THE BIRTH OF AN AIRPLANE
Out in the forests of the great Northwest there stands a giant spruce
tree, tall and straight and strong, whose top looks out across the
gentle slopes of the Rocky Mountain foothills to the Pacific. For eight
hundred years, perhaps, it has stood guard there. Great of girth, its
straight trunk rising like a stately column in the forest, it is easily
king of all it surveys.
Someday the woodsmen of Uncle Sam come and fell that mighty spruce. And
then begins the story of its evolution, from a proud, immovable
personage whose upper foliage seemed to touch the clouds, to a strong
and lithesome bird who goes soaring fearlessly across the sky.
Uncle Sam has had an army of over ten thousand men in the woods of
Oregon and Washington during the past year, selecting and felling
spruces for airplane manufacture. Only the finest of the trees are
chosen, and lumber which shows the slightest defect is instantly
discarded. The great logs are sawed into long, flat beams, and are
carefully examined for knots or pitch pockets or other blemishes which
might impair their strength when finally they have been fashioned into
airplane parts. These beams then start on their journey to the aircraft
plants, where skilled laborers get to work on them. For the days of the
homemade airplane have passed. It is only about fifteen years since the
Wright brothers built their first crude flying machine, and, not without
some misgivings, made the first trial of their handiwork. Since then
airplane manufacture has made many a stride. The flying machine of those
days was largely a matter of guesswork. Nobody knew exactly what it
might do when it took to the air. Nobody knew whether it would prove
strong enough to bear the pilot's weight, or whether it might suddenly
capsize in the air and come crashing with its burden to the earth. For
the parts had been crudely fashioned by the inventor's own hands.
Naturally he was very seldom a skilled cabinet maker, painter and
mechanician. He knew very little about the laws of aerodynamics, about
stress and strain and factors of safety. He just went ahead and did the
best he could and took his chance about losing his life when his great
bird took to the air.
No wonder the early fliers dreaded to set forth in even a gentle breeze!
No wonder there used to be so much talk about "holes in the air" and all
the other atmospheric difficulties that beset the pioneers. The wonder
is that any of the early fliers ever came off alive with the fickle
mounts to whom they trusted their lives.
To-day the manufacture of an airplane has been reduced to the most exact
of sciences. Every part is produced in large quantities by skilled
workmen, and its strength is scientifically determined before it is
passed on to become a member of the finished airplane. Sometimes whole
factories specialize on a particular detail of the airplane. Here they
make only airplane propellers; there only engines; while in this factory
the wings and fuselage are produced.
Let us imagine ourselves on a visit to one of the great aircraft
factories which have suddenly sprung up in the United States and become
so busy with the work of turning out a huge aerial fleet. The great
trees which were felled in the Northwestern woods have changed greatly
in appearance since we saw them last. As a matter of fact for certain
parts of the airplane they should have been allowed to lie out in the
sun and rain for several years to "season," but the rush to put planes
in the air has made this impossible. Instead they have been treated with
a special process in order to rid the wood of its impurities. Now the
big beams go to the carpenters to be fashioned into the airplane
fuselage. The separate boards are carefully cut and fitted and trimmed
down to perfect smoothness and symmetry. Painted and varnished the
fuselage resembles a fine automobile body. In the top or roof of the
fuselage one or more circular openings have been cut. Below, almost on
the floor are the seats for pilot and observer, in what are known as the
cockpits. While the carpenters and cabinet makers have been busy on the
fuselage, more skilled workmen still have been fashioning the airplane
wings. This is one of the most difficult and delicate tasks of all.
Remember that the curve of the wing determines to a large extent the
speed and climbing powers of the completed airplane. The wing is built
up of a number of ribs which give it the proper curve and shape. Each of
these ribs must be accurately manufactured from a prescribed formula.
First a piece of board is turned out which looks exactly like a cross
section of a wing. But there is no need for solid wood to add to the
weight of the wing, and so all over its surface the workman goes, boring
out circular pieces, until only a framework remains. On its upper and
lower edges a flexible strip of wood is bent down to its shape and
strongly attached. The rib is now complete. A number of ribs placed in a
row begin to suggest the outlines of a wing. They are connected by long
beams which run from tip to tip of the wing. When these have been
fastened in place the skeleton is completed and the work of the
carpenters is over for a little while.
The next step is to place upon this wing skeleton its linen covering.
The linen is usually cut in gores or strips which are sewed together,
and then the whole piece is stretched as taut as possible upon its
framework, above and below the ribs. Sometimes the seams run parallel to
the ribs and are tacked down to them, but seams which run diagonally
across the wing have been found more satisfactory. Of course it is
practically impossible to stretch the fabric absolutely tight over the
frame so that it will not sag when subjected to the heavy pressure of
the air. Various methods were tried in the early days to tauten and
strengthen the fabric. To-day the covered wing is treated with a
substance known as "dope," which shrinks it till it is "tight as a
drum."
