NINETEENTH CENTURY MAN-FLYERS
Having traced the growth of winged models from their earliest beginning
to the time when they proved the possibility of mechanical flight, we
may now study the evolution of larger machines, designed to carry human
beings. Considering first the aëroplane, we may follow the two general
methods advocated by various inventors for launching a man safely in
the air, both of which led to success. The first of these may be called
Henson’s method, the second Lilienthal’s, coupling them with the names
of their distinguished pioneer exponents. Henson in 1842 proposed
that the pilot should mount a full-power machine, run along a smooth
course, and glide into the air without previous experience in the art
of navigating. Lilienthal recommended careful preliminary training on a
glider, by which the novice should acquire sufficient skill in parrying
the wind to qualify him to manage a dynamic machine, under its more
complex conditions of control. Others, more cautious still, contended
that automatic equilibrium should be secured before a rider risked his
bones on the aërial bronco; while still others thought the uncertain
beast should be tethered to some point in the sky, say a balloon or
taut wire, or the end of a pole; so that however he bucked, or reared,
he should not fall over on his rider.
We have noticed in the first chapter some picturesque man-flights,
usually deplorable or tragic; and always fruitless for lack of
scientific method in experimentation and report to the world. There can
be no doubt that such flights were accomplished, mainly, of course,
by the aid of gravity; but the difficulty is to ascertain the exact
nature of any given performance, the specifications of the apparatus,
and the principles of equilibrium and control. Gradually, however, the
experimenters improved both in the construction of man-carrying devices
and in the manner of imparting their results to their colleagues, or
successors; and so the flying enterprise began to assume a progressive
aspect, attended with that scientific dignity which invests secure
and continuous advance in any branch of knowledge. Little of value,
however, can be gleaned from any such flights made prior to the middle
of the nineteenth century. From that time forward observers and
inventors made definite and fairly methodical efforts to develop the
art of gliding and soaring in the air, the first fruit of which was to
hasten the advent of the modern aëroplane.
A French novelist and aëronautic writer, G. de la Landelle, relates
an amazing adventure in the art of soaring, which may have some
foundation in fact, though savoring strongly of fiction. An experienced
sailor, Captain Le Bris, having observed the albatross soaring without
wing-beat, determined to imitate the fascinating flight of that
limber-winged spirit of the sea. To such end he built the bird shown in
Fig. 38, a ninety-pound albatross, with arched wings fifty feet across
and articulated to the boat-like body. In this the brave aviator would
stand upright, turn the wings and tail to maintain his balance, and
steer grandly through the sky. Placing this long-winged creature across
a cart driven by a peasant, he stood erect and headed against a breeze;
the wings set low to prevent lifting till an opportune moment, and the
bird held down to the car by a rope which the captain could quickly
release. When the horse was a-trot, and the wind blowing freshly, Le
Bris raised the front edges of the wings. Thereupon the albatross
tugged upward, and the mooring rope was slipped, but accidentally
whipped around the driver’s waist. The horse galloped away with the
cart; the bird, with the exultant sailor on its back, soared 300 feet
into the air, and incidentally carried up the peasant, dangling at
the end of the rope and howling with fright. Noting the distress of
his passenger, the kindly captain sailed close to earth, so that the
peasant might disembark and run to his horse, meaning then to hie away
for a long cruise in the clouds. But with this change of weight the
vessel seemed not to navigate well; so she was brought skimming to
land, with no mishap save a slight damage to the advancing wing, which
broke as it touched the ground.
[Illustration: FIG. 38.—LE BRIS’ AËROPLANE, 1855.]
Having repaired the great bird’s wing, Captain Le Bris next made
a launching from the arm of a derrick, 30 feet above the ground,
overlooking a quarry 70 feet deep. The attendant swains stood
open-mouthed, wondering whether this madman would overleap the clouds,
or promptly butt out his brains on a jagged rock. When the wind blowing
from the quarry seemed to float him in perfect poise, he tripped the
suspension hook, and headed for the precipice on even keel. He was now
happily launched, and keen for an aërial journey; but after passing
the brink, he seemed to encounter an eddy which tilted his craft
forward. The vessel dipped and rose; the captain plied his levers,
turning now the tail, now the pinions. He crossed safely over the
invisible breakers, and reached the quiet air of the quarry on level
wing. But now his forward speed was lost, the great bird sank rapidly
and crashed upon the rocky bed below. The wary seaman anticipating a
bump, sprang upward to soften his fall; but a lever rebounding from the
shock, hit one of his legs and broke it.
Some twelve or thirteen years later, in 1867, Le Bris, aided by a
public subscription at Brest, built a second albatross, with which
he made a number of small flights, sometimes riding it himself, and
sometimes replacing his weight by ballast. On one occasion the loaded
bird, held by a light line, rose 150 feet and advanced against the
wind. Suddenly the sailors holding the line observed it slacken, and
saw with amazement the long-winged creature soar forward 600 feet, as
stately and serene as its living prototype. Presently encountering a
sheltered and quiet region of air before some rising ground, it settled
softly to earth in perfect equipoise. But on a subsequent launching
from the same favorable ground, the dumb creature pitched forward and
plunged to the earth where it lay shattered and torn in a hopeless
tangle. Le Bris looked on the wreck in despair, surveying sadly the
remains of his once cherished bird; then sat upon the débris a long
time, his head between his hands, his heart broken, his mind tortured
with anguish. Impoverished, chagrined, derided, he now must abandon
the albatross business. Five years later this intrepid sailor of sea
and air was killed by some ruffians, in 1872, while a constable in his
native place, and after a period of honorable service to the state in
the Franco-Prussian War.
The story is more romantic than instructive, for want of exact data.
To give the experiments their proper value to others, fuller details
of the mechanism should be furnished, and adequate measurements of the
speed and direction of the aërial currents. At one time the sailing
was even, at another, rough, though outwardly the conditions appeared
the same. Apparently the successful flights occurred when the bird was
launched to windward from rising ground, that is, when the current had
an upward slant, to exert a propulsive effort. This species of soaring
has been observed frequently in nature, and has been imitated both with
models and with man-carrying gliders. Nevertheless Le Bris’ experiments
were very remarkable for the time, and, if adequately reported, might
have proved to be of much interest and value to aëronautical science.
