between Stringfellow’s final achievement and the work of such men as
Lilienthal, Pilcher, Montgomery, and their kind; in spite of this, the
later middle decades of the nineteenth century witnessed a considerable
amount of spade work both in England and in France, the two countries
which led in the way in aeronautical development until Lilienthal gave
honour to Germany, and Langley and Montgomery paved the way for the
Wright Brothers in America.
Two abortive attempts characterised the sixties of last century in
France. As regards the first of these, it was carried out by three
men, Nadar, Ponton d’Amecourt, and De la Landelle, who conceived the
idea of a full-sized helicopter machine. D’Amecourt exhibited a steam
model, constructed in 1865, at the Aeronautical Society’s Exhibition in
1868. The engine was aluminium with cylinders of bronze, driving two
screws placed one above the other and rotating in opposite directions,
but the power was not sufficient to lift the model. De la Landelle’s
principal achievement consisted in the publication in 1863 of a book
entitled _Aviation_, which has a certain historical value; he got out
several designs for large machines on the helicopter principle, but did
little more until the three combined in the attempt to raise funds
for the construction of their full-sized machine. Since the funds were
not forthcoming, Nadar took to ballooning as the means of raising
money; apparently he found this substitute for real flight sufficiently
interesting to divert him from the study of the helicopter principle,
for the experiment went no further.
The other experimenter of this period, one Count d’Esterno, took out a
patent in 1864 for a soaring machine which allowed for alteration of
the angle of incidence of the wings in the manner that was subsequently
carried out by the Wright Brothers. It was not until 1883 that any
attempt was made to put this patent to practical use, and, as the
inventor died while it was under construction, it was never completed.
D’Esterno was also responsible for the production of a work entitled
_Du Vol des Oiseaux_, which is a very remarkable study of the flight of
birds.
Mention has already been made of the founding of the Aeronautical
Society of Great Britain, which, since 1918, has been the Royal
Aeronautical Society. 1866 witnessed the first meeting of the Society
under the Presidency of the Duke of Argyll, when in June, at the
Society of Arts, Francis Herbert Wenham read his now classic paper
_Aerial Locomotion_. Certain quotations from this will show how clearly
Wenham had thought out the problems connected with flight.
‘The first subject for consideration is the proportion of surface
to weight, and their combined effect in descending perpendicularly
through the atmosphere. The datum is here based upon the consideration
of safety, for it may sometimes be needful for a living being to drop
passively, without muscular effort. One square foot of sustaining
surface for every pound of the total weight will be sufficient for
security.
‘According to Smeaton’s table of atmospheric resistances, to produce
a force of one pound on a square foot, the wind must move against the
plane (or which is the same thing, the plane against the wind), at the
rate of twenty-two feet per second, or 1,320 feet per minute, equal to
fifteen miles per hour. The resistance of the air will now balance the
weight on the descending surface, and, consequently, it cannot exceed
that speed. Now, twenty-two feet per second is the velocity acquired at
the end of a fall of eight feet--a height from which a well-knit man or
animal may leap down without much risk of injury. Therefore, if a man
with parachute weigh together 143 lbs., spreading the same number of
square feet of surface contained in a circle fourteen and a half feet
in diameter, he will descend at perhaps an unpleasant velocity, but
with safety to life and limb.
‘It is a remarkable fact how this proportion of wing-surface to
weight extends throughout a great variety of the flying portion of
the animal kingdom, even down to hornets, bees, and other insects.
In some instances, however, as in the gallinaceous tribe, including
pheasants, this area is somewhat exceeded, but they are known to be
very poor fliers. Residing as they do chiefly on the ground, their
wings are only required for short distances, or for raising them or
easing their descent from their roosting-places in forest trees, the
shortness of their wings preventing them from taking extended flights.
The wing-surface of the common swallow is rather more than in the ratio
of two square feet per pound, but having also great length of pinion,
it is both swift and enduring in its flight. When on a rapid course
this bird is in the habit of furling its wings into a narrow compass.
The greater extent of surface is probably needful for the continual
variations of speed and instant stoppages for obtaining its insect food.
‘On the other hand, there are some birds, particularly of the duck
tribe, whose wing-surface but little exceeds half a square foot,
or seventy-two inches per pound, yet they may be classed among the
strongest and swiftest of fliers. A weight of one pound, suspended
from an area of this extent, would acquire a velocity due to a fall of
sixteen feet--a height sufficient for the destruction or injury of most
animals. But when the plane is urged forward horizontally, in a manner
analogous to the wings of a bird during flight, the sustaining power is
greatly influenced by the form and arrangement of the surface.
