ARTICLE

February 2003

Digital Visual-Aid Technology Helps Pilots ‘Own the Weather’

by Sandra I. Erwin

Air Force transport-aircraft pilots are testing a so-called “synthetic-vision” system that would make landings in rough terrain and poor visibility conditions safer and easier.

The technology creates a digital picture of the environment around the aircraft, so aviators can see their surroundings more clearly at night, in bad weather.

The synthetic-vision project, managed by the Air Force Research Laboratory, is designed to let pilots “own the weather” in much the same way that night-vision technology lets them “own the night,” said Guy French, a program official at AFRL. The technology is aimed particularly at the C-130 aircraft. If synthetic vision works as promised, other candidate platforms would be the heavy-lift C-17 and the special operations tilt-rotor, the CV-22.

Synthetic vision has been around for at least a decade and has been installed aboard commercial jets. Only in the past couple of years has the Air Force shown interest, said Ray Liss, manager of integrated applications at Rockwell Collins.

The company originally decided to invest in this technology for commercial aviation customers. NASA also was an early sponsor. It turned out, however, that synthetic vision “has greater potential for military applications,” said Liss.

At the core of synthetic vision is a high-fidelity graphics database that replicates the environment, such as an airport. The artificial imagery is enhanced with sensors, for real-time updates.

If a jet lands in bad weather, for example, the system provides “cues and indicators that the air crews would get once they touched down, to help them navigate the airport,” Liss said. The idea is to prevent collisions on the ground.

Three-dimensional digital maps of most major airports already exist, he said. The 3-D imagery can assist the pilot establish the position of the airplane relative to the airport. Sensors on the aircraft help to avoid obstacles.

In late November, test pilots at Wright Patterson Air Force Base, Ohio, demonstrated low-level military approaches using synthetic-vision technology.

The flight tests—aboard an Air Force C-135 Speckled Trout aircraft—capped a two-year research contract that AFRL awarded to Rockwell Collins.

The Speckled Trout is an extensively modified C-135C that, during the past two decades, has served as an advanced avionics and communications test bed for guidance, control, navigation and communication equipment. It also is used to evaluate future transport aircraft design.

The 412th Flight Test Squadron, based at Edward Air Force Base, Calif., operates the Speckled Trout.

The name was chosen in honor of a former program manager, Faye Trout. The word “speckled” was added because Trout apparently had a lot of freckles.

For the synthetic-vision project, pilots performed more than 20 hours of tests, flying low-level terrain sorties in simulated night instrument meteorological conditions. Rockwell claims that, in these tests, synthetic-vision displays performed, for the first time in a military aircraft, a zero/zero approach to landing on an assault strip.

Evaluation pilots from the 412th Flight Test Squadron and the Air Force Test Pilot School also conducted blind low-level profiles and approaches using head-up and head-down displays that were equipped with synthetic-vision elements.

Synthetic vision, however, does not replace other collision-avoidance and situational awareness sensors now used, such as the terrain awareness warning system. According to Liss, “the system provides intuitive guidance cues, to reduce pilot workload and enhance safety.”

For warning functions, synthetic vision relies on traditional subsystems similar to traffic-alert collision avoidance, ground-proximity warning system, flight management system and displays.

The Air Force, said Liss, “wants the ability to fly an airplane in mountains, depressions, close to the earth and have assurance that they won’t collide with the ground.” The synthetic vision, he said, would help them land in austere, unmapped or unprepared runways.

The system operates with a head-up display, but Rockwell also added a head-down display, to provide navigation cues.

“We populated the aircraft with an additional processor [a mission computer], where we put the graphics into the head-up and head-down displays,” said Liss.

The pilot sees a synthetic view of the terrain below and a “corridor in the sky,” he added. “He can see where he is going and also track to see if there is an increase in elevation.”

The graphics come from different databases, commonly used for mapping terrain. Real-time updates to the map database come from the inertial navigation and the GPS systems.

A basic synthetic-vision setup requires two displays, a mission computer and the database software. “It’s debatable whether the head-down displays are even necessary,” said Liss.

For the Air Force demonstration program, he said, Rockwell installed cross-polarizers on the glare shield and the windows. Polarizers render the pilots blind when they look out the clear shield. The polarizers denied the visual cues to the pilot, not the instructor.

“The pilot was able to fly the corridor in the sky intuitively,” said Liss.

French, the AFRL official, said that the technology has enormous potential to improve pilots’ ability to “freely conduct operations in weather conditions that prevent or hinder enemy operations and render visually targeted weapon systems ineffective. ... Combined with an image sensor for integrity and additional situation awareness, this technology will enable truly autonomous operations, including landing.”

