AD/CF34/11 Lufthansa A.E.R.O. Undertorqued LP Turbine Rotors (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 - CF34 Series

AD/CF34/11 Lufthansa A.E.R.O. - Undertorqued
LP Turbine Rotors 7/2006

Applicability:

General Electric Engine model CF34-3 serial numbers (S/N) 872579, 807566, 807346C, 872278, 872334, 873070 last overhauled by Lufthansa A.E.R.O., Germany.

Requirement:

Action in accordance with the requirements of German LBA Airworthiness Directive D-2006-139 at any revision status.

Note 1:  Lufthansa A.E.R.O. Shop Information Letter (SIL) CF34-3 SIL 06-001 pertains to the subject of this AD.

Note 2:  German LBA Airworthiness Directive D-2006-139 dated 18 May 2006 refers.

Compliance:

For engine serial numbers 872579, 807566 and 807346C - Within 500 hours since last shop visit.

For engine serial numbers 872278, 872334 and 873070 - At the next aircraft letter-check or scheduled or unscheduled engine shop visit, whichever occurs first.

This Airworthiness Directive becomes effective on 6 July 2006.

Background:

During routine tool calibration in February 2006, Lufthansa A.E.R.O. detected a malfunctioning torque wrench.  The deviation of the malfunctioning torque wrench was 38% below the target value (e.g. at 40 lb-in setting, the actual torque value was 24.8 lb-in).  The subject torque wrench was last calibrated in February 2005.

On review of all internal work orders since February 2005, Lufthansa A.E.R.O. identified six engines on which this torque wrench was used for final assembly.  The defective torque wrench was used for assembling rotating LP Turbine hardware on three engines while on the other three engines, the wrench was used for assembly of the stationary LP Turbine hardware.

Actions specified in this AD are aimed at preventing uncontained turbine wheel failure, loss of engine power and probable damage to and/or loss of the aircraft.

James Coyne
Delegate of the Civil Aviation Safety Authority

24 May 2006