AD/A330/89 Flight Control Primary Computer (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.

Airbus Industrie A330 Series Aeroplanes

AD/A330/89 Flight Control Primary Computer 10/2008 DM

Applicability:	A330 aircraft, models -201, -202, -203, -223, -243, -301, -302, -303, -321, -322, -323, -341, -342 and -343, all serial numbers, with Airbus modification 49144 (install rudder fly by wire) embodied during production.
Requirement:	The following operational limitation is required:
Dispatch restriction: Dispatch with the FCPC “PRIM 3” inoperative (item numbered 27-93-01-C) in the associated MMEL) is prohibited.
Note 1:  This operational limitation is covered by Temporary Revision (TR) A330 TR 01-27/04Z Issue 01 of the Master Minimum Equipment List (MMEL).
Incorporation of the appropriate MMEL TR or inserting the above dispatch restriction or a copy of this Directive into the Aircraft Operations Manual (AOM) and strict adherence to above dispatch restriction by the flight crew is acceptable to comply with the requirements of this Directive.
Later revision accepted by the European Joint Aviation Authorities (JAA) of the MMEL TR or any general MMEL revision including this dispatch restriction is acceptable to comply with the requirements of this Directive.
Note 2:  EASA AD 2008-0131 refers.
Compliance:	Before 6 August 2008.
This Airworthiness Directive becomes effective on 25 July 2008.
Background:	During a Back-up Control Module (BCM) retrofit campaign in accordance with European Aviation Safety Agency (EASA) AD 2006-0313 (AD/A330/68) requirements, some BCMs have been found with gyrometer screws unscrewed.  The gyrometer is installed on Delrin plate by internal screws and the Delrin plate is installed on BCM casing by external screws.  Investigations done by the manufacturer Sagem have shown that the root cause of these events is a lack of design robustness of the BCM.

When the aircraft is in control back up configuration (considered to be an extremely remote case), an oscillation of BCM output order may cause degradation of the BCM piloting laws, potentially leading to erratic motion of the rudder and then to possible impact on the Dutch Roll, which constitutes an unsafe condition.

This Directive aims to prohibit aircraft dispatch with FCPC3 inoperative (from GO IF to NO GO) as an interim solution.  Further mandatory action is expected to eliminate the root cause and alleviate the above operational restriction by the introduction of a BCM modification which is under development.

James Coyne
Delegate of the Civil Aviation Safety Authority

22 July 2008