‘In the case of perpendicular descent, as a parachute, the sustaining
effect will be much the same, whatever the figure of the outline of the
superficies may be, and a circle perhaps affords the best resistance of
any. Take, for example, a circle of twenty square feet (as possessed
by the pelican) loaded with as many pounds. This, as just stated, will
limit the rate of perpendicular descent to 1,320 feet per minute.
But instead of a circle sixty-one inches in diameter, if the area is
bounded by a parallelogram ten feet long by two feet broad, and whilst
at perfect freedom to descend perpendicularly, let a force be applied
exactly in a horizontal direction, so as to carry it edgeways, with the
long side foremost, at a forward speed of thirty miles per hour--just
double that of its passive descent: the rate of fall under these
conditions will be decreased most remarkably, probably to less than
one-fifteenth part, or eighty-eight feet per minute, or one mile per
hour.’
And again: ‘It has before been shown how utterly inadequate the mere
perpendicular impulse of a plane is found to be in supporting a weight,
when there is no horizontal motion at the time. There is no material
weight of air to be acted upon, and it yields to the slightest force,
however great the velocity of impulse may be. On the other hand,
suppose that a large bird, in full flight, can make forty miles per
hour, or 3,520 feet per minute, and performs one stroke per second.
Now, during every fractional portion of that stroke, the wing is
acting upon and obtaining an impulse from a fresh and undisturbed body
of air; and if the vibration of the wing is limited to an arc of two
feet, this by no means represents the small force of action that would
be obtained when in a stationary position, for the impulse is secured
upon a stratum of fifty-eight feet in length of air at each stroke. So
that the conditions of weight of air for obtaining support equally well
apply to weight of air and its reaction in producing forward impulse.
‘So necessary is the acquirement of this horizontal speed, even in
commencing flight, that most heavy birds, when possible, rise against
the wind, and even run at the top of their speed to make their
wings available, as in the example of the eagle, mentioned at the
commencement of this paper. It is stated that the Arabs, on horseback,
can approach near enough to spear these birds, when on the plain,
before they are able to rise; their habit is to perch on an eminence,
where possible.
‘The tail of a bird is not necessary for flight. A pigeon can fly
perfectly with this appendage cut short off; it probably performs an
important function in steering, for it is to be remarked, that most
birds that have either to pursue or evade pursuit are amply provided
with this organ.
‘The foregoing reasoning is based upon facts, which tend to show
that the flight of the largest and heaviest of all birds is really
performed with but a small amount of force, and that man is endowed
with sufficient muscular power to enable him also to take individual
and extended flights, and that success is probably only involved in
a question of suitable mechanical adaptations. But if the wings are
to be modelled in imitation of natural examples, but very little
consideration will serve to demonstrate its utter impracticability when
applied in these forms.’
Thus Wenham, one of the best theorists of his age. The Society with
which this paper connects his name has done work, between that time
and the present, of which the importance cannot be overestimated, and
has been of the greatest value in the development of aeronautics,
both in theory and experiment. The objects of the Society are to give
a stronger impulse to the scientific study of aerial navigation, to
promote the intercourse of those interested in the subject at home
and abroad, and to give advice and instruction to those who study the
principles upon which aeronautical science is based. From the date of
its foundation the Society has given special study to dynamic flight,
putting this before ballooning. Its library, its bureau of advice and
information, and its meetings, all assist in forwarding the study
of aeronautics, and its twenty-three early _Annual Reports_ are of
considerable value, containing as they do a large amount of useful
information on aeronautical subjects, and forming practically the basis
of aeronautical science.
Ante to Wenham, Stringfellow and the French experimenters already
noted, by some years, was Le Bris, a French sea captain, who appears
to have required only a thorough scientific training to have rendered
him of equal moment in the history of gliding flight with Lilienthal
himself. Le Bris, it appears, watched the albatross and deduced, from
the manner in which it supported itself in the air, that plane surfaces
could be constructed and arranged to support a man in like manner.
Octave Chanute, himself a leading exponent of gliding, gives the best
description of Le Bris’s experiments in a work, _Progress in Flying
Machines_, which, although published as recently as 1894, is already
rare. Chanute draws from a still rarer book, namely, De la Landelle’s
work published in 1884. Le Bris himself, quoted by De la Landelle as
speaking of his first visioning of human flight, describes how he
killed an albatross, and then--‘I took the wing of the albatross and
exposed it to the breeze; and lo! in spite of me it drew forward into
the wind; notwithstanding my resistance it tended to rise. Thus I had
discovered the secret of the bird! I comprehended the whole mystery of
flight.’
