AD/A330/76 Amdt 4 Electrical Power/APU Generator Inspection (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/A330/76 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.

Airbus Industrie A330 Series Aeroplanes

AD/A330/76 Amdt 4 Electrical Power/APU Generator Inspection 12/2008

Applicability:

AIRBUS A330 aeroplanes.

Requirement:

1.    Carry out the inspections and other actions detailed in paragraphs 1 through 5 inclusive of EASA AD 2008-0173 dated 15 September 2008.

Terminating Action

2.    Install a secondary housing Line Replaceable Unit (LRU) over the end of the APU generator in accordance with Airbus Service Bulletin (SB) A330-24-3045 or later approved revision.

Compliance:

For Requirement 1 - As detailed in EASA AD 2008-0173 with a revised effective date of 20 November 2008.

For Requirement 2 - Not later than 31 March 2009, unless previously accomplished.

Note:  EASA AD 2008-0173 supersedes EASA AD 2008-0017R1.

This Amendment becomes effective on 20 November 2008.

Background:

Two A330 operators have reported uncontained APU generator failures on ground.  Preliminary investigations confirmed an uncontained APU Generator failure with subsequent aircraft structural damages to the APU compartment and, in one case, to the stabiliser compartment.

Further investigations are ongoing to determine the root causes.  It has been evident that for both events, this unknown root cause initiates a collapse of the Drive End Bearing (DEB) leading to an uncontained failure.  Evidence shows also that the DEB failures were not instantaneous, and therefore, the detection of small debris could indicate early stage DEB failure.

A one-time inspection which would allow for detection of large-scale debris in the Generator Scavenge inlet screen (last chance filter) of the APU has been rendered mandatory by CASA AD/A330/73 Amendment 1.

Amendment 1 of this AD was to mandate a repetitive inspection of the APU generator Scavenge filter element and filter housing and APU Generator Drain plug for signs of small debris coming from the APU Generator and therefore to detect an APU Generator failure in an early stage.

Amendment 2 added the following actions:

A visual inspection of the APU Generator sealing plate fitting, and

An additional inspection for aircraft operating under MMEL item 36-11-01 or 24-22-01, and

An additional inspection at each time a generator or APU is installed in an aircraft.

Amendment 3 cancelled the requirements of paragraph 4 of EASA AD 2008-0017 for A330 aircraft flying under MMEL item 36-11-01 further to ETOPS certification of the A330 APU.

Amendment 4 provides a mandatory modification which also provides a terminating action to the repetitive inspection requirements of this AD.

The original issue of this AD became effective 16 July 2007.

Amendment 1 of this AD became effective on 26 July 2007.

Amendment 2 of this AD became effective on 3 July 2008.

Amendment 3 of this AD became effective on 3 July 2008.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

3 October 2008