Dope renders the wing both air-proof and rainproof. It strengthens the
fabric and makes it able to bear the terrible stresses to which it will
be subjected when the airplane is racing through the sky. But it cannot
be applied carelessly, and right here the skill of the very best
painters is brought into play. These painters spread first two very thin
coats of it over the fabric, filling up the pores so that later coats
will not run through into the interior of the wing. Next two or three
thicker coats are applied. After this the wing may receive several coats
of varnish, while if it is a U. S. service plane it gets a final
covering of white enamel, which protects the fabric from the injurious
action of the sun's rays.
Now the wings and fuselage of our airplane are ready, and the rudder,
the elevating surfaces and the ailerons are in course of production.
They are made in the same manner as the wings, with a wooden framework
over which fabric is stretched and "doped." We begin to think our big
bird is almost ready to be put together, but we have forgotten two
important items: the engine and the propeller.
The airplane manufacturer usually does not attempt to build his own
engines or propellers. He buys his engine all ready to be installed and
procures his propeller from a factory which makes this its specialty.
For the propeller is one of the most difficult parts of the airplane to
produce. Above all things it must be strong, and for this reason steel
has been tried in its manufacture. Curiously enough it was found that
the metal propeller could not stand up under high speeds and stresses as
well as one built of wood.
Many kinds of wood are used in propeller construction, and the choice
depends very largely on the speed and stress--in other words on the
horsepower of the engine. Sometimes a propeller is built of alternating
layers of two different kinds of wood. But with high-powered engines oak
is very generally employed on account of its strength.
An airplane propeller is not carved out of a single block of wood, for
in this case it would not be strong enough for the difficult task it has
to perform of cutting its way through the atmosphere and drawing the
airplane after it. Instead it is built up of a number of thicknesses of
specially seasoned wood, so arranged that the surface is formed by the
cross grains of the various layers. This result is produced by first
piling up a number of boards to form a block out of which the propeller
can be carved. The boards are glued firmly together and then they are
subjected to tremendous pressure. Now expert wood carvers begin their
delicate task of turning out a propeller of a given pitch. Their work
requires the utmost skill, but they succeed, until gradually the
finished article begins to take form out of the crude block. A coat of
varnish, a fine metal hub--and our propeller is ready to be shipped to
join the wings and the fuselage and complete the manufacture of a modern
airplane.
There are several other items--such as the steel landing chassis, the
steering instruments and the upholstery--which we must have on hand
before we are ready to commence the work of assembling. When all have
been procured the happy task begins. The wings are put in place, and
carefully secured by wires and supporting struts. The steering apparatus
is installed, the cushioned seats are placed in the cockpits, the
fuselage is mounted on the wheeled chassis, and finally when all is
complete the big bird is sent out for its first test flight.
If there is any one way in which the airplane of to-day differs
radically in its process of manufacture from the airplane of a few years
ago it is in this: that it is a _tested_ machine. The greatest enemy of
the aviator was and always will be, not so much the bullets of an enemy
as the hidden flaw in his machine's construction, which makes it "go
back on him" when he least expects. The pioneer aviator built himself
what he considered a "strong airplane," but when he attempted flight
under weather conditions not so favorable as those on which he had
counted, some untested part gave way. So in the early days there were
many tragedies. To-day, the airplane has become a safe mount indeed, for
not only is the finished machine tried out before it is put into use,
but each separate part is subjected to the most exacting series of
tests. If it does not bear up under at least six times the strain it
will ever be called on to endure in flight, it is rejected as unfit.
That is the reason the aviator of to-day dares to perform all the
marvelous tricks in the air of which we read. Back of the stories of
heroism and daring that have come from the battle line during the Great
War, and back of the great commercial feats and enterprises that are
being planned for the near future, we must not lose sight of the
remarkable progress in airplane manufacture and the careful painstaking
research and experiment that have resulted in greater safety in the air.
Of course it was the war that spurred every one on to do his best in the
design and construction of airplanes. Before that time England and
America had made very poor showings, and France, although deeply
interested in aviation, had nothing in the way of a flying machine that
would not seem ancient compared with the airplanes of the present time.
America came into the field of action late, and up to the time she
entered the war she had practically no airplane industry whatever. Yet
when she did get in she set to work with a will, and as every one knows
she succeeded in making a real contribution to aviation in the war.
Every brain that could be of service in our great country was mobilized.
The automobile manufacturers did much for the cause, some surrendering
their trade secrets for the good of the cause, and others turning over
their large organizations to airplane construction. As a result, a
recent report stated that there were 248 factories in the United States
making planes, with over 150,000 men working on aircraft. In a single
year this giant industry has sprung up, and the mechanical genius of
America has been focussed upon this latest problem: the heavier-than-air
machine.
It is inconceivable that our country, which can boast the invention of
the airplane, should in peace times allow this great industry to wane.
For a long time we slept while France was forging ahead in the design
and construction of machines. The commercial uses of the airplane will
be numberless, and it is bound to assume an ever more important and
practical role in everyday life. America has the natural resources, and
now that she has developed the tools with which to work and has trained
a large body of young men to be capable pilots, she should look forward
in the future to maintaining her proper place among the nations in
airplane manufacture. The big bird of the sky who had his birth in
America and who grew to such enormous proportions during the strenuous
days of war, must not be allowed to lose his American manners when he
turns to peace pursuits.