Another Frenchman alert to the glory of aërial motion was L. P.
Mouillard, the poet-farmer of Algeria. From boyhood he studied the
birds with unabated interest and pleasure. He would journey miles to
attend the “morning prayer” of the starlings in the forest of Baba-Ali;
noting, just before sunrise, how their melodies suddenly hushed, and
the forest seemed to bound upward, and heaven filled with the music of
innumerable wings. He would time the shadow of the high bird of passage
riding the hurricane from continent to continent. He saw the tyrant
eagle fold his wings in mid air and plunge a thousand feet in ferocious
swoop after the swift-fleeing duck or rabbit. He loved to watch the
great tawny vulture on the mountain top shake the dew from his vast
plumes, straddle the morning wind, and all day long, with never a beat
of those grand pinions, soar godlike through immensity, the marvel
and delight of the nether world. When the electric wind of the desert,
blowing from Central Africa, brought the big scavengers and noble birds
of prey, he sat on the ground scrutinizing their majestic flight and
planning to imitate it. He would lie in ambush where the silent-rowing
owl darted at dusk through the timber, fierce and swift as the eagle;
a dreadful thing, with its night piercing eyes, its big ears and beak,
its horrid talons, its sudden shriek startling the forest with ominous
echoes. No feature escaped him, and least of all an aërodynamic one.
For thirty years he continued these studies. He would bring home
the birds, lay them on their backs and mark their contour on paper,
measure their projected area, weigh and compare them. He formulated
curious conclusions about sailors and rowers, the functions of tail and
quill feathers, weight and wing-spread, bulk, agglomeration of mass,
resistance and velocity. He notes that only massive birds soar well,
the broad-winged ones requiring a moderate wind, the narrow-winged ones
requiring a gale, and sailing with perfect ease in a tempest; and he
concludes that man may imitate both types. His book[24] is replete with
charming anecdotes, observations and quaint theories, interesting alike
to ornithology and aviation.
But Mouillard did more than theorize; he built soaring machines and
soared a little. His third and best glider, illustrated in Fig. 39, was
a tailless monoplane made of curved agave sticks screwed to boards,
and covered with muslin. The aviator, standing in the open space C,
harnessed the plane on with straps looped round his legs and shoulders,
and fastened to the points D D. His forearms, passing under straps,
rested on the board, enabling him to tilt the whole by shifting his
weight. In order to vary the dihedral angle between the wings, they
were hinged together and actuated by rods running from the man’s feet
to the ends of the boards, hardly as far out as the center of wind
pressure, thus apparently stressing his legs like a wishbone.
[Illustration: FIG. 39.—MOUILLARD’S AËROPLANE.]
He now sent the home folks away from the farm, buckled on his wings and
walked along the prairie road waiting for a breeze. The road was raised
five feet above the plain and bordered by ditches ten feet wide. His
wings felt light; he ran forward to test their lift, and he thought to
amuse himself by jumping the ditch. The result is thus expressed in his
own words:[25]
“So I took a good run across the road and jumped at the ditch.
But, oh, horrors; once across the ditch my feet did not come
down to earth; I was gliding on the air, and making vain
efforts to land; for my aëroplane had set out on a cruise. I
dangled only one foot from the soil, but, do what I would, I
could not reach it, and I was skimming along without the power
to stop. At last my feet touched the earth; I fell forward
on my hands; broke one of my wings, and all was over; but
goodness, how frightened I had been! I was saying to myself
that if even a light wind-gust occurred, it would toss me up
30 to 40 feet into the air, and then surely upset me backward,
so that I would fall on my back. This I knew perfectly, for I
understood the defects of my machine. I was poor, and I had not
been able to provide myself with a more complete aëroplane.
All’s well that ends well. I then measured the distance between
my toe marks, and found it to be 138 feet.
“Here is the rationale of the thing. In making my jump I
acquired a speed of 11 to 14 miles per hour, and just as I
crossed the ditch I must have met a puff of rising wind. It
probably was traveling some 8 to 11 miles per hour, and the
two speeds added together produced enough pressure to carry my
weight.”
He repaired his wing and repeated the test a few days later. A violent
wind gust came; picked him up from the earth, and whelmed him over. In
his alarm he allowed his “wish-bone” to spread, and the wings to fold
up like those of a butterfly at rest, pinching him between them like
a nut in a nutcracker. One wonders whether the overwheeling vultures
witnessed this gentleman’s flight with any sense of humor.
After mature reflection, Mouillard concluded that he should give his
aëroplane a rudder, and flex the wings, in order to insure adequate
control. But here he halted, being a poor man unskilled in the art
of construction. He had reached the limit of his endowments. He had
observed faithfully and described charmingly the wonderful flights
of various birds; but he must leave to his technical successors the
pleasure of imitating or excelling those extraordinary maneuvers—leave
them the pleasure, the sacrifice, the long years of toil and danger,
accompanied perhaps by indiscriminate applause or derision.
In the meantime another distinguished disciple of the birds was
energetically at work in Germany. No less ardent than Le Bris, or
Mouillard, Otto Lilienthal was far better equipped and circumstanced.
He was a graduate of the Potsdam Technical School, and a student
for three years in the Berlin Technical Academy. He was engaged in
practical construction ten years in various machine shops at Berlin.
After 1880 he operated a flourishing machine factory of his own. From
boyhood he with his brother Gustavus had carefully studied the flight
of birds, and had made numerous experiments in aviation. On moonlight
nights in their little home place of Anclam, in Pomerania, the boys
would run downhill, flapping their home-made wings, like Dædalus and
Icarus, but with no other danger than discovery and teasing by their
neighbors. At Potsdam and Berlin they continued to experiment and to
construct wings of increasing size and power. Thus Otto Lilienthal
reached early manhood thoroughly trained by his long courses in the
technical schools and shops, brimming with well pondered ideas,
strengthened by continuous observation and experiment, and in financial
circumstances which permitted him to devote time and money to the
unremunerative pursuit of aviation. To this may be added that his
mature years were cast in a time when the allied sciences could aid
him far more than they had aided his predecessors of the preceding
generation.
