Ice and Rain Control Systems What is the principle characteristic of a windshield pneumatic rain removal system? a. An air blast spreads a liquid rain repellant evenly over the windshield that prevents raindrops from clinging to the glass surface. b. An air blast forms a barrier that prevents raindrops from striking the windshield surface c. A pneumatic rain removal system is simply a mechanical windshield wiper system that is powered by pneumatic system pressure.