AD/FMS/3 Honeywell NZ-2000 and IC-800 Navigation Computers (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Flight Management Systems

AD/FMS/3 Honeywell NZ-2000 and
IC-800 Navigation Computers 6/2007 DM

Applicability:	Honeywell NZ-2000 navigation computers approved under United States Federal Aviation Administration (FAA) Technical Standard Order (TSO) TSO-C115a and IC-800 integrated avionics computers approved under FAA TSOs C9c, C52a, and C115a.
Note 1:  These computers are known to be installed on, but not limited to, the following Transport Category aeroplanes:
Manufacturer Bombardier, Inc Dassault Aviation Gulfstream Aerospace Corporation Lockheed Raytheon Aircraft Company	Model CL-600-2B16 (CL-601-3A, CL-601-3R and CL-604) Mystère-Falcon 900 G-1159A, G-IV and GV 382G series BAe.125 Series 800A (including C-29A and U-125) Hawker 800XP and 1000
Requirement:	1.    Determine if the installed NZ-2000 navigation computers and IC-800 integrated avionics computers serving flight management systems (FMS) have computer part numbers and software modification levels identified in Honeywell Technical Newsletter (TN) A23-6111-008, Revision 001, dated 22 February 2007.
Note 2:  For purposes of this Directive, aeroplanes with FMS computers having a part number and software modification level identified in the newsletter are "affected aeroplanes.''
2.    For any affected aeroplane, revise the Limitations Section of the applicable Aircraft Flight Manual (AFM) to incorporate the information included in Appendix A of TN A23-6111-008, Revision 001.  This may be accomplished by inserting a copy of Appendix A of the newsletter into the AFM.
Note 3:  FAA AD 2007-07-12 Amdt 39-15009 refers.
Compliance:	For Requirements 1 and 2 - Within 14 days after the effective date of this Directive.

This Airworthiness Directive becomes effective on 18 April 2007.
Background:	The FAA has received reports of in-flight unannunciated shifts of computed position in aeroplanes with Honeywell NZ-2000 navigation and IC-800 integrated avionics computers serving Honeywell FMSs.  The computed position shift, attributed to a software design error induced during a previous software modification, occurs when the number of inertial reference units (IRUs) supplying data to the FMS degrades from 3 to 2 or from 2 to 1, or increases from 2 to 3 or from 1 to 2.
If the FMS system is coupled to an autopilot or flight director system, this shift in the FMS computed position could result in uncommanded deviations from the intended flight path of the aeroplane and, if those deviations are undetected by the flight crew, compromise terrain and/or traffic avoidance.
This Directive requires affected units to be identified and, if necessary, introduces a temporary revision to the AFM Limitations Section.  This is an interim action, as the manufacturer is currently developing a modification that will address the unsafe condition.

David Punshon
Delegate of the Civil Aviation Safety Authority

5 April 2007