An aircraft propeller , the propeller rotatable about a longitudinal axis (A) and comprising a plurality of blades each rotatable through a range of blade angles, and a blade angle position feedback system , the system comprising: a feedback device rotationally coupled to the propeller for rotation with the propeller about said longitudinal axis (A), the feedback device comprising at least one pair of position markers spaced from one another around a circumference of said feedback device and oriented at an angle relative to one another and relative to said longitudinal axis (A); at least one sensor mounted adjacent the feedback device , the at least one sensor configured for successively detecting passage of said position markers and generating a sensor signal indicative of passage of said position markers , the feedback device and the at least one sensor configured for relative axial displacement between a first relative axial position and a second relative axial position along said longitudinal axis (A), the first axial position corresponding to a first mode of operation and the second axial position corresponding to a second mode of operation, the feedback device rotationally coupled to the propeller for rotation relative to the at least one sensor ; a detection unit connected to the at least one sensor configured for receiving the sensor signal therefrom, determining on the basis of the sensor signal a time interval and computing from the time interval a blade angle position for the plurality of blades, wherein the time interval is a time interval elapsed between passage of the position markers , characterised in that : both position markers of the at least one pair of position markers are angled to said longitudinal axis (A) at angles of equal magnitude such that both position markers diverge from one another and from said longitudinal axis (A). a feedback device rotationally coupled to the propeller for rotation with the propeller about said longitudinal axis (A), the feedback device comprising at least one pair of position markers spaced from one another around a circumference of said feedback device and oriented at an angle relative to one another and relative to said longitudinal axis (A); at least one sensor mounted adjacent the feedback device , the at least one sensor configured for successively detecting passage of said position markers and generating a sensor signal indicative of passage of said position markers , the feedback device and the at least one sensor configured for relative axial displacement between a first relative axial position and a second relative axial position along said longitudinal axis (A), the first axial position corresponding to a first mode of operation and the second axial position corresponding to a second mode of operation, the feedback device rotationally coupled to the propeller for rotation relative to the at least one sensor ; a detection unit connected to the at least one sensor configured for receiving the sensor signal therefrom, determining on the basis of the sensor signal a time interval and computing from the time interval a blade angle position for the plurality of blades, wherein the time interval is a time interval elapsed between passage of the position markers , <EOS>