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Rockwell Collins Upgrading Its WXR-2100 Multi-Scan Radar
Aviation Week & Space Technology
07/03/2006, page 50

David Hughes
En Route From Iowa to Florida

Tuning a weather radar usually takes lots of skill, but pilots can fly
this one hands-off

Printed headline: Radar on Auto

Times are changing in the world of avionics systems used for
surveillance on commercial transports. After a decade or more of relative
stagnation in weather radar technology, Rockwell Collins and Honeywell are
expanding the envelope. Both companies have invested heavily in new
technology to make it easier for pilots to find storms and assess the
hazards ahead.

Rockwell Collins's WXR-2100 multi-scan radar for the Boeing 787 and
other transports, and Honeywell's RDR-4000 flying on the Airbus A380 and
other airliners, bring new capability to track storms automatically and
"slice and dice" them for easy analysis.

Senior Editor David Hughes, a veteran USAF Reserve C-5 pilot with
earlier-generation weather radar, observed the WXR-2100 in action on
Rockwell Collins's Sabreliner testbed. His report follows. On a trip to
Honeywell, the weather did not cooperate for a proposed flight over Puget
Sound (there were no storms to look at), so the RDR-4000 was demonstrated in
the laboratory. That report will appear in the July 10 issue.

In addition to new innovations in radar, both companies have developed
integrated surveillance combining radar, a terrain awareness warning system,
a transponder and a traffic-alert and collision avoidance system.

We are flying toward Florida in Rockwell Collins's Sabreliner testbed.
Ahead of us, a strong line of thunderstorms is spawning along our planned
route. The WXR-2100 weather radar on board is already picking up the storms
for us automatically from 320 naut. mi. out--just one of the system's
impressive capabilities.

The company had arranged for me to fly on its Sabreliner to observe
the radar during a trip from Cedar Rapids, Iowa, to Melbourne, Fla. Daniel
L. Woodell, senior principal radar engineer and one of the inventors of
multi-scan technology, accompanied me in the back of the aircraft and
described how the system works on a repeater scope. Engineers later
downloaded the radar images from the flight and replayed them in the lab so
they could be captured and shown here (see photos above).

No technical finesse on my part was required to operate the color
weather radar on the Sabreliner: I just put the WXR-2100 on automatic and
watched it work. "That's the best thing about this radar," says Woodell.
"You turn it on and it's hands-off."

He and his fellow principal engineer, Roy Robertson, are responsible
for many of the more than 30 patents behind the technology that drives this
automatic radar. So far, the company has invested about $25-30 million in
research and development for its multi-scan work.

The line of storms ahead on our flight path was clearly depicted on
the radar display free of any ground clutter. As we drew within visual
range, it was soon apparent that strong cells were embedded in cumulus
clouds--making them hard to pick out unless they popped through the top of
the cloud cover.

On the radar display, some of these cells were red in the center,
indicating fairly heavy rainfall (at or greater than 0.5 in. per hour). On a
dark and stormy night, it would be very difficult to figure out what's going
by using the naked eye alone. In this type of situation, occasional flashes
of lightning would show just enough detail to make a pilot wonder if he had
adjusted the radar correctly.

And that's what the WXR-2100 is all about: Rather than having pilots
set the antenna tilt and radar gain and range manually--and then try to pick
out a thunderstorm from ground clutter on the display--computer algorithms
do this automatically and remove the ground clutter by digitally processing
stored radar return data (AW&ST Sept. 13, 2004, p. 58).

Rockwell Collins says 80 airlines have chosen the WXR-2100, which has
been on the market for four years. The radar is available on all Boeing and
Airbus aircraft except the A380 and A300.

In addition, a new, modular version of the WXR-2100 with software
enhancements will be included as standard equipment on the Boeing 787. The
787 will include the radar in a configurable integrated surveillance system.
CISS will combine radar functions in one box, along with a traffic-alert and
collision avoidance system (TCAS), a terrain awareness warning system (TAWS)
and a Mode-S transponder (see p. 53).

The WXR-2100's cleverest design feature is the use of multiple beams
of radar energy at different tilt angles to scan a storm. Then, the system
applies software algorithms to subtract ground clutter returns from the
picture. The process clearly worked during my flight; but I did not see it
demonstrated in mountainous terrain, for example, where the software would
have to make other adjustments. The WXR-2100 has a terrain data table so it
can look up the local elevations before determining the correct radar
settings.

The WXR-2100 also has algorithms to adjust for the differences in
storm cells in various geographic regions. When the radar first came out,
Qantas pilots said it needed to be improved in oceanic areas. Rockwell
Collins engineers discovered that oceanic weather is, on average, 200 times
less reflective than storms of similar height over land masses. Now the
radar "knows" when it's not in Kansas and is out over the ocean, and makes
adjustments accordingly. Algorithms are being developed for other geographic
regions as well.

Once the software code did its work, a clean view of the line of
thunderstorms ahead was all that was left on the display. It's noteworthy
that picking up storms starting at 320 naut. mi. is farther away than was
possible with previous technology.

At one point, I switched the radar to manual and tried to achieve a
similar image of the storm, but the always-present ground clutter made it
hard to see. Once switched back to auto, however, the algorithms cleaned up
the display in a matter of seconds.

