration with a fly-by-wire control system, 3) incorporation of flight test experience into the engine design, and 4) utilization of unique test facilities.</div>