Business & GA, Military

Weathering Fog and Darkness — HUDs With Enhanced Vision

By James W. Ramsey | June 1, 2001
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Enhanced vision systems (EVS) using infrared sensors to penetrate certain kinds of fog and low-visibility conditions are the latest enhancement to head-up displays (HUDs). They are in increasing demand in the regional airline and high-end business jet markets, as well as for air transports.

And beyond that, when fog becomes too dense for EVS to solve, millimeter wave imaging radar is being explored by manufacturers seeking the Holy Grail of all-weather operations.

Airlines are moving slower, more cautiously than the bizjet community in acquiring EVS. One reason is that the new autoland systems in airliners combined with HUD are allowing low-visibility landings with 700 feet runway visual range (RVR). But for corporate operators, many of whom fly into smaller airports with less sophisticated runway landing equipment, EVS provides both increased operability and added safety.

Both groups recognize the safety benefits provided by EVS even if lower minimums are discarded. After the Singapore Airlines accident on takeoff at Taipei on Oct. 31, 2000, operators small and large alike are seeking a way to avoid such disasters on a runway and to allow better visibility at night, in clear or inclement weather. EVS providers stress "increased situational awareness" and use terms like "supplemental safety device" when describing their products. The U.S. Federal Aviation Administration (FAA) labels the EVS technology "novel" or "unusual" (see sidebar).

Regardless, two North American companies, an airframe manufacturer and a systems integrator, are vying to take the lead in EVS.

Racing to be First

Gulfstream, a subsidiary of General Dynamics, and CMC Electronics, formerly BAE Systems Canada, are vying to offer the first EVS certified for operational use–possibly by the end of this year. "It looks like the EVS thing is going to be a horse race," says Bruce Bailey, CMC vice president of aviation electronics.

If there is in fact a horse race, it would appear that competitor Gulfstream, which is teamed with Honeywell and Kollsman, has the early lead. But EVS’s long-term potential would indicate that there will be plenty of business for both companies, as well as for possible newcomers to the field. Which means more than two horses probably will enter the field.

Flight Dynamics, the leading HUD provider in the commercial market, is developing a surface guidance system, but also is exploring a "full-up" EVS in the future (see sidebar). Thales Avionics, with its own commercial HUD system, has not entered the EVS chase–yet. But the European avionics company is "currently assessing the market and evaluating required investments."

Meanwhile, the FAA has entered the picture, perhaps slowing the race for EVS, by proposing a "special condition." The agency calls for careful examination of the infrared image to ensure it does not restrict "or distort" the pilot’s view on landing approach or could not be used as a means of flight guidance.

Gulfstream and HUD 2020

Gulfstream’s EVS evolved from its HUD 2020 program launched in 1993. The Savanah, Ga.-based bizjet manufacturer then teamed with Honeywell and BAE-Canada (now CMC) to provide a Category II landing HUD for its G-IVSP and G-V aircraft. (Gulfstream reports that 85% to 90% of its G-V customers, and half of its G-IVSP buyers, elect the HUD option, which has been certified on both aircraft.)

Taking what Gulfstream Senior Vice President Pres Henne calls "the next big step, near-term," the company has combined the HUD with an EVS that uses a forward-looking infrared (IR) camera. Gulfstream’s EVS development began in conjunction with the Maryland Advanced Development Laboratories (MADL), which devised the HUD/EVS certification methodology. This was followed by "proof of concept" flight testing using a MADL Cessna 402 and later a G-V. Completed last October under FAA supervision, the tests involved hundreds of EVS approaches in various weather conditions. They paved the way for final certification testing to begin during the second quarter of this year.

After G-V certification, Gulfstream plans to certify EVS on its G-IVSP, beginning in the first quarter of 2002. EVS will be standard equipment on the company’s new extended range G-VSP model, which features new cockpit avionics and was announced at last year’s National Business Aviation Association exhibition.

Kollsman Inc., based in Merrimack, N.H., has a background in flight instruments and IR work for the military and produces the infrared sensor. Its camera collects IR signals both from runway lights and from emitting surfaces (e.i., terrain, animals, etc.). It processes the images, then translates them into a (TV-like) raster-type video format, which is displayed on the HUD together with flight information.

