AD/PW4000/15 14th and 15th Stage Rubstrips (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.

Pratt and Whitney Turbine Engines - PW4000 Series

AD/PW4000/15 14^th and 15^th Stage Rubstrips 15/2010

Applicability:

Pratt and Whitney (PW) models PW4164, PW4168, and PW4168A turbofan engines, serial numbers P733301 through P733500, that have HPC inner case assembly part number (P/N) 53H272-01 installed.

Note 1:  These engines are installed on, but not limited to Airbus Industrie A330 aeroplanes.

Requirement:

Unless previously accomplished, to prevent engine power loss during takeoff due to high pressure compressor (HPC) surge, perform the following:

1.    Borescope-inspect in accordance with paragraphs 1.A. through 1.I of the Accomplishment Instructions, Borescope Inspection of Pratt & Whitney (PW) Alert Service Bulletin (ASB) PW4G-100-A72-170, Revision 3, dated
31 January 2003, using schedules in Table 1 of this AD:

Table 1. - Installed-Engine Initial Borescope Inspection Schedule

Accumulated engine cycles on the effective date of this AD:	Initial borescope-inspect 14th and 15th stage rubstrips:
(1)  Fewer than 900 cycles-since-new (CSN) or cycles-since-refurbishment (CSR) of the HPC inner rear case assembly.	Before accumulating 1,500 CSN or CSR, whichever occurs later.
(2)  900 or more CSN or CSR	Within 600 cycles-in-service (CIS) after the effective date of this AD.

2.    Perform the applicable action as specified in the following Table 2:

Table 2. - Borescope Inspection Results and Required Action

Results observed at last borescope inspection:	Action:
(1)  14th stage rubstrip shows wear through to the parent material of the stator, with the circumferential length of the wear being 1.0" or more.	Remove engine from service within 250 CIS.

(2)  15th stage rubstrip shows wear through to the parent material of the stator, with the circumferential length of the wear being 2.0" or more.	Remove engine from service within 250 CIS.
(3)  14th stage rubstrip shows wear through to the parent material of the stator, with the circumferential length of the wear being less than 1.0".	Reinspect every 300 CIS.
(4)  15th stage rubstrip shows wear through to the parent material of the stator, with the circumferential length of the wear being less than 2.0".	Reinspect every 300 CIS.
(5)  Both 14th and 15th stage rubstrips show no wear through to the parent material of the stator.	Reinspect every 600 CIS.

3.    For aeroplanes with two affected engines installed, perform the actions as specified in following Table 3:

Table 3. - Borescope Inspection Results and
Required Actions for Two Affected Engines

First engine borescope results:	Second engine borescope schedule:	Second engine borescope results:	Action:
(1)  Wear as specified in Table 2, Steps (1) through (4).	Within 10 CIS since borescope inspection of first engine.	Wear as specified in Table 2, Steps (1) through (4).	Remove either the first or second engine from service within 25 CIS since borescope inspection of the second engine and replace with a serviceable engine. Remove or re-inspect in accordance with Table 2 for remaining engine and if still applicable perform actions as specified in Requirement 3 of this AD.

(2)  Wear as specified in Table 2, Steps (1) through (4).	Within 10 CIS since borescope inspection of first engine.	Wear as specified in Table 2, Step (5).	For both engines, remove or re-inspect in accordance with Table 2 and, if still applicable, perform actions as specified in Requirement 3 of this AD.
(3)  Wear as specified in Table 2, Step (5).	Inspect as specified in Table 1.	Wear as specified in Table 2.	For both engines, remove or inspect in accordance with Table 2 and, if still applicable, perform actions as specified in Requirement 3 of this AD.

Definition of Serviceable Engine.

For the purposes of this AD, a serviceable engine is:

a.     An engine that incorporates an HPC with zero CSN; or

b.    An engine covered by the Terminating Action detailed in this AD; or

c.     An engine inspected as specified in Requirements 1 through 3 of this AD, and is following the 600 CIS re-inspection interval as specified in Table 2 of this AD.

Engines borescope-inspected before the effective date of this AD in accordance with PW ASB PW4G-100-A72-170, Revision 1, or Revision 2, must follow Requirements 1 through 3 of this AD, after the effective date of this AD.

Later revisions of the above ASB, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2003-09-02, are considered acceptable for compliance with the equivalent Requirements of this AD.

Terminating Action.

Replacement of HPC inner rear case assembly with an HPC inner rear case assembly containing a Haynes 242 rear hook, including assemblies modified or replaced by PW SB No. PW4G-100-72-159, PW SB No. PW4G-100-72-187, or Chromalloy Repair Procedure 00-CFL-039-0, constitutes terminating action for the repetitive engine borescope inspections of this AD.

Note 2:  FAA AD 2003-09-02 Amdt 39-13131 date 21 April 2003 refers.

Compliance:

For Requirement 1 - As detailed in Table 1 of this AD.

For Requirement 2 - As detailed in Table 2 of this AD.

For Requirement 3 - As detailed in Table 3 of this AD.

This Airworthiness Directive becomes effective on 14 August 2010.

Background:

This AD requires operators to initially and repetitively borescope-inspect 14th and 15th stage rubstrips located on the 13th and 14th stage stator set for wear.  This AD is prompted by reports of high pressure compressor (HPC) surges during the takeoff phase of flight that have been attributed to increased stage 14 and stage 15 HPC blade tip clearances caused by excessive wear on the HPC inner rear case rear hook.  The actions specified by this AD are intended to prevent engine power loss during takeoff due to HPC surge.

From a review of State of Design ADs, CASA has determined that this AD may be applicable to Australian aircraft.

David Punshon
Delegate of the Civil Aviation Safety Authority

28 July 2010