Abstract: A system is provided to adjust the operating angle of attack of a variable pitch impeller blade in response to different conditions. The impeller blade is pivotally mounted around a pivot axis and a small control surface attached to the blade provides a turning moment around the pivot axis to oppose a similar moment provided by the lift component of the blade. The operating angle of attack of the blade is determined by the angle at which the moment from the control surface tapers off as it approaches stall range, thus equalizing the moment from the impeller blade.