Volume 9, Issue 6 - November/December 2007

Off the Line
oem glass manufacturing

Parallel Glass Universes
by Russ Corsi

It didn’t take the Wright brothers very long to realize that they didn’t like getting “bugs in their teeth” when their aircraft was finally able to fly, any more than the Duryea brothers did when their horseless carriage started successfully moving down the road. Because the auto pilot was years away, both modes required that the driver also see where he was going, as well. A piece of window glass initially worked in both applications. However, as engines became refined and the speeds increased, laminated flat glass (laminated with either cellulose nitrate or cellulose acetate) took its place.

Historians would disagree as to which automobile had the first laminated windshield; however, most would agree that the Ford Tri-motor (a.k.a., the “Tin Goose”) was the first aircraft with a laminated windshield (circa 1926).

Technology Abounds
Although aircraft innovations appear to have outpaced automotive new product developments, the list of similar technologies is very impressive.

The cellulose nitrate/acetate product was replaced by polyvinyl butyral (PVB) as the interlayer of choice in the late 1930s. While automotive laminated glass still uses a refined PVB product, aircraft transparency technology has moved through quite a variety of products from cast-in-place (CIP) interlayer, to urethanes and silicone products.

While in-dash defrosters helped to defrost/defog/deice windshields, scientists soon discovered that a metallic coating built into the laminate could easily be heated via an electrical current to clear the windshield faster than heated air could. Alternate frost clearing technologies, which appeared on both cars and planes, included painted, screened, conductive ceramic grids or fine wires that are sewed onto one of the interlayer surfaces.

As we know, radio communication always has been a necessity on aircraft. While the initial radios on automobiles were optional, it didn’t take long for consumers to require radio receivers on their cars. Whether for one- or two-way communication, antennas can now be found, screened on the glass, sewed into the interlayer, or embedded into the pinchwelds of both cars and planes. 

As an aircraft makes its approach for landing, projecting the instrumentation on the windshield in the pilot’s site line has proved to be an excellent way to make landing a lot safer. Of course we know that the heads-up display (HUD) currently is available on many motor vehicles.

Key Factors
Weight and cost are critical factors that influence both aircraft and motor vehicle design. Thus, the introduction of tempered glass (thermally strengthened) in the mid-1930s, quickly found its way to both the air and the land. A more refined version of tempered glass (chemically tempered) has replaced the thermally tempered glass on many aircraft applications. Although the chemically strengthened product is more expensive to make, the aircraft industry places a good deal of value on the weight reductions and the additional product strength realized. Currently, car companies are more reluctant to spend the additional money.

There is nothing more comforting than driving/flying in the rain or snow while experiencing the value of a water repellant coating on your windshield literally shedding the water. You guessed it—there are parallel technologies that utilize hydrophobic coatings to accomplish this task in both arenas. In fact, the aircraft products are so effective that there are several current airplane designs that no longer require windshield wipers.

What about plastic applications for both modes of transportation? Airplanes have used acrylic and polycarbonate products for many window openings for quite some time. The cost, weight and durability advantages of these products have allowed them to migrate to many applications where pilot vision issues do not come into play. Federal Motor Vehicle Safety Standards (FMVSS) 205-Z26.1 requirements currently prohibit plastic products from appearing in windshield applications; however, more and more plastic products are being found in fixed positions in other locations in the vehicle.

As new motor vehicle or aircraft designs become reality, it’s always fun to speculate if there is a feasible application of any new glass technology that would benefit both modes of travel. 

Russ Corsi retired as manager of technical services from PPG Industries’ Automotive Replacement Glass business unit after 31 years in the glass industry. He now serves as a consultant to the industry. Mr. Corsi’s opinions are solely his own and not necessarily those of this magazine. 



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