The Trent 700 blade manufacturing process produced a variation in internal membrane-to-panel acute corner geometry that, in combination with the inherent high level of blade panel stress, could lead to increased localised stresses in those corner areas and the initiation and propagation of fatigue cracking.
While Roll-Royce are continuing to work on gaining an understanding of the manufacturing processes that may influence the acute corner radius, the ATSB is satisfied that the blade improvements are sufficient on their own to reduce the likelihood of further fatigue crack initiation in Trent 700 fan blades.
Rolls-Royce have initiated a review of the design and manufacturing of the Trent 700 fan blade to address potential contributing factors that could lead to the failure of the fan blade. This review activity has identified areas for improvement such as introducing local panel thickening to reduce blade panel stress to a level that will mitigate the acute corner variations observed in production. It is anticipated that a modified blade will be available in service in the second half of 2021. Rolls-Royce are continuing to try to understand what manufacturing processes may influence the acute corner radii.
The ATSB welcomes the proactive safety actions taken by Rolls-Royce with regards to understanding the potential contributing factors to the fatigue crack development and attempting to mitigate them.
