Avionics Giants Pursue Synthetic Vision For Credit

By Graham Warwick
May 14 , 2012

Graham Warwick/Cedar Rapids, Iowa

Having gained a foothold in the flightdecks of high-end business jets, synthetic-vision displays are moving down-range to light jets and turboprops, and preparing to step across to the military arena. Eventually the commercial airline market will follow. Meanwhile, the ability to generate flight displays from onboard databases is acting as a springboard for new cockpit capabilities.

Replacing the traditional artificial horizon with a computer-generated three-dimensional view of the outside world has improved pilots’ situational awareness. Now developers want to exploit the “always daylight” environment of synthetic vision to enable lower-visibility landings at a wider range of airports.

The spread of synthetic vision is being assisted by the development of integrated modular avionics systems that are allowing common hardware and software to be used across aircraft ranging from business jets to commercial airliners and military platforms. This is evident from a visit to Rockwell Collins, where 13 applications of its Pro Line Fusion integrated avionics system are in development, ranging from mid-size business jets to the Bombardier CSeries airliner and Embraer KC-390 airlifter.

Cockpit integration rigs here underline the commonality being achieved and how it is enabling system capabilities to be added with each new platform. The first Fusion application, Bombardier’s Global 5000/6000 large business jets, entered service in March with synthetic vision on both the head-down and head-up displays. The integration rig for Embraer’s Legacy 450/500 mid-size jets shows the next steps, including an airport moving map, while the electronic charts displayed on the CSeries rig are a situational-awareness enhancement ported over from the business-jet side of Fusion.

Across the platform applications now in development, “90% of the Fusion product line is common. The rest is in the graphical user interface, which is customized for each customer,” says Adam Evanschwartz, business development manager for commercial systems. Compared with the Legacy, the CSeries may have additional avionics cabinets, but the hardware modules and core software functions are the same—as they will be for the KC-390, the first military Fusion application.

Rockwell Collins is taking the next step in Fusion capabilities with the development of an “embedded display system” (EDS) version aimed at light jets and turboprops, as well as the retrofit market. In addition to a new hardware configuration, Fusion EDS introduces touchscreen flight displays and an optional compact HUD, both with synthetic vision. All processing is moved from the cabinets to the displays, allowing the system to be installed on smaller aircraft—where the screens are closer to the pilot and lend themselves to finger-on-glass interaction.

The displays will look familiar to iPad users, but there are differences driven by cockpit use. Apple uses a capacitive touchscreen, which detects a finger electrostatically and is susceptible to electromagnetic interference. Fusion EDS uses a resistive touch, which senses deformation of the screen. A firm finger press is required to select a function, which will only activate on release of the pressure. This should help in turbulence, but Rockwell Collins expects most interaction with the screens will be while still on the ground, setting up the flight plan before takeoff. Even the primary flight display is touchable, and can be split to also show maps or charts for single-pilot operation.

The user interface is based on icons and other shortcuts such as toolbars that are context-sensitive, changing with each display page, enabling the most common map tasks to be pre-stored under themes such as departure/arrival, visual flight rules and low- or high-altitude instrument flight rules. Maps and charts can be panned by pressing and sliding a finger across the screen, and flight plans can be redrawn graphically by selecting waypoints and dragging them to new locations, after which the flight management system will recalculate aircraft performance and fuel consumption. The rotary cursor control is a tabbing device, grabbing and jumping the cursor to the next spot rather than moving it smoothly across the screen, giving it an automotive feel, says Evanschwartz.

Rockwell Collins is modifying a Hawker Beechcraft King Air 250 for flight-test and supplemental type certification (STC) of the touchscreen EDS as an upgrade for King Airs equipped with its Pro Line 21 cockpit. Flight tests will begin this year, with certification and availability planned for 2013. In addition to the company-funded King Air retrofit STC, an undisclosed aircraft manufacturer has selected EDS for a “low-end” turboprop/light jet application, says Kent Statler, executive vice president and chief operating officer of Rockwell Collins Commercial Systems.

Flight testing of the HGS-3500 compact HUD is to begin within the next year, with the display to be available from 2015 for any Fusion or EDS customer. Expanding the use of head-up guidance systems is key to Rockwell Collins’ strategy, and the new HUD is significantly smaller and cheaper than existing displays. Using waveguide optics, which inject imagery directly into the holographic combiner, the system eliminates the bulky and power-hungry overhead projector and its optics. This allows the compact HUD to be installed in a wider range of aircraft with cockpits too small to accommodate conventional head-up displays.

With dual Rockwell Collins LCD-projector digital HUDs now standard on the Boeing 787 and optional on the CSeries, Statler foresees demand for head-up guidance systems in countries that lack the airport infrastructure to maintain capacity and safety as weather deteriorates. The company has been working with the Civil Aviation Administration of China to enable operators with head-up guidance systems to gain credit for lower landing visibility minima on Category 1 instrument landing system (ILS) approaches at airports across country. “China is within a couple of years of a HUD mandate,” he believes.

