Abstract: The monitoring method includes the steps of: acquiring a signal from an acceleration sensor; calculating a transform in the frequency domain of the signal to obtain a sequence of samples; acquiring a sample in the sequence of samples; calculating an actual amplitude value of the acquired sample; calculating a relative deviation between the actual amplitude value of the acquired sample and a reference amplitude value; and comparing the relative deviation with at least one predetermined threshold to immediately detect any irregularity in, and so prevent in-flight failure of, the helicopter transmission assembly.

Abstract: The monitoring method includes the steps of: acquiring a signal from an acceleration sensor associated with an epicyclic assembly; sampling the signal at a predetermined sampling frequency to obtain an initial sequence of samples; dividing the samples in the initial sequence into groups, each defined by a predetermined number of samples; acquiring predetermined groups of samples; filtering the acquired groups of samples to obtain an intermediate sequence of samples; processing the intermediate sequence of samples to obtain a final sequence of samples; calculating a sixth-order moment of the final sequence of samples; and comparing the sixth-order moment with at least one predetermined threshold to detect any vibrational irregularity in the epicyclic assembly of the helicopter.

Abstract: The method includes the steps of: acquiring a signal from an acceleration sensor; calculating the Fourier transform in the frequency domain of the signal to obtain a sequence of samples; acquiring from the sequence of samples a set of samples including samples at the meshing frequency of the gears monitored by the sensor, and samples at the harmonic frequencies of the meshing frequency; calculating the energies associated with the set of samples and the signal; calculating a noise energy parameter correlated to the ratio between the energy of the set of samples and the energy of the signal; comparing the noise energy parameter with at least one predetermined threshold; and generating an alarm signal in the event the noise energy parameter exceeds the threshold value.

Abstract: The method includes the steps of: acquiring a signal from an acceleration sensor; calculating the Hilbert transform of the signal filtered and sampled beforehand; defining a complex signal having the filtered and sampled signal as the real part and the Hilbert transform of the filtered and sampled signal as the imaginary part; calculating a phase signal given by the difference between the phase of the complex signal and a reference phase; calculating the variance of the phase signal; comparing the variance with at least one predetermined threshold; and generating an alarm signal if the variance exceeds the threshold value.

Abstract: The monitoring method includes the steps of: acquiring a first signal from an acceleration sensor; calculating a transform in the frequency domain of the first signal to obtain an initial sequence of samples, each of the samples having a respective amplitude and a respective frequency; processing the initial sequence of samples to obtain a final sequence of samples; calculating a sixth-order moment of the final sequence of samples; and comparing the sixth-order moment with at least one predetermined threshold to detect any vibrational irregularity in the helicopter transmission assembly.