After careful research for the most efficient form of alar surface,
Lilienthal resolved to imitate the birds. First he would build a pair
of arched wings, and learn to coast down the atmosphere, balancing
and steering like a stork in the gusty and treacherous current. He
would thus acquire the pilot’s skill, and ascertain the towline power
required to sustain a given weight. Then he would add a suitable
propelling mechanism, test it cautiously, and acquire the mastery of
dynamic flight. Incidentally, perhaps, he would learn to ride all over
creation without motive power; for he was convinced that certain great
birds soar without muscular effort, and that man could acquire this
delightful art in favorable weather. To strengthen the plausibility
of that doctrine, he announced his discovery that the general trend
of the wind is three and a half degrees upward, a fact inexplicable
and almost incredible to his illustrious confrère of the Smithsonian
Institution.[26] Such was Lilienthal’s ample program; more, indeed,
than he would live to accomplish, though possibly not beyond his power
of achievement, if he could have lived to enjoy the hale long years of
his illustrious countryman aëronaut, Count Von Zeppelin.
In the year 1891 Lilienthal made his first series of trials in sailing
flight. His glider was the bird-shaped apparatus shown in Plate XVI,
made of willow wood covered with waxed sheeting. It weighed about 40
pounds, and spread 107 square feet of surface. Taking this in his arms
he first ran 24 feet along a raised board and jumped off, gliding
through still air. Then, elevating the board to a height of six feet,
he repeated the run, jump and glide, always landing very softly. Thus
he became “king of the air in calm weather,” a title still creditably
sustained by his numerous successors of the present day; for as yet no
one “mounts the whirlwind and directs the storm.”
Next he went to some little mounds in a field beyond Werder, and jumped
from these, gradually lengthening his flights till he attained a range
of nearly 80 feet. As he was now gliding in light winds, he found it
necessary to add a vertical rudder, in order to preserve his balance
easily, and keep his bow toward the direction of the wind. His complete
apparatus was, therefore, a birdlike affair, with two rigid wings and
a double tail for steering vertically and horizontally. He found also
that he could fly longer and alight more softly when the wind was
blowing—an obvious possibility.
Encouraged by this experience Lilienthal explored the country about
Berlin for sailing ground where he could make long glides, whatever
the direction of the wind. Such a region he found near Rathenow, where
the Rhinow hills, covered with grass and heather, slope gently upward
from the flat plowland to a height of over 200 feet. This he thought
an ideal coasting ground; for he felt the aërial currents very smooth,
and he could always select clear land sloping ten to twenty degrees
toward the wind. Here in the summer of 1893, with a new and improved
glider, he made many flights, finally ranging from 200 to 300 yards,
steering up and down, or to right and left at will; sometimes pausing
in mid air, and several times returning to the starting point. This was
more than coasting; for a mere coaster never maintains, nor returns
to, his original level. It was a fair start at true soaring, the ideal
locomotion. A glorious sport it was, sailing like an eagle high over
the landscape and over the heads of the astonished spectators.
The new machine resembled its predecessors in form and maneuver; but
differed in dimensions. It was a birdlike craft with parabolically
arched wings and a double tail. It measured 7 meters across, spread
14 square meters of surface, weighed with the rider 200 pounds, and
in calm air could sail down a slope of 9°, at a speed of 9 meters
per second. This was very efficient sailing, the work of gravity
being hardly two horse power. With the man lying prone, as eventually
planned, the economy would be still greater.
PLATE XVI.
[Illustration: LILIENTHAL’S MONOPLANE GLIDER.
(Courtesy W. J. Hammer.)]
[Illustration: LILIENTHAL’S BIPLANE GLIDER.
(Courtesy W. J. Hammer.)]
[Illustration: PILCHER’S MONOPLANE GLIDER.]
The craft was thought also to possess stability; and this it had, in a
measure, about those two axes corresponding to the two rudders; but the
control about the third axis, effected by dangling the legs to right
or left, was extremely crude and primitive. It was in keeping with his
adage: “to contrive is nothing; to construct is something; to operate
is everything.” If he had contrived more intelligently, he would have
operated more easily, and avoided those wild and dangerous dancings in
space. A more scientific adage would read: “To design effectually is
everything, to construct is routine, to operate is play.”
The marvel is that Lilienthal, the observant, the technically trained,
the practically skilled, should operate for three years, then patent,
an aërial glider having two rudders, but lacking the third rudder,
or torsional wing, now so commonly used throughout the world. But
doubtless he contemplated a device for preserving the lateral balance
without shifting his weight; for he acknowledged the economic advantage
of lying prone on the machine, and stated that this might be done after
some important improvements in the apparatus had been made.
Having executed nearly two thousand flights with his monoplane,
Lilienthal in 1895 built a two-surface glider. He found this still
easier to control, and now thought he had sufficiently acquired the
art of sailing to justify his undertaking the next and more difficult
art of imitating the rowing flight of birds. He had constructed a
ninety-pound engine, of two and a half horse power, to actuate the
wings of his glider; but, before applying this motor, he went to the
Rhinow Hills for a little further experience in sailing. Previously
he had remained in the air twelve to fifteen seconds; but he wished to
exceed this record.
On the 9th of August, 1896, he made a long glide to prove the
effectiveness of the horizontal rudder, and then wished to undertake
a second flight of the greatest duration feasible. No intimation had
he that this sail would prove disastrous. Giving the timepiece to his
assistant, he set forth on a level course, but suddenly dipped forward
and plunged headlong to earth through a height of fifty feet. He was
dragged out from the débris with a broken spine, from which he died the
following day.
