AOPA Pilot Magazine - July 2014 - 18

SAFETY PILOT

Weather wonder

BRUCE LANDSBERG
President, AOPA Foundation

Standing on the shoulders of giants

BRUCE LANDSBERG

has logged
more than 6,000
hours as an airline
transport pilot.

18 | AOPA PILOT July 2014

A HIGH OVERCAST in the western sky was rapidly morphing into the angry gray of an approaching cold front.
Here in the Midwest they build them long, tall, and
mean. My fuel stop in Mt. Vernon, Illinois, was abbreviated because of the weather 100 miles west. Destination:
Wichita. Go north, south, or stay put?
The year: 1979. My ride: a Cessna Turbo 210. It
would be more than 10 years before the first weather
datalink displays appeared in general aviation cockpits.
This particular aircraft, which belonged to the Cessna
Aircraft Co.-my employer at the time-didn't even
have the little digital radar pod that graced many of our
demonstrators' right wings. Bad luck to have drawn a
barefoot airplane on such an active weather day!
But much farther to the east-at about the same
time at NASA's Langley Research Center in Virginia-
the Storms Hazard Program was just getting under way.
The objective was to evaluate lightning strikes in aircraft with special emphasis on protecting composite
components and airframes to understand why an airplane might get blown out of the sky. A hell-for-stout
F-106 was used for strike bait. The NASA crew was
going boldly where few had gone before-intentionally.
Research abounds with useful serendipitous discoveries. To get lots of lightning juice the jet needed to
find boomers quickly. Ground-based radar was moderately helpful but there had to be a better, faster way.
The NASA team soon figured out that one datalink
picture direct to the cockpit was worth a thousand vectors. That's when the NASA program manager, Norm
Crabill, AOPA member, three-decade employee of
NACA/NASA, and private pilot, started asking, "If we
can datalink precipitation pictures up to an F-106, why
not a general aviation aircraft?" It took from 1982-when
the first uplinked radar pix were sent to the jet-until
1988 when Crabill wrote the paper, "Cockpit Weather
Research, Development, and Applications-Survey and
Recommendations" that a new direction emerged.
By 1989 Crabill had retired from NASA and was
working as a contractor. With Ernie Dash and Scott
Shipley, the three managed to finagle, persuade, and
cajole scarce research dollars into one of the most useful and revolutionary technologies that GA has seen in
recent times. The patent application stated the obvious: pilots needed current weather en route in both text
and pictorial form because weather is dynamic and, in
many cases, hazardous. With more accurate and timely

weather information, pilots could make better decisions
and more flights could be completed safely.
What we get in today's cockpit is pretty intuitive,
but the system behind it was not. This quote from
the patent application may give you some appreciation for the complexity and genius that went into the
marvelous equipment we now take for granted: "The
weather information is edited and packaged into compressed coded digital data blocks, usually of five-minute
lengths, and transmitted as digital signals to the ground
transmitter of a satellite communications system. This
transmission is via an uplink data stream and, typically,
at 6 GHz. The satellite communication system then
provides a direct broadcast (typically at 1.6 GHz) of the
suitably coded weather information to all aircraft within
its coverage area, either in the air, or on the surface of
the Earth. The rebroadcast data blocks may be picked
up by an antenna on any aircraft flying, or on the ground,
within the coverage area. The received data blocks are
expanded and decoded, if needed, by a flight processor on-board the aircraft into several types of graphic
depictions for display on a small screen and using a standard map with shapes and colors to define the various
pilot-oriented display classifications. All the weather
information needed for flight operations within the satellite coverage area is transmitted from the satellite to
all aircraft operating within that coverage area." Whew!
Back to 1979: I left the Indy Center IFR frequency
for Flight Watch. The party line was humming and
it was five solid minutes before I could get a word in
edgewise. That's a long time when you're moving three
miles a minute toward weather that's moving quickly
toward you. The specialist suggested a hole 100 miles
south as the best way to go. Back on Center frequency,
it was hopping, too, with everyone shucking and jiving
to get around the cells. I had one ear listening to Flight
Watch hoping to gather what little extra info might be
had when they called, asking if I was still there. Why,
yes. OK, the southern hole had closed up and north over
St. Louis looked much better. I asked Indy for a course
reversal and worked through the line quite a bit farther north, but not without some trepidation because
it looked pretty dark. No rain, mostly light turbulence,
and one good thump. How much different would it have
been today with datalink?
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AOPA Pilot Magazine - July 2014

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