Paul Phillips

No Fault Found events in maintenance engineering Part 1: Current trends, implications and organizational practices

This 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.

No Fault Found events in maintenance engineering Part 2: Root causes, technical developments and future research

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.

A knowledge driven approach to aerospace condition monitoring

Aircraft operators are continually striving to reduce both the amount and the cost of aircraft maintenance. Whilst at the same time ensuring that the aircraft safety, reliability and integrity are not compromised. One solution which has seen a lot of attention is known as condition monitoring. The aim of condition monitoring is to develop the ability to detect, diagnose and locate damage, even predicting the remaining useful life of the structure or system. There are difficulties associated with developing aerospace condition monitoring which transcends technical, financial and regulatory. Aerospace legislation requires that any decisions on maintenance, safety and flightworthiness to be auditable and data patterns to relate to known information. The use of data, physical models and knowledge approaches can individually produce reliable health related decisions, but the fusing of these different solutions within an appropriate framework will enhance the intelligence in the decision making process. This paper reviews such a framework and design methodology being used for the development of knowledge based condition monitoring systems for aircraft landing gear actuators.

The impact of no fault found on through‐life engineering services

Purpose – The purpose of this paper is to provide a platform for discussion on the problem of no fault found (NFF) events which continues to plague maintenance operations of complex engineering systems.Design/methodology/approach – The research has been collated from many sources: academic literature, industrial discussions and the authors’ experiences. The study defines the NFF problem, its causes, impacts and costs as well as an evaluation of the available scientific research.Findings – The paper identifies a continuing serious problem with NFF; it is not just a technical problem but also encompasses organisations, culture and behaviours. Focusing only on one of these at a time is no longer enough to solve the NFF problem in modern maintenance operations and solutions will require each category to be addressed as an integrated problem.Originality/value – The overall value is a detailed picture of the NFF field seen from both an industrial and academic viewpoint. The originality of the paper is that it a...

The adoption and use of Through-life Engineering Services within UK Manufacturing Organisations

Manufacturing organisations seek ever more innovative approaches in order to maintain and improve their competitive position within the global market. One such initiative that is gaining significance is ‘through-life engineering services’. These seek to adopt ‘whole life’ service support through the greater understanding of component and system performance driven by knowledge gained from maintenance, repair and overhaul activities. This research presents the findings of exploratory research based on a survey of UK manufacturers who provide through-life engineering services. The survey findings illustrate significant issues to be addressed within the field before the concept becomes widely accepted. These include a more proactive approach to maintenance activities based on real-time responses; standardisation of data content, structure, collection, storage and retrieval protocols in support of maintenance; the development of clear definitions, ontologies and a taxonomy of through-life engineering services in support of the service delivery system; lack of understanding of component and system performance due to the presence of ‘No Fault Found’ events that skew maintenance metrics and the increased use of radio-frequency identification technology in support of maintenance data acquisition.

A review on the optimisation of aircraft maintenance with application to landing gears

Current maintenance programmes for key aircraft systems such as the landing gears are made up of several activities based around preventive and corrective maintenance scheduling. Within today’s competitive aerospace market innovative maintenance solutions are required to optimise aircraft maintenance, for both single aircraft and the entire fleet, ensuring that operators obtain the maximum availability from their aircraft. This has led to a move away from traditional preventive maintenance measures to a more predictive maintenance approach, supported by new health monitoring technologies. Future aircraft life will be underpinned by health monitoring, with the ability to quantify the health of aerospace systems and structures offering competitive decision-making advantages that are now vital for retaining customers and attracting new business. One such aerospace system is the actuator mechanisms used for extension, retraction and locking of the landing gears. The future of which will see the introduction of electromechanical replacements for the hydraulic systems present on the majority of civil aircraft. These actuators can be regarded as mission critical systems that must be guaranteed to operate at both take-off and landing. The health monitoring of these actuation systems can guarantee reliability, reduce maintenance costs and increase their operational life span. Aerospace legislation dictates that any decisions regarding maintenance, safety and flight worthiness must be justified and strict procedures followed. This has inevitably led to difficulties in health monitoring solutions meeting the necessary requirements for aerospace integration. This paper provides the motivation for the research area through reviewing current aircraft maintenance practices and how health monitoring is likely to play a future strategic role in maintenance operations. This is achieved with reference to current research work into developing a health monitoring system to support novel electromechanical actuators for use in aircraft landing gears. The difficulties associated with integrating new health monitoring technology into an aircraft are also reviewed, with perspectives given on the reasons for the current slow integration of health monitoring systems into aerospace.