This apparently took place while at sea; later on Le Bris, returning to
France, designed and constructed an artificial albatross of sufficient
size to bear his own weight. The fact that he followed the bird outline
as closely as he did attests his lack of scientific training for his
task, while at the same time the success of the experiment was proof
of his genius. The body of his artificial bird, boat-shaped, was 13½
ft. in length, with a breadth of 4 ft. at the widest part. The material
was cloth stretched over a wooden framework; in front was a small mast
rigged after the manner of a ship’s masts to which were attached poles
and cords with which Le Bris intended to work the wings. Each wing
was 23 ft. in length, giving a total supporting surface of nearly 220
sq. ft.; the weight of the whole apparatus was only 92 pounds. For
steering, both vertical and horizontal, a hinged tail was provided,
and the leading edge of each wing was made flexible. In construction
throughout, and especially in that of the wings, Le Bris adhered as
closely as possible to the original albatross.
He designed an ingenious kind of mechanism which he termed ‘Rotules,’
which by means of two levers gave a rotary motion to the front edge
of the wings, and also permitted of their adjustment to various
angles. The inventor’s idea was to stand upright in the body of the
contrivance, working the levers and cords with his hands, and with his
feet on a pedal by means of which the steering tail was to be worked.
He anticipated that, given a strong wind, he could rise into the air
after the manner of an albatross, without any need for flapping his
wings, and the account of his first experiment forms one of the most
interesting incidents in the history of flight. It is related in full
in Chanute’s work, from which the present account is summarised.
Le Bris made his first experiment on a main road near Douarnenez, at
Trefeuntec. From his observation of the albatross Le Bris concluded
that it was necessary to get some initial velocity in order to make the
machine rise; consequently on a Sunday morning, with a breeze of about
12 miles an hour blowing down the road, he had his albatross placed on
a cart and set off, with a peasant driver, against the wind. At the
outset the machine was fastened to the cart by a rope running through
the rails on which the machine rested, and secured by a slip knot on
Le Bris’s own wrist, so that only a jerk on his part was necessary
to loosen the rope and set the machine free. On each side walked an
assistant holding the wings, and when a turn of the road brought the
machine full into the wind these men were instructed to let go, while
the driver increased the pace from a walk to a trot. Le Bris, by
pressure on the levers of the machine, raised the front edges of his
wings slightly; they took the wind almost instantly to such an extent
that the horse, relieved of a great part of the weight he had been
drawing, turned his trot into a gallop. Le Bris gave the jerk of the
rope that should have unfastened the slip knot, but a concealed nail
on the cart caught the rope, so that it failed to run. The lift of the
machine was such, however, that it relieved the horse of very nearly
the weight of the cart and driver, as well as that of Le Bris and his
machine, and in the end the rails of the cart gave way. Le Bris rose in
the air, the machine maintaining perfect balance and rising to a height
of nearly 300 ft., the total length of the glide being upwards of an
eighth of a mile. But at the last moment the rope which had originally
fastened the machine to the cart got wound round the driver’s body, so
that this unfortunate dangled in the air under Le Bris and probably
assisted in maintaining the balance of the artificial albatross. Le
Bris, congratulating himself on his success, was prepared to enjoy just
as long a time in the air as the pressure of the wind would permit,
but the howls of the unfortunate driver at the end of the rope beneath
him dispelled his dreams; by working his levers he altered the angle of
the front wing edges so skilfully as to make a very successful landing
indeed for the driver, who, entirely uninjured, disentangled himself
from the rope as soon as he touched the ground, and ran off to retrieve
his horse and cart.
Apparently his release made a difference in the centre of gravity, for
Le Bris could not manipulate his levers for further ascent; by skilful
manipulation he retarded the descent sufficiently to escape injury to
himself; the machine descended at an angle, so that one wing, striking
the ground in front of the other, received a certain amount of damage.
