A method for estimating a closing dead zone (ZM RECH) of a first gate of a first discharge valve mounted on a first casing of a turbomachine to be investigated, which can operate in flight to propel an aircraft, the first casing delimiting in its inside a primary gas flow of the turbomachine, the first gate being designed to be able to be moved angularly by a first actuator depending on a first control signal of the first actuator between one and the other of: - a first opening position of a first orifice of the first casing configured to discharge by this first orifice a portion of the primary flow into a secondary gas flow located outside the first casing, - and a first closing position of the first orifice configured to prevent the primary flow from passing through the first orifice, the first gate being provided with a first gas seal gasket, able to be compressed against a first edge of the first orifice in the first closing position to seal the closure of the first orifice, characterized in that for the turbomachine to be investigated, operating in flight, the first actual position of the first actuator is measured when the first control signal is equal to a first set point closing signal (SCPF1) of the first gate, based on the first actual position, a measured droop angle (Stat MES) of the first gate with respect to the first casing is determined, for the turbomachine to be investigated, operating in flight, a measured closing dead zone (ZM RECH) of the first gate is determined, in which the first gasket remains compressed and thus seals the closure of the first orifice, by the fact that the measured closing dead zone (ZM RECH) is equal to a reference dead zone (ZM REF), which was predetermined during operation on the ground on a reference turbomachine which can operate in flight and on the ground, to which has been added the measured droop angle (Stat MES) and from which has been subtracted a reference droop angle (Stat REF) which was predetermined on the reference turbomachine operating in flight to propel an aircraft. - a first opening position of a first orifice of the first casing configured to discharge by this first orifice a portion of the primary flow into a secondary gas flow located outside the first casing, - and a first closing position of the first orifice configured to prevent the primary flow from passing through the first orifice, the first gate being provided with a first gas seal gasket, able to be compressed against a first edge of the first orifice in the first closing position to seal the closure of the first orifice, characterized in that for the turbomachine to be investigated, operating in flight, the first actual position of the first actuator is measured when the first control signal is equal to a first set point closing signal (SCPF1) of the first gate, based on the first actual position, a measured droop angle (Stat MES) of the first gate with respect to the first casing is determined, for the turbomachine to be investigated, operating in flight, a measured closing dead zone (ZM RECH) of the first gate is determined, in which the first gasket remains compressed and thus seals the closure of the first orifice, by the fact that the measured closing dead zone (ZM RECH) is equal to a reference dead zone (ZM REF), which was predetermined during operation on the ground on a reference turbomachine which can operate in flight and on the ground, to which has been added the measured droop angle (Stat MES) and from which has been subtracted a reference droop angle (Stat REF) which was predetermined on the reference turbomachine operating in flight to propel an aircraft.