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 vary the respective angles of attack; - an 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; and - a first bearing interposed between said control rod and said 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 element with respect to said control rod about said first axis in a normal operating condition; said first bearing, in turn, comprising: - a first ring rotatable integrally with said element about said first axis; - a second ring radially internal to said first ring with respect to said first axis and sliding integrally with said control rod along said first axis; - a plurality of first rolling bodies, which are interposed between said first and second rings (30, 31) and adapted to roll on respective first tracks (33, 34) of said first and second rings (30, 31); said rotor further comprising: - a third ring slidable integrally with said control rod along said first axis and angularly fixed with respect to said first axis; - a plurality of second rolling bodies, which are interposed between said second and third rings (31, 50) and are adapted to roll on respective second tracks (52, 53) of said second and third rings (31, 50); and - a locking element arranged in a standard configuration, wherein it prevents the relative rotation of said second and third rings (31, 50), when said first bearing is, in use, in a normal operating condition; said locking element being movable from said standard configuration to at least one emergency configuration, wherein it makes said second ring free to rotate with respect to said third ring about said axis, when said first bearing is, in use, in a failure condition; characterized in that said second ring comprises a radially outer surface with at least one tapered stretch axially interposed between said first rolling bodies; said first ring comprising at least one blocking element with at least one tapered first surface radially facing said stretch and separated with a clearance by said stretch, when said first bearing is, in use, in said normal operation. - 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 vary the respective angles of attack; - an 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; and - a first bearing interposed between said control rod and said 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 element with respect to said control rod about said first axis in a normal operating condition; - a first ring rotatable integrally with said element about said first axis; - a second ring radially internal to said first ring with respect to said first axis and sliding integrally with said control rod along said first axis; - a plurality of first rolling bodies, which are interposed between said first and second rings (30, 31) and adapted to roll on respective first tracks (33, 34) of said first and second rings (30, 31); - a third ring slidable integrally with said control rod along said first axis and angularly fixed with respect to said first axis; - a plurality of second rolling bodies, which are interposed between said second and third rings (31, 50) and are adapted to roll on respective second tracks (52, 53) of said second and third rings (31, 50); and - a locking element arranged in a standard configuration, wherein it prevents the relative rotation of said second and third rings (31, 50), when said first bearing is, in use, in a normal operating condition; said locking element being movable from said standard configuration to at least one emergency configuration, wherein it makes said second ring free to rotate with respect to said third ring about said axis, when said first bearing is, in use, in a failure condition; characterized in that said second ring comprises a radially outer surface with at least one tapered stretch axially interposed between said first rolling bodies; said first ring comprising at least one blocking element with at least one tapered first surface radially facing said stretch and separated with a clearance by said stretch, when said first bearing is, in use, in said normal operation.