White Paper

Selecting Optimal Avionic and Vetronic Displays for Your Application

Issue link: https://read.uberflip.com/i/1264211

Contents of this Issue

Navigation

Page 3 of 5

w w w. m r c y. c o m WHITE PAPER 3 No Single Point of Failure Aircraft designs have advanced steadily in providing pilots and aircrews with fully integrated flight information. A key component for the real- time information access is a large area display (LAD) that presents clear, crisp, high-fidelity images across multiple windows and video overlays. These displays, 20-plus inches diagonally, are also equipped with touch technology similar to smartphones and tablets. With flexible windows and touch controls, a single LAD replaces multiple system-specific displays and controllers. Navigation, weapons control, engine control, communications, tactical situation monitoring and other systems are all viewed and controlled using the LAD, reducing the overall weight and power requirements. Equally important, users have the flexibility to enlarge or reduce the display area devoted to any system, based on immediate mission need. While a large cockpit screen delivers great application flexibility, a single monolithic display also represents a single point of failure. If it stops working, all the systems 'go dark,' putting the aircrew in a life- threatening situation. An elegant and effective design solution is achieved by implementing two independent cells on a single LCD substrate, with no visible vertical gap down the center of the display. While they can display a single image with no visual separation, there is redundancy between the two cells. Multiple windows can be displayed, driven by multiple applications, and moved seamlessly between the two halves of the LAD. However, if one cell fails, the other still provides display support for all the aircraft systems. Operating in Extreme Temperatures If a commercial-quality LCD screen is operated in a warm-weather environment and then exposed to direct sunlight, the temperature can quickly reach a point where the liquid crystal material no longer functions. Higher-quality display fluid is needed for high-temperature operation. On the other hand, in temperatures below -20°C, the liquid crystal material begins to thicken, reducing its reaction to small voltages and thus changing what is displayed on the screen. The solution for this is the addition of a heater element to the LCD, which permits normal operating performance at cold temperatures and reduces the amount of warm-up time required from a cold start. Depending on the expected range of operating environments, displays for aircraft and defense platforms may need designs that can deal with both types of extreme temperature. Business Factors Closely related to some of the technical issues already discussed, there are a set of often-overlooked business factors to consider during evaluation of deployable displays. These factors directly impact the total cost of ownership for a program and should not be underestimated. Extended Display Life Replacing an aircraft or ground vehicle display panel is expensive and can interfere with mission availability. Extended display life mitigates these issues, with economic and operational improvements proportional to the life extension. Display life is usually quantified utilizing mean time between failures (MTBF), a convenient measure of reliability. Higher-reliability designs begin with flexible control of luminance. As referenced above, commercial-grade LCDs must often be driven at 100%, or higher, of their rated voltage potential just to yield sufficient luminance for an effective user interface, especially when operating in direct sun/daylight conditions. This reduces display longevity, as LEDs continuously delivering maximum capacity luminance degrade quickly. On the other hand, display MTBF is increased significantly by using LEDs that can normally operate at some fraction of their maximum capacity, only increasing luminance when needed. LEDs with extra luminance capacity can further increase MTBF when combined with an adaptive design. Over time, some strings of LEDs, in any display, will inevitably fail. An adaptive LCD implements high-density LED packing, then uses internal luminance sensors to detect when a string of or single LED has failed. At that point, the luminescence of adjacent strings are increased to compensate; the user will not perceive any difference. Working in combination, these design features result in displays with reliability that far exceeds anything offered by standard commercial or industrial products. The value of the difference in reliability should be included in any life-cycle cost analysis. Embedded Systems Business Practices In addition to the unique technologies that support deployable displays, programs for aircraft and ground vehicles need partners who support embedded systems business practices. A commercial LCD provider cannot make any guarantee for performance in a deployed systems operational environment. In fact, a commercial warranty is voided when the LCD materials are operated outside of normal office conditions. Deployed systems need display designs Figure 4: Light from display is flooding the entire cockpit (canopy reflections) Figure 5: Light is no longer flooding the entire cockpit (NO canopy reflections)

Articles in this issue

view archives of White Paper - Selecting Optimal Avionic and Vetronic Displays for Your Application