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the one most directly into the wind; in
either case, there should be no tailwind.
Chicago O’Hare International
Airport must cope with winter weather
while maintaining 178 aircraft gates, 13
mi (21 km) of runway and 48 mi (77
km) of taxiways. George Lyman, Chicago
Department of Aviation general manager
of airfield operations, described the
planning and coordination needed.
Weather forecasting is obtained
from six different sources, he said.
The airport is divided into airside and
landside snow operational areas, with
four snow removal manuals published
annually. Snow alerts to airport personnel
are as detailed as possible, including
wind direction, temperature, expected
snow accumulation, expected duration
of the storm and type of snow.
For the most severe storms, as many
as 196 workers are on the job to keep
the airport open. A total of 199 vehicles
— deicers, brooms, plows, sanders,
etc. — are available. The airport uses
new technology, including three-inone
equipment, a combination of plow,
broom and blower in a single unit.
Jacques Leroux, account executive
with Dow Chemical, emphasized that
anti-icing fluids protect for a limited
period, measured as holdover time
(HOT). Depending on the type of
fluid, the HOT can range from 20 to 80
minutes. He described the procedures
for receiving, testing and storing fluids,
noting, “The spray operator should be
trained to notice and report anything
unusual about the fluid as it is applied,
such as abnormal foaming or the agent
being the wrong color for the type of
anti-icing fluid.”
Additional forms of anti-icing
and deicing are now in wide use, said
Kelvin Williamson, corporate director,
Basic Solutions North America.
Chemicals include potassium acetate
for anti-icing and sodium formate for
deicing. “Potassium acetate is virtually
odorless, contains a corrosion inhibitor
and is 100 percent nontoxic,” he said.
“It is effective in very low temperatures.”
The chemical is also effective at
cleaning rubber, grease, oil and fuel off
runway surfaces. During snow clearing
operations, these surface contaminants
along with frozen contaminants can be
removed at the same time, leaving an
improved surface, he said.
Sodium formate is effective to minus
22 degrees C (minus 8 degrees F),
fast-acting and environmentally sound,
Williamson said. It is used to melt
through packed snow and ice, breaking
ice-to-pavement bonds and making
mechanical removal easier.
Clint Tanner, Bombardier senior
technical adviser, flight sciences, Core
Engineering, discussed the recent history
of takeoff accidents and incidents
in winter operations involving CRJ200
and CL600 aircraft, in which, he said,
“Generally, it has been found that there
was a failure to follow the published
operational procedures for the aircraft.”
Speakers from left: Williamson, Wiszniowski and Leroux Photos: Rick Darby
26 | flight safety foundation | AeroSafetyWorld | October 2009
threatanalysis
Among the analytical findings, he
said, were that “in all cases, a premature
wing stall occurred during the
takeoff rotation. It is believed that
the premature wing stall was caused
by ice contamination along the wing
leading edge.”
Accidents involved failure to deice
or anti-ice properly, he said. In every
accident, the wing anti-icing system
was not used. In-service experience
with the two Bombardier models
showed that “no ‘winter operations’
accident has ever occurred where the
wing anti-ice system was selected ‘ON,’”
he said. Tanner said that a review of
operators’ documentation found that
several operators had pilot checklists
lacking a pre-takeoff check for wing
anti-ice selection. Another causal factor
was excessive rate of rotation, with the
average maximum pitch rate greater
than 6 degrees per second.
Airplane flight manuals (AFMs) for
the CRJ200 and CL600 now call for tactile
inspection of the wing leading edge
and upper surface when the outside air
temperature is lower than 5 degrees C
(41 degrees F), or the wing fuel temperature
is 0 degrees C (32 degrees F), or
“the atmospheric conditions have been
conducive to frost formation,” he said.
Such definite criteria are better than
vague conditions such as “water on the
wing” or “visible moisture.” In another
　
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