It may have been on account of the reluctance of this same or another
driver that Le Bris chose a different method of launching himself in
making a second experiment with his albatross. He chose the edge of a
quarry which had been excavated in a depression of the ground; here
he assembled his apparatus at the bottom of the quarry, and by means
of a rope was hoisted to a height of nearly 100 ft. from the quarry
bottom, this rope being attached to a mast which he had erected upon
the edge of the depression in which the quarry was situated. Thus
hoisted, the albatross was swung to face a strong breeze that blew
inland, and Le Bris manipulated his levers to give the front edges of
his wings a downward angle, so that only the top surfaces should take
the wing pressure. Having got his balance, he obtained a lifting angle
of incidence on the wings by means of his levers, and released the hook
that secured the machine, gliding off over the quarry. On the glide
he met with the inevitable upward current of air that the quarry and
the depression in which it was situated caused; this current upset
the balance of the machine and flung it to the bottom of the quarry,
breaking it to fragments. Le Bris, apparently as intrepid as ingenious,
gripped the mast from which his levers were worked, and, springing
upward as the machine touched earth, escaped with no more damage than
a broken leg. But for the rebound of the levers he would have escaped
even this.
The interest of these experiments is enhanced by the fact that Le
Bris was a seafaring man who conducted them from love of the science
which had fired his imagination, and in so doing exhausted his own
small means. It was in 1855 that he made these initial attempts, and
twelve years passed before his persistence was rewarded by a public
subscription made at Brest for the purpose of enabling him to continue
his experiments. He built a second albatross, and on the advice of his
friends ballasted it for flight instead of travelling in it himself.
It was not so successful as the first, probably owing to the lack of
human control while in flight; on one of the trials a height of 150 ft.
was attained, the glider being secured by a thin rope and held so as
to face into the wind. A glide of nearly an eighth of a mile was made
with the rope hanging slack, and, at the end of this distance, a rise
in the ground modified the force of the wind, whereupon the machine
settled down without damage. A further trial in a gusty wind resulted
in the complete destruction of this second machine; Le Bris had no
more funds, no further subscriptions were likely to materialise, and
so the experiments of this first exponent of the art of gliding (save
for Besnier and his kind) came to an end. They constituted a notable
achievement, and undoubtedly Le Bris deserves a better place than has
been accorded him in the ranks of the early experimenters.
Contemporary with him was Charles Spencer, the first man to practise
gliding in England. His apparatus consisted of a pair of wings with
a total area of 30 sq. ft., to which a tail and body were attached.
The weight of this apparatus was some 24 lbs., and, launching himself
on it from a small eminence, as was done later by Lilienthal in his
experiments, the inventor made flights of over 120 feet. The glider in
question was exhibited at the Aeronautical Exhibition of 1868.
VI
THE AGE OF THE GIANTS
Until the Wright Brothers definitely solved the problem of flight and
virtually gave the aeroplane its present place in aeronautics, there
were three definite schools of experiment. The first of these was
that which sought to imitate nature by means of the ornithopter or
flapping-wing machines directly imitative of bird flight; the second
school was that which believed in the helicopter or lifting screw; the
third and eventually successful school is that which followed up the
principle enunciated by Cayley, that of opposing a plane surface to the
resistance of the air by supplying suitable motive power to drive it at
the requisite angle for support.
Engineering problems generally go to prove that too close an imitation
of nature in her forms of reciprocating motion is not advantageous;
it is impossible to copy the minutiae of a bird’s wing effectively,
and the bird in flight depends on the tiniest details of its feathers
just as much as on the general principle on which the whole wing is
constructed. Bird flight, however, has attracted many experimenters,
including even Lilienthal; among others may be mentioned F. W. Brearey,
who invented what he called the ‘Pectoral cord,’ which stored energy
on each upstroke of the artificial wing; E. P. Frost; Major R. Moore,
and especially Hureau de Villeneuve, a most enthusiastic student
of this form of flight, who began his experiments about 1865, and
altogether designed and made nearly 300 artificial birds. One of his
later constructions was a machine in bird form with a wing span of
about 50 ft.; the motive power for this was supplied by steam from a
boiler which, being stationary on the ground, was connected by a length
of hose to the machine. De Villeneuve, turning on steam for his first
trial, obtained sufficient power to make the wings beat very forcibly;
with the inventor on the machine the latter rose several feet into the
air, whereupon de Villeneuve grew nervous and turned off the steam
supply. The machine fell to the earth, breaking one of its wings, and
it does not appear that de Villeneuve troubled to reconstruct it. This
experiment remains as the greatest success yet achieved by any machine
constructed on the ornithopter principle.
It may be that, as forecasted by the prophet Wells, the flapping-wing
machine will yet come to its own and compete with the aeroplane in
efficiency. Against this, however, are the practical advantages of
the rotary mechanism of the aeroplane propeller as compared with the
movement of a bird’s wing, which, according to Marey, moves in a figure
of eight. The force derived from a propeller is of necessity continual,
while it is equally obvious that that derived from a flapping movement
is intermittent, and, in the recovery of a wing after completion of one
stroke for the next, there is necessarily a certain cessation, if not
loss, of power.
