Читать книгу Flight Theory and Aerodynamics - Joseph R. Badick - Страница 46

The aerodynamic forces and moments acting on an aircraft in flight are due, in great part, to the properties of the air mass in which the aircraft is flying. By volume, the atmosphere is composed of approximately 78% nitrogen, 21% oxygen, and 1% other gases. The most important properties of air that affect aerodynamic behavior are its static pressure, temperature, density, and viscosity.

It is important to remember at this point that air is a fluid, and like other gases takes on the shape of its container. Just as a liquid can fill a container, air has the capacity to expand and fill the container as well, though the density will differ significantly. Throughout this textbook, we will expand on this introduction to the fluid properties of air, especially as it relates to an airfoil and ultimately the impact on aircraft performance calculations.