Evening star., 1929-12-08
AVIATION
BY JOSEPH S. EDGERToN.

/ The study of ice formations or
airplane wings and parts has beer
undertaken by the National Ad.
visory Committee for Aeronautics
which has constructed at the
| Langley Memorial Laboratories
Langley Field, Va, small vino
tunnel equipped with refrigeratine
apparatus. In this tunnel ice for
nations resembling those observed
in flight may be obtained or
round wires, struts and airfoil sec
tionS and the effects studied.
The effect of ice formation Oh
an airfoil section, such as a wing
the experiments show, is to de-
crease the lift and to increase the
drag or air resistance, as we'll aS
loading the surface heavily. These
tests are to be continued with a
view to devising means of avoiding
or overcoming the effects of ice
formation.
A number of fight tests also
have been made by the commit
tees test pilots to study the con-
ditionS under which ice forms. In
these fights records are made OF
cloud formations, altitude, tenn
perature and other weather con-
ditions. Various methods of pre-
venting or avoiding ice formation
are being studied and the data
obtained will be correlated with
those from the wind-tunnel tests.
Pilots who have had experience
with ice formation say that the
most dangerous conditions are
found when there is a fog or low
clouds, with temperature slightly
below freezing, but not cold
enough to CONCEAL the water parti-
cles in the air. It is known that
under certain conditions the tenn
perature Of water may be carried
below the freezing point without
freezing. Fogs and clouds COM
posed of unfrozen drops of water
frequently are found, according
to officials Of the Weather Bureau,
in temperatures below the freezing
point.
Aviation Danger Point.
Water cooled below the freezing
point, however, is inclined to con-
geal very rapidly if violently dis
turbed or upon coming in con-
tact with ice or snow. This con-
dition is the aviation danger
point. An airplane flying through
the fog or clouds cooled to slightly
below the freezing point collides
violently with the water particles
and they CONCEAL instantly. The
presence of ice upon the leading
edges of the wings then, in itself,
hastenS the formation of more
ice.
Another condition propitious to
the formation of ice is that which
was found in this part of the
country during the past week.
Rain, falling from relatively warm
areas above the earth, passes
through a very cold layer of air
closer to the ground and is chilled
to the freezing point or slightly
below without freezing. Upon
striking any object, however, it
freezes almost instantly, sheathing
branches, twigS, wires and other
exposed objects in a coating Of
clear ice.
In a discussion of ice formation
and its aeronautical aspects in
the Boston Transcript, Carl Gustaf
RosSby, professor of meteorology
at the Massachusetts, Institute Of
Technology, points out that sound
ingS of the upper air are impera-
tive if dependable warnings are
to be issued against ice formation.
Weather Hampers Forecasts.
Unfortunately" Prof. Rossby
said, when the danger is most
imminent and upper air data most
needed, namely, in case of fog or
low clouds at critical temperatures.
the airplane usually fails as a
sounding instrument, since it re-
quires reasonable ceiling for safe
operation. Captive balloons or
kites may then be used, but the
captive balloon does not work vel.
except in very light winds, and
kites require too much personnel
and are too slow for universal use.
The airport meteorologiSt is there
fore forced to recognize the oc-
currence of dangerous strata from
ordinary surface observations and
from the weather map.
Accumulation of experience
through daily contact with the
airmail pilots plus upper air obser-
vations, plus an intelligent inter
probation of the weather map, will
eventually solve the problem of
forecaSting ice formation"