Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-01-25

The field can be wrapped in fog or dark; he
knows whether he Is SO or 100 or IS feet above
the ground But how get down in the dark?
The pilot, when he can see worlds horizon
before him in flight. is sitting pretty. But
when visibility has been shut on he has either
to come down or depend upon some instrument
on his instrument board to keep the altitude
Of his plane normal This problem has been
solved for him by the artificial horizon. It is
nothing more than the horizon of the earth
transferred to the dash Of the plane.
THE artificial horizon lis . small circular
faced instrument Of about four inches
diameter, constructed for flush mounting IN
the instrument board and weighing only about
i've pounds The face Of the instrument con-
sists Of a smooth background. blue on the upper
half to represent the sky, Shading to Q dark
gray on the lower half to represent the ground.
Horizontally across the middle Of this field Is
a straight bar, both ends of which extend be-
yond the mask which surrounds the instru-
ment face. This bar Stimulates the horizon.
In front Of the bar and the field IS small
tail view Of an airplane held at the center
Of the instrument face as part Of the mask
which Tits with the plane. If the plane climbs
or noses down, the horizon bar respectively
falls or rises in Just the same manner as the
actual horizon appears to fall or rise as the
pilot looks over the nose. As the plane banks
the bar remains horizontal, whereas the dial
The horizon bar is thus free to RISE fall and
tilt and can assume any possible combination
Of these positions. The instrument win indi-
cate banks up to 30 degrees and climbs or
glides up to As degrees The bar is held in the
horizontal position by a small airSpun gyro-
scope mounted in gimbal ring and having
its spinning axis vertical"
The radio direction finder is an old friend
Of the pilot but improvements are being made
In it from time to time, so much so that early
users of 1t would not recognize 1t today. The
standard finder is that of the beacon broad
cast from towers at intervals of about 200
miles. pilot on q course plugs in his set of
earphones on his receiving instrument. He
gets dot and a dash If he is one side of his
course, dash and dot signal If he is the other
side. If he is truly on his course he gets Q
long dash-the blend of the dot and DASH
This Is the aural or ear type Of radio direc-
ton finder. It now has been supplemented by
the visual type This consists Of two vibrating
reeds, one either side Of an upright graduated
dial. The whole is mounted In = tiny box no
larger much than an ordinary cigarette pack
age. The box, when in use, is plugged into the
dash Of planes receiving set. The position
Of pilot in flying Is indicated with respect to
the beam center. That Is the center of the
beam from the station in the direction of which
ne Is flying. When to the right Of the beam
the right reed vibrates through longer field;
when to the left the white marking caused by
the left reed becomes longer than the right.
When the pilot is on the true course the reeds
vibrate equally. As the flyer approaches the
beacon whose beam is being recorded ON his
reed instrument it becomes necessary for him
to cut down the volume Of his receiving set.
At the exact moment that he is over the sta
ton housing the beacon the reeds stop vfbrat-
ing. They start again, this time in opposite
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