AIRWORTHINESS DIRECTIVE On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/AIRCON/14 Amdt 3 and issues the following 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. Airconditioning Equipment AD/AIRCON/14 Amdt 4 Zonal Drying System Regeneration 7/2009 Air Duct Overheat Applicability: CTT Systems AB Zonal Drying System P/N 1000-001, 2000-000, 2000-005, 2001-001, 2001-006, 3000-000 Rev.A, 3000-001, 3000-002 Rev.A and 3000-002 Rev.D. Note 1: These are known to be installed in, but not limited to, Airbus A330-243 and A330-322; Boeing 737-700, 737-800, 747-400, and 767-300 series; Bombardier CL-600-2B19; and McDonnell Douglas MD-11 series aeroplanes. The following STCs have been identified to be affected by the requirements of this AD. The approval list for the installation of the affected Zonal Drying System in Table 1 of this AD may be not exhaustive. In case the relevant aircraft are not listed therein, this does not exempt any aircraft having an affected Zonal Drying System P/N installed from compliance with this directive. Table 1. STC Number Issued by Holder Applicable to TA0259 LBA Lufthansa Technik AG Airbus A330-322 (s/n 120) LBA.21E2.TA0270 LBA Lufthansa Technik AG Bombardier CL-600-2B19 LBA.21E2.TA0307 LBA Lufthansa Technik AG Boeing 737-700 LBA.21E2.TA0609 LBA Lufthansa Technik AG Airbus A330-243 LBA.21E2.TA0636 LBA Lufthansa Technik AG Boeing 737-800 (See Note 2) TA0733 LBA Lufthansa Technik AG Boeing 747-400 SA 0003 NL RLD CTT Systems AB McDonnell Douglas MD-11 SA 0009 NL ** RLD CTT Systems AB Boeing 767-300 (See Note 3) EASA.A.S.02547 EASA CTT Systems AB Boeing 767-300 Z 21-74-01 FOCA SR Technics, TEC McDonnell Douglas MD-11 Z 25-20-77 FOCA Jet Aviation Basel, AG Boeing 737-700 (s/n 32627) Note 2: LBA.21E2.TA0636 was approved by EASA under Approval Number 2004-4416. Note 3: RLD STC SA 0009 NL has been superseded by EASA.A.S.02547 on 1 March 2006. Requirement: Switch off the Zonal Drying System installed in accordance with one of the STCs listed in Table 1 of the Applicability section of this AD and set system inoperative by pulling and securing the affected circuit breaker in accordance with relevant maintenance instructions. Terminating Action. On aircraft where the following STCs are installed, the actions detailed in this AD are no longer applicable and the Zonal Drying System accordingly modified can be re-activated. Table 2. STC Number Issued by Holder Applicable to EASA.A.S.03502 Revision 1 EASA Lufthansa Technik AG Bombardier CL-600-2B19 EASA.A.S.03504 Revision 1 EASA Lufthansa Technik AG Boeing 737-700 EASA.A.S.03505 Revision 1 EASA Lufthansa Technik AG Boeing 737-800 EASA.A.S.03506 Revision 1 EASA Lufthansa Technik AG Boeing 747-400 EASA.A.S.03507 Revision 1 EASA Lufthansa Technik AG Airbus A330-200 EASA.A.S.02547 Revision 2 EASA CTT Systems AB Boeing 767-300 EASA.A.S03738 EASA CTT Systems AB Boeing MD 11 EASA.A.S.03844 Revision 1 EASA Jet Aviation Boeing 737-100 IGW (S/N 32627) CTT Systems AB Information Letters IL06-01 dated 5 May 2006, IL06-02 issue 2 dated 8 May 2006 and IL06-03 dated 10 May 2006; and (for Lufthansa Technik STCs only) Lufthansa Technik AG Service Information Letter LHT 06-001, Revision IR dated 12 May 2006 pertains to this AD. The use of later approved revisions of these documents is acceptable for compliance with the requirements of this AD. Note 4: EASA AD 2006-0140R4 dated 17April 2009 refers. Compliance: Before further flight after the effective date of this AD, unless previously accomplished. This Amendment becomes effective on 2 July 2009. Background: One incident had been reported where the regeneration air ducting downstream of a Zonal Drying System P/N 3000-002, installed in a Boeing 747-400 aircraft, showed signs of premature material failure. As the root cause for the failure was initially not known, all other Zonal Drying Systems of similar design could have been affected by the same unsafe condition, the original issue of this AD mandated their de-activation. Investigation showed that such failure was caused by combustion of contaminants in the dryer unit. This amendment is issued following the development of a new dryer unit which removes this combustion risk. The installation of the new dryer unit is now approved through the EASA STCs listed in Table 2 of the Required action and Compliance Time section of this AD and once installed in a subject aircraft corrects the unsafe condition and terminates the requirements of this AD. Consequently, the Zonal Drying System can be re-activated. Amendment 4 includes additional STCs that are approved as terminating action to this AD and updates the revision status of STC EASA.A.A.02547 in Table 2 of this AD. Amendment 3 included additional STCs that are approved as terminating action to this AD. Amendment 2 became effective on 20 November 2008. Amendment 1 of this AD became effective on 26 May 2006. The original issue of this AD became effective on 19 May 2006. James Coyne Delegate of the Civil Aviation Safety Authority 22 May 2009