Health and Usage Monitoring Systems (HUMS) has received considerable
attention from the helicopter community in recent years with the declared aim to increase
flight safety, increase mission reliability, extend duration of life limited components and of
course reduce the maintenance costs. The latter is about 25 per cent of the direct operating
cost of the helicopter, thus playing an important role especially in the case of the ageing
aircrafts. In particular, with respect to helicopter fuselages, only some attempts were carried
out to monitor directly on-line the damage accumulation and propagation during life. In this
field, and in particular in the military applications, an integrated and reliable system for
monitoring the damage in the fuselage and for evaluating the time inspections and remaining
life (prognosis) is missing. However, because of the presence of many vibratory loads, the
diagnosis of helicopter structures is very critical. From one hand, a very large number of
sensors would be needed for a robust appreciation of the structural health, from the other hand
the industrialization of the product brings the need for a low impact over the existing
structures, or toward a reduction in the allowed amount of sensors. As a result, comes the
importance for an optimization of the sensor network, with the aim to find out the regions
inside the structure which are the most sensible to a damage and at the same time robust to
noise. The aim of the present work is to define a methodology for optimising the sensors
position inside an helicopter fuselage panel in order to obtain the best compromise between
the simplicity and the robustness of a sensor network. In particular, a Finite Element (FE)
model will be used to create a database of various damages inside the structure, thus
consequently optimising the network sensitivity to any damage. The evaluation of the
network performances is provided when some realistic noise [1,2] is added to the FE
calculation
