New technology tests its wings aboard 737

 - May 15, 2008, 10:50 AM

For a glimpse into aviation’s future one need look no farther than Seattle Boeing Field, the home of a specially modified Boeing 737-900 outfitted with an array of experimental avionics and flight controls. For much of the spring Boeing has been inviting select groups of airline representatives aboard its technology demonstrator for flights to Moses Lake Airfield in Central Washington to showcase the cutting-edge systems.

The compendium of products installed aboard the new 737–in various stages of research, development and commercial deployment–is designed to meet the FAA’s goal of cutting accidents by 80 percent and squeezing more utilization out of crowded airspace and airports in the years ahead. Although much of what Boeing has in mind should help strengthen airline balance sheets as well, the technology applies broadly across all segments of aviation.

The advanced avionics under evaluation include synthetic-vision flight displays; a head-up guidance system married to two infrared enhanced vision systems (EVS); highway-in-the-sky navigation cues; a virtual-traffic-cone surface guidance system (SGS); GPS landing system (GLS); a software upgrade to the 737’s enhanced ground proximity warning system (EGPWS) and other developmental systems. Boeing is demonstrating the technology to repre- sentatives from about 40 of the world’s airlines who are coming to Seattle for flights aboard the highly modified 737. Once the demonstration program is complete, all the equipment except the HUD will be removed and the airplane will be delivered to Alaska Airlines.

A Ride into the Future

At times the Boeing demonstration flight seems reminiscent of one of James Bond’s briefings inside Q’s gadget workshop–except that this trip aloft replaces cinematic fantasy with tomorrow’s reality. In fact, not only are the technologies used aboard the demonstrator airplane real, in some instances they have already gained FAA approval.

Enhanced vision, for example, was certified last October aboard the Gulfstream V and is scheduled to enter service this summer. Another product called the Quiet Climb System (QCS), which automatically reduces power on climbout over noise-sensitive areas by comparing GPS- and FMS-derived position information, has been installed by Aloha Airlines on airplanes that operate from John Wayne Airport outside Los Angeles, where noise fines can run as high as $500,000 per incident.

Departing Seattle Boeing Field one Tuesday evening in March, pilots Mike Carriker and Ray Craig headed west to shoot a series of GPS-guided approaches to Moses Lake Airfield. On the way, Carriker swung the nose of the 737-900 directly at the rocky summit of Mount Rainier some 60 mi away. As the airplane descended almost 2,000 ft below the peak the outline of the mountain on the EGPWS display turned from green to amber to an ominous red, a metamorphosis that an alert pilot would find hard to ignore.

On the navigation display, a new type of vertical situation indicator made possible by a software modification developed by Rockwell Collins offered a sideways profile of an airplane symbol that showed its path over a cutaway view of the ground. The indicator’s vertical trend vector–a straight white line that pilots call the “noodle”–projected the flight path well ahead of the airplane, giving the crew a clear indication of where they would hit terrain if the descent continued.

The system, called the vertical situation display (VSD), will be standard equipment in all new 737s by August, and other Boeing models by 2004, said Carriker. VSD should be particularly useful on approach because it overlays a second magenta line on the display showing the glideslope after the final approach fix.

From beginning to end, Boeing’s demonstration flight was designed to showcase the remarkable technology at the pilots’ disposal, a collection of advanced avionics that the manufacturer believes will convince its airline customers that technology is indeed transforming the modern aircraft cockpit–and by extension the art of flying itself–in ways that until recently were simply unimaginable.

Although much of the technology presented during the flight is far from market-ready, Boeing wants to get out to an early lead and show customers precisely how cockpit products such as those installed aboard the demonstrator 737 can enhance efficiency and shave dollars from bottom-line operating costs.

From the vantage point of pilots along for the flight, this airplane symbolized the coalescing of a diverse assortment of avionics, much of it considered revolutionary, some of it even radical–but all of it representing the full possibility and potential of aviation’s modern era. What was perhaps most striking about the demonstration was that it allowed a major airframe manufacturer–in this case the world’s biggest–for the first time to provide customers and the public a look not at what could be or what should be, but at what almost certainly will be the norm for the next generation of aviators. Tomorrow’s pilots–and that includes corporate pilots–will adapt to cockpits crammed with electronics that would have been totally foreign to crews flying only a decade ago.

