Abstract: An avionic tray has a base plate for supporting a line replaceable unit (LRU) and a plenum beneath and substantially coextensive in length with the base plate to provide for discharge of coolant air from the plenum into the LRU. The base plate has an opening leading to the plenum and the cylindrical casing of a motor driven fan is coupled to the base over the hole for air from the fan to be discharged into the plenum. The outlet end of a ram tube is coupled coaxially with the fan casing to increase the volume that would be delivered without the ram tube. The inlet end of the ram tube is preferably cut at an angle relative to a plane to which the axis of the tube is perpendicular so the inlet is elliptical rather than circular. The fan is mounted to a special transition adapter in some cases. The adapter is configured to provide a clearance space for cables that run out of the rear side of a connector block on whose front side connector prongs on the LRU are inserted.