System for monitoring the health of a helicopter

A monitoring system for monitoring the health of a helicopter having at least one engine, said system comprising:

• at least one engine sensor measuring an engine variable, at least one external conditions sensor measuring variables outside of the at least one engine, and a device for memorizing data measured by the at least one engine and the at least one external condition sensors, and
• a device for determining a change of state of the at least one engine configured to collect, from the memorization device, the data measured by the at least one engine and the at least one external conditions sensors during at least one stable flight phase of a first flight the device for determining a state being a computer on board the helicopter or on the ground, implementing the following operations to detect unrecorded pilot actions and differentiate them from changes of state of the at least one engine:
• a) comparison of said measured data with a reference model of the at least one engine, the reference model being a digital model hosted by the computer and representing a behavior of an engine in good health during at least one stable flight phase,
• b) determination, at each time step of the stable flight phase, of an instant offset between each measured datum and each datum estimated by the reference model of the at least one engine,
• c) determination, over the whole of the stable flight phase, of an overall offset between the measured data and the data estimated by the reference model of the at least one engine, the overall offset being calculated from a part at least of the instant offsets determined at step b),
• d) determination, at each time step of the stable flight phase, of an intrinsic residual corresponding to a difference between the instant offset and the overall offset,
• e) determination of one or more deviant portions corresponding to one or more parts of the intrinsic residual not meeting a predetermined criterion, each deviant portion, when it exists, containing information relating to a non-recorded pilot action, and
• f) determination of a corrected residual corresponding to the instant offset from which the one or more deviant portions have been removed,
• the corrected residual being analyzed by the computer in order to determine if it is the result of a pilot action having an incidence on the engine or if it is the result of a change of state of the at least one engine, such a change of state of the at least one engine requiring a servicing of the helicopter.