Gone are the days of heavy, bulky window shades with accordion pleats. Gone are the sliding shades that always seemed to jam in the wrong place at the wrong time. Welcome to the “smart window” from InspecTech Aero Service and Research Frontiers, makers of a window without a shade that changes from clear to opaque with the movement of a flat-panel sliding switch.

Those looking for a practical application of this new technology can find it on a Learjet 25C, owned by National Jets of Fort Lauderdale, Fla. (see photo). The installation is the first ever in a business jet and was completed by InspecTech at its Fort Lauderdale facility.

The SPD window was invented by Research Frontiers of Woodbury, N.Y. InspecTech is licensed to produce and market the windows for aerospace applications. The SPD technology is also licensed to a growing number of companies in various industries and is covered by approximately 365 patents and patent applications held by Research Frontiers.

Here’s How It Works

The technology involved in the SPD windows isn’t new. It’s actually been in development for more than three decades. But only in the last year did the maturation process reach a point where its promise is being fulfilled as certification is being granted by the FAA, and it can be produced in sufficient quantity to meet demand.

The technology takes the form of a thin SPD (suspended particle device) film laminated between layers of the acrylic or polycarbonate that commonly make up the entire thickness of the nonstructural inner window. By adjusting the alignment of the suspended particles through varying the voltage, the window can be “tuned” from clear to dark, or to any point between the two.

Not only can each window be individually adjusted, but the controls can be incorporated into the cabin management system so that windows can be managed individually or as a group from a cabin or cockpit panel, or programmed for automatic adjustment.

According to Alex Martinez, InspecTech’s head of engineering and new product development, the initial installation might have come earlier, but the company wanted a wider-ranging, more rigorous certification to lay the groundwork that would allow SPD window installations in a broader range of large and small aircraft. “Once the FAA issued approvals, our technical engineering completed the installation on this [Learjet 25C] in-service aircraft in eight hours.”

Martinez added that InspecTech is already into full production, “producing SPD laminates on one end of the process and installing FAA-approved windows on the other.” InspecTech claims smart windows are now available for installation by “any of hundreds of completion centers around the world,” and by next year the company expects to be able to meet its goal of selling and installing 5,000 windows a month.

While SPD raw film is priced in the $11- to $25-per-sq-ft range, the process of lamination and certification currently drives the cost up considerably to the $800- to $1,200-per-sq-ft range. “But we expect pricing to come down quite a bit as sales volume goes up and additional STCs are acquired.”

Research Frontiers also claims that the weight difference by the SPD windows and current shade systems on a 737 airliner might mean an annual saving of $75,000 to $90,000 in terms of reduced fuel burn.

Weight Savings = One Lightweight Pax

Martinez noted that a single pleated shade system in a Gulfstream IV window weighs about 12 lb, compared to two pounds for a single SPD window. “Replacing all the old pleated shade windows with SPD window systems in a Gulfstream would mean a weight savings of about 120 pounds,” he said. That includes a one-hour auxiliary/backup battery system that allows operation of the windows even when the aircraft is not powered up.

For Russell Boy, v-p of National Jets, the Learjet 25C launch airplane is just the first bizjet in his fleet to be converted to the smart window. “We’ll be getting rid of the old shades that were constant maintenance hogs.”

More information is also available on the Inspec-Tech Web site at www.inspectech.net, or the Research Frontiers site at www.refr-spd.com.