When taxiing or braking on an icy ramp or runway, tapping or pumping the brakes will usually increase stopping effectiveness. It’s the way ABS braking systems work on automobiles, gripping and releasing the brakes in short, staccato intervals. Our toes cannot work as fast as the sensors and computers that control anti-lock brakes, but the lost art of manually pumping the brakes can save the day when simply pressing harder and harder would lead to inevitable loss of control.
My father taught me about pumping the brakes of our ’63 Chevy, but he never explained why it worked. A tire in motion exerts its greatest stopping friction at the instant the brakes are first applied. A skid starts when the tire that is stopped cold by the brakes begins to slide on the ice — or any other surface for that matter. The physics involved can actually cause the vehicle to accelerate. While not intuitive, pumping the brakes allows the tire to recommence rolling, then stop again, repeating the high-traction event over and over for a net result of improved stopping power.