The matter of experiment along any lines in connection with aviation is
primarily one of hard cash. Throughout the whole history of flight up
to the outbreak of the European war development has been handicapped
on the score of finance, and, since the arrival of the aeroplane,
both ornithopter and helicopter schools have been handicapped by
this consideration. Thus serious study of the efficiency of wings in
imitation of those of the living bird has not been carried to a point
that might win success for this method of propulsion. Even Wilbur
Wright studied this subject and propounded certain theories, while
a later and possibly more scientific student, F. W. Lanchester, has
also contributed empirical conclusions. Another and earlier student
was Lawrence Hargrave, who made a wing-propelled model which achieved
successful flight, and in 1885 was exhibited before the Royal Society
of New South Wales. Hargrave called the principle on which his
propeller worked that of a ‘Trochoided plane’; it was, in effect,
similar to the feathering of an oar.
Hargrave, to diverge for a brief while from the machine to the man,
was one who, although he achieved nothing worthy of special remark,
contributed a great deal of painstaking work to the science of flight.
He made a series of experiments with man-lifting kites in addition to
making a study of flapping-wing flight. It cannot be said that he set
forth any new principle; his work was mainly imitative, but at the
same time by developing ideas originated in great measure by others he
helped toward the solution of the problem.
Attempts at flight on the helicopter principle consist in the work of
De la Landelle and others already mentioned. The possibility of flight
by this method is modified by a very definite disadvantage of which
lovers of the helicopter seem to take little account. It is always
claimed for a machine of this type that it possesses great advantages
both in rising and in landing, since, if it were effective, it would
obviously be able to rise from and alight on any ground capable of
containing its own bulk; a further advantage claimed is that the
helicopter would be able to remain stationary in the air, maintaining
itself in any position by the vertical lift of its propeller.
These potential assets do not take into consideration the fact that
efficiency is required not only in rising, landing, and remaining
stationary in the air, but also in actual flight. It must be evident
that if a certain amount of the motive force is used in maintaining the
machine off the ground, that amount of force is missing from the total
of horizontal driving power. Again, it is often assumed by advocates
of this form of flight that the rapidity of climb of the helicopter
would be far greater than that of the driven plane; this view overlooks
the fact that the maintenance of aerodynamic support would claim the
greater part of the engine-power; the rate of ascent would be governed
by the amount of power that could be developed surplus to that required
for maintenance.
This is best explained by actual figures: assuming that a propeller 15
ft. in diameter is used, almost 50 horse-power would be required to get
an upward lift of 1,000 pounds; this amount of horse-power would be
continually absorbed in maintaining the machine in the air at any given
level; for actual lift from one level to another at a speed of eleven
feet per second a further 20 horse-power would be required, which means
that 70 horse-power must be constantly provided for; this absorption
of power in the mere maintenance of aerodynamic support is a permanent
drawback.
The attraction of the helicopter lies, probably, in the ease with
which flight is demonstrated by means of models constructed on this
principle, but one truism with regard to the principles of flight
is that the problems change remarkably, and often unexpectedly,
with the size of the machine constructed for experiment. Berriman,
in a brief but very interesting manual entitled _Principles of
Flight_, assumed that ‘there is a significant dimension of which
the effective area is an expression of the second power, while the
weight became an expression of the third power. Then once again we
have the two-thirds power law militating against the successful
construction of large helicopters, on the ground that the essential
weight increases disproportionately fast to the effective area. From a
consideration of the structural features of propellers it is evident
that this particular relationship does not apply in practice, but it
seems reasonable that some such governing factor should exist as an
explanation of the apparent failure of all full-sized machines that
have been constructed. Among models there is nothing more strikingly
successful than the toy helicopter, in which the essential weight is so
small compared with the effective area.’
De la Landelle’s work, already mentioned, was carried on a few years
later by another Frenchman, Castel, who constructed a machine with
eight propellers arranged in two fours and driven by a compressed
air motor or engine. The model with which Castel experimented had a
total weight of only 49 lbs.; it rose in the air and smashed itself
by driving against a wall, and the inventor does not seem to have
proceeded further. Contemporary with Castel was Professor Forlanini,
whose design was for a machine very similar to de la Landelle’s,
with two superposed screws. This machine ranks as the second on the
helicopter principle to achieve flight; it remained in the air for no
less than the third of a minute in one of its trials.
