AD/CT7/13 No. 3 Bearing (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.

General Electric Turbine Engines - CT7 Series

AD/CT7/13 No.3 Bearing 4/2009

Applicability:

General Electric Company (GE) CT7-8A turboshaft engines that have a serial number (SN) listed in Table 1 of this AD.

Note 1:  These engines are installed on, but not limited to, Sikorsky S92 helicopters.

Table 1 - Affected Engines by Serial Number

Engine Serial Number
947205	947215	947230	947243	947254	947265
947206	947217	947232	947244	947255	947274
947207	947218	947233	947245	947256	947277
947208	947219	947235	947247	947258	947278
947209	947220	947238	947248	947260	947279
947210	947221	947240	947249	947261	947280
947211	947223	947241	947250	947262	947284
947212	947225	947242	947253	947263	947285
947214	947228

Requirement:

No further action is required if:

-      The engine has a SN that is not listed in Table 1 of this AD; or

-      The engine has a SN listed in Table 1 of this AD, but the engine log specifies that the front frame was flushed and the No. 3 bearing was replaced.

1.    For engines with a SN listed in Table 1 of this AD, remove the engine from service and flush the front frame and replace the No. 3 bearing.

GE CT7-8 Shop Manual, GEK 10517, contains information on replacing the
No. 3 bearing and GE Aircraft Engines Service Bulletin No. CT7-8 S/B 72-0017, Revision 02, dated 14 May 2008, or earlier revision, contains information on flushing the front frame and replacing the No. 3 bearing.

2.    Do not install any No. 3 bearing removed as detailed in Requirement 1 of this AD.

Note 2:  FAA AD2008-26-02 Amdt 39-15768 dated 9 December 2008 refers.

Compliance:

For Requirement 1 - Within 6,200 cycles-since-new.

For Requirement 2 - After the effective date of this AD.

This Airworthiness Directive becomes effective on 9 April 2009.

Background:

This AD results from investigation for the root causes of two failures of the No. 3 bearing.  The issuing of this AD is intended to prevent failure of the No. 3 bearing due to contamination by aluminium oxide, which could result in a possible in-flight shutdown of the engines and loss of control or forced landing of the aircraft.

James Coyne
Delegate of the Civil Aviation Safety Authority

26 February 2009