The FAA issued a new Airworthiness Directive today that warns of a failure by the flight guidance control system (FGCS) in certain Embraer E170s and E190s to display some “caution” messages when warranted. Embraer has found that that certain Honeywell Primus Epic software loads–namely, versions 17.3, 17.4, 17.5, 17.6 and 17.7 installed in the E170 and versions 4.3, 4.4, 4.5, 4.6 and 4.7 installed in the E190–triggered the failures. If the failure of one FGCS channel during a given flight goes undetected and another failure occurs on the second FGCS channel, the system’s autopilot could issue a hardover command, causing a sudden roll, pitch or yaw movement and reduced controllability of the airplane, according to the AD.

The AD takes effect on October 2. It requires that operators perform a functional check of the FGCS channels engagement within 300 flight hours of that date and then at least every 600 flight hours thereafter until they install Primus Epic software version 19.3 or higher. The AD requires operators to install the new software within 10 months of the effective date.