Later experimenters in this direction were Kress, a German; Professor
Wellner, an Austrian; and W. R. Kimball, an American. Kress, like most
Germans, set to the development of an idea which others had originated;
he followed de la Landelle and Forlanini by fitting two superposed
propellers revolving in opposite directions, and with this machine he
achieved good results as regards horse-power to weight; Kimball, it
appears, did not get beyond the rubber-driven model stage, and any
success he may have achieved was modified by the theory enunciated by
Berriman and quoted above.
Comparing these two schools of thought, the helicopter and bird-flight
schools, it appears that the latter has the greater chance of eventual
success--that is, if either should ever come into competition with the
aeroplane as effective means of flight. So far, the aeroplane holds
the field, but the whole science of flight is so new and so full of
unexpected developments that this is no reason for assuming that other
means may not give equal effect, when money and brains are diverted
from the driven plane to a closer imitation of natural flight.
Reverting from non-success to success, from consideration of the two
methods mentioned above to the direction in which practical flight
has been achieved, it is to be noted that between the time of Le
Bris, Stringfellow, and their contemporaries, and the nineties of
last century, there was much plodding work carried out with little
visible result, more especially so far as English students were
concerned. Among the incidents of those years is one of the most
pathetic tragedies in the whole history of aviation, that of Alphonse
Penaud, who, in his thirty years of life, condensed the experience of
his predecessors and combined it with his own genius to state in a
published patent what the aeroplane of to-day should be. Consider the
following abstract of Penaud’s design as published in his patent of
1876, and comparison of this with the aeroplane that now exists will
show very few divergences except for those forced on the inventor by
the fact that the internal combustion engine had not then developed.
The double-surfaced planes were to be built with wooden ribs and
arranged with a slight dihedral angle; there was to be a large aspect
ratio and the wings were cambered as in Stringfellow’s later models.
Provision was made for warping the wings while in flight, and the
trailing edges were so designed as to be capable of upward twist while
the machine was in the air. The planes were to be placed above the car,
and provision was even made for a glass wind-screen to give protection
to the pilot during flight. Steering was to be accomplished by means
of lateral and vertical planes forming a tail; these controlled by a
single lever corresponding to the ‘joy stick’ of the present day plane.
Penaud conceived this machine as driven by two propellers;
alternatively these could be driven by petrol or steam-fed motor,
and the centre of gravity of the machine while in flight was in the
front fifth of the wings. Penaud estimated from 20 to 30 horse-power
sufficient to drive this machine, weighing with pilot and passenger
2,600 lbs., through the air at a speed of 60 miles an hour, with the
wings set at an angle of incidence of two degrees. So complete was the
design that it even included instruments, consisting of an aneroid,
pressure indicator, an anemometer, a compass, and a level. There,
with few alterations, is the aeroplane as we know it--and Penaud was
twenty-seven when his patent was published.
For three years longer he worked, experimenting with models,
contributing essays and other valuable data to French papers on the
subject of aeronautics. His gains were ill health, poverty, and
neglect, and at the age of thirty a pistol shot put an end to what had
promised to be one of the most brilliant careers in all the history of
flight.
Two years before the publication of Penaud’s patent Thomas Moy
experimented at the Crystal Palace with a twin-propelled aeroplane,
steam driven, which seems to have failed mainly because the internal
combustion engine had not yet come to give sufficient power for
weight. Moy anchored his machine to a pole running on a prepared
circular track; his engine weighed 80 lbs. and, developing only three
horse-power, gave him a speed of 12 miles an hour. He himself estimated
that the machine would not rise until he could get a speed of 35 miles
an hour, and his estimate was correct. Two six-bladed propellers were
placed side by side between the two main planes of the machine, which
was supported on a triangular wheeled undercarriage and steered by
fairly conventional tail planes. Moy realised that he could not get
sufficient power to achieve flight, but he went on experimenting in
various directions, and left much data concerning his experiments which
has not yet been deemed worthy of publication, but which still contains
a mass of information that is of practical utility, embodying as it
does a vast amount of painstaking work.
Penaud and Moy were followed by Goupil, a Frenchman, who, in place of
attempting to fit a motor to an aeroplane, experimented by making the
wind his motor. He anchored his machine to the ground, allowing it two
feet of lift, and merely waited for a wind to come along and lift it.
The machine was stream lined, and the wings, curving as in the early
German patterns of war aeroplanes, gave a total lifting surface of
about 290 sq. ft. Anchored to the ground and facing a wind of 19 feet
per second, Goupil’s machine lifted its own weight and that of two men
as well to the limit of its anchorage. Although this took place as late
as 1883 the inventor went no further in practical work. He published
a book, however, entitled _La Locomotion Aérienne_, which is still of
great importance, more especially on the subject of inherent stability.
