Sunday, November 7, 2010

QANTAS superjumbo engine failure MAY have been due to inadequate maintenance

Following is an excerpt from an EU notification which says that Rolls Royce Trent engines have a component with a high wear rate -- and that unusually frequent inspections of the component are therefore required. It specifies that engine failure is likely if this is not done

Wear, beyond Engine Manual limits, has been identified on the abutment faces of the splines on the Trent 900 Intermediate Pressure (IP) shaft rigid coupling on several engines during strip. The shaft to coupling spline interface provides the means of controlling the turbine axial setting and wear through of the splines would permit the IP turbine to move rearwards. Rearward movement of the IP turbine would enable contact with static turbine components and would result in loss of engine performance with potential for in-flight shut down, oil migration and oil fire below the LP turbine discs prior to sufficient indication resulting in loss of LP turbine disc integrity. Some of these conditions present a potential unsafe condition to the aeroplane.

This AD requires inspection of the IP shaft coupling splines and, depending on the results, requires further repetitive inspections or corrective actions. Since issuance of AD 2010-0008 Rolls-Royce has inspected several additional engines subject to IP shaft coupling spline wear. Inspections were carried out on-wing as well as in-shop.

Analysis of the results EASA AD No : 2010-0008R1 EASA Form 110 Page 2/3 provides a better modelling of the wear rate and allow to redefine reinspection periods based on: - average wear measured on each individual engine rather than maximum wear. - individual engine wear rates rather than an assumed worst case rate.

These inspection periods are extended compared to original issue of AD 2010-0008, and are deemed sufficient to prevent unacceptable wear. Effective Date: Revision 1: 18 August 2010 Original issue: 29 January 2010


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