Performing the Rolls Royce Trent XWB non-modification service bulletin 72-AL055 at Finnair Technical Services

Abstract

This thesis clarifies the process of performing the Rolls Royce NMSB 72-AL055 according to the on-wing methods for the Airbus A350-900 aircraft equipped with Rolls Royce Trent XWB-84 engines. It focuses on how the NMSB can be completed with tools already available at Finnair Technical Services and tries to find the best practices for them.

Both on-wing methods listed in the NMSB were tested in the practice. This thesis gives tool selection tips for the method A borescope inspection and points out the best practices for successful completion. For the method B data quantity verification, a digital tool was created by using Microsoft’s Power Query and Excel to speed up and automate the data handling process. A step-by-step guide was created for its use, which is included as an appendix in this thesis.

The NMSB was found to be performable by either of the on-wing methods. However, the data quantity verification should be the first choice if all the conditions for its completion are met. It can bring large time savings since it can be performed to the whole fleet simultaneously and it can be attempted without risk of additional delays or expenses since it does not need physical maintenance activities to be performed for the aircraft. Borescope inspection was found to be risky due to high skill requirements and possible damage to the overtemperature probe when getting access to the borescope hole. However, with proper preparations and the suggestions presented in this thesis, the inspection can also be performed smoothly.