Airworthiness Directives; Honeywell Flight Management Systems (FMSs) Served by Honeywell NZ-2000 Navigation Computers Approved Under Technical Standard Order (TSO) TSO-C115a, and IC-800 Integrated Avionics Computers Approved Under TSOs C9c, C52a, and C115a; as Installed on Various Transport Category Airplanes

The FAA is adopting a new airworthiness directive (AD) for all Honeywell FMSs served by Honeywell NZ-2000 navigation computers and IC- 800 integrated avionics computers. This AD requires identifying affected computers by part number and software modification level and revising the Limitations section of applicable airplane flight manuals to provide procedures for retaining optimum position determination and intended navigation. This AD results from reports of in-flight unannunciated shifts of computed position in airplanes with the subject flight management system (FMS) computers. We are issuing this AD to prevent a shift in the FMS computed position, which could result in uncommanded deviations from the intended flight path of the airplane and, if those deviations are undetected by the flight crew, compromised terrain/traffic avoidance.