Bombardier’s Global Vision flightdeck, with its digital HUD, is the first to provide synthetic vision on the head-up display. The synthetic image is certified for situational awareness only—infrared sensor-based enhanced vision on the HUD providing an ability to see runway and land in reduced visibility—but Rockwell Collins is pursuing operational approval for lower landing minimums using just synthetic vision on both the head-down and head-up displays.

This is where the company’s approach diverges from the path taken by its major rival in the civil avionics market. Honeywell developed synthetic vision primary flight displays (PFD) for the Primus Epic-based integrated flightdecks in Gulfstream and Dassault Falcon business jets, and believes HUDs are not necessary to gain credit for lower landing minima. Instead it is convinced that synthetic vision—and eventually combined synthetic and enhanced vision—on the head-down PFD can be sufficient, opening up the potential to equip thousands of aircraft where HUDs would be considered too expensive to install.

Where Rockwell Collins’s approach includes bringing down the cost and size of HUDs, Honeywell is taking a different route in tackling the barriers to approval of synthetic vision for reduced-visibility landings. The benefit will be the ability to land in lower visibility at a larger number of runways without the ground equipment, crew training and aircraft maintenance required for higher-category instrument landing systems (ILS). The initial target is lower minimums at runways with Cat. 1 ILS, moving on to the much larger number with so-called localizer performance with vertical guidance (LPV) approaches using a GPS space-based augmentation system (SBAS) such as WAAS (wide-area augmentation system) in the U.S.

The issue with using synthetic vision is in monitoring the integrity of the database. GPS is used to both the navigate the aircraft and position the synthetic scene on the primary flight display, so a flightpath error might not be apparent to the pilot until GPS reaches its vertical or horizontal alert limits. As a first step, industry is seeking operational credit for synthetic vision to reduce visibility minima on ILS approaches. In this case, ILS will provide the standard guidance cues to the pilot while GPS positions the synthetic scene.

In Honeywell’s approach, which it calls SmartView Lower Minimums (SVLM), the additional position assurance required to descend below Cat. 1 minimums is provided by a new function called the runway approach indicator. This takes the two different airport databases in Honeywell’s runway-awareness-and-advisory system and Jeppesen’s navigation database in the flight-management system and compares them to cross-check the runway position. “We validate the runway picture, not the entire synthetic-vision scene,” explains Sandy Wyatt, Honeywell test pilot. The runway is then positioned on the display independent of the synthetic scene and ILS, providing the integrity required.

As a second step, for runways with LPV and not ILS approaches, Honeywell will employ integrity monitoring using SBAS and the aircraft’s inertial reference system (IRS) to position the runway indicator independently. “The hazard with an LPV approach is the risk of misleading information,” says Wyatt. “It can take GPS 6.2 seconds to detect an error. We are using an algorithm and an IRS to eliminate that uncertainty.” The company will conduct proof-of-concept flights for the FAA this year, aiming for approval of approaches down to 150-ft. decision altitude and 1,400-ft. runway visual range. This compares with 200 ft./2,400 ft. for conventional Cat. 1 ILS. SVLM will be offered as a software upgrade on any Primus Epic platform—and will work with HUDs as well as head-down displays.

Rockwell Collins’s plan is to take FAA rules allowing so-called Special Authorization Cat. 1 ILS approaches down to 150-ft. decision height with a HUD and use synthetic vision to remove the requirement that these be flown by aircraft and crew-certified and qualified for Cat. 2. “We use ILS as a cross-check on the goodness of the image,” says Sarah Barber, principal systems engineer. This is achieved through additional system monitoring. “We look at the ILS deviations, compare them with GPS position and alert the pilot if the image is off by 50 ft. That’s well within the GPS alerting limits.”

The second phase of synthetic vision for credit—LPV approaches—will open up thousands of runways, Barber says, but needs a second integrity source because GPS is used for both navigation and scene positioning. For this, Rockwell Collins has chosen to use its MultiScan weather radar. “We know our GPS altitude, we know the runway elevation, so we tell the radar where to look for the runway touchdown zone,” she says. The radar can recognize the runway signature, and compute height above the threshold from range and elevation to provide the cross-check required for position assurance.

“We use the radar to bound the vertical error,” says Tim Etherington, principal systems engineer. Weather radar is already installed in the aircraft, so Rockwell Collins is looking at ways to expand its capability. Tests of a switched-aperture antenna, which splits the unit horizontally or vertically and compares phase between the two halves to provide a 10:1 beam sharpening, have shown that the performance of a 20-in. airliner antenna to be provided by a 12-14-in. unit that fits all business-jet types, he says.

Rockwell Collins is now looking at how the weather radar could be used to detect obstacles and runway incursions. “There is a lot to be done on airport obstacles because the radar beam size is fairly large, but it’s good at picking out lighting structures, which we could sharpen up and place on the HUD” to help the pilot acquire the runway on a low-visibility approach. The radar could also be used as a Doppler groundspeed sensor to provide additional position integrity for HUD flightpath guidance. “It’s in the early stages of research and will be in flight test later this year,” says Etherington.


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