A weeping wing is a chemical aircraft ice protection system wherein a glycol-based chemical is released onto the wing surface using small orifices on the leading edge of the wing. This system provides both anti-icing (ice formation prevention) and deicing (removal of ice which has already formed).
The system is activated using a switch in the cockpit. This turns on the fluid pump, which pumps fluid out of the reservoir, through the ducting, and out onto the calibrated orifices on the wing leading edge. As the fluid flows along the airstream (both on the top and bottom surfaces of the wing), it leaves a thin coat of fluid which protects the surface from icing. The excess fluid then leaves the wing surface sliding out behind the wing's trailing edge.