Evening star., 1936-12-27
BY ALICE ROGERS HAGER.

allied subjects.
BY ALICE ROGERS HAGER.
CHEYENNE, Wyo., December 26
(NAN.A)-This little city. once ia
nous for its violently colorful life in
the days when cattle and cowboys came
up the long trail from Texas. has now
at its broad prairie airport an in
dustry as modern as tomorrow.
In the United Airlines shops here.
one of the most remarkable set-ups
Of the sort in the world, aviation
science is developing new instruments
) of precision with which to increase
the efficiency of ships in flight. So
delicate are some Of these instruments
that the men working on them must
use surgically sterile methods and a
patience so great that only few be-
come really qualified.
Seeing streamlined plane on the
runways, ready to take off. the average
passenger nowadays assumes that it
will function as a successful unit and
that its pilots are trained to handle
1t in the same way that an engineer
handles train. But the extent of the
knowledge necessary to the pilot and
the complicated and important work
that goes on day and night to make
him able to use it are little known.
Overhaul Every 500 Hours.
Uniteds policy has been a COM
plete overhaul On all its ships every
500 hours-not mere cleaning up Of
equipment and checking over of an
engine that probably has been rum
ming perfectly, but a tearing down
of every tiniest part and an almost
microscopic search for flaws. Usually,
about four ships are in for overhaul
at one time. During peak travel in
the Summer, a complete job is turned
out every "a hours, although it re-
quires five days to make the total
overhaul of a single plane. Alto
gether. some $50 ships are torn down
and put together again each year.
Beginning with the nose, the pro-
pellers come of and are taken to the
propeller shop. Here, working be-
fore newly constructed exhausts which
suck up the metal filings for the
protection Of the workmen, each blade
is resurfaced by an electrical emery
wheel, with the edges given a special
filing down by hand. These modern
propellers are of steel and they suf-
fer particularly from pebbles blown
!, against them when ship takes off.
After the bufing and filing, the
blades go into caustic soda solution
which makes visible, under a mag
nifying glass, any cracks. A further
cleaning in nitric acid follows, then
q polish is given them and they are
repainted with their proper stencils.
Each blade is checked for width by
hand and eye against chart and on
a balance for trueness When all the
parts are reassembled the entire pro-
peller goes on master balance and
the three blades are checked against
each other. Other parts, in the mean
time, have come in for equally expert
supervision.
Seek Simplified Equipment.
Alth hough United's experimental
work with radio is being done largely
at Oakland and Chicago-some of it
of such importance that the govern
ment will not allow it to be discussed
the radio section of these shops has
many features especially developed
for the testing processes. The princi-
pal object of the research being done
here is to simplify equipment for the
benefit of the pilot. One process alone
has been so perfected that change
over which formerly took him half
an hour to make can now be done by
turning a single knob on his ship.
Radio antennae that had to be re-
placed frequently now have a life of
from l,500 to 1000 hours.
When failure is apparent in any in
strument the shops are not content
merely with making repairs, but 60
behind the failure to determine the
cause and eliminate it. Here was
invented mechanical head set tester,
which gives an absolute reading on
both headphones and nicrophones
Instead of the old method of testing
by ear, which was subject to human
deficiencies, this tester checks the in
dividual sets against a standard set
and gives q numerical reading. This
must be done every two months, no
matter how well the pilots sets are
functioning.
It is in the Sperry room of the in
strument shop that the finest preci.
sion work Is done. Here the tests are
made on the gyro-pilot, the directional
gyro and the gyro-horizon. The men
at work are like surgeons in an op-
Grating room. Nothing is touched
with the naked hand. Bench models
of the huge instruments in use at the
original factory give a reproduction of
the planes motion in flight On the
gyro-horizon the wheel Is driven IA
600 revolutions per minute, which Is
seven times faster than the engine.
Ball Bearings Super-Tested.
The finest manufacturers selection
Of balls for the ball bearings are here
brought under a breakdown into
five more selections, made under spe-
cial optical flats. Parts affected by
engine heat are tested in an oven
which raises their temperature to that
Of actual flight. Finally. the entire
life history of every instrument is
kept on file, so that, each time it
comes in for checking, its past per-
formance is Immediately available.
One of the most interesting spots
in the shops is the floating test stand
for reviewing engine action, another
united development. Each engine in
turn goes on this stand, where it is
suspended by cables, again to repro
duce flight conditions. Formerly, en-
gines were tested by running In q
stationary plane on the ground, but.
this was hard on the ship and not
altogether accurateA On the test
stand, the motor runs for eight hours,
being started at 1000 revolutions per
minute and moved up gradually to
1000, its final speed. The amount Of
fuel consumed iS comulIted bv weight