Flight Training - May 2013 - 51

From the transcript:
18:04:18 CAM-2: “There’s lightning
coming out of that one.”
18:04:19 CAM-1: “What?”
18:04:21 CAM-2: “There’s lightning
coming out of that one.”
18:04:22 CAM-1: “Where?”
18:04:23 CAM-2: “Right ahead of us.”
(Flight 191 hit the ground at 18:05:52.)
“That one” was a towering cumulus
cloud producing rain that was falling on
the runway on which the L-1011 had been
cleared to land. The shower became a
thunderstorm as soon as lightning came
from it. Pilots learn early in their training
that they should avoid thunderstorms, but
as the Dallas-Fort Worth crash shows, a
towering cumulus on the way to becoming
a thunderstorm can also hide danger.
The danger hidden by the cloud was a
microburst—a phenomenon that no one
really knew about until the mid-1970s and
wasn’t named until 1978.
THE DISCOVERY OF MICROBURSTS. At
the time of the 1985 Flight 191 crash, a
few atmospheric scientists, pilots who
were especially interested in weather, and
others who were well aware of the microburst danger were developing programs
to train pilots how to recognize and avoid
them. They were working on Doppler
radars that could help controllers alert

pilots about potential microbursts. Until
the Flight 191 crash, however, neither
the FAA nor many others in the aviation
industry saw a need to spend much time
or money trying to reduce microburst
crashes.
The growing awareness of the microburst danger had begun with the June 24,
1975, crash of an Eastern Air Lines Boeing
727 at New York’s Kennedy International Airport, which killed 112 of the 124
people aboard. Theodore “Ted” Fujita
of the University of Chicago, a highly
regarded severe storms expert, conducted
a detailed study of the New York City
area’s weather at the time of the crash
and concluded that air blasting down
from a thunderstorm—which he called
a “downburst”—caused the crash. He
later sharpened his conclusion by coining
another new term, “microburst”—a downburst concentrated in an area 2.5 miles or
less in diameter—to refine his explanation
of the crash’s cause. (Today’s Enhanced
Fujita Scale of tornado strength is named
for Ted Fujita.)
Fujita’s extensive study of the Flight 191
crash found that the L-1011 had encountered a 50-knot downward tailwind as it

flew through the downburst, which was
1.9 nautical miles in diameter. As descending air hit the ground it formed three
concentric vortex rings—somewhat like
horizontal tornadoes—which the airplane
flew through.
How could microbursts have been
missed until 1975? Fortunately, they are
rare and the odds are small that one will
happen to hit a weather station. Even if
one did, the station’s single anemometer
would show only the wind in one place,
not the starburst pattern of winds hitting
the ground that Fujita visualized as he
studied the data from the New York crash.
Until Fujita advanced his theory,
meteorologists had blamed thunderstorm gust fronts for the quick changes
in wind speed and direction that sometimes occur in the vicinity of showers and
thunderstorms. A gust front is the air that
descends and spreads out as rain begins
falling from a shower or thunderstorm.
They are dangerous to aircraft taking off
and landing, but are easier to detect than
microbursts and aren’t as strong as the
worst microbursts. Until the Dallas-Fort
Worth crash, microbursts had been causing an airline accident in the United States

THIS DIAGRAM shows one of the principal dangers of encountering a microburst during takeoff or landing:
a sudden shift from a headwind to a tailwind with a resulting loss of lift. Unlike in the diagram, this occurs
inside a maelstrom of heavy rain and turbulence.

MAY 2013 FLIGHT TRAINING

/ 51



Flight Training - May 2013

Table of Contents for the Digital Edition of Flight Training - May 2013

Flight Training - April 2013
Contents
Right Seat
Centerline
Letters
Soaring in New Zealand
News Success Story
How It Works
Since You Asked
After the Checkride
ASI News
Final Exam
Flight Training Excellence Award Winner AOPA Action
News
Member Products
News
Flying Carpet
Flight Lesson
Checkride
North to Alaska
Make Order Out of Chaos
Time Is Money
Technique
Weather
Fortune Teller
Career Advisor
Tech Talk
A Real Workout
Great Influence, Great Responsibility
Time for a Change
Advertiser Index
Debrief
Flight Training - May 2013 - Flight Training - April 2013
Flight Training - May 2013 - Cover2
Flight Training - May 2013 - Contents
Flight Training - May 2013 - 2
Flight Training - May 2013 - 3
Flight Training - May 2013 - Right Seat
Flight Training - May 2013 - 5
Flight Training - May 2013 - Centerline
Flight Training - May 2013 - 7
Flight Training - May 2013 - Letters
Flight Training - May 2013 - 9
Flight Training - May 2013 - Soaring in New Zealand
Flight Training - May 2013 - 11
Flight Training - May 2013 - News Success Story
Flight Training - May 2013 - How It Works
Flight Training - May 2013 - Since You Asked
Flight Training - May 2013 - After the Checkride
Flight Training - May 2013 - ASI News
Flight Training - May 2013 - Flight Training Excellence Award Winner AOPA Action
Flight Training - May 2013 - Final Exam
Flight Training - May 2013 - 19
Flight Training - May 2013 - News
Flight Training - May 2013 - 21
Flight Training - May 2013 - 22
Flight Training - May 2013 - 23
Flight Training - May 2013 - Member Products
Flight Training - May 2013 - News
Flight Training - May 2013 - 26
Flight Training - May 2013 - 27
Flight Training - May 2013 - Flying Carpet
Flight Training - May 2013 - 29
Flight Training - May 2013 - Flight Lesson
Flight Training - May 2013 - 31
Flight Training - May 2013 - Checkride
Flight Training - May 2013 - 33
Flight Training - May 2013 - North to Alaska
Flight Training - May 2013 - 35
Flight Training - May 2013 - 36
Flight Training - May 2013 - 37
Flight Training - May 2013 - 38
Flight Training - May 2013 - 39
Flight Training - May 2013 - Make Order Out of Chaos
Flight Training - May 2013 - 41
Flight Training - May 2013 - 42
Flight Training - May 2013 - 43
Flight Training - May 2013 - Time Is Money
Flight Training - May 2013 - 45
Flight Training - May 2013 - 46
Flight Training - May 2013 - 47
Flight Training - May 2013 - Technique
Flight Training - May 2013 - 49
Flight Training - May 2013 - Weather
Flight Training - May 2013 - 51
Flight Training - May 2013 - 52
Flight Training - May 2013 - Fortune Teller
Flight Training - May 2013 - Career Advisor
Flight Training - May 2013 - 55
Flight Training - May 2013 - Tech Talk
Flight Training - May 2013 - A Real Workout
Flight Training - May 2013 - Great Influence, Great Responsibility
Flight Training - May 2013 - Time for a Change
Flight Training - May 2013 - Advertiser Index
Flight Training - May 2013 - 61
Flight Training - May 2013 - 62
Flight Training - May 2013 - 63
Flight Training - May 2013 - 64
Flight Training - May 2013 - 65
Flight Training - May 2013 - 66
Flight Training - May 2013 - 67
Flight Training - May 2013 - 68
Flight Training - May 2013 - 69
Flight Training - May 2013 - 70
Flight Training - May 2013 - 71
Flight Training - May 2013 - Debrief
Flight Training - May 2013 - Cover3
Flight Training - May 2013 - Cover4
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