The inadequate annual/100-hour inspection of the engine by the mechanic for his failure to properly secure the tailpipe assembly to the turbocharger resulting in separation of the tailpipe and subsequent in-flight fire. Contributing factors in the accident were the inadequate design of the plastic brake line in the cockpit adjacent to the firewall by the airplane manufacturer, and the inadequate certification of the airplane by the FAA for failure to take into account radiant heat when designing components aft of the firewall.