Method (20, 30, 40) for monitoring and detecting the formation of degradation in at least one moving part of a rotating mechanism forming all or part of a kinematic chain for transmission of an engine torque, the said rotating mechanism being fitted to an aircraft, the said method (20, 30, 40) comprising: • at least one first measurement step (21, 31) comprising a measurement of the vibrations along at least one direction and generating a operational vibration signal of the said rotating mechanism as a function of time, the said first measurement step (21, 31) being carried out by means of at least one vibration sensor secured to a fixed casing of the said aircraft, • at least one second measurement step (22, 32) comprising a measurement of an angular position of the said at least one moving part, the said at least one moving part having at least one degree of freedom in rotation about an axis of rotation, characterised in that the said method (20, 30, 40) comprises at least: • a preprocessing step (23, 33) for calculating a synchronous variance of the vibrations of the vibration signal which are measured by the said at least one vibration sensor over a cycle of a predetermined number n of rotations of the said at least one moving part about the said axis of rotation, the said synchronous variance being determined on the basis of a mean squared difference between an acceleration value measured at a predetermined instant and a mean value calculated at the same said predetermined instant, • a mapping step (24, 34, 44) for generating at least two maps M 1, M 2 respectively representing a value of the said synchronous variance as a function on the one hand of the said angular position of the said at least one moving part and on the other hand of a range of predetermined harmonics of the said vibration signal, the said at least two maps M 1, M 2 respectively corresponding to successive acquisitions of the said synchronous variance at two instants t 1, t 2 that are different from one another, • an analysis step (25, 35, 45) for comparing the said values of the said synchronous variance between at least two successive maps M 1, M 2, the said analysis step (25, 35, 45) making it possible to generate an indicator CI as a function of a comparison between a first map M 1 of the said synchronous variance at a first instant t 1 and a second map M 2 of the said synchronous variance at a second instant t 2 following the said first instant t 1, and • an alarm step (26, 36) for generating an alarm when a current value CI t1, CI t2 of the said indicator CI exceeds a predetermined threshold value corresponding to the said degradation in the said at least one moving part of the said rotating mechanism. • at least one first measurement step (21, 31) comprising a measurement of the vibrations along at least one direction and generating a operational vibration signal of the said rotating mechanism as a function of time, the said first measurement step (21, 31) being carried out by means of at least one vibration sensor secured to a fixed casing of the said aircraft, • at least one second measurement step (22, 32) comprising a measurement of an angular position of the said at least one moving part, the said at least one moving part having at least one degree of freedom in rotation about an axis of rotation, • a preprocessing step (23, 33) for calculating a synchronous variance of the vibrations of the vibration signal which are measured by the said at least one vibration sensor over a cycle of a predetermined number n of rotations of the said at least one moving part about the said axis of rotation, the said synchronous variance being determined on the basis of a mean squared difference between an acceleration value measured at a predetermined instant and a mean value calculated at the same said predetermined instant, • a mapping step (24, 34, 44) for generating at least two maps M 1, M 2 respectively representing a value of the said synchronous variance as a function on the one hand of the said angular position of the said at least one moving part and on the other hand of a range of predetermined harmonics of the said vibration signal, the said at least two maps M 1, M 2 respectively corresponding to successive acquisitions of the said synchronous variance at two instants t 1, t 2 that are different from one another, • an analysis step (25, 35, 45) for comparing the said values of the said synchronous variance between at least two successive maps M 1, M 2, the said analysis step (25, 35, 45) making it possible to generate an indicator CI as a function of a comparison between a first map M 1 of the said synchronous variance at a first instant t 1 and a second map M 2 of the said synchronous variance at a second instant t 2 following the said first instant t 1, and • an alarm step (26, 36) for generating an alarm when a current value CI t1, CI t2 of the said indicator CI exceeds a predetermined threshold value corresponding to the said degradation in the said at least one moving part of the said rotating mechanism.