AD/Aircon/14 Amdt 1 Zonal Drying System Regeneration Air Duct Overheat (Cth)

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 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 1 Zonal Drying System Regeneration Air Duct Overheat 7/2006 TX

Applicability:

All airplanes equipped with Zonal Drying System Part Numbers 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; manufactured by CTT Systems AB, Nykoping, Sweden.

Applicable CTT Zonal Drying System Part Numbers are installed on, but not limited to the aircraft types listed in Table 1.

Note 1:  Non-listing of relevant aircraft in the Table 1 does not exempt any aircraft having an affected Part Number Zonal Drying System installed from compliance with this AD.

Table 1 – List of STC / Aircraft

STC Number	NAA	STC 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 (See Note 2)	LBA	Lufthansa Technik AG	Boeing 737-800
TA0733	LBA	Lufthansa Technik AG	Boeing 747-400
SA 0003 NL	RLD	CTT Systems AB	McDonnell Douglas MD-11

Table 1 continued…

STC Number	NAA	STC Holder	Applicable to
SA 0009 NL        (See Note 3)	RLD	CTT Systems AB	Boeing 767-300
EASA.A.S.02547	EASA	CTT Systems AB	Boeing 767-300
Z 21-74-01	FOCA	SR Technics, TEC	McDonnell Douglas MD-11
Z 25-02-77	FOCA	Jet Aviation Basel, AG	Boeing 737-700 (S/N 32627)

Note 2:  STC 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Note 3:  RLD STC SA 0009 NL has been superseded by EASA.A.S.02547 on 01 March 2006.

Requirement:

Unless previously accomplished in accordance with the original issue of this AD, switch off the zonal drying system and render the system inoperative by pulling and securing the appropriate circuit breaker in accordance with the related maintenance instructions.

Note 4:  EASA AD Number 2006-0140 -E dated 24 May 2006 refers.

Note 5:  CTT Systems AB Information Letters IL06-01 dated 05 May 2006, IL06-02 Issue 2 dated 08 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 refer.

Compliance:

Before further flight, after the effective date of this Airworthiness Directive.

This Amendment becomes effective on 26 May 2006.

Background:

One incident has been reported where the regeneration air ducting downstream of a zonal dryer P/N 3000-002, installed in a Boeing B747-400 aircraft, showed signs of premature material failure.  The problem is probably caused by high regeneration air temperature.  The zonal dryer’s normal safety protection devices should have prevented the regeneration air temperature from rising above 80^o C.  It is yet to be determined why this function did not work properly.

Amendment 1 of this AD expands the applicability list through addition of new CTT Zonal Drying System part numbers, STCs and aircraft types/models.

The original issue of this AD became effective on 19 May 2006.

David Villiers
Delegate of the Civil Aviation Safety Authority

25 May 2006