EVS can be ordered with a new HUD or retrofitted on a HUD already on the aircraft. All G-V and G-IVSP HUDs can be upgraded, according to Mike Mena, Gulfstream EVS program manager. The retrofit includes installing the camera, which is mounted behind the radome in the lower portion of the nose. The radome is modified to incorporate a small window in the bottom.

Some customers have already committed to buying the EVS, according to Mena. Gulfstream currently is selling some G-Vs and G-IVSP s with EVS wiring installed.

The EVS system is particularly sensitive to the runway lights’ IR radiation (close to 1 micron in wavelength span), Mena explains, and "when the pilots come in on an approach using ILS [instrument landing system] guidance, with EVS they pick up the lights sooner. They can get down to lower minimums, but still must use the ILS guidance."

One might assume that with EVS’s capability to look through fog or haze and detect runway lights sooner, ILS categories (Cat I, II and III) could become unnecessary. Not so, says Mena. Gulfstream backs the FAA in stressing that certification requires the use of ILS or another means of guidance.

"EVS is just an added benefit to increase situational awareness," Mena maintains. "It serves as an independent monitor of the guidance system. FAA allows aircraft equipped with EVS along with ILS to continue an approach below Cat I (normally 200 feet decision height, 2,600 feet RVR). But once reaching 100-feet decision altitude, a pilot must acquire the lights visually without using EVS, or execute a go-around. Gulfstream is working to get even lower minimums (50 feet, 700 RVR) in the EVS program’s phase II.

The enhanced vision system offers other benefits, as well. The IR camera also is sensitive in the 3-to-5-micron range, which picks up not just lights, but the surrounding environment.

"We wanted to improve the customer’s ability to land in IFR conditions," says Mena, "but the added benefits are that you can see beautifully at night. There is a good image of taxiways and the surrounding area. Even on a clear night, you can see trees and rivers."

He cites an example involving the 402 test aircraft at a small airport where deer run across the runway. The pilot in the left seat could see the deer clearly, as the IR camera detected the animal’s body heat. But the right-seat pilot (without IR imagery) saw no deer.

At many airports served by business jets or regional carriers, Cat I ILS is fairly standard. Using EVS allows a pilot to operate down to Cat II minimums (100 feet, 1,200 RVR) at a Cat I facility, using the same runway.

But if you have a certified EVS, are you automatically qualified for Cat II approaches? It is not that simple, says Mena. "All crews that use EVS must be trained before they use it." Gulfstream is working with FAA to offer crew training to enable EVS use. The company has negotiated an agreement with FlightSafety International that would provide training as part of an EVS sale package. Mena believes FAA may require this training, which would be noted in the aircraft fight manual.

Mena admits EVS’s limitation, especially when water particles become large. "If you are in zero-zero conditions, EVS won’t see through it," he says.

The other primary EVS player is CMC Electronics, formerly BAE Aerospace Canada and Canadian Marconi Co., a world leader in the HUD market. CMC has delivered more than 11,000 HUD systems, mostly for military fighters. It had its commercial HUD certificated for use on Boeing 737-800s and has deliveries and orders for 200 HUDs for Gulfstream.

Pioneering work on CMC’s enhanced visual guidance system (EVGS) began in the early 1990s, with tests under contract to the Defense Advanced Research Projects Agency (DARPA), NASA and Boeing. Last summer (2000), CMC conducted demonstration flight trials of its infrared imaging system at Everett, Wash., and announced that it was offering an enhanced vision option to its VGS (visual guidance system) head-up display.

CMC currently offers a later version of the VGS for the Bombardier Global Express, the Gulfstream V’s head-to-head competitor in the bizjet market. The VGS’s initial certification is planned by the end of this month (June).

Once certified, it will move into the first EVGS certification, estimated to take about six months. CMC plans to use a plane owned by its second (Global Express) HUD customer and first EVGS customer, according to Jean Menard, CMC director of business development for corporate aircraft products.

CMC produces its own IR camera at its Cincinnati Electronics subsidiary. The company boasts that it is the only manufacturer that produces all components for its enhanced vision system. Like Gulfstream’s HUD/EVS, the IR sensor and image processing system is mounted in the radome, which has a small IR window. The camera is mounted on the forward bulkhead behind the radome and is boresighted so the captured image can overlay the real world as the pilot sees it through the HUD combiner.

Total weight of the EVGS, including wire harness and connectors, is 22.5 pounds (10.2 kg). The system initially will sell at $500,000, but that price will be reduced once it has been certified and is in production, Menard says.

