Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to all Honeywell FMSs served by Honeywell NZ-2000 navigation computers and IC-800 integrated avionics computers. The existing AD currently 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 proposed AD would require uploading new software, which would terminate the existing requirements. This proposed AD results from reports of in-flight unannunciated shifts of computed position in airplanes with the subject FMS computers. We are proposing 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.