An anti-torque rotor for a helicopter, comprising: - a mast, rotatable about a first axis; - a plurality of blades, hinged on said mast, extending along respective second axes transversal to said first axis and rotatable about respective said second axes to alter the respective angles of attack; - a control element, sliding along said first axis with respect to said mast, integrally rotating with said mast, and operatively connected to said blades to cause the rotation of said blades about respective said second axes following a translation of said element along said axis; - a control rod, sliding axially along said first axis with respect to said mast and angularly fixed with respect to said first axis; - a first bearing, interposed between said control rod and said control element, sliding along said first axis with respect to said mast and integrally with said control rod, and configured to enable the relative rotation of said control element with respect to said control rod about said first axis; and - a transmission unit, which is operatively connected to said control rod and to said control element; said transmission unit being selectively available: - in an active configuration, wherein it causes said control element to slide, following the translation of said control rod, along said first axis; or - in an inactive configuration, wherein it is disengaged from said control element; wherein said transmission unit being arranged in said active configuration in the event of failure of said first bearing, wherein said bearing is no longer able to transmit an axial load from said rod to said control element, causing the axial translation in both directions of said element, following the axial translation of said rod; and said transmission unit being arranged in said inactive configuration when said first bearing correctly allows relative rotation of said element and said rod and prevents any relative translation between said element and said rod; said transmission unit, in turn, comprising: - an annular ridge axially integral with said control rod and radially projecting from said control rod; and - a seat engaged by said ridge and angularly and axially integral with said control element; characterized in that it comprises a second bearing (100, 101) interposed between said ridge and said seat; said rotor further comprising detection means; said detection means, in turn, comprising a first sensor adapted to generate a signal associated with the fact of said transmission unit being in said active configuration. - a mast, rotatable about a first axis; - a plurality of blades, hinged on said mast, extending along respective second axes transversal to said first axis and rotatable about respective said second axes to alter the respective angles of attack; - a control element, sliding along said first axis with respect to said mast, integrally rotating with said mast, and operatively connected to said blades to cause the rotation of said blades about respective said second axes following a translation of said element along said axis; - a control rod, sliding axially along said first axis with respect to said mast and angularly fixed with respect to said first axis; - a first bearing, interposed between said control rod and said control element, sliding along said first axis with respect to said mast and integrally with said control rod, and configured to enable the relative rotation of said control element with respect to said control rod about said first axis; and - a transmission unit, which is operatively connected to said control rod and to said control element; - in an active configuration, wherein it causes said control element to slide, following the translation of said control rod, along said first axis; or - in an inactive configuration, wherein it is disengaged from said control element; - an annular ridge axially integral with said control rod and radially projecting from said control rod; and - a seat engaged by said ridge and angularly and axially integral with said control element;