Aviation Week & Space Technology - January 15, 2015

AviationWeek.com/awst AVIATION WEEK & SPACE TECHNOLOGY/JANUARY 15-FEBRUARY 1, 2015 61

John Croft Washington

Rockwell Collins tests radar

as a runway-finder

R

ockwell Collins is cautiously optimistic that its com-

mercial aviation weather radar can map the physical

environment around a runway. This capability could

help boost pilots’ situational awareness so they can indepen-

dently verify a synthetic-vision landing aid for low-visibility

operations.

In a series of flight tests in a company-owned Bombardier

Challenger 601 business jet over the past two years, engineers

have been able to verify that the radar—using modified soft-

ware algorithms—can consistently detect reflective airport

light structures, including approach lights and runway edge

lights at airports in the Midwest, Northeast and Southern

U.S. In terms of a visual image, the

radar return infers the location of

the runway by mapping the lighting

systems that lead to—and outline—

the runway surface.

The finding could help the compa-

ny develop and certify a synthetic-

vision guidance system (SVGS) that

qualifies for FAA approval for lower

landing minimums for instrument

approaches, a key NextGen capabil-

ity for increasing airport capacity

without installing and maintaining

new airport lighting and precision

landing infrastructure. The modi-

fied MultiScan weather radar ide-

ally will complement the company’s

head-up display-based synthetic-

vision system that includes input

from a new tri-band uncooled infra-

red enhanced vision system (EVS).

The first certified application of the

EVS-3000 sensor—which is being

tested in parallel with the runway-

seeking radar—is on Embraer’s

Legacy 500 business jet, which is

also the launch platform for Rock-

well Collins’s new lightweight, com-

pact HGS-3500 head-up guidance

system. Embraer plans to certify

the HGS-3500 with infrared cameras this year.

While the infrared sensor adds a real-time imaging capability

to the static, database-derived synthetic vision scene, its vis-

ible, mid-wave and long-wave cameras can have limited forward

visibility due to attenuation by the water content in rain or

fog. Enhanced flight vision systems (EFVS)—which use cooled

infrared sensors and head-up displays to boost performance in

those conditions—can be used to gain landing “credit,” although

at a steep cost: about $500,000 per installation for the EVS

alone. For Category-1 instrument approaches, the credit allows

a pilot to use the EFVS in lieu of natural vision down to 100-ft.

above the ground, rather than the typical 200 ft.

Avionics manufacturers, however, are seeking a middle

ground with SVGS, where a validated synthetic-vision

representation might be used to gain a lesser amount of

landing credit—down to 150 ft.—at least initially. Honey-

well is actively pursuing one version using an independent

database and other onboard precision guidance to validate

synthetic vision. Rockwell Collins may opt to use weather

radar, which at 10-GHz operating frequency, is not impeded

by haze, rain, snow, fog or clouds, and may be an ideal syn-

thetic vision verification tool. John Borghese, vice president

of the Rockwell Collins Advanced Technology Center, says

the company investigated 94-GHz millimeter-wave radar

several years ago, but the price was too high and there were

technical issues.

Engineers have overcome several hurdles, not the least of

which was taking a weather radar built to “kick out” ground

clutter and reconfiguring it to image the ground. Borghese

says the system needed more accuracy in azimuth “to pick

out” the reflective lead-in approach lights and runway edge

lights. An air transport weather radar beam is generally

about 4 deg. wide, and Borghese says that number had to

be reduced by “close to an order of

magnitude.”

Matt Carrico, senior engineering

manager and fellow of advanced

concepts at Rockwell Collins, says

engineers have been studying the

topic since the early 2000s. A key

issue had to do with physics: The

lower frequency (compared to infra-

red sensors) meant lower resolution

of the image, but the trade-of was

better weather penetrability. “We

knew we’d have to come up with

ways to enhance the resolution,” he

says. “That has been the focus of the

research.”

Carrico says the company is mak-

ing “significant progress in getting

enough resolution for the pilot or the

automation to recognize the landing

environment,” in terms of the reflec-

tive properties of the approach and

runway lights. “We still have a deci-

sion to make as to what we do with

image data we get back from the

radar. Do we process it and, based

on how the return looks, determine

if there’s a runway environment in

front to confirm synthetic vision, or

do we further process and present

the image to the crew?” He says the pictures are “very com-

pelling” so far, but engineers are not yet convinced “the image

will look that good under all conditions.” He says there is also

a latency associated with presenting the picture that “may

not make it presentable.” Another issue Borghese is studying

is whether the radar can both image the lights and look out

for weather threats, particularly wind shear. Currently the

system can do either one or the other.

Borghese says flight testing will wrap up by this fall, but

there is no firm schedule to introduce the capability as a

product. If a product does result, he says, it will likely come

to the business aviation market first. c

Radar Diversity

Modified MultiScan weather radar that re-

veals approach light structures may be part

of Rockwell Collins’s low-visibility landing

aids in the future.

ROCKWELL COLLINS