Detecting cracks in airplane bodies is crucial to safety. Usually, such flaws are found by tedious visual inspection and "eddy current" systems that use detectors to record any distortions in the magnetic field created when a high-frequency electric current is induced into a plane's metal skin.
But those systems produce a mishmash of squiggly lines that are hard to read. Now, Litton Systems Inc.'s Airtron unit and Physical Research Inc. in Torrance, Calif., have gone a step further. The key is Airtron's magneto-optic, single-crystal film that changes the magnetic-field data into easy-to-read patterns that show cracks, subsurface flaws, and corrosion as small as 1/1000 of an inch long, says Airtron Research Director Roger F. Belt. The new systems have Federal Aviation Administration approval for use on Boeing Co.'s 727s, 737s, and 747s and McDonnell Douglas Corp.'s DC-10s.