Wind tunnels are machines for “flying” aircraft on the ground. They are tubelike structures or passages in which wind is produced, usually by a large fan, to flow over objects such as aircraft, engines, wings, rockets or models of these objects. A stationary object is placed in the test section of a tunnel and connected to instruments that measure and record airflow around the object and the aerodynamic forces that act upon it. From information gathered in these observations, engineers can determine the behavior of an aircraft or its components at takeoff, while cruising, and during descent and landing.
Wind tunnels also help engineers determine the performance of, and eliminate “bugs” in, new designs of civil and military aircraft without risk to a pilot or costly aircraft. Responses to flight condition of new materials and shapes for wings, ailerons, tails, fuselages, landing gear, power systems and engine cowlings can be assessed before these designs are incorporated into aircraft.
Today, no aircraft, spacecraft or space launch or reentry vehicle is built or committed to flight until after its design and components have been thoroughly tested in wind tunnels. Every modern aircraft and space rocket has made its maiden flight in a wind tunnel. Wind tunnels have been among the key tools which have made American aircraft and aeronautical equipment the most desired and most widely used in the world.
The National Aeronautics and Space Administration maintains the largest number and variety of wind tunnels ever operated by any single agency or company. NASA’s 42 major wind tunnels vary in size from those large enough to test a full-size airplane to those with a test section only a few inches square where models as small as a match are tested.