The machine on which the father of aërial gliding made his last flight
is shown in Plate XVI. Of the hazardous nature of its construction Mr.
Chanute thus writes: “The two surfaces were kept apart by two struts,
or vertical posts, with a few guy wires, but the connecting joints were
weak, and there was nothing like trussing. This eventually cost his
most useful life. Two weeks before that distressing loss to science,
Herr Wilhelm Kress, the distinguished and veteran aviator of Vienna,
witnessed a number of glides by Lilienthal with his double-decked
apparatus. He noticed that it was much wracked and wabbly, and wrote to
me after the accident: ‘The connection of the wings and the steering
arrangement were very bad and unreliable. I warned Herr Lilienthal very
seriously. He promised me that he would soon put it in order, but I
fear that he did not attend to it immediately.’”
It will be observed that Lilienthal gave fair attention to the merits
of both the monoplane and the biplane, the two familiar types in
lively competition at the present hour. The first he found in Nature;
the second he could have found in England, as the developments
principally of Wenham and of Phillips. His example and prestige did
much to promote the biplane; but he seems to have had no very decided
preference for either. Though he found his biplane very satisfactory,
he thought of returning to the monoplane.
In April, 1896, he wrote:[27] “I am now engaged in constructing an
apparatus in which the position of the wings can be changed during
flight in such a way that the balancing is not effected by changing
the position of the center of gravity of the body. In my opinion this
means considerable progress, as it will increase the safety. This will
probably cause me to give up again the double sailing surfaces, as it
will do away with the necessity which led me to adopt them.” He thus
seems to have studied the two types impartially, and to have invented a
means for balancing the machine without shifting the center of mass.
Lilienthal had given a powerful and permanent impulse to aviation,
both by his writings and by his practical experience in the air. He
first showed quantitatively the advantage of arched wings, by carefully
derived tables of wind pressure; then he mounted the wings himself
and taught the world, by bold and frequent flight, the art of aërial
gravity sailing. The two remaining achievements, dynamic and soaring
flight, he was to undertake as promptly as possible. If his life had
been spared, no doubt he would have contributed much to the advancement
of these arts, both by example and by direct effort; for he was in the
prime of life, full of energy and daring, highly equipped, and ardently
devoted to his favorite science. He began his studies in aviation at
the age of thirteen and died at the age of forty-eight years.
Among the admirable traits of the father of sailing flight must be
mentioned his scientific liberality and _esprit de corps_. Though he
patented his invention he did not conceal, or withhold, his discoveries
when he could publish them properly. These discoveries were made at
a great sacrifice of time and means, and must have appeared to him
valuable trade secrets; yet he published all his scientific data, his
theories, and observations; he encouraged his confrères in various
countries to witness and emulate his experiments, to share intimately
his laboriously developed knowledge of aviation, to join hands with
him in hastening the advent of practical flight. Such is the _esprit
de corps_ which has ever prevailed among truly scientific men, as
distinguished from the mercenary and commercial; such are the unselfish
investigators whom the world delights to honor, both for their genius
and for their liberal contributions to the common and permanent
possessions of humanity.
Before his death Lilienthal had the pleasure of knowing that competent
disciples were emulating him in doctrine and practice. One of the
earliest and cleverest of these was Percy S. Pilcher, Assistant
Lecturer in Naval Architecture and Marine Engineering at the University
of Glasgow. In the summer of 1895 he built the glider shown in Plate
XVI. This, like Lilienthal’s, was a double-tailed monoplane arched fore
and aft; but, better than his for manual control, it was straight from
tip to tip, like the designs of Henson, Penaud, and other predecessors.
This improvement was introduced to prevent side gusts from rocking the
craft so readily as they do the V-shaped gliders. His best sailer, the
_Hawk_, shown in the figure, had wings curved one in twenty, about one
third from their front edge.[28] Sometimes he sailed downhill; again
he was towed or launched, like a kite, by means of a cord, running
through five-fold multiplying gear, and drawn by running boys, or a
horse. In both cases he controlled the machine to his own satisfaction,
making in 1897 smooth downhill glides of 700 feet length, from an
elevation of 70 feet.[29] He had also visited Lilienthal, but only
after achieving success at home.
Having acquired some skill in sailing, Mr. Pilcher began work on a
power machine. This was to be propelled by a screw actuated by an
oil engine, and was to be mounted on wheels backed by stiff springs.
Having observed his speed of descent in gliding, he computed that
two tow-line horse power would float him and his machine, weighing
together 220 pounds. A like result was obtained when he was flown as
a kite. He was, therefore, on the straight road to achieving human
flight on a screw-propelled, wheel-mounted monoplane. If he had been
more cautious he might have been the first person to achieve human
flight in a practicable type of dynamic machine; for he seems to have
equaled, if not excelled, his German master in aëroplane design. But
like the master he provided inadequately for the structural strength
of his glider, and braved too far the dangers of gusty weather. One
stormy day, September 30, 1899, wishing to please several persons who
had come a long distance to see him, he made two trial flights in a
gentleman’s park near Rugby. The second of these proved fatal. The
spectators heard a cracking noise, saw the tail break, and the whole
craft plunge headlong to the ground. Poor Pilcher was mortally hurt and
died thirty-four hours later, without ever regaining consciousness. He
was then in his thirty-third year.
Had this talented young Briton and his German tutor both lived, there
would doubtless have been a pleasant race and rivalry between them;
for the pupil was forming opinions and plans sufficiently divergent
from those of his master and friend. He did not approve Lilienthal’s
high wings and low center of gravity, nor his V-shape for lateral
equilibrium, nor his flapping wing tips for propulsion, nor his method
of launching the dynamic machine. Fortunately both published their
ideas and experiments, leaving to their successors the task of judging
the merits of their designs, and of adding any improvements that might
still be required in order to achieve final success.
