NORDAM HAS introduced a new airliner cabin-window designed to counter crazing - the thousands of scratches on airliner windows - which has reached epidemic proportions, according to airlines. The Tulsa, Oklahoma-based company's new Nordex EL cabin windows are being flight tested by 15 airlines.

"Nordex EL has been proven to outperform standard acrylics approximately five-to-one in laboratory tests," says Nordam Transparency division general-manager Bob Hart. More than 4,000h have been accumulated on some flight-test aircraft, with flawless results, it claims.

Other suppliers' windows have obscured vision in as little as 250h, Nordam maintains.

Crazing is a normal aging process that has become an increasing problem since early 1992.

Traditionally, acrylic cabin windows display linear cracking patterns, concentrated in the centre of the viewing area. The new pattern is evenly distributed and has a sparkling appearance, consisting of thousands of tiny "stars" which increase in number and severity as flights are accumulated.

While the exact cause of the damage is uncertain, the 1991 eruption of Mount Pinatubo and subsequent volcanic activity is believed to be partially responsible. It is possible that sulphur compounds are circulating in the atmosphere and creating the new craze pattern.

Aircraft manufacturers and major airlines are conducting in-service evaluation of several new windows. Some test windows feature coatings, but recent flight test results indicate that coatings have not yielded a satisfactory service life Nordam says.

The transparency division duplicated the star-crazing pattern through laboratory simulation of pressure and temperature cycles and other flight conditions. "Duplicating results in a controlled environment is very beneficial in developing an improved cabin window," explains Hart.

Marketing manager Bob Brooks says Nordex EL is not a new material but is produced using improved processes. "While we are investigating several coatings in an effort to find the optimum solution, Nordex EL is currently available to operators worldwide," he says.

Cabin window cracking and crazing can be removed through hand-held sanding, machine slurry polishing or diamond milling. "Nordam Transparency offers operators diamond-milling cabin-window repair for premium edge-to-edge optics, the smoothest surface finish, and a maximised service life," Brooks says.

"The secret to accomplishing the best repair is to avoid polishing or buffing after the diamond milling," he explains.

Source: Flight International