Due to gravity, when skydivers jump out of an airplane, they immediately fall toward the earth, falling several thousand feet in less than a minute before opening their parachutes. For indoor skydiving, where you float less than 100 feet above ground level, there is no parachute and a rather sophisticated process is involved that uses sensing technologies.
To simulate free-fall conditions in a vertical wind tunnel (VWT), iFly, a company with numerous international indoor skydiving locations, uses a total of four 450 hp fans to draw air through a flight chamber and return the air down the sides of Return Air Towers (RATs). Each fan is 56 ft tall and 16 ½ ft in diameter.
The tunnel’s airspeed is controlled by setting a percentage of the total available capability. For instance, a setting of 68% may result in 100 mph airspeed. The tunnel is tapered so the airspeed changes as the flier travels up the tunnel’s chamber. For a specific, individual or group of individuals, the percentage is set by a person (the controller) at the console on the flight deck. The precise level is selected based upon the flier’s weight and body type with additional feedback from the flight instructor. The use of most of the sensors in the flight experience revolves around safety.
To detect issues before they become critical, each of the four motors has two vibration sensors. One is at the fan or drive end and the other at the non-drive end. Wilcoxon Sensing Technologies vibration sensors are used to monitor motor/fan vibration. When an abnormal vibration level is detected, the airspeed can safely be reduced and stopped to perform system analysis. During initial start-up each morning, the entire system is subjected to series of self-tests.
Additional sensors in the system include two pitot tube/static air pressure sensors to measure the wind speed for testing and tracking efficiency.
Finally, temperature sensors are used in the extensive heating ventilating and air conditioning (HVAC) system to maintain the tunnel’s air temperature.
As in industrial applications, sensors play an essential role for safety and efficient operation.