AD/A320/212 Braking and Steering Control Unit (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 A319, A320 and A321 Series Aeroplanes

AD/A320/212 Braking and Steering Control Unit 5/2008

Applicability:	Aeroplane Models listed in Table 1 that are equipped with one conventional pre-Enhanced Manufacture and Maintainability (pre-EMM) Braking and Steering Control Unit (BSCU) part number (P/N):
a.     C20216332292C (standard 7) installed by Airbus modification 24449 during production or by Airbus Service Bulletin (SB) A320-32-1124 whilst in service, or
b.    C202163372D32 (standard 9) installed by modification 31106 during production or by SB A320-32-1227 or SB A320-32-1232 whilst service, or
c.     C202163382D32 (standard 9.1) installed by modification 32500 during production or by SB A320-32-1254 whilst in service.
Table 1
A319-111 A319-112 A319-113 A319-114 A319-115	A319-131 A319-132 A319-133 A320-111 A320-211	A320-212 A320-214 A320-215 A320-216 A320-231	A320-232 A320-233 A321-111 A321-112 A321-131	A321-211 A321-212 A321-213 A321-231 A321-232
Requirement:	1.    Modify or replace the BSCU in accordance with the instructions given in SB A320-32-1336, original issue, dated 19 September 2007, or later revision approved by the European Aviation Safety Agency (EASA) to install BSCU standard 10.
2.    Remove Dunlop 46x16-20 tyres part numbers (P/N) 11659 T and 11661 T.
3.    Dunlop 46x16-20 tyres P/N 11659 T and 11661 T may not be installed on any aeroplane equipped with a BSCU standard 10.
Note:  EASA AD 2008-0048 refers.
Compliance:	For Requirement 1 - Before 30 September 2009.
For Requirement 2 - Before further flight after accomplishing Requirement 1.

For Requirement 3 - As of the effective date of this Directive.

This Airworthiness Directive becomes effective on 8 May 2008.

Background:

The EASA has advised that during 2005 a lateral runway excursion occurred on an A320 aircraft.  Such excursions are classified as hazardous with a large reduction in safety margins.  Investigation has shown that the aircraft landed with the nose wheels rotated nearly 20 degrees from centre.  During subsequent tests on the removed BSCU, a BSCU hardware failure was found, affecting the monitoring function, including the system reconfiguration management, and leading to a runaway of nose wheel steering.

AD/A320/27 (Direction Générale de l’Aviation Civile of France Airworthiness Directive F-1992-117-025(B) Revision 1), mandated the BSCU upgrade in order to improve the steering logic, but this modification has shown not to be sufficient to address the identified failure mechanism.

A software modification is now implemented in BSCU standard 10 which improves the system reconfiguration management when this failure mechanism is detected.  BSCU standard 10 also includes other improvements as detailed in the associated Service Bulletin.

This Directive mandates the modification or replacement of the BSCU standard 7, 9 or 9.1 by the BSCU standard 10.  SB A320-32-1336 notes at paragraph 1.A.(2).(a) that BSCU standard 10 is not compatible with Dunlop 46x16-20 tyres P/N 11659 T and 11661 T therefore this Directive also requires that these tyres be removed when BSCU standard 10 is installed and prohibits the fitment of these tyres to aircraft with BCSU standard 10.

David Punshon
Delegate of the Civil Aviation Safety Authority

6 March 2008