Contemporary with Pilcher, Mr. Octave Chanute and Mr. A. M. Herring,
in America, were emulating the work of Lilienthal. Mr. Chanute was an
experienced civil engineer, who had previously written a history of
aviation, and experimented with numerous flying models; Mr. Herring,
his employee for the time, was a mechanical engineer who had assisted
in Langley’s experiments, and previously had flown a Lilienthal glider,
and had made researches in the science of mechanical flight. On June
22, 1896, accompanied by two assistants, they went into camp among the
sand dunes, on the southern shore of Lake Michigan, to study the art of
navigating an aëroplane without artificial motive power. Mr. Chanute
thought that the maintenance of equilibrium under all circumstances
was at that time the most important problem of aviation; and that
until automatic stability was secured, it would be premature and
dangerous to apply a motor. He wished to evade, for he did not relish,
Lilienthal’s way of balancing by shifting the body and kicking wildly
at the stars. His main purpose, therefore, was to acquire the pilot’s
science; but secondarily he would learn much about the architecture
of gliders, the behavior of air currents, the elements of propulsion
and sustentation.
PLATE XVII.
[Illustration: CHANUTE’S FIVE DECK GLIDER.]
[Illustration: HERRING IN CHANUTE BIPLANE.]
[Illustration: HERRING’S COMPRESSED-AIR BIPLANE.
(Courtesy Carl Dientsbach.)]
They made some flights with a Lilienthal monoplane; but, finding this
unsafe and treacherous, they discarded it in favor of a multiple-wing
glider designed by Chanute, which after many empirical modifications
in the placement of the sustaining surfaces, assumed the form shown in
Plate XVII. This glider resembled the Lilienthal biplane in having the
surfaces vertically superposed, the rider below them, and the rudder in
the rear; but it was a five-decker whose wings, on either side, could
swerve fore and aft, so as to bring the center of lift always over the
center of gravity, in order to prevent excessive rearing or plunging.
This glider was found very tractable in a twenty-mile wind, and in a
thirteen-mile breeze would sail down a slope of one in four.
After further study, the five-decker was replaced by a three-decker;
which presently was deprived of its obtrusive and unessential lower
surface, thus assuming the familiar form shown in Plate XVII. As will
be observed, this was a radically new and elegant design, consisting
of two superposed arched surfaces held together by vertical posts and
diagonal wires, like a Pratt truss. It was, in fact, the renowned
“Chanute glider” which has been copied by so many succeeding designers
of biplanes.
The Chanute glider weighed 23 pounds, spread 135 square feet, and
readily carried a total weight of 178 pounds at 23 miles an hour. It
was provided, as shown, with side planes and a double rudder, and
this latter was elastically connected to the main body to insure
steadiness of flight, on the principle of the elastic wing margins used
by D. S. Brown in 1874. This craft was found easy to manipulate in
launching, sailing and landing, a two-inch shift of the pilot’s weight
equivalencing a five-inch shift on the Lilienthal monoplane. It was
steady at a speed of twenty to forty miles an hour through the air,
even when the wind was blowing seventeen miles an hour overground. The
angle of descent was 7.5° to 11°, depending on the speed and trend of
the wind. The work of gravity expended in maintaining steady flight was
at the rate of two horse power for the 178 pounds, a good showing with
the rider vertical.
Summer passed before Mr. Chanute could perfect the invention for
automatic stability by means of swerving wings; but otherwise the
gliding experiments were very satisfactory. The strong and simple
biplane evolved during those few weeks of fruitful study, though not
an original creation, having been foreshadowed theoretically and
experimentally, in the work of Wenham,[30] Stringfellow, Lilienthal,
Phillips, and Hargrave, was nevertheless an important contribution to
the science of aviation, by reason of its strength and simplicity of
design, its efficiency, its stability, and, best of all for that day,
its record for good flights and safety. All who could appreciate it
understood that the addition of a light motor would transform it to
a dynamic flyer, navigable at least in mild weather. The most eager,
perhaps, was Mr. Herring; for he had not only mastered this glider,
but some years previously had flown successfully rubber-driven models
very much resembling it in design. These two aviators, therefore, came
to a parting of the ways, Chanute still pursuing automatic stability,
Herring impatiently heading for dynamic flight by the shortest route
available. Had they continued together on a practical course, they
might, ere the close of the century, have anticipated at least the
early flights of the French aviators, if they could have constructed or
purchased an adequate motor.
After some further development of the aërial glider to adapt it
to power flight, Mr. Herring began the construction of a dynamic
aëroplane. He had previously built very light steam and gasoline
engines,[31] and deemed the latter best for a perfected flyer, though
preferring steam or compressed air in a first experimental test.
When seen by the present writer in October, 1898, at St. Joseph,
Mich., Mr. Herring was about to launch himself in the compressed-air
driven biplane shown in Plate XVII. It was essentially a powered
Chanute-Herring glider, steadied by a double tail, and controlled by
shift of the pilot’s weight, the tail being elastically attached.
The writer then suggested that both a glider and a dynamic aëroplane
should be controlled entirely by steering and balancing surfaces, on
the principle set forth in his paper of 1893; and, in particular,
indicated that the lateral balance should be controlled by changing the
inclination of the wings on either side, while the double tail should
be used to steer and steady the aëroplane sidewise and vertically; in
other words, that a torque about each of the three rectangular axes of
the machine should be secured from impactual pressure, thus obviating
the need for shifting the pilot’s weight. Mr. Herring, while making no
objection to this proposal, intimated that he had a device for insuring
control without shifting the pilot’s weight, but believed the most
important effort for the moment should be to make a short flight with
the machine as it stood, for the purpose of enlisting capital, then
to add the controlling devices at leisure. He expected to remove the
wheels shown in the figure, hold the aëroplane against a stiff breeze
from Lake Michigan, start the propellers, strike a soaring attitude,
and fly forward for a few seconds against the wind.
The successful accomplishment of such a flight covering an overland
distance of seventy-three feet in eight or ten seconds, against a wind
of thirty miles an hour, was reported in the Chicago _Evening News_,
of November 17th of that year; but the present writer has not been
able to ascertain the reporter’s name, or that of any other witness to
the event, which, if true, is well worthy of verification and detailed
record.
