"While pitot tubes have use in many different industries, no industry is more controversial in their use than the aerospace industry. They are a great tool that measures the stagnation pressure as air moves into the tubes. Then as air passes through, a side hole in the tube measures the static pressure. Based on the simple Bernoulli's equation, the tube can then measure the dynamic pressure and be used to calculate the velocity of the aircraft. In more recent years, several major flight crashes have been linked back to malfunctions in the pilot-static system that included a pitot tube and pitot-static instruments for the pilot. I'm very familiar with some of the new pitot tube designs that do a great job of limiting ice formation and have used these in more recent designs."