In 1884 came the first patents of Horatio Phillips, whose work lay
mainly in the direction of investigation into the curvature of plane
surfaces, with a view to obtaining the greatest amount of support.
Phillips was one of the first to treat the problem of curvature of
planes as a matter for scientific experiment, and, great as has been
the development of the driven plane in the 36 years that have passed
since he began, there is still room for investigation into the subject
which he studied so persistently and with such valuable result.
At this point it may be noted that, with the solitary exception of
Le Bris, practically every student of flight had so far set about
constructing the means of launching humanity into the air without any
attempt at ascertaining the nature and peculiarities of the sustaining
medium. The attitude of experimenters in general might be compared to
that of a man who from boyhood had grown up away from open water, and,
at the first sight of an expanse of water, set to work to construct a
boat with a vague idea that, since wood would float, only sufficient
power was required to make him an efficient navigator. Accident,
perhaps, in the shape of lack of means of procuring driving power,
drove Le Bris to the form of experiment which he actually carried out;
it remained for the later years of the nineteenth century to produce
men who were content to ascertain the nature of the support the air
would afford before attempting to drive themselves through it.
Of the age in which these men lived and worked, giving their all in
many cases to the science they loved, even to life itself, it may be
said with truth that ‘there were giants on the earth in those days,’ as
far as aeronautics is in question. It was an age of giants who lived
and dared and died, venturing into uncharted space, knowing nothing
of its dangers, giving, as a man gives to his mistress, without stint
and for the joy of the giving. The science of to-day, compared with
the glimmerings that were in that age of the giants, is a fixed and
certain thing; the problems of to-day are minor problems, for the great
major problem vanished in solution when the Wright Brothers made their
first ascent. In that age of the giants was evolved the flying man,
the new type in human species which found full expression and came to
full development in the days of the war, achieving feats of daring and
endurance which leave the commonplace landsman staggered at thought of
that of which his fellows prove themselves capable. He is a new type,
this flying man, a being of self-forgetfulness; of such was Lilienthal,
of such was Pilcher; of such in later days were Farman, Bleriot, Hamel,
Rolls, and their fellows; great names that will live for as long as
man flies, adventurers equally with those of the spacious days of
Elizabeth. To each of these came the call, and he worked and dared and
passed, having, perhaps, advanced one little step in the long march
that has led toward the perfecting of flight.
It is not yet twenty years since man first flew, but into that twenty
years have been compressed a century or so of progress, while, in
the two decades that preceded it, was compressed still more. We have
only to recall and recount the work of four men: Lilienthal, Langley,
Pilcher, and Clement Ader to see the immense stride that was made
between the time when Penaud pulled a trigger for the last time and
the Wright Brothers first left the earth. Into those two decades was
compressed the investigation that meant knowledge of the qualities of
the air, together with the development of the one prime mover that
rendered flight a possibility--the internal combustion engine. The
coming and progress of this latter is a thing apart, to be detailed
separately; for the present we are concerned with the evolution of
the driven plane, and with it the evolution of that daring being, the
flying man. The two are inseparable, for the men gave themselves to
their art; the story of Lilienthal’s life and death is the story of his
work; the story of Pilcher’s work is that of his life and death.
Considering the flying man as he appeared in the war period, there
entered into his composition a new element--patriotism--which brought
about a modification of the type, or, perhaps, made it appear that
certain men belonged to the type who in reality were commonplace
mortals, animated, under normal conditions, by normal motives, but
driven by the stress of the time to take rank with the last expression
of human energy, the flying type. However that may be, what may be
termed the mathematising of aeronautics has rendered the type itself
evanescent; your pilot of to-day knows his craft, once he is trained,
much in the manner that a driver of a motor-lorry knows his vehicle;
design has been systematised, capabilities have been tabulated; camber,
dihedral angle, aspect ratio, engine power, and plane surface, are
business items of drawing office and machine shop; there is room for
enterprise, for genius, and for skill; once and again there is room for
daring, as in the first Atlantic flight. Yet that again was a thing of
mathematical calculation and petrol storage, allied to a certain stark
courage which may be found even in landsmen. For the ventures into the
unknown, the limit of daring, the work for work’s sake, with the almost
certainty that the final reward was death, we must look back to the age
of the giants, the age when flying was not a business, but romance.
[Illustration: Lilienthal with his glider folded after a glide.]