Rockwell currently is in negotiations with another military customer to demonstrate the technology. Liss declined to provide details.

In general, large-aircraft operators are more likely to benefit from synthetic vision. Most tactical aircraft already have advanced navigation aids.

The recent flight tests and demonstration notwithstanding, synthetic vision is not mature to the point that it would pass FAA certification, said industry experts.

The system has potential in the military market, but it’s nowhere near fully developed, said Steve Russell, from Kollsman Corp., a supplier of avionics and electro-optic instrumentation.

“Certain simple aspects have been used,” he said. “But to its full extent, it’s just getting to the point where it can be done in real time. It’s not something that is simple to do.”

Another drawback may be the cost of the hardware, which Rockwell would not disclose. Generating the high-level imagery required for synthetic vision makes the technology “very computer intensive,” said Russell.

Enhanced Vision
Kollsman helped design a different type of situational-awareness and vision aid for pilots, called the all-weather window enhanced-vision system.

The EVS, in development for the last seven years, employs a FLIR (forward-looking infrared) sensor. It projects an image on a head-up display that combines the FLIR picture with the real-world scenery. The system allows the pilot to detect lights and ground features (runways, aircraft, mountains, buildings) at night and in low visibility conditions.

Gulfstream Aerospace Corp. has installed the EVS on its G-V executive business jets. Elbit Systems (Kollsman’s parent company) did the EVS systems integration. Honeywell supplied the cockpit software and head-up display interface. Opgal Optronics manufactures the FLIR, and BAE Systems makes the displays.

Elbit so far delivered three EVS-equipped G-Vs, and has pending orders worth $25 million.

Jim Gallagher, program manager at Gulfstream, said that the G-V is the only business jet that has an FAA-certified EVS system. He said that the Gulfstream G-IV was scheduled to be certified by late 2002.

The U.S. Army, Navy and Air Force have purchased 16 G-Vs so far. “Acceptance has been very good [in the military services],” said Gallagher. “I think they want to transition EVS into other aircraft.”

A variety of technologies current are dubbed “enhanced vision,” but not all work the same, he said. At Gulfstream, “we went with the infrared camera and head-up display, because for FAA certification, the criteria are very rigorous.”

In the enhanced-vision field, he said, the commercial market is “a little bit ahead of the military sector.”

In the years ahead, Gallagher predicted, EVS will be a standard item on commercial aircraft. “The feedback we get from our customers is that it’s like the TCAS (traffic-alert collision avoidance system): You didn’t know you needed it until you flew with it.”

Unlike ground-proximity warning radar, which gives a two-dimensional display, the EVS is three-dimensional, said Gallagher. “It’s not a computer-generated image, it’s the real-world.” Most proximity-warning systems provide a graphical representation of the terrain.

In remote airfields, where the navigation equipment may not be accurate and lighting may be poor, “EVS would definitely be a benefit, because you have a daylight view when you are flying at nighttime,” said Gallagher. “The pilot knows where he is, versus knowing what position he might be in, based on the aircraft instruments.”

At night, EVS displays a daylight image of the scene plus, if there are any lights on, they will be superimposed on the real-world lights. “He has a cross check of what the instruments are telling him and he can see where he is,” he added.

EVS-outfitted Gulfstreams don’t have conventional head-up displays, but a next-generation technology called “visual guidance system.”

The G-V has an option to add a head-down display for the copilot. “We have a remote monitor that can be installed in the cockpit, so the copilot can, as a cross-check, see what the pilot sees,” said Gallagher.

“In the future, the technology with synthetic vision is moving toward a head-down display,” he said. But it may be a long time before the FAA is ready to approve this technology. “The certification effort for enhanced-vision head-up was quite enormous. ... A head-down display is breaking additional new ground with FAA.”

With head-down, the pilot is relying entirely on instruments. “You are saying that the instruments can take the outside, real-world view out of the loop,” said Gallagher. “It’s going to be an interesting discussion with the FAA to go through all that. That is new technology that will require a lot of reviews.”

Regarding future military applications for EVS, Gallagher said he expects the demand for this technology to grow. “The reports I get from [military] pilots suggest that EVS is better technology than they’ve flown in military aircraft.” Their overall impression is that it’s “more carefully integrated into the aircraft ... Takes advantage of newer technologies.”

Russell said that it would be relatively easy to install EVS on military transports and tankers, because there is much more room available than on business jets.

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