Dependability Upgrade -- Display Unit Of Military Aircraft Radar Warning Receiver Revamped By GTRI Researchers

The Georgia Tech Research Institute (GTRI) team recently finished revamping the display unit found on the ALR-69 Radar Warning Receiver (RWR), a system used on 2,000 U.S. and 1,000 foreign aircraft. The refurbished display unit has all-new electronics that improve its predicted reliability by more than 500 percent, researchers say.

The work was supported by the Warner Robins Air Logistics Center.

"In layman's terms, the ALR-69 is the military version of a Fuzzbuster (consumer radar-warning device)," says Michael J. Willis, a senior research engineer with GTRI's Electronic Systems Laboratory. "It's the same basic principle, though much more complex in design. It lets pilots know when an enemy has a radar pointed at them, so they can take evasive action."

Because any such device is useless if it cannot relay a visible or audible warning signal, the dependability of the ALR-69's display hardware is critical. In place of the old model's oblong 3-inch by 9-inch cathode ray tube (CRT), Willis and his colleagues installed a flat-panel electro-luminescent screen — chosen because of its relatively low power requirements — and three printed circuit cards. The new model's container is identical in size and shape to the old model, allowing plug-in unit-swapping in the field. The only visible difference between the two designs is the new model's amber monochrome screen, a departure from the green used by the old model.

The new display unit offers higher brightness, night vision compatibility, sunlight readability and is fully compatible with the rest of the system, Willis says. It has a predicted reliability of some 14,000 hours — versus an actual reliability of about 2,500 hours on the old CRT-based model.

A major element in such improved reliability and maintainability is the better capabilities, features and reliability of today's electronics than the decades-old electronics used in the CRT-based display unit, Willis explains. The new model has no adjustable components, better fault diagnostics and built-in test capability.

"Twenty or 30 years ago the electronics of that day didn't have the features and capabilities that we have today because of newer integrated circuits," he says. "The reliability improvements are more a function of improved electrical performance and integrated circuit performance than any special mechanical changes."

GTRI's current work on the display unit is the most recent chapter of an extensive involvement with the ALR-69 RWR system going back more than 15 years. GTRI has worked extensively on both hardware and software aspects of the complex system, which includes radio-frequency, microwave, analog, digital and other kinds of circuits — all of which require the support of embedded software, ground equipment and laboratory tools.

Among the GTRI accomplishments was the Class IV Reliability and Maintainability Upgrade, which was completed in the early 1990s. The Class IV Upgrade consists of a series of circuit card assemblies that provided the ALR-69 with a large computational power increase by expanding the microprocessor count from one to three. That upgrade is now flying throughout the world on some 2,000 U.S. and 1,000 foreign aircraft. The U.S. military uses the ALR-69 on the B-52 bomber; A-10 and F-16 fighters; MH-53J and H-60 helicopters, and C-130 and C-141 cargo planes.

"There's a wide variety of platforms, and that's one of the challenges of the system — being able to support all of the different aircraft that the system is on," Willis says.

The redesigned display unit is now undergoing extensive electrical, environmental and field testing. If all goes well, the new model should begin service around the world within two years.