i. The process of changing the pitch of a propeller's blades to produce zero torque and to reduce drag to the minimum so as to prevent further damage to an engine that has been shut down either automatically or manually after a malfunction. In this process, the propeller blades are turned until the blade-chord lines are almost parallel to the airflow, and there are no rotating forces acting on the propeller as a whole. See
feather (ii).
ii. The ability of a rotor blade to rotate about its chord axis. This takes place as a result of a change in the collective, or cyclic, pitch. See
feather (i).
iii. The action that changes the pitch angle of helicopter blades by rotating them about their feathering axis.