This line of cells was spewing out hail in a few places along a line
from the southern Mississippi border with Alabama all the way up into
central Tennessee. Woodell noted that when the radar displays red areas, it
means there's a 30% chance of 0.5-in.-dia. hail being present.

Seeing the storms on a radar display while they are still beyond where
the pilots can spot them out the cockpit window (about 200 naut. mi. at
most) is clearly something that will help pilots plan an early deviation
strategy to minimize fuel burn.

As we moved within visual range of the storms, it didn't look to me
like the cells reached up to our Flight Level 300 cruise altitude. But
Sabreliner pilot-in-command David Tschudi and copilot Tom Yerke estimated
that the cells did in fact top out above 30,000 ft.

While the aircraft is at cruise altitude, the WXR-2100 aims radar
energy into the rain below, which is found under the freezing level (about
15,000-20,000 ft.). The rain is the most reflective part of the storm, but
this downward tilt angle also produces a lot of ground clutter, which is
then removed from the picture. By spotting the heavy rain below, the radar
shows when a powerful cell is building.

In the mid and upper levels of a storm cell, the water content takes
the form of supercooled water droplets and ice crystals. The WXR-2100
increases radar gain as temperature decreases to depict the upper level of
the storm more accurately.

One key goal is to help pilots avoid surprises. If an airline pilot
using a conventional weather radar fails to detect how powerful a storm is,
or one that's building, the aircraft could stumble into the bow wave of
turbulence in clear air above a growing cell. Unexpected encounters like
this can cause injuries to passengers and crew. Such incidents are often
described as "clear air turbulence."

Rockwell Collins is working on a major WXR-2100 upgrade to make it the
"Multi-Scan Hazard Detection" system using Version 2 software. The new
software will be fielded in two years, and will contain improvements that
are setting the future path for this key product. The company wants to move
toward a hazard detector and assessment tool that will keep airline aircraft
out of harm's way, instead of just selling a "rain gauge" that tells pilots
where the heaviest precipitation is located.

While areas of red currently depict heavy rain, this phenomenon by
itself is not a hazard to aircraft. As thunderstorm cells grow in intensity,
turbulence, lightning and hail are what can cause serious problems.
Ultimately, Rockwell Collins engineers want to detect these hazard areas and
change the color-coding scheme entirely. They aim to paint the hazards red,
rather than the current practice of showing areas of heavy rain in red. In
this new scheme, red would signal a hazard to avoid, yellow would be a
hazard requiring caution, and green would be an area that pilots could fly
through with confidence that hazards will not be present. Such a major
color-coding change will require a new certification from the FAA. The
company hopes to obtain this when Version 2 is completed in 2008.

The new WXR-2100 Version 2 features include:

*Direct sequential hazard assessment. This patented software will
allow multi-scan to determine the level of threat to an aircraft by
performing a comprehensive assessment of a storm cell. The measure will be
taken with vertical and horizontal scans using the optimum radar pulse
width, pulse rate and antenna movements. Then, analysis will determine the
amount of convective activity, growth rate and maturity of the cell.

*Flight path hazard assessment. This takes information from the direct
sequential hazard assessment and combines it with flight path data to assess
the threats ahead. Different radar techniques are used in different phases
of flight. For example, in flight below the freezing level (during airport
arrivals and departures), water droplets are very reflective. Radar
engineers and pilots know this as "the bright band." This new radar feature
will allow WXR-2100 to determine if the rain represents a substantial threat
for any reason or is simply a rain shower the aircraft can fly through
safely. This capability will make pilots aware of hazards along the flight
path during climbs and descents as well as during cruise.

*Storm-top information. This will be developed for cells within 80
naut. mi. of the aircraft for display to the pilots. It can be presented on
vertical situation displays. Woodell says vertical displays will become
commonplace on airliners in the future. In addition, the WXR-2100 will be
able to show the tops of storms with icons placed next to cells on
horizontal displays of weather.

*Predictive overflight protection. It analyzes the growth rate of a
storm to see if clear air turbulence above the cell will reach the
aircraft's flight level. This feature is designed to help pilots avoid nasty
surprises.

*Enhanced turbulence detection. This feature is based on technology
developed in a NASA-funded demonstration in 2004 of Rockwell Collins
technology on an in-service Delta Air Lines Boeing 737NG. It will allow the
WXR-2100 to find light to moderate turbulence up to 40 naut. mi. ahead in
areas of low reflectivity. The hazards will be presented to pilots as
speckled magenta areas (mild turbulence) and solid magenta (moderate to
severe turbulence), or as an icon marking an area of turbulence.

In 2008, Rockwell Collins plans to offer Version 2 software with all
these major new features to WXR-2100 customers. Other upgrades will occur in
the interim.

Clearly, this type of improved weather radar technology that can help
pilots identify airspace they can transit safely may help with what the FAA
sees as a looming problem. FAA Chief Operating Officer Russell Chew has
noted that if better ways are not found to minimize the disruption caused by
thunderstorms in the U.S. during the summer, there could be 29 days of delay
by 2014 that will be worse than the worst single day of delay in 2004 (AW&ST
Mar. 27, p. 46). This is because traffic is increasing. So a variety of new
tools is needed to avert cascading delays and what Chew says could be dire
financial consequences for the airlines.