During the demonstration flights, which are scheduled to end this month, Boeing pilots fly GPS autoland flight procedures to all four of the runways at Moses Lake Airfield using the airport’s single Honeywell/Pelorus local-area augmentation system (LAAS) ground station. LAAS allows aircraft to fly complex approaches and curved flight procedures to avoid noise-sensitive residential areas while maintaining safe separation between airplanes. The LAAS station monitors signals from GPS satellites, checks them against its own precisely surveyed location and broadcasts correction information to properly equipped aircraft. The technology-demonstrator airplane has been fitted with a Rockwell Collins multimode receiver that includes ILS, VOR, MLS and GLS sensors.

Tunnels in the Sky

The most far-reaching of the technologies installed aboard the 737-900 is a synthetic-vision flight display system that provides a conformal view of the world outside using the EGPWS database to paint a picture of terrain, obstructions and airports. Under development for the past few years by Rockwell Collins and NASA, the synthetic vision system (SVS) in the 737-900 is intended for use on approach or takeoff during low-visibility conditions. It gives pilots realistic visual cues and easy-to-follow flight-path guidance.

Highway-in-the-sky software draws a series of boxes on the displays that appear to stay fixed in the sky as the airplane flies along its course. To stay on course the pilot need only fly through the boxes. This tunnel created by the boxes curves, tilts, rises or descends as the airplane flies along, allowing the pilot to follow a precise course all the way to touchdown.

Though it may resemble a video game, synthetic vision is no child’s toy, say developers. Troy Brekken, a Boeing technology analyst, said this type of advanced system represents a revolutionizing opportunity for aviation that could one day dramatically curb the CFIT accident rate.

“The idea is to provide pilots with a clear view of the outside world in any weather or lighting condition,” said Brekken. “Synthetic vision coupled with other technologies will go a long way toward allowing Boeing to advance one if its key tenets, which is to design as safe and efficient an air-transportation system as is possible.”

Aerospace researchers are exploring the possibility that synthetic vision could be coupled with infrared sensors to provide pilots with an exact view of the world ahead of the airplane. By combining infrared and computer-generated inputs, designers hope one day to develop a device that will present aviators with a clear sense of situational awareness, integrating electronic visual input with nose-mounted sensors.

The result, developers believe, will produce for pilots a more or less natural “picture” of the outside world on the flight displays or a HUD. Canada’s National Research Council (NRC) last fall demonstrated a prototype enhanced synthetic vision system (ESVS), conducting a full takeoff and landing in a fly-by-wire Bell 205 helicopter controlled by a pilot completely “under the hood” and receiving all his visual cues via a helmet-mounted ESVS.

CMC Electronics of Montreal is working with NASA to define and develop an ESVS that integrates sensor-based enhanced vision and terrain-data-based artificial vision for airliners. The goal of the project is to replace current primary flight displays with perspective view displays of the outside world, providing clear-day visibility for pilots in all weather conditions.

CMC Electronics designed one of the EVS sensors installed aboard the 737-900. Max-Viz of Portland, Ore., designed the other. Both systems use an infrared camera to overlay a picture of the scene ahead of the airplane on the HUD. The major difference between the competing systems, both of which are still in development stages, is that CMC’s SureSight system has a single focal plane array while Max-Viz’s EVS-2000 is a dual-sensor system.

The CMC sensor is tuned to detect light at wavelengths of one to five microns, while Max-Viz has designed a system that fuses shortwave (1.4 to 1.6 microns) and longwave (eight to 12 microns) infrared views. Brekken said it is still too early to say which system does a better job at capturing images in the terminal environment, but added that Boeing pilots have been impressed with both.

CMC’s SureSight is in the final stages of product integration, with FAA and Transport Canada certification flight testing scheduled to start late this year. Total installed weight of SureSight is expected to be about 22 lb, including the wiring harness, brackets, connectors and radome modification. After certification the company plans to begin developing other EVS products with additional sensor options that perhaps would include the use of millimeter wave radar in place of or in conjunction with infrared.

