The FAA last month issued another airworthiness directive related to the Primus Epic avionics system, this time calling for GIV and GV operators to revise their flight manuals to include crew procedures should the cockpit displays go blank.

Honeywell, maker of the Primus Epic PlaneView and EASy cockpits installed in new Gulfstreams and Dassault Falcons, is developing a software modification that will address the glitches that are the subject of the ADs. Gulfstream has already issued similar flight manual revisions for operators of the G350, G450, G500 and G550, which were targeted in an earlier AD. This latest action, effective March 13, covers the earlier Gulfstreams affected by the malfunctions.

This most recent AD was prompted by a report that all four cockpit flight displays simultaneously went blank during flight in a GV-SP. The displays did not recover until the crew pulled the circuit breakers associated with the displays, after which three of the afflicted screens again started functioning normally. An initial investigation revealed discrepancies with the “reversion logic” of the advanced graphic modules that drive the displays. Similar failures occurred during ground testing, leading the FAA to conclude that urgent action was needed.

The AD requires flight manual revisions that describe new procedures for crews to follow in the event that the flight displays go blank or malfunction. Also affected are weather minimums, which have been increased to mitigate the potential effects of display failures on takeoff or landing, the FAA said.

Earlier airworthiness directives issued a year ago pertained to EASy-equipped Falcon 900EXs and 2000EXs, PlaneView-equipped Gulfstreams and the Embraer 170. The ADs called for integrity checks of the aviation standard communications bus (ASCB) and installation of avionics software updates.

The FAA at the time said it issued the ADs after engineers discovered that ASCB faults could lead to a near total system shutdown of the Primus Epic system in flight, causing all the cockpit displays to show invalid information–or go blank–and disrupting autopilot, autothrottle, radio communications and other cockpit functions. The directives also required changes to the aircraft flight manuals with instructions on how to deal with the malfunctions.