A vernier duct blocker (31) comprises a plurality of vanes (21) each having a width and comprising a forward portion (15) and an aft portion (13) defining a plurality of gas paths each of the plurality of vanes being separated by a plurality of widths. It further comprises a rotatably movable ring (11) interposed between the forward portion (15) and the aft portion (13) and comprising a plurality of openings (17) each having a width. The width (W) of one of the plurality of vanes (21) differs from the width (W 1 ) of another one of the plurality of vanes (21).
