Reliability model for helicopter main gearbox lubrication system using influence diagrams

This paper presents the development of a model to assess the reliability of helicopter main gearbox (MGB) lubricating systems. The loss of oil from a helicopter MGB will lead to increased friction between components, a rise in component surface temperatures, and subsequent mechanical failure of gearbox components. A number of significant helicopter accidents have been caused due to such loss of lubrication. Current certification requirements for Category A helicopters require that gearboxes which use pressurized lubrication systems must show a capability to continue operation for a period of 30 minutes after suffering a loss of oil. This paper reports on methods for assessing reliability of pressurized MGB lubrication systems. Safety risk modeling was conducted for MGB oil system related accidents and incidents in order to analyse the key failure mechanisms and the contributory factors. As such, the dominant failure modes for lubrication systems and key contributing components were identified. The Influence Diagram (ID) approach was then employed to investigate reliability issues of the MGB lubrication systems at the level of primary causal factors. Early indications show significant benefits from this approach where multiple influences would render alternative approaches overly complex. The ID tool can systematically investigate complex context of events, conditions, and influences that are direct triggers of failures. Within this study, an ID model was introduced to describe the interrelationships between MGB lubrication system failure types. In this way the influence of each of these factors on the overall MGB lubrication system reliability may be assessed

Helicopter Shaft Heating Parameters for Polyamide-11 Coating

In this study, the heating parameters required for polyamide-11 (P11) coating of the helicopter shaft were investigated. The torsion value created by the force applied to the middle of the helicopter\u27s shaft is measured. Heating before coating affects the torsion value of the shaft. A new heating mechanism has been designed to cover the shaft surface without changing the torsion value of the shaft. Thus, the coating surface is left inside the furnace and the torsion measurement area outside of the furnace. Taguchi method was used to determine heating parameters such as furnace type, initial temperature and heating time. The heating process was performed by connecting K type probes to the shaft surface and temperature changes were recorded. It has been determined that with the fanless furnace, the coating surface does not reach the required minimum temperature, the shaft surface reaches the sufficient temperature with the fanned furnace, and PA11 coating can be applied effectively

On the Estimation of the Useful Lifespan of Lubrication Oil under Constrained Functioning Conditions an ANN / Fuzzy Logic Approach

Lubrication oil in automotives is a multi-billion-pound business but the non-optimization of its lifespan entails colossal harm to societies, global resources and the environment. Losses are caused by premature oil change or by machinery wearing due to deteriorated oil. The actual practice in the automotive field follows a predetermined routine-replacement policy that does not consider the wide spectrum of operating conditions. In this paper a decision support model is developed for the determination of the optimum life span of oil under specific working conditions. A data gathering scheme is set to capture the most relevant oils' characteristics from real samples over specific ranges of operation. The relationship between the causal factors and the resulting condition of oil is programmed in an ANN which is complemented with a fuzzy-logic approach in order to predict the optimum lifespan of oil under any set of causal factors. The approach is applied on a case study in Egypt; the model is tested, validated and is believed to fulfil its objectives satisfactorily

Aplicação dos diagramas causais no âmbito da qualidade : um caso de estudo

Trabalho final de mestrado para obtenção do grau de Mestre em Engenharia MecânicaO estudo aqui apresentado é sobre a solução de um caso de estudo utilizando os diagramas causais. O caso de estudo é a falha na operação de um gerador E-82, que equipa uma turbina eólica. O trabalho inclui uma descrição da teoria que serve de base aos diagramas causais, importância da informação gráfica e a sua aplicação na Qualidade, o seu uso presente e futuro. Os diferentes tipos de diagrama são descritos. A descrição do caso de estudo, a falha na operação de um gerador de uma turbina eólica, os danos resultantes e a procura das causas é feita através de diagramas causais. Serão consideradas várias hipóteses como causa do acidente, ligando as causas possíveis aos danos resultantes. A causa mais provável para o acidente é determinada por a comparação de todas as hipóteses, com recurso à utilização dos diagramas causais. A aplicação dos diagramas causais enquadra –se no âmbito da Qualidade, sendo uma fonte de informação e um modo de compreender a estrutura do sistema que representam. O objectivo deste estudo é introduzir o leitor à aplicação e conhecimento dos diagramas causais, as suas potencialidades e ao contexto no qual a sua aplicação tem lugar.The present study is about the solution of a case study using causal diagrams. In this study a problem affecting the operation of a wind turbine generator will be identified and put in context, using causal diagrams. The aim of the study is to show that causal diagrams are a relevant and accessible tool in problem solving and in representation of systems and their relationships. The study will include a description of the theory behind causal diagrams, the importance of graphical information in Quality, present uses and developments. Different types of diagrams and their common characteristics, relevant to each type will also be addressed. A description of the case study, the accident in operation of a wind turbine generator, the resultant damages are evaluated using causal diagrams. Various hypotheses for the cause of the accident are considered, linking the possible causes to the resultant damage. The most likely cause is determined after comparing all the different hypotheses, through the use of causal diagrams. Diagrams are used to give a structured view of the events that take place in production, transport and deployment of a wind turbine generator. This study aims to introduce the reader to the use and knowledge of causal diagrams, and the context in which their application takes place.N/