WILBUR AND ORVILLE WRIGHT
How two American engineers followed up Lilienthal’s
work--Their biplane glider and its ingenious
control--First experiments and successes.
For those who might care to study them, Lilienthal had written papers
and essays as explanations of his work, and when the news of his death
was flashed round the world, inventors were induced to turn to these
teachings and read for themselves what he had done. Among those who were
interested were two young Americans, unknown then, but now
world-famous--Wilbur and Orville Wright. Living in Dayton, Ohio, they
were the sons of Milton Wright, a prominent church worker of that city,
and they carried on a bicycle store and engineer’s shop. Both were born
engineers--keen, clever, patient, and enthusiastic in their work; and
they had discussed many times--before they read of Lilienthal’s
death--the problem of building an aeroplane. Now this interest was
re-awakened; and as Wilbur Wright himself said:
“The brief notice of his (Lilienthal’s) death which appeared in
the telegraphic news at that time, aroused a passive interest
which had existed from my childhood, and led me to take down from
the shelves of our home library a book on “Animal Mechanism” by
Professor Marey, which I had already read several times. From this
I was led to read more modern works, and as my brother soon became
equally interested with myself, we passed from the reading to the
thinking, and finally to the working stage.”
What the Wrights first set themselves to do was to investigate previous
data. They wanted to prove, if they could, whether this data was sound
or badly reasoned: they needed a firm and definite basis of their own
before they would build any large machine. So they tested the theories
of their predecessors and made experiments, particularly as to the
sustaining power of surfaces of various shapes and curves. To this end
they built and flew kites, studying the lift they exercised; then they
decided to build a light gliding machine, such as Lilienthal had used.
But there was a drawback to be faced in all such practical work, and the
Wrights saw it clearly; this was to get a sufficient amount of actual
flying. It was Wilbur who wrote:
“It seemed to us that the main reason why the problem had remained
so long unsolved was that no one had been able to obtain any
adequate practice. It would not be considered at all safe for a
bicycle rider to attempt to ride through a crowded city street
after only five hours’ practice, spread out in bits of 10 seconds
each over a period of five years; yet Lilienthal, with this brief
practice, was remarkably successful in meeting the fluctuations
and eddies of the wind gusts.”
They made up their minds to build a glider with ample wing-surface, so
that it would be sustained in light breezes, and to take the machine to
where they might be sure of a steady wind, and there fly it as a kite;
allow it, that is to say, to ascend into the air at the end of a rope,
and hold it steady against the wind while the operator practised his
balancing movements.
[Illustration: FIG. 28.--The 1900 Wright Glider (operator’s position).]
Their first glider was a biplane, with 165 square feet of lifting
surface, as illustrated in Fig. 28; several of its features need
explanation. First there is the position of the operator; he can be seen
lying prone across the centre of the lower plane. This attitude was
adopted by the Wrights to minimise wind-pressure. Should a man be
upright in his machine, they calculated that his body would, as the
glider passed through the air, offer an appreciable resistance; while,
in lying flat, he would offer scarcely any resistance at all.
A small horizontal plane will be noted in front of the main-planes; this
was to govern the rising and descending of the machine. The Wrights came
to the conclusion that any body-moving method for controlling their
craft, such as Lilienthal had adopted, would not be sufficiently
powerful in a wind. Lilienthal, it will be remembered, had found his
control weaken when he used a machine of large surface. So the Wrights
decided that, instead of altering the centre of gravity of their machine
when gusts struck it, they would leave the centre of gravity immovable
and shift the centre of pressure upon their planes. This was done partly
by the elevating plane, as it came to be called. Tilted upward, this had
the effect of raising the front of the glider, and causing the centre of
pressure to travel backward upon the planes. Tilted down, it made the
planes dip forward, and brought the centre of pressure nearer their
front edge. When he wanted to rise, the pilot raised the elevator; when
he wished to glide earthward, he inclined it down. Here, indeed, was the
method such as was described in Fig. 13, when dealing with the machine
Sir Hiram Maxim built; and this system of the lifting plane is worthy of
special mention. In one way or another, fitted in front of the planes or
behind them, it is the recognised method for controlling the rise or
descent of an aeroplane.
Apart from governing the ascending or descending movement, there was the
question of preventing a machine from slipping sideways; and this the
Wrights solved ingeniously. They saw, of course, that when their glider
lurched to one side or the other, they would need some power to tilt it
back again. So they devised a system by which the plane-ends of their
machine--being made flexible--might be warped, or caused to shift up and
down. This action the operator controlled, as he lay across the lower
plane, by a movement of cords, and its operation is shown in Fig. 29.
The effect upon the machine may be described thus: should a wind-gust
tilt down one plane-end, the “warp” upon that side of the machine was
drawn down also, and the effect of this--seeing that it caused the plane
to assume a steeper angle to the air and exercise a greater lift--was to
raise the plane-ends that had been driven down by the gust. By a system
of connecting the control cords, this balancing influence was made to
act with double force; when one wing warped down, the other moved up;
and, in this way, while the side of the machine tilted down was made to
rise, the other plane-ends, which had been lifted, were made to descend.