Max-Viz claims that its EVS-1000 and EVS-2000 systems will be smaller, lighter and more reliable than any competing products. The EVS-1000 will incorporate a longwave-only IR camera that has a 40-deg forward field of view. The larger, more expensive EVS-2000 will combine dual images that can detect runway lights, as well as terrain for what the company claims is a superior IR image.

As mentioned earlier, Gulfstream last October received certification for the first non-military EVS, an infrared camera system designed by Kollsman of Merrimack, N.H. EVS in the GV consists of a cryogenically cooled FLIR camera that transfers its view to a Honeywell 2020 HUD, allowing the pilot to see a conformal image of the airport and terrain overlaid on the combiner glass.

The Kollsman system enhances not only safety but also utility by allowing crews to make Cat II ILS landings even at Cat I airports. According to the revised aircraft flight manual, properly trained pilots flying GVs equipped with HUD and EVS may continue below published minimums at Type 1 airports, meaning that they can descend below 200 ft height above terrain (HAT) to 100 ft HAT, at which point the pilot must be able to see the airport unaided to land. Eventually, Gulfstream believes EVS can allow a descent to 50 ft HAT. CMC and Max-Viz are seeking similar reduced-minimum approvals for their devices.

Avoiding Runway Incursions

At Cat III airports, properly equipped aircraft piloted by properly trained crews may land in zero-zero conditions. After landing, however, the question becomes how to get the airplane safely from the landing runway to the gate.

Rockwell Collins believes it has the answer. The company’s experimental surface guidance system (SGS) provides cues on the HUD using super-accurate airport data supplied by Boeing subsidiary Jeppesen. Cues provided to the pilot include an artificial-traffic-cone picture on the HUD of exactly where the pilot should turn to reach the ramp, as well as hold lines and crossing cues.

Once datalink communications between controllers and pilots come online in the next few years, ground controllers will be able to issue full taxi clearances sent directly to the SGS. Holds, crossing clearances and taxi instructions will be issued without the pilots or controllers having to say a word. Experts believe such a system could sharply reduce or even eliminate runway-incursion accidents by dispelling the confusion and uncertainty that can sometimes accompany low-visibility surface operations. SGS coupled with datalink, for instance, could have prevented the crash of a Singapore Airlines 747-400 in Taiwan in October 2000. In that accident, the pilot tried to take off from a closed runway parallel to the active runway where heavy construction vehicles were parked.

Not all of the technologies demonstrated by Boeing are so far-reaching in concept, however. A software upgrade called navigation performance scales, for example, will soon be certified. The scales, presented on a cockpit display, are based on the familiar approach concepts of runway centerline indication, scale limits and deviation pointer, but they incorporate additional symbology to simplify the pilot’s job.

The display enhances the pilot’s ability to monitor the dynamic relationship among actual navigation performance (ANP), required navigation performance (RNP) and flight-path deviations. RNP is the accuracy required for an airplane to operate within a given block of airspace. When overlaid onto RNP-defined airspace, lower RNP ratings for an airplane result in lower decision heights. ANP is the estimated real-time measure of the quality of an airplane’s navigation system. ANP is based on probable position determination and guidance errors.

Using the navigation performance scales, airlines are expected to be allowed to fly RNP.1 (0.1-nm accuracy) procedures. Magenta arrows on the PFD will tell the pilot at a glance whether he has exceeded the vertical or horizontal limits on approach. This will allow operators to incorporate Lnav/Vnav approaches that previously could not be flown. Eight airlines have ordered the upgrade, which requires software modifications costing between $10,000 and $20,000.

Another technology demonstrated by Boeing is integrated approach navigation. This too is a software enhancement to the flight management computer. Essentially, the upgrade turns any FMS approach into an ILS-like procedure, providing for pilots the same lateral and vertical deviation guidance they would see on an ILS approach. Integrated approach navigation also eliminates the need for stepped descents during FMS approaches.