Increasing importance is being attached to the role of helicopter health and usage monitoring to improve the safety of civil helicopters. The application of advanced technologies for health and usage monitoring will have a major impact upon achieving this goal.
The 4 European helicopter manufacturers, Aerospatiale, Agusta, MBB and Westland Helicopters, supported by engine manufacturers Rolls Royce and operators Irish Helicopters, have agreed to collaborate in research in this field. This will ensure that each benefits from the others' experiences in planning and executing a future European strategy. By combining experience, the collaborating companies are uniquely qualified to undertake this study.
A review of accident and defect data was undertaken; this identified those areas that would benefit from the application of monitoring systems.
Various configurations of HUM systems wee assessed. A combined system incorporating on-board data processing and additional ground based analysis was preferred. This was considered the most practical configuration to cover a wide range of applications. It was considered that additional reductions in overall operating costs could be achieved by integrating the HUM system diagnostic outputs with current maintenance procedures.
Certification issues were reviewed. Existing procedures for the certification of avionics are not directly applicable to HUM systems and require further development.
HUM systems must produce highly reliable diagnostic indications. Clearly instrumentation technology is crucial to achieving this goal. A review of sensor performance identified current weaknesses and some potential solutions. Improved methods of processing can also help to reach this goal and to this end some novel analysis techniques were assessed; these show promise but require further development.
Usage monitoring (principally for rotor systems and transmissions) offers the potential to reduce the frequency of overhauls and thereby reduce costs. At the same time airworthiness can be improved by more accurately identifying damaging flight regimes. A trial transmission usage monitoring system was developed during the programme.
Various rotor monitoring systems were reviewed. Whilst achieving satisfactory performance, additional development should permit a wider range of defect modes to be identified.
Established transmission monitoring techniques (both vibration and debris analysis) were assessed in test programmes using seeded faults to replicate a variety of defect modes. Fault seeding methods were developed which demonstrate that naturally occurring defect modes can be reliably reproduced.
Existing monitoring techniques developed for large fixed-wing aircraft engines have been reviewed for potential application to helicopter engines. In addition, current methods of transmission vibration monitoring have been tested on engine vibration data. Although certain differences were noted, in both cases it should be possible to adopt these techniques. Reduced operating costs are again predicted, with added safety benefits.
Further work is now required to expose advanced HUM techniques to widespread in-service operation. Improved safety and reduced operating costs can be expected.
The work will commence with a detailed study of previously encountered or potentially likely modes of failure and the efficiency with which these modes of failure are presently monitored. Possible monitoring strategies will be reviewed and their impact upon certification and operation assessed.
Having established the need and identified priority areas, consideration will be given to the development of monitoring techniques where they are presently shown to be inadequate.
In addition to their impact upon airworthiness improvements, application of these technologies is expected to lead to reduced maintenance costs and improved aircraft availability, directly reducing operating costs and therefore improving the marketability of the companies' products.
Helicopter health and usage monitoring is a field in which European manufacturers have developed a worldwide lead. The results of the study will enable this position to be maintained.
Funding SchemeCSC - Cost-sharing contracts
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