The invention relates to a method for estimating a dead zone at closing of a flap (P1) of a discharge valve (VBV1) of a turbomachine, in which the actual position of the actuator (V1) is measured for a setpoint closing signal of the flap (P1), a static angle is determined from the actual position, a closing dead zone is determined, corresponding to the fact that the joint (J1) is compressed so as to not let the primary flow pass through the orifice (O1) in the secondary flow, by the fact that the dead zone is equal to a reference dead zone, which has been predetermined on a reference turbomachine operating on the ground, to which the measured static angle has been added and from which a reference static angle, which has been predetermined on the reference turbomachine operating in flight, has been subtracted.