In following the votaries of passive flight, as represented by
Lilienthal and his school, we have overlooked the great man-carrying
bird of Clément Ader, one of the most prominent and successful aviators
of that active period. If the reports be true, Ader may justly claim to
be the first person to navigate the air in a dynamic flying machine.
However, it must be observed that his achievements did not at first
arouse in France a great pitch of exultation and enthusiasm. There
seemed at the time to be some skepticism as to the practicability of
his device. But later cordial reparation was made by placing it on the
Stand of Honor at the Aëronautical Salon, held in the Grand Palais, at
Paris, in December, 1908.
Clément Ader set out in life with the fixed determination to make
a fortune, then to build a practical flying machine. Adopting the
profession of electrical engineer, he quickly accumulated enough
capital, as he thought, to realize his early ambition. He next visited
Africa to study at close range the great soaring birds that Mouillard
had described with so much admiration and vivacity. Going to Algeria
he disguised himself as an Arab, and, with two Arab guides, journeyed
to the interior where he watched the great soaring vultures, which
he enticed with bits of meat to perform before him their marvelous
maneuvers, wheeling in wide circles, and without wing beat, from earth
to sky.
After several years of study of the anatomy and flight of birds, Ader
began, at the age of forty-two years, to construct an aëroplane. His
first machine was a birdlike monoplane mounted on skids, or wheels,
and driven by a 40-horse-power steam engine actuating a screw, placed
forward. The total weight was 1,100 pounds, the spread 46 feet, the
length 21 feet. The _Eole_, as he called it, received its first
open-air test on the morning of October 9, 1890, in the grounds
surrounding the Chateau d’Armainvilliers, near Gretz, a portion of the
course being so prepared that the trace of the wheels would be visible.
When everything was ready for the trial, Ader mounted the machine, in
presence of a few friends, ran quickly over the ground, urged by the
propeller thrust, then rose into the air and sailed 150 feet. Such is
the report of the witnesses to what is claimed as the first flight of a
human being in a power-driven flying machine.
Subsequently this bold inventor built _Eole No. 2_, which, by special
permission of the War Department, he tested on a prepared track, 2,400
feet long, on the Satory Camp. Over this course he ran his machine
several times, and on one occasion flew 300 feet; but on alighting
broke one of the wings.
Ader, now having spent one and a half million francs on his
experiments, placed the _Eole_ on exhibition in order to raise money
for their continuation. In this venture also he was successful,
being presently subventioned by the French War Department to build an
aëroplane for its use. His subsequent labors are concisely set forth in
_Automobilia and Flight_ for February, 1909, as follows:
“Under these new conditions the workshop in the Rue Pajou was
abandoned for larger premises in the Rue Jasmin, where the
construction of the _Avion_ was commenced in May, 1892, all
persons engaged with the construction being under a military
vow of secrecy. The motor was built first, and tested before a
commission composed of army officers and some of the leading
technicians of France. It was found to develop 30 horse power
for a total weight of 32 kilogrammes; and even now, though
seventeen years old, is regarded as a _chef d’œuvre_. In the
spring of 1897 the _Avion_ was ready to make flights. Like its
predecessors it was modeled on the form of a bat; but, although
the wings could not be flapped, they could be folded, and
could be advanced or retarded horizontally.
“Everything appearing satisfactory, Ader informed the military
commission that he was ready to undergo tests; the committee
met at the workshops in the Rue Jasmin on August 18, 1897;
were pleased with the machine, and ordered flights to be made
immediately at Satory. It was not, however, until October 12th
that a flight was attempted on the carefully guarded military
ground, and in the presence of General Mesnier. The apparatus
covered a distance of 1,600 yards, and although it did not fly,
for this distance it is certain that on several occasions it
completely left the ground. Ader declared that according to
whether the wings were carried forward or to the rear, it was
the front or the rear wheels only which left the ground. The
pressure in the generator at this moment varied between 3 and 4
atmospheres. On increasing it to 6 or 7 atmospheres none of the
wheels touched.
“Satisfied with the results of the test, General Mesnier called
the commission together for further trials on the following
day, October 14, 1897. Unfortunately it was a rough, squally
morning, that would have prevented many a modern aviator from
bringing a machine into the open. But as the officers had been
brought together specially for this purpose, a flight was
attempted.
“‘After several revolutions of the propellers, and a few yards
covered at a moderate speed, we were off at a high rate of
travel,’ wrote Ader, who was at the wheel on this memorable
occasion. ‘The pressure was about 7 atmospheres. Almost
immediately the vibrations of the rear wheel ceased, and,
directly after, those of the front wheels were no longer felt,
showing that we had entirely left the ground. Unfortunately
the wind had increased in strength, and I had some difficulty
in keeping to the line that had been marked out. I increased
the pressure to 9 atmospheres, and immediately the speed
increased considerably, the vibrations ceased again, showing
that we had once more left the ground. Under the influence of
the wind the aëroplane had a constant tendency to drift to
the right, away from the circular track that had been marked
for it. Finally, with the wind broadside on, the machine was
in a rather dangerous position, for it was being still more
rapidly driven out of its course. I increased the pressure
still more and put the rudder hard over to the left, with the
result that for a few seconds the machine worked back towards
the track and still maintained itself in the air. But it was
impossible to struggle against the wind, and finding that the
machine was being carried towards some artillery sheds, and
somewhat unnerved by the speed at which the ground appeared to
be rushing past, I stopped the engine; there was a shock, and I
was on the ground.’
“Ader was uninjured, but his machine was rather badly smashed.
It had certainly flown, but with such difficulty in the face of
the wind that the army commission was evidently little inclined
to report favorably upon it. Several weeks passed without any
communication being received from the War Department; then it
became apparent to Ader that the Government had no longer faith
in his invention. This was proved early in the following year
by an official communication to the effect that no further
funds could be allotted to this work. Discouraged at the
abandonment after forty years’ labor and the expenditure of
about two million francs, Ader commenced the destruction of his
machines. The earlier ones were destroyed, but the _Avion_, the
one which had appeared before the army commission, was saved
and sent to the Museum of the Arts et Métiers in Paris.”
