When Gulfstream’s G650 enters service later this year, pilots will find a pleasant surprise, a Honeywell RDR 4000 3-D weather radar that is far easier to operate than earlier systems. The radar has been flying for a few years on airliners, and the G650 is the first business jet application. New features just implemented on the RDR 4000 include turbulence detection, hail and lightning display and a new attenuation display.

What makes the RDR 4000 so easy to use is its elimination of manual antenna tilting and ground returns. The new radar does all the work, tilting automatically while targeting sectors of the sky, storing results and painting a picture on the cockpit display. By referencing a terrain database, the radar knows which parts of the data it receives contain ground returns that can be deleted. The resulting colorful view of the weather shows only what the pilot cares about, thunderstorms and their associated hazards.

“When we first started looking at this in 2003,” said Ratan Khatwa, Honeywell senior chief engineer for human factors, “we asked ourselves, ‘What can we do to make this better?’” The problems that still weren’t being solved by conventional weather radar systems were costs associated with turbulence incidents and weather-related delays and cancellations. Conventional radars require extensive pilot training and operational experience. They also require pilots to operate the system manually and then interpret the results, all at a time of high workload when pilots’ attention might better be focused on other issues.

Honeywell interviewed pilots and conducted surveys and focus groups all over the world, including airline pilots and corporate operators. As the technology developed, Honeywell did simulator evaluations, comparing conventional radars to the new system. “There was a disciplined process to get to where we are today,” Khatwa said. “It’s a pilot-centric design; it’s not about the loudest voice on the design team.”

In studying pertinent accidents, researchers found that the data supported what pilots were complaining about, particularly tilt management. “We saw there was large variability in pilots’ use of radar. Training standards went from on-the-job training to full-blown ground school. Variability in training leading to knowledge gaps, poor tilt management and [poor] management of the radar. That’s the chain of events that leads to some of these incidents.”

Military Technology

The RDR 4000 (or IntuVue in the airline world) 3-D weather radar takes advantage of pulse-compression technology developed by the military. According to Honeywell radar systems engineer Brennan Kilty, “Pulse compression uses pulses that are long in duration and wide in bandwidth with specially designed receive filters to enable low-power transmitters to obtain both long-range target detection and a high-resolution picture. This allows us to replace the magnetron power oscillator with more reliable and controllable solid-state transmitters that produce less noise to interfere with other electronic systems and are less expensive to maintain.” The associated electronics for the RDR 4000 take up much less space and weigh less. The RDR 4000 fits into a 3 MCU space, versus 8 MCU for a conventional radar, and it weighs about 30 percent less and costs 35 percent less to operate. Price compared with a previous generation RDR4B is about 5 percent lower.

The RDR 4000 automatically scans everywhere the antenna can capture pulses reflected by moisture, in this case as distant as 320 nm and from the ground to 60,000 feet, while removing ground returns. According to Honeywell, the IntuVue system is the first airborne weather radar certified to new enhanced turbulence minimum operating performance standards. In addition to detecting moisture to build a picture of thunderstorm activity, the RDR 4000/IntuVue detects turbulence up to 60 nm away, does predictive lightning and hail detection and what Honeywell calls rain echo attenuation compensation technique (React). This clearly identifies areas where the radar view is attenuated, so instead of not painting something on the display–that is, just leaving it blank and black, which could suggest there is no return and therefore no hazardous weather–React shows magenta arcs to highlight attenuated areas. Hail and lightning are highlighted by magenta circles surrounding hail and lightning symbols.

The design of the RDR 4000 was carefully shepherded through Honeywell’s human-factors process. “What we do first is ask a question,” said Khatwa. “What problem are we trying to solve?” The answer must lead to improved safety but also be easy for pilots to understand and learn. The process begins with prototyping early designs and, he said, “making sure we address all the issues we’ve got.” This involves human factors and other engineers and pilots. As the range of candidate products narrows, simulator testing helps refine the look and feel. Running scenarios created from actual accidents helps show if the new product prevents pilots from getting into a hazardous situation, he added. More refinement and simulator testing with airline and corporate pilots, including learnability and trainability studies, helps bring the final product to market. The IntuVue system has flown on Boeing 777s for four years and is installed on many Boeing and Airbus airplanes. The hail and lightning display, turbulence detection and React capability were added recently.

Real-World Demo

To demonstrate the RDR 4000’s capabilities, Honeywell invited journalists to fly in the company’s flight-test Convair CV-580, which was used to develop the new radar. The test equipment includes the RDR 4000 and a complete data gathering system installed in the spacious cabin. While there is an electronic flight bag in the cockpit that displays a live Nexrad view of the storms, which can be compared to the radar view, the equipment in the cabin also runs the RDR 4000 next to a Nexrad view. The flight-test pilots who flew the Convair on this trip, Markus Johnson and Randy Moore, have extensive experience observing thunderstorms and the way they play on the RDR 4000 and Nexrad displays.

The RDR 4000 beam is three degrees wide, and although it can detect storms 320 nm distant, accuracy improves as the aircraft flies closer to the weather. The system scans 180 degrees to either side of the airplane and from zero to 60,000 feet to 320 nm. The system stores these scans in its 3-D volumetric buffer, removes any ground returns and displays the resulting image to pilots, updating it continuously. The system also compensates for the curvature of the earth and changes in the airplane’s attitude or track.

The Convair and airline antenna measures 30 inches, while the G650’s is 24 inches. Honeywell is developing an 18-inch antenna for Falcons and is testing it in Florida on the Convair.

The pilot’s controls for the RDR 4000 are simple. A switch offers map, automatic or manual mode. In manual, the user can view a slice of the sky in 1,000-foot increments by using the altitude knob. This enables views of different levels to try to find storm tops or altitudes where the weather is better or worse. Another handy feature is vertical profiling along a track, selected azimuth or flight plan route. Map mode can show ground returns instead of weather.

We took off from Dallas Love Field in the Convair and flew east at 21,000 feet, looking for storms. We had a good Nexrad view of some building activity over the Louisiana-Arkansas border and we chased those storms for about an hour and a half. From a distance, the Nexrad view looked perfectly adequate. Both the Nexrad and RDR 4000 displays showed about the same view of the storm, although it was clear that the RDR 4000 was able to build an accurate picture from hundreds of miles away.

We took some manual slices of the view and found the tops to be around 40,000 feet. But from maximum range, these slice views can be off by as much as 10,000 feet. Once the aircraft is within 150 miles of the storm, accuracy improves considerably and the slices can resolve tops to within about 2,000 feet. As we got closer to the storms, we could see the anvil of the dissipating storm, but it was still a significant area of weather. The Nexrad view was still a great help because it showed areas that one would not want to try to pick through. The RDR 4000 also helped highlight areas with lightning, hail and attenuation React symbols. As we flew even closer, magenta areas of turbulence popped up on the RDR 4000 display. The closer we got to the storm, the more it became apparent that only the radar would be helpful in picking a safe route through the storm. (Not that this is always possible, of course.)

Nexrad is useful for strategic and especially long-range planning, but onboard radar, especially one as simple to learn to use as the RDR 4000, is essential for real-time tactical decision-making.