AD/Tay/17 Low Pressure Turbine Disc Corrosion (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.

Rolls Royce Turbine Engines - Tay Series

AD/TAY/17 Low Pressure Turbine Disc Corrosion 12/2006

Applicability:

TAY 650-15 Engines serial numbers 17251, 17255 17256, 17273, 17275, 17280, 17281, 17282, 17300, 17301, 17327, 17332, 17365, 17393, 17437, 17443, 17470, 17520, 17521, 17523, 17539, 17542, 17556, 17561, 17562, 17563, 17580, 17581, 17612, 17618, 17635, 17637, 17645, 17661, 17686, 17699, 17701, 17702, 17736, 17737, 17738, 17739, 17741, 17742 and 17808 with Module M05300AA (LP Turbine Module) installed.

Note 1:  These engines are known to be installed in Fokker F28 Mark 0100 aircraft.

Requirement:

1.    Inspect the low pressure turbine discs stage 2 and stage 3 for corrosion in accordance with Rolls-Royce Deutschland Non-Modification Alert Service Bulletin TAY-72-A1524, Revision 1 or later LBA approved revisions.

2.    When, during any of the inspections as required by Requirement 1 of this AD, corrosion is found, replace the affected parts using the rejection criteria described in the Rolls-Royce TAY 650 Engine Manual - E-TAY-3RR, latest revision.

All necessary inspections must be accomplished in accordance with the TAY 650 Engine Manual - E-TAY-3RR, Chapters 72-52-23 and 72-52-24.

Note 2:  EASA AD 2006-0288 dated 15 September 2006 refers.

Compliance:

1.    Prior to accumulating 11,700 flight cycles (FC) and thereafter at intervals not exceeding 11,700 FC of the engine.

2.    Before further flight after the effective date of this AD.

This Airworthiness Directive becomes effective on 23 November 2006.

Background:

Strip results from some of the engines listed in the applicability section of this AD revealed excessively corroded low pressure turbine stage 2 and stage 3 discs.  The corrosion is considered to be caused by the environment in which these engines are operated.

Following a life assessment based on the strip findings, it was determined that inspections for corrosion attack are required.

The action specified by this AD are intended to avoid a failure of a low pressure turbine stage 2 or stage 3 disc due to potential corrosion problems which could result in uncontained engine failure and damage to the aeroplane.

This AD supersedes AD/TAY/7.  This AD extends the applicability of those engines listed in AD/TAY/7.

James Coyne
Delegate of the Civil Aviation Safety Authority

12 October 2006