Abstract: An upstanding helmet window panel has a pressurized fluid manifold extending along the upper margin of the window panel including longitudinally spaced spray jet outlet structure for spray discharging fluid from the manifold onto the upper margin of the window panel at an acute angle relatively thereto. A combination of cleaning liquid (water) and gas (air) is supplied to the manifold under pressure and the water and air are discharged from the jet outlet structures in a pulsating manner with the pulsating discharges of water serving to increase the cleaning action on the window panel and forming a layer of water flowing over the panel and the pulsating discharges of air serving to form a curtain of air over the layer of water on the window to smooth out and maintain a generally constant thickness of the water layer and thus increase visibility therethrough.