AS a member of a Rolls‐Royce team of engineers I have been engaged upon the study of the cause of turbine blade failure on the test‐bed and in flight, but I should like to mention here that the views expressed in this paper are entirely my own and do not necessarily represent the views or the policy of Rolls‐Royce Limited. I have not hesitated to put forward some views, although the data are not available at this stage to provide rigid proofs that the views are correct. I hope that in doing this I may add to the interest of the discussion that will follow this paper.