A control damper for regulating an air flow for a ventilation duct, comprising: - a cylindrical body extending along an axis of blowing, defining an air duct, - an adjustment device comprising: • a flap for blocking the duct, the flap being received in the duct and being movable in rotation with respect to the body about a pivot axis orthogonal to the axis of blowing, between an open position, wherein the duct is minimally closed, and a closed position, wherein the blockage of the duct is maximum, • means of adjustment, configured for adjusting a nominal position of the flap, the nominal position being intermediate between the open position and the closed position, the flap in the nominal position defining, along with a median plane of the damper, a nominal angle (α NOM), the median plane being parallel with the axis of blowing and with the pivot axis, - a return device, configured for returning the flap to the nominal position thereof when the flap is moved away from the nominal position by the air flow, characterized in that: - the adjustment device further comprises: • a shaft, which extends along an axis of adjustment and which is pivotally mounted with respect to the body about the axis of adjustment, the axis of adjustment being parallel to the pivot axis, an angular position of the shaft about the axis of adjustment being adjustable, and • at least one adjustment cam, each adjustment cam protruding radially from the shaft and cooperating with a respective first stop of the flap, so as to limit the movements of the flap between the nominal position thereof and the open position thereof when the user defines the angular position of the shaft, - the return device comprises a tension spring with a first end and an opposite second end, wherein the first end is connected to a hard point provided on the shaft, whereas the second end is connected to an attachment point provided on the flap, so that the spring is tensioned when the flap is in the nominal position. - a cylindrical body extending along an axis of blowing, defining an air duct, - an adjustment device comprising: • a flap for blocking the duct, the flap being received in the duct and being movable in rotation with respect to the body about a pivot axis orthogonal to the axis of blowing, between an open position, wherein the duct is minimally closed, and a closed position, wherein the blockage of the duct is maximum, • means of adjustment, configured for adjusting a nominal position of the flap, the nominal position being intermediate between the open position and the closed position, the flap in the nominal position defining, along with a median plane of the damper, a nominal angle (α NOM), the median plane being parallel with the axis of blowing and with the pivot axis, • a flap for blocking the duct, the flap being received in the duct and being movable in rotation with respect to the body about a pivot axis orthogonal to the axis of blowing, between an open position, wherein the duct is minimally closed, and a closed position, wherein the blockage of the duct is maximum, • means of adjustment, configured for adjusting a nominal position of the flap, the nominal position being intermediate between the open position and the closed position, the flap in the nominal position defining, along with a median plane of the damper, a nominal angle (α NOM), the median plane being parallel with the axis of blowing and with the pivot axis, - a return device, configured for returning the flap to the nominal position thereof when the flap is moved away from the nominal position by the air flow, - the adjustment device further comprises: • a shaft, which extends along an axis of adjustment and which is pivotally mounted with respect to the body about the axis of adjustment, the axis of adjustment being parallel to the pivot axis, an angular position of the shaft about the axis of adjustment being adjustable, and • at least one adjustment cam, each adjustment cam protruding radially from the shaft and cooperating with a respective first stop of the flap, so as to limit the movements of the flap between the nominal position thereof and the open position thereof when the user defines the angular position of the shaft, • a shaft, which extends along an axis of adjustment and which is pivotally mounted with respect to the body about the axis of adjustment, the axis of adjustment being parallel to the pivot axis, an angular position of the shaft about the axis of adjustment being adjustable, and • at least one adjustment cam, each adjustment cam protruding radially from the shaft and cooperating with a respective first stop of the flap, so as to limit the movements of the flap between the nominal position thereof and the open position thereof when the user defines the angular position of the shaft, - the return device comprises a tension spring with a first end and an opposite second end, wherein the first end is connected to a hard point provided on the shaft, whereas the second end is connected to an attachment point provided on the flap, so that the spring is tensioned when the flap is in the nominal position.