The last aëroplane, or _Avion_, weighed 1,100 pounds, spread 270 square
feet, and was driven by a 40-horse-power steam engine actuating twin
screws projecting before the bird-shaped flyer. The engine weighed but
7 pounds per horse power—quite a remarkable achievement for that day.
In following the votaries of passive flight, as represented by
Lilienthal and his school, we have overlooked the great dynamic
aëroplane of Mr. Maxim, one of the most prominent aëroplane builders of
that active period. Having in 1889 made elaborate experiments on the
atmospheric resistance of sustaining surfaces, and on the thrust of
screw propellers, he proceeded to build the gigantic aëroplane shown
in Plate XVIII, the greatest flyer thus far known to history. It was a
twin-screw multiplane mounted on a platform forty feet long by eight
feet wide, and having four wheels running along a track eight feet
wide and half a mile long. Above the rails of this track were guard
rails to prevent the flyer from rising more than three inches during
the tests. The whole machine weighed 3.5 tons, spread 5,500 square
feet of surface, and, at a speed of 40 miles an hour, lifted more than
a ton, in addition to the weight of the three men and 600 pounds of
water. Its propelling plant comprised a naphtha tubular boiler, and a
compound steam engine of 350 horse power actuating twin screws 17 feet
10 inches in diameter which gave a thrust approximating 2,000 pounds.
These screws were made of American yellow pine, covered with canvas and
painted, then smoothly sandpapered to reduce the friction; for Maxim,
like certain French aviators, erroneously imagined that a polished
surface has less air friction than a dead even surface. The framework
was composed of seamless steel tubing stayed with steel wire. The
aëroplane was to be steered right and left by a rudder, and up and down
by horizontal planes, one fore, another aft, and its lateral stability
was to be secured by side planes set at a dihedral angle. A meritorious
feature for that day were the superposed arched surfaces whose framing
was smoothly covered below and above by skillfully stretched fabric,
causing the air to flow evenly without wasteful eddies.
PLATE XVIII.
[Illustration: MAXIM’S AËROPLANE.
(Courtesy W. J. Hammer.)]
[Illustration: LANGLEY’S LARGE AËROPLANE.
(Courtesy Smithsonian Institution.)]
Many runs along the track were made to test the working of this
great apparatus before trusting it to launch forth in free flight.
Dynamometers gave independently the thrust of the screws, and the lift
of the wings on the front and rear axles. The ascensional planes for
controlling the fore and aft equilibrium were tested during the run,
as also the practical operation of the propelling plant. During the
trials of 1893 the machine frequently lifted clear of the lower track,
and flew forward resting against the guard rails above the wheels.
Finally, on a gusty day, the lift against the upper track caused this
to give way, whereupon the machine rose into the air with Mr. Maxim
and his assistant, then toppled over on the soft earth, suffering
some damage to its framework. Here the experiments were discontinued
for lack of funds, having indeed demonstrated that a large weight
can be carried in dynamic flight, but having proved little as to the
feasibility of controlling an aëroplane in launching, in free flight,
and in landing.
Compared with the work of his contemporaries this achievement of Mr.
Maxim was herculean, both in construction and expenditure, the cost
being reported as nearly one hundred thousand dollars. It raised high
hopes for aviation. It proved conclusively not only that a flying
machine could be made to lift a pilot, but that it could carry hundreds
of pounds additional weight. It still holds the world’s record for
magnitude of machine and cargo. But it had two great defects; it was
improperly balanced and it was inadequately powered; for, as Mr. Maxim
says, “the quantity of water consumed was so large that the machine
could not have remained in the air but a few minutes, even if I had had
room to maneuver and learned the knack of balancing in the air.”[32]
These defects, however, would soon be remedied by the work of others,
and particularly by the costly experiments of the automobilists, who
were rapidly developing a light gasoline motor suitable for aviation.
The inventors thus far noticed had developed most of the important
features of the present-day flying machines, but had not provided
adequate mechanism for preserving a steady lateral balance. The present
writer had proposed the combination of a double rudder and torsional
wings to steer and control a flyer, and had published a paper setting
forth its general principle and describing a specific device; but
inventors had little need for a third rudder till they encountered
the dangers of dynamic flight in gusty weather. The paper referred
to was presented to the Third International Conference on Aërial
Navigation, in August, 1893, under the title, _Stability of Aëroplanes
and Flying Machines_, and was published with the proceedings of the
conference.[33] It discusses mainly the question of automatic stability
and steadiness; but recommends personal control during the experimental
period. It concludes as follows:
“We have been considering the question of automatic stability,
in so far as it may be secured in the construction of the
craft itself,[34] apart from a pilot, or special equilibrating
devices. The application of the latter would give exercise
to an infinite amount of ingenuity, and would, perhaps, best
be left to the fancy of the individual inventor. One curious
design, however, occurs to me, which, since I have not seen it
described elsewhere, may be worth a moment’s notice.
“Suppose a Phillips’s machine (see Plate XIV) to be provided
with a double tail, and to have a vertical fin extending
longitudinally along its entire length, well above the
center of gravity. These would steady its flight and promote
stability. _Suppose also that its sustaining slats were
pivoted, so that a pilot could at pleasure change their
inclination on the right and left side independently. He could
then set the engine for a desired speed, sweep forward along
the earth with the sustainer slats horizontal, and at will
mount into the air, by giving the slats an upward inclination.
Once in the air he could raise or lower the machine by slightly
changing the angle of the slats; he could wheel to right or
left by giving one set of slats a little different slope from
the other; he could arrest all pitching, rocking and wheeling
by a slight counter movement of the sustainers._ It would be
necessary, of course, to preserve a rapid forward motion, for
it is a peculiarity of the compound aëroplane that, if it comes
to a standstill in the air, it will drop plumb down with a
frightful plunge until it acquires headway.”