CMC currently is taking orders for its EVGS, and is offering it to Global Express and Boeing Business Jet operators, as well as other customers who have raster scan-capable head-up guidance systems. Orders are predominantly from Global Express customers who have selected CMC’s HUD–a system that requires only a software upgrade and IR sensor.

Launch for EVGS is in the bizjet market, but CMC claims there is strong interest from regionals and larger air carriers and from the original equipment manufacturers (OEMs). Some are interested from a safety standpoint, but all ultimately would like to achieve lower minimums, says Menard.

CMC claims to take a different approach with its EVGS program. "We are going to certify our EVGS as a flight safety and situational awareness tool. We are not going for landing credit from the get-go," says Bailey. "If it turns out to warrant credit for lower minimums, we will go for that later."

After FAA certification, CMC will seek Canadian and then European approval for the EVGS. In the HUD market, CMC competes with Flight Dynamics and Sextant. But as for EVGS, "we don’t perceive that we have any significant competition other than the work Kollsman is doing with Gulfstream," Bailey says.

Millimeter Wave Radar

CMC Electronics appears to be leading the way to the next step of enhanced vision systems–millimeter-wave imaging radar (MWR). It is developing such a system and plans to begin flight tests in January 2002.

"When molecule droplet size is in the order of 20 to 30 microns in diameter, fog starts to attenuate the IR signal," says Menard. "At a minimum, IR doubles the RVR. However, to have an all-weather system with the reliability you need, we believe you need MWR as an adjunct to penetrate the heavy fog."

The MWR technology has been improving over the past decade and is now practical for aerial applications, Menard adds. Higher power devices, more sensitive detectors, and new antenna technology are now becoming available.

Menard says CMC is "treading cautiously" in this area, beginning with prototype development, and then flight characterization. If performance is as expected, it will be demonstrated for potential users, and if the interest is there, it could be available a year later–two years from now."

CMC has been working with NASA, Bailey says, to define and develop a flight display system of the future. NASA awarded contracts to CMC and to the sector of Rockwell Collins that formerly was Kaiser Electronics, to conduct independent development work. CMC’s contribution involves synthetic vision and EVS, and Collin’s involves X-band radar. The two companies are developing hardware that will be test flown on a NASA B757.

Flight Dynamics’ Phased Approach

Flight Dynamics–part of Rockwell Collins–is another major HUD producer, and its HGS (head-up guidance system) is the market leader in the commercial and regional airline and business aircraft markets. The Portland, Ore.-based firm has delivered 900 of the systems to 20 airlines and has orders for another 800.

The company is developing a surface guidance system (April 2001) but currently is not working on an in-flight enhanced vision system (EVS). However, the company is following EVS developments closely and talking to several sensor manufacturers about the possibility of producing a "full-up" EVS system, according to Tom Kilbane, director of airline marketing. Flight Dynamics HUDs are capable of accommodating the raster format and could be used for any enhanced vision system sensor.

Kilbane foresees a phased approach for EVS at Flight Dynamics, starting with its use on the ground, possibly as a "subset" of the surface guidance system the company currently is developing.

FAA’s Slight Snag

The U.S. Federal Aviation Administration (FAA) on March 16 issued a notice of proposed special conditions for Gulfstream V aircraft with HUDs being modified to display IR imagery. The conditions do not appear to be at odds with positions taken by Gulfstream Aerospace or other EVS providers, but they could slow the certification process.

The special conditions contain "additional safety standards" that the agency feels are necessary to establish a level of safety equivalent to that provided by the existing airworthiness standards. In the notice, FAA reiterates its position that "IR-based EVS will not be certified as a means to satisfy the requirements for descent below 100 feet height above touchdown." Nor will the EVS imagery alone be certified either as flight guidance or as a substitution for the outside view for maneuvering the airplane during approach, landing, rollout or takeoff.

However, FAA says, "EVS may be used as a supplemental device during any phase of flight or operation in which its safe use has been established." The agency adds that while the EVS image projected on the HUD can interfere with the pilot’s view, an equivalent level of safety may be possible with the combined view of the image and the outside scene that the pilot is able to see through the image. The pilot must be able to use this combination of information as safely and effectively as a pilot without an EVS image.

FAA intends to develop guidance material for use of the EVS that will cover operations, pilot qualification and training.

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