If my memory serves me correctly the DC-3 fitted with the P&W 1830 and Hamilton Standard Propeller, a loss of total oil pressure will cause the propeller to become uncontrollable at the low pitch stop (18 degrees). It requires positive pressure backed up by the feather pump to feather the prop.
In this condition there is a danger of an over speed and the propeller should be feathered. Note: The oil tank has a reserve of approx 2.8 gallons specifically for the feather pump.
An additional safety feature is a balance spring in the governor system that will stabilize the engine at approximately 2050 RPM if the control cable or governor pulley shaft fails. The prop governor has a range of 18 to 23 degrees, with high pitch (full-feathered) set at 88 degrees.