The succeeding paragraph disclosed a specific contrivance embodying
the principle just given. This showed two levers rotating drum shafts
for actuating wires adapted to change the impact angles of the wing
surfaces. Accordingly this much of the mechanism of control, together
with the broad device of the torsion wings, has been the common
property of inventors since the publication of that paper. Furthermore,
the combination of torsional wings and a double rudder, either fixed or
movable, has been public property since that date.[35]
Little was said about the manner of manipulating the double rudder and
torsional wings; for the rules of manipulation would vary in different
machines, depending upon structural design and external conditions.
For example, if the proposed fin and vertical rudder were ample and
suitably placed, the lateral balance could be controlled by merely
twisting the wings, without touching the vertical rudder; but if the
fin and rudder were not adequate, the lateral poise would be controlled
by twisting the wings and working the vertical rudder conjunctively.
A novice might prefer leaving the rudders fixed and controlling the
poise in short flights by twisting the wings by means of a single lever
having two independent movements, one to rotate the wings oppositely,
the other to rotate them identically.
The principle of control expressed in italics had been set forth also
in a preceding paragraph. Having proposed means for securing both
stability and steadiness about each of the three axes of an aëroplane,
the text continued:
“These ends could probably be attained very well by mounting
two compound aëroplanes on a long backbone,[36] somewhat after
the manner of the Hargrave cellular kites, and adding a
compound rudder to the whole.” ... “_If the inclination of the
sustainers, front and back, could be altered independently,
it might be feasible for a pilot to preserve the equilibrium
of the machine even when its center of gravity was frequently
shifted, as by the moving of passengers to and fro._”[37]
At that date, 1893, an inventor doubtless could have secured a broad
claim on a mechanism embodying the torsion-wing-and-double-rudder
mechanism of control. But in those days aviation was pursued largely
as a liberal study by scientific men who wished to hasten the advent
of practical flight, by presenting important physical measurements
and principles which could be freely employed by all. Accordingly the
three-rudder system of control seems not to have been claimed by an
inventor much before the close of the nineteenth century. Since then it
has been patented in one form or other by many practical aviators, some
endeavoring to claim the whole broad contrivance, others claiming more
restricted devices.
The static principle of the torsion wing is a familiar one in
elementary mechanics. It is this: a torque of given magnitude and
direction has the same effect on a rigid body whatever its point of
application. The longitudinal torque, or moment, may therefore be
exerted by the wings, by suitable rudders, by forward planes, by any
auxiliary planes, or fins, however placed or moved for the purpose.
Accordingly there seems to be an unlimited variety of concrete
patentable devices available to the inventor for securing impactual
torque about the longitudinal axis, or either of the other two axes.
But in planning such devices it is well to remember that the moment of
a couple increases with its arm, so that in a wide aëroplane the wing
tips may best furnish the torque; while in a high short-winged machine,
vertical planes, fins, or rudders may give the desired longitudinal
moment. Obviously such vertical guiding or controlling surfaces may be
so placed as to tilt the machine toward the center of curvature of its
path, at the same time opposing the centrifugal force, and exerting a
torque about the vertical axis tending to steer the flyer along its
path.[38]
The principle of projectile stability is another consideration of
some importance in aviation, or more generally in all submerged
navigation, whether of air or water. A submerged body has projectile
stability if its nose tends always to forerun its centroid, and follow
a steady course. A dart is a good example; a fish, a torpedo. Thus if
a torpedo-shaped homogeneous solid be hurled in any manner through a
fluid, obliquely or even tail foremost, it promptly turns its nose to
the front and proceeds steadily along an even course; but if the body
has not true dynamical balance, it may oscillate or gyrate, or flit
about in the most erratic manner.
Projectile stability in a flyer, as in an arrow, may be attained by
playing the centroid in or near the line of forward resistance, and
well ahead of the side resistance. The reasons for this are manifest.
If, however, this arrangement be neglected, a special damping, or
controlling, device is required to preserve headlong and steady motion.
In particular, the objections to placing the centroid too low were
emphasized in the above quoted paper as follows:
“I have mentioned the advantage of placing the center of mass
below the center of surface; this has also its objections.
While the stability against inversion is increased, the
stability against rocking is sacrificed. The aëroplane so
constructed may not easily overturn; but it will sway to
and fro with a pendular motion. This, when lateral, is very
objectionable, when fore and aft it is fatal to uniform
progress, as we shall see in studying the longitudinal
stability of flying machines. We shall then see that the center
of mass cannot be lowered with impunity.”
Of the various flyers and models thus far studied, some manifest fairly
good, others very imperfect projectile stability. Many inventors have
been more alert to the gravitational stability and safety of the
parachute than to the kinetic stability and keen, direct flight of the
arrow. Some of the most pretentious machines imitated the thistle down
more nearly than the dart or swallow. But the exigencies of actual
flight would easily rectify such imperfections of design.
Tractional balance also is a property of some importance in fluid
navigation. This requires that the line of propulsive thrust coincide
with the line of fluid resistance. It is a property, however, that
inventors readily apprehend, and usually provide for.
In general a flyer is subject to four forces: weight, thrust, air
pressure and inertia. When these balance about any axis the craft has
equilibrium about that axis; when they balance about the three axes
the craft is completely balanced, and preserves its orientation in
flight. Devices for preserving this complete balance have already been
described; as also provision for propulsion and sustentation, launching
and landing safely.
Thus at the close of the nineteenth century all the essential
principles and contrivances of pioneer flight were worked out, except
one—a suitable motor. This was the real problem of the ages. The rest
was easy by comparison. A light enduring motor, if available to the
old time inventors, would have brought dynamic flight centuries ago.
That only could have baffled Da Vinci, Cayley, Henson, Wenham and the
long line of pioneer aviators. Eventually, of course, steam engines had
come, endowed with ample power; but costly to build and wasteful to
operate. The light automobile engine appeared in the latter nineties;
promptly thereafter followed the dynamic flyer, the snow-winged herald
of the twentieth century.