A dual righting influence was thus obtained. This system, which imitates
the flexing movements made by a bird, was an important device; the
Wrights patented it--combining the movement with an action of the
rudder--and brought cases at law to enforce their rights.
[Illustration: FIG. 29.--The Wright Wing-warp.]
In the summer of 1900, with their first machine, the brothers went for
experiments to Kitty Hawk, North Carolina. They had chosen this lonely
settlement, located on a strip of land that divides Albemarle Sound from
the Atlantic Ocean, because they hoped it would provide them with a
strong, steady wind; there were also, fairly close to the settlement,
suitable sand-hills for gliding.
Upon the first day of their trials the wind was blowing at nearly 30
miles an hour, and they allowed the glider to rise as a kite. Flown in
this way, it bore the weight of a man; but they were disappointed at
the position it assumed when in the air. Its planes set themselves at
an angle which was too steep, and it seemed to give less lifting power
than they had expected. They tested their system of control, and found
that the wing-warping for sideway balance acted extremely well, proving
quicker and more certain than would the shifting from side to side of
the operator’s body. The elevating plane was also efficient.
[Illustration: FIG. 30.--Launching the Wright Glider.]
Then they took the glider to the sand-hills. At first the wind was too
high, but after waiting a day it dropped to 14 miles an hour, and they
were able to make nearly a dozen glides down the side of a slope which
had a drop of 1 foot in 6. It had been their idea, in building the
machine, that the operator should run before gliding, as Lilienthal had
done, and only lie upon the plane when the speed was sufficient to give
the surfaces their lift. But in practice they found a better method than
this. Two assistants, as illustrated in Fig. 30, took the machine by its
plane-ends and ran forward with it, the pilot assuming beforehand his
position upon the plane; then, when they had gained a pace sufficient
for the machine to soar, they released their hold and it glided forward.
Beneath the glider, under the centre of the lower plane, there were two
wooden skates or runners, and these took the weight of the machine when
it alighted, and allowed it to slide forward across the ground before
coming to rest. By the use of these landing skids, and by steering at as
fine an angle as possible, the Wrights found they could touch ground,
even at 20 miles an hour and lying across the machine, without injury
either to themselves or the craft.
The first glides were short, and all close to the ground; but they bore
out the tests when the machine had been flown as a kite, and showed that
the elevating plane and wing-warp would do their work. The Wrights were,
indeed, astonished at the celerity with which the glider responded to
the fore-plane.
Writing afterwards of this first visit to Kitty Hawk, Wilbur summarised
the experiments thus:
“Although the hours and hours of practice we had hoped to obtain
finally dwindled down to about two minutes, we were very much
pleased with the general results of the trip, for setting out as
we did with almost revolutionary theories on many points and an
entirely untried form of machine, we considered it quite a point
to be able to return without having our pet theories completely
knocked on the head by the hard logic of experience, and our own
brains dashed out into the bargain.”
[Illustration: PLATE III.--FARMAN’S VOISIN BIPLANE.
The airman is seen making one of his first flights over the
parade-ground at Issy-les-Moulineaux, the machine flying low as it was
its wont, and a scattered crowd of spectators watching from afar.]
When they came to plan a new craft for the summer of 1901, they agreed
they could not better either the theory or the manipulation of their
first machine; but they decided to make one nearly double the size.
Their reason for doing this was that, having a greater lifting surface,
they hoped to fly in quite light breezes and also prolong their glides;
and they were encouraged to build a larger machine by the readiness with
which the first had responded to its controls. They therefore
constructed a biplane which had 308 instead of 165 square feet of
surface, and was the largest machine of its kind that had been built.
In July they went into camp on their remote sand-hills, housing the new
machine in a wooden shed. The first tests were made in a 13-mile-an-hour
wind, but proved disappointing. The machine dived, in spite of a quick
movement of the elevator, and landed after gliding only a short
distance. The cause was found to be this: the centre of gravity was too
far forward. Therefore the pilot took his place some few inches farther
back. But in the next glide the craft behaved alarmingly. It reared
almost vertically in the air, and would have slipped backwards had not
the operator turned down the elevator to its limit, and moved his body
forward as well. The machine, when he did this, recovered its balance
and settled without injury.
Further tests were made and the curve of the planes reduced--a change
which could be effected by altering the trussing of the ribs. Then they
obtained striking success. One glide, for instance, measured a distance
of 366 feet; and this was bettered by one of 389 feet; while the
operator found that he had perfect control over his machine in a wind
of 14 miles an hour. A day or so later an attempt was made in a wind of
22 miles an hour, and was successful. Then, in subsequent tests, they
glided in a wind as strong as 27 miles an hour.
The success of these trials led them to think of fitting a motor to
their machine; and they calculated at first that a petrol engine of
about 6 h.p., weighing 100 lbs., would be sufficient to drive a craft
through the air; but they hoped to obtain one more powerful than this.
Here it should be pointed out that, owing to the experiments of
motor-car builders, and the spending of many thousands of pounds, there
was now available a petrol motor which might be adapted to aviation.
Such engines were heavily built--when considered, that is, from the
point of view of fitting to aeroplanes; and the brothers agreed that, as
they wanted such a motor for aerial use, and not for placing in a car,
they would probably need to build one, specially lightened, in their own
workshops.