DESCRIPTION
Aircraft have many systems that can be checked ultrasonically. Some of the more common applications include: testing leaks in fuel cells, oxygen systems, hot air ducts, cabin pressure, tire leaks, floatation devices, hydraulic valves and actuators. It is also used to locate leaks in cockpit windows as well as to identify potential problems with bearings, pumps, motors and gears.
How Ultrasonic Detection Works
Operating systems such as compressed gas systems, valves, motors, pumps, etc., all produce ultrasound. Some high frequency sounds are generated from turbulence, others from friction. As components begin to wear, fail or leak, there is a change in the normal ultrasonic pattern. This can be detected as an increase in amplitude, a change in sound quality or a change in sound pattern. Due to portability, ease of use and flexibility any Ultraprobe may be used all around the aircraft.
The Ultraprobe detects minute changes in ultrasound and converts these signals so that they may be heard through headphones, and observed as intensity increments, usually decibels, on a display panel. By using plug-in modules for either a scanning mode or a contact mode, equipment may be inspected for leakage or for mechanical problems.
Digital instruments with on-board sound recording and data logging help inspectors record sound samples and data for accurate condition analysis. There are instruments rated intrinsically safe for those conditions that require such ratings.
Detection Methods
For general leak detection, in a scanning mode, move along the area to be tested using a slight waving motion, listen for the loudest "hissing" sound and follow the sound to the loudest point, making adjustments with the sensitivity dial as needed. Use the patented Warble Tone Generator to test for cabin pressure and cockpit window leaks in the same manner. For valves and actuators, touch upstream and reduce the sensitivity to a mid-line reading. Compare with the downstream reading. Test bearings and mechanical equipment by setting a baseline sound level and sound quality conditions. Compare readings and sound samples over time for trending. It's that simple.
