Bleed valves for gas turbine engines

A bleed valve, comprising:

• a valve body having an inlet end, an outlet end, and a flapper seat arranged along an axis between the inlet end and the outlet end, the valve body defining a flow path extending through the flapper seat;
• a flapper having a pivot end and a free end, the flapper being pivotally connected to the valve body at the flapper pivot end and movable relative to the flapper seat between open and closed positions;
• and
• a spring coupled between the flapper and the valve body biasing the flapper toward the open position, wherein the flapper seats against the flapper seat and blocks the flow path in the closed position,
• wherein the flapper is angled toward an inlet of the valve body in the open position such that only a pressure differential across the flapper urges the flapper towards the closed position, and
• wherein the free end of the flapper is positioned such that an angle between the flapper and the axis is less than 90 degrees in both the open and closed positions, and
• wherein a pivot axis of the flapper is co-planar with the flapper seat, and a movement angle of the flapper between the open position and the closed position is within a range between about 27.5 degrees and about 37.5 degrees to limit valve flutter during valve opening and/or closure.