A study of no fault found phenomenon

摘要

No-Fault-Found (NFF) refers to a situation where a user found a fault while using a product but the fault is not found in re-using it thereafter or in the process of cause analysis thereof. NFF emerges importantly in diverse industrial areas including the aviation industry, in particular. Although NFF occurrence rate varies slightly according to product characteristics and industrial sectors, to sum the study findings so far, NFF accounts for over 50 percent of the total failures or even higher especially in the aviation sector. In this situation, NFF makes a good research topic. If such NFF occurrence is not prevented, it would have a negative effect on a corresponding specific organization in three aspects of cost, dependability and safety.;In this thesis, it was identified that the causes of NFF occurrence had two different steps. In the first step, four causes of NFF were found: people, machine, environment and intermittent failure. In the second step, a major cause of NFF, intermittent failure, was further divided into three dimensions of the electronic system, mechanical system and software system. The cause and effect diagram devised by Ishikawa was employed in this study to more effectively analyze and display the consequences of each NFF cause. Lastly, NFF control methods, or, that is, methods to prevent NFF causes and reduce its consequences were presented in three categories: data management, organization management and expert system.