since the first airplane flight in 1903
flying in winter has been a problem
because of dangerous situations created
by ice formations on aircraft
during the 1920s and 30s when aviation
was still in its infancy the limitations
of winter flying were very apparent
one example was the attempt to establish
transatlantic routes between the united
states and europe over the north
atlantic which were considered much too
dangerous to fly
during the second world war more than
100 c-46 aircraft were lost while flying
over the himalayas between india and
china
this route was known as the hump
responding to this need the national
advisory committee for aeronautics naca
directed that an icing research tunnel
be constructed at the aircraft engine
research laboratory which was the former
name of the lewis research center
the icing research tunnel was designed
and constructed from 1942
to 1944 for six hundred seventy thousand
dollars
the first icing test was run on june 9th
1944
the icing research within naca first
started in the 1920s at langley research
center in virginia
icing research was also conducted at
ames research center in california prior
to the research at lewis research center
in the 1940s
soon naca turned to nasa
and their attention from aeronautics to
space
the icing technology developed through
the 40s and 50s at naca nasa formed the
basis of what the u.s aircraft industry
used to solve various icing problems
dr joe shaw deputy chief for applied
dynamics at the nasa lewis research
center
explains the icing research program
the icing research program at lewis was
begun in the early forties it was felt
that an icing research activity
including
the construction of a ground icing test
facility or the icing research tunnel
was needed to address the wartime icing
problems that that the military was
having there was expressed a need for an
icing test facility ground test facility
that would accurately and adequately
duplicate natural icing conditions
and you need to generate a cloud in that
tunnel an icing cloud that simulates the
right amount of liquid water content and
droplet size distribution to be typical
of those you might find in natural icing
as well as you need to control the
temperature of the airflow in the tunnel
so again that you would be able to
simulate accurate conditions that you
would expect to see in flight it is not
the weight of the ice on the various
parts of the aircraft that causes the
problem
but the altered aerodynamics that change
the performance stability and control
characteristics of the airplane
the ice forms may be small but they do
have a significant effect on the
airplane and its actions when ice
secretes or grows on the surfaces of the
airplane wings tails fuselage whatever
the
result is a change or degradation the
performance of the airplane as well as a
degradation and the stability and
control of the airplane if the ice
shapes or ice secretions as we call them
become severe enough
the stability and control of the
aircraft can be completely lost and your
craft cannot be controlled
the irt is similar to other subsonic
wind tunnels in that a wing or other
aircraft component when placed in the
test section may be subjected to various
air speeds
the airflow being created by a motor
driven fan
the irt has several unique features to
simulate icing conditions a heat
exchanger and a refrigeration plant to
achieve the desired temperature and a
unique spray system to generate a cloud
of microscopic droplets of unfrozen
water
this makes the irt capable of
duplicating the icing conditions that an
aircraft might encounter
all aircraft whatever their size can be
susceptible to icing
general aviation aircraft can be more
susceptible to icing because they have
smaller wing sections
smaller wing sections tend to accrete
ice at a faster rate than larger wing
sections
helicopters also have icing problems
because helicopter rotors are small and
are spinning at high speeds
they therefore tend to build up ice
quickly and it does not take long before
you get some severe icing conditions on
the helicopter rotor
now dr shaw will tell us about
anti-icing
anti-icing simply means that you are
using some technique which prevents the
buildup of ice that is when the water
droplets hit the surface and
of the airplane of course they're in the
liquid state and they remain in the
liquid state de-icing means that you
allow the ice to grow that is you form
an ice accretion or an ice growth and
then you get rid of or de-ice
that ice accretion before it it reaches
a size that can significantly impact the
aerodynamic performance and stability
and control performance of that airplane
in the 1970s the aircraft industry
realized that there was a need for
additional icing technology
and nasa reinstituted an icing research
program to meet the new icing technology
needs which occur as a result of the
ever-changing aircraft design problems
from basically 1950 through 1957 when
the knack or nasa program was concluded
a tremendous icing technology database
was developed and the technology being
used today
on today's aircraft came from largely
from that program examples of that would
be the hot gas anti-icing system that is
used by all transports today for ice
protection
today about 90 percent of the smaller
general aviation aircraft certified for
flight into forecast icing conditions
are using the pneumatic boot system for
de-icing
it was developed in the 1930s by the bf
goodrich company
the pneumatic boot is a rubber boot
placed over the leading edge of the wing
or tail
when the ice secretes or grows a
pneumatic air source is used to inflate
the boot which destroys the ice aircraft
surface bond to clean the surface of the
craft
the nasa lewis icing research tunnel was
named an international historic
mechanical engineering landmark in 1987.
it is the oldest and largest
refrigerated icing wind tunnel in the
world
two major achievements of this
installation are the unique heat
exchanger and the spray system that
simulates a natural icing cloud of tiny
droplets
icing is no longer a major problem for
many of today's aircraft because of the
ice protection systems technology
largely developed in the nasa lewis
research center icing research tunnel
as new aircraft are developed and
operating practices are changed the
recently modernized irt will continue to
lead the way
in solving the icing problems of the
future
you