[Illustration: Lilienthal’s biplane glider alighting.]
[Illustration: Pilcher’s ‘Bat.’]
[Illustration: The ‘Bat’, side view.]
VII
LILIENTHAL AND PILCHER
There was never a more enthusiastic and consistent student of the
problems of flight than Otto Lilienthal, who was born in 1848 at
Anklam, Pomerania, and even from his early school-days dreamed and
planned the conquest of the air. His practical experiments began when,
at the age of thirteen, he and his brother Gustav made wings consisting
of wooden framework covered with linen, which Otto attached to his
arms, and then ran downhill flapping them. In consequence of possible
derision on the part of other boys, Otto confined these experiments
for the most part to moonlit nights, and gained from them some idea
of the resistance offered by flat surfaces to the air. It was in 1867
that the two brothers began really practical work, experimenting with
wings which, from their design, indicate some knowledge of Besnier
and the history of his gliding experiments; these wings the brothers
fastened to their backs, moving them with their legs after the fashion
of one attempting to swim. Before they had achieved any real success in
gliding the Franco-German war came as an interruption; both brothers
served in this campaign, resuming their experiments in 1871 at the
conclusion of hostilities.
The experiments made by the brothers previous to the war had convinced
Otto that previous experimenters in gliding flight had failed
through reliance on empirical conclusions or else through incomplete
observation on their own part, mostly of bird flight. From 1871 onward
Otto Lilienthal (Gustav’s interest in the problem was not maintained as
was his brother’s) made what is probably the most detailed and accurate
series of observations that has ever been made with regard to the
properties of curved wing surfaces. So far as could be done, Lilienthal
tabulated the amount of air resistance offered to a bird’s wing,
ascertaining that the curve is necessary to flight, as offering far
more resistance than a flat surface. Cayley, and others, had already
stated this, but to Lilienthal belongs the honour of being first to
put the statement to effective proof--he made over 2,000 gliding
flights between 1891 and the regrettable end of his experiments; his
practical conclusions are still regarded as part of the accepted theory
of students of flight. In 1889 he published a work on the subject of
gliding flight which stands as data for investigators, and, on the
conclusions embodied in this work, he began to build his gliders and
practise what he had preached, turning from experiment with models to
wings that he could use.
It was in the summer of 1891 that he built his first glider of rods
of peeled willow, over which was stretched strong cotton fabric; with
this, which had a supporting surface of about 100 square feet, Otto
Lilienthal launched himself in the air from a spring board, making
glides which, at first of only a few feet, gradually lengthened. As
his experience of the supporting qualities of the air progressed he
gradually altered his designs until, when Pilcher visited him in the
spring of 1895, he experimented with a glider, roughly made of peeled
willow rods and cotton fabric, having an area of 150 square feet and
weighing half a hundredweight. By this time Lilienthal had moved from
his springboard to a conical artificial hill which he had had thrown up
on level ground at Grosse Lichterfelde, near Berlin. This hill was made
with earth taken from the excavations incurred in constructing a canal,
and had a cave inside in which Lilienthal stored his machines. Pilcher,
in his paper on ‘Gliding,’[1] gives an excellent short summary of
Lilienthal’s experiments, from which the following extracts are taken:--
‘At first Lilienthal used to experiment by jumping off a springboard
with a good run. Then he took to practising on some hills close to
Berlin. In the summer of 1892 he built a flat-roofed hut on the summit
of a hill, from the top of which he used to jump, trying, of course,
to soar as far as possible before landing.... One of the great dangers
with a soaring machine is losing forward speed, inclining the machine
too much down in front, and coming down head first. Lilienthal was the
first to introduce the system of handling a machine in the air merely
by moving his weight about in the machine; he always rested only on his
elbows or on his elbows and shoulders....
‘In 1892 a canal was being cut, close to where Lilienthal lived, in the
suburbs of Berlin, and with the surplus earth Lilienthal had a special
hill thrown up to fly from. The country round is as flat as the sea,
and there is not a house or tree near it to make the wind unsteady, so
this was an ideal practising ground; for practising on natural hills is
generally rendered very difficult by shifty and gusty winds.... This
hill is 50 feet high, and conical. Inside the hill there is a cave for
the machines to be kept in.... When Lilienthal made a good flight he
used to land 300 feet from the centre of the hill, having come down at
an angle of 1 in 6; but his best flights have been at an angle of about
1 in 10.
‘If it is calm, one must run a few steps down the hill, holding the
machine as far back on oneself as possible, when the air will gradually
support one, and one slides off the