Vapor pressure called partial pressure. For example, air at sea level, and saturated with water vapor at 20 °C, has partial pressures of about 2.3 kPa of water, 78 kPa of nitrogen, 21 kPa of oxygen and 0.9 kPa of argon, totaling 102.2 kPa, making the basis for standard atmospheric pressure. Vapor pressure is measured in the standard units of pressure. The International System of Units (SI) recognizes pressure as a derived unit with the dimension of force per area and designates the pascal (Pa) as its standard unit. One pascal is one newton per square meter (N·m or kg·m·s). Experimental measurement
Piper PA-24 Comanche tail, laminar flow airfoil, and all-flying stabilator. The standard fuel capacity of the PA-24-180 was . The flaps were manually actuated, controlled by the same Johnson bar actuator as the Piper Cherokee. The aircraft specifications were for cruise speeds of and fuel burns between 7.5 and 10.5 gph at 55-percent and 75-percent power settings. Full-fuel payload with standard fuel was 715 pounds, with a gross weight of and range with 45-minute reserve of 700 nautical miles. When new, standard, average-equipped Comanche 180s sold between $17,850 (1958) and $21,580 (1964). A total of 1,143 were built. In 1958 Piper introduced a