Browsing by Author "Hockley, Chris"
Now showing 1 - 6 of 6
Results Per Page
Sort Options
Item Open Access Analysis of short form maintenance records for NFF using NLP, phrase matching, and Bayesian learning(Elsevier, 2017-03-02) Pelham, Jonathan G.; Hockley, ChrisNo Fault Found (NFF) is a well discussed phenomenon within the maintenance sector but which requires work to quantify how much of an issue it may be and provide metrics by which it may be tracked and various approaches to its reduction evaluated. Previous studies have relied on expert classification to identify NFF, however this approach is time consuming and costly. Maintainer classification (MC), expert classification (RC), phrase matching (PM), and Bayesian matching (NBPM) are all evaluated and contrasted as methods to identify NFF. The results demonstrate the utility of all 4 methods and discusses their place within a maintenance ecosystem.Item Open Access Automated shot counter system for through-life support of target rifles(Elsevier, 2015-10-27) Gagar, Daniel; Hockley, Chris; Foote, PeterCompetitive target shooting requires rifles with high levels of performance and small margins of error. Optimal performance of rifles in terms shot velocity can be expected over a period of use until an indeterminate but critical number of rounds has been fired when it will start to deteriorate. The rifle barrel must then be renewed. Accurate and reliable record-keeping of number of shots fired is therefore critical to minimise the through-life cost of owning a target rifle and also maintaining maximum performance. This can be most effectively done using an automated means for monitoring the number of rounds fired. In this paper the acoustic emission technique is used to monitor and identify shot rounds fired based solely on the features of Acoustic Emission (AE) signals for the first time. The results obtained from experiments showed unambiguous identification of shots fired and the capability to monitor degradation of the barrel as a function of number of shots fired.Item Open Access No Fault Found events in maintenance engineering Part 1: current trends, implications and organizational practices(Elsevier, 2013-12-01) Khan, Samir; Phillips, Paul; Jennions, Ian K.; Hockley, ChrisThis paper presents the first part of a state of the art review on the No Fault Found (NFF) phenomenon. The aim has been to compile a systematic reference point for burgeoning NFF literature, and to provide a comprehensive overview for gaining an understanding of NFF knowledge and concepts. Increasing systems complexities have seen a rise in the number of unknown failures that are being reported during operational service. Units tagged as ‘NFF’ are evidence that a serviceable component was removed, and attempts to troubleshoot the root cause have been unsuccessful. There are many reasons on how these failures manifest themselves and these papers describe the prominent issues that have persisted across a variety of industrial applications and processes for decades. This article, in particular, deals with the impact of NFF from an organizational culture and human factors point of view. It also highlights recent developments in NFF standards, its financial implications and safety concerns.Item Open Access No Fault Found events in maintenance engineering Part 2: Root causes, technical developments and future research(Elsevier, 2013-12-01) Khan, Samir; Phillips, Paul; Hockley, Chris; Jennions, Ian K.This is the second half of a two paper series covering aspects of the no fault found (NFF) phenomenon, which is highly challenging and is becoming even more important due to increasing complexity and criticality of technical systems. Part 1 introduced the fundamental concept of unknown failures from an organizational, behavioral and cultural stand point. It also reported an industrial outlook to the problem, recent procedural standards, whilst discussing the financial implications and safety concerns. In this issue, the authors examine the technical aspects, reviewing the common causes of NFF failures in electronic, software and mechanical systems. This is followed by a survey on technological techniques actively being used to reduce the consequence of such instances. After discussing improvements in testability, the article identifies gaps in literature and points out the core areas that should be focused in the future. Special attention is paid to the recent trends on knowledge sharing and troubleshooting tools; with potential research on technical diagnosis being enumerated.Item Open Access A research study of no fault found (NFF) in the Royal Air Force(Elsevier, 2017-03-02) Hockley, Chris; Lacey, Laura J.The No Fault Found (NFF) problem continues to reduce operational availability and have an impact on cost and resources in the RAF. Following extensive research by the Centre for Innovative Manufacturing in Through-Life Engineering Services, access was provided to a significant number of RAF aircraft maintenance personnel under the sponsorship of Air Command at RAF High Wycombe. Maintenance personnel from seven different aircraft fleets, including large aircraft, fast jets and rotary platforms were involved. A number of substantial conclusions were made resulting in 26 recommendations. The paper reviews and substantiates these conclusions and recommendations.Item Open Access Towards standardisation of no fault found taxonomy(2012-11-06T00:00:00Z) Khan, S.; Phillips, P.; Hockley, Chris; Jennions, Ian K.; Roy, Shebab and Hockley, KhanThere is a phenomenon which exists in complex engineered systems, most notably those which are electrical or electronic which is the inability to diagnose faults reported during operation. This includes difficulties in detecting the same reported symptoms with standard testing, the inability to correctly localise the suspected fault and the failure to diagnose the problem which has resulted in maintenance work. However an inconsistent terminology is used in connection with this phenomenon within both scientific communities and industry. It has become evident that ambiguity, misuse and misunderstanding have directly compounded the issue. The purpose of this paper is to work towards standardisation of the taxonomy surrounding the phenomena popularly termed No Fault Found, Retest Okay, Cannot Duplicate or Fault Not Found amongst many others. This includes discussion on how consistent terminology is essential to the experts within organisation committees and, to the larger group of users, who do not have specialised knowledge of the field.