After publishing a series of airworthiness directives earlier this year aimed at operators of certain aircraft equipped with Honeywell Primus Epic avionics, the FAA last month added the Cessna Citation Sovereign to the list of airplanes affected by the directive. This latest Primus Epic AD, published on April 14, inserts the Citation Model 680 onto a previous list of ADs covering Dassault Falcon 900EXs and 2000EXs with EASy cockpits, Gulfstreams with PlaneView avionics and the Embraer 170 regional jet. The ADs require installation of avionics software updates to correct faults that could cause flight displays to show invalid information or go blank, according to the FAA.