AD/CT7/12 Stage 2 Turbine Aft Cooling Plate (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/CT7/12 Stage 2 Turbine Aft Cooling Plate 13/2005

Applicability:

General Electric Company (GE) CT7-5A2, - 5A3, -7A, -7A1, -9B, -9B1, and -9B2 turboprop engines, with stage 2 turbine aft cooling plate, part number (P/N) 6064T07P01, 6064T07P02, 6064T07P05, or 6068T36P01 installed.

Note 1:  These engines are installed on, but not limited to, Construcciones Aeronauticas, SA CN-235 series and SAAB Aircraft AB SF340 series aeroplanes.

Requirement:

1.    Unless previously carried out in accordance with GE ASB No. CT7-TP S/B
72-A0464 Revision 3 dated 23 July 2004 or earlier revisions;  Perform a onetime eddy current inspection (ECI) of the stage 2 turbine aft cooling plate boltholes in accordance with paragraph 3.B. of General Electric (GE) Alert Service Bulletin (ASB) No. CT7-TP S/B 72-A0464 Revision 3 or later FAA approved revision.

2.    Remove from service any stage 2 turbine aft cooling plate that does not pass the return to service criteria specified in paragraph 3.B. of the ASB detailed in Requirement 1 of this AD.

Note 2:  FAA AD 2005-18-01 Amdt 39-14241 refers.

Compliance:

1.    At the next engine or hot section module shop visit, but before accumulating an additional 6,000 cycles-in-service after the effective date of the AD.

2.    After the effective date of this AD.

This Airworthiness Directive becomes effective on 22 December 2005.

Background:

This AD results from reports of six stage 2 turbine aft cooling plates found cracked during inspection.  The actions specified in this AD are intended to prevent stage 2 aft cooling plate separation, resulting in uncontained engine failure and damage to the aeroplane.

James Coyne
Delegate of the Civil Aviation Safety Authority

10 November 2005