Story ID: 
EVS, SVS spurring HUD interest
By: Stephen Pope
Caption: Head-up display (HUD) manufacturers have carved a respectable niche for themselves in the business aviation realm in the last decade or so, but if the mark
Word Count: 1472
Head-up display (HUD) manufacturers have carved a respectable niche for themselves in the business aviation realm in the last decade or so, but if the marketing gurus at Rockwell Collins Flight Dynamics are right the technology could be on the verge of entering the segment’s mainstream, at least in larger jets.

More operators of big iron are starting to view the safety and operational benefits of a HUD as outweighing the technology’s high price. And while HUD prices aren’t coming down, the capabilities being extended to flight crews flying HUD-equipped airplanes are on the rise.

Many operators, for example, are viewing with envy the operational credits extended to pilots flying the big Gulfstreams equipped with Honeywell HUDs and a Kollsman infrared enhanced vision system (EVS). Those airplanes are permitted by a special section in the FARs to descend below published precision approach minimums to 100 feet above the runway if the EVS image of the airport environment is visible through the HUD.

After a few trips get postponed or, equally unappealing, alternates have to be dialed into the FMS because of low visibility at the destination airport, the $500,000 price of entry into the head-up display world starts to seem more reasonable. And, quite likely, there will be further inducements to install a HUD in the future, experts believe.

Portland, Ore.-based Flight Dynamics is in the midst of developing a range of en-hancements that officials predict will help stimulate interest in such equipment among operators of large business jets not currently fitted with a HUD. Among these are LCD projection techniques (as opposed to current CRT raster scanning), new types of EVS sensor technology, synthetic-vision overlay capability and surface-guidance technology designed to prevent runway incursions.

Craig Peterson, Flight Dynamics marketing manager, said the uptake of HUD technology has been strong for a number of years among airline buyers, but business aviation has been slow to adopt the technology. Now, with added capabilities making headlines, operators appear to be far more amenable to the idea of buying and installing a HUD.

“It’s a technology that certainly has made inroads within the air transport world for the capabilities and efficiencies that it can provide to fleet operators,” Peterson said, “but of late it has caught fire in the corporate world as well, due largely to the situational awareness that it can provide and, emerging among that, newer technologies such as HUD-based enhanced vision and, further into the future, synthetic vision.”

Rockwell Collins acquired Flight Dynamics in 1999, leveraging the firm’s HUD technology to help it market its avionics systems in the air transport and business aviation markets. Today, several business jet models are offered with Flight Dynamics head-up guidance systems (HGS is the company’s own marketing term for HUD), most notably the Falcon line spanning the Falcon 900EX, 2000EX and, once the airplane gains its type certificate (anticipated late next year), the Falcon 7X.

Peter Howell, an HGS engineer for Flight Dynamics, said the company is currently involved in EVS certification programs for the 900EX and 2000EX with Honeywell EASy avionics, adding that both of these projects are scheduled for FAA certification by the middle of next year. Flight Dynamics is also in the early stages of an EVS certification program for the Boeing Business Jet, a system that should be certified in 2007.

Each of these programs uses infrared EVS sensors supplied by CMC Electronics, but Howell said the supplier in the case of the BBJ could change depending on the capabilities that are deemed necessary as the engineering team moves forward with system development.

“We’re continuing to look at the EVS sensors that are out there, and as technology evolves we’re making sure that we stay up with the latest so that we provide the best vision to the pilot,” Howell said of the BBJ program.

New EVS Technology

One promising technology under study, he said, is based on the use of thermal microbolometers, a technology that would be less expensive to use than some other EVS sensors because microbolometers do not need to be cooled. Howell also said sensor fusion, in which one EVS camera is tuned to the near infrared range and the other to long-wave IR, is a technique under consideration for the BBJ because it provides a better image.

One of the particular issues that is a concern to EVS developers is the transition to LED landing lights at many airports. “Sensors tuned only to the IR spectrum do not pick out LED lighting very well,” Howell explained. However, the fusion of a long-wave IR camera with a second camera tuned more closely to the visible light spectrum would solve the problem.

Howell said Max-Viz, a neighbor of Flight Dynamics in Portland, is one candidate to supply the BBJ EVS sensor system, but he added that other manufacturers are under consideration as well.

Technologies such as millimeter wave radar are showing less promise now than in earlier trials, Howell added, primarily because of the high price of the technology and government regulations that place restrictions on exports of systems developed using militarily sensitive technology.

LCD HUD is sure to make a big impact in the years ahead because of its ability to present brighter video images than CRT-based systems. Flight Dynamics is currently testing two LCD HUDs, one for the Embraer 170/ 190 series and the other for the Falcon 7X. The major advantage of presenting bright video on the HUD again goes back to the EVS view, which is really little more than a feed from a video camera (or cameras) installed in the nose or atop the tail pointing forward.

Synthetic Vision

LCD will also be useful for portraying synthetic-vision views on the HUD, Howell said. In Flight Dynamics’ case, engineers are exploring using a wire-frame view to present terrain. While the company has demonstrated versions of HGS using colors other than green on the combiner glass, this technique is not ideal, first, because the optics are optimized for green and, second, because other colors appear weak and get washed out against certain backgrounds (red color in front of a red sunset, for example).

For this reason, the wire-mesh SVS world on the HUD would appear as thin green lines to create scenes of rolling hills or jagged mountains. (To get a sense of what this would look like, imagine an eighth grader’s science project made of chicken-wire mountains before he has applied the papier-mache.)

The biggest question facing HUD designers is whether synthetic vision will be worth the expense to operators, especially considering that the FAA, at this point, appears unlikely to offer additional takeoff and landing credits to aircraft that carry the technology.

“I certainly think synthetic vision has appeal for the business aviation segment,” said Peterson. “It is a technology that has sex appeal to a crew, but as yet it doesn’t have a tangible, measurable benefit where I can petition the FAA for lower minimums because of that capability.”

Still, synthetic vision is appealing to a number of business jet OEMs, who are considering the possibilities for fused EVS and SVS displays that would overlay an IR camera view on top of a video-game-like presentation of the world ahead. Along with NASA and the FAA, Rockwell Collins has performed extensive tests of such concepts and engineers are currently poring over data from the most recent round of FAA test flights, which concluded a few months ago.

Even without EVS or SVS, there are tangible benefits to flying with a HUD. The device’s internal guidance algorithms allow pilots to hand fly the airplane to extremely tight tolerances. For example, flying with a Flight Dynamics HGS, a properly trained crew can hand fly a Category IIIa approach to a 50-foot decision height.

Without a HUD, that same crew would have to settle for Category II minimums, which might not always get the airplane to the runway. The HUD also allows for low-visibility takeoffs and Category II landings at most Type I airports. This last capability is especially important in the corporate world, Howell said, because there are so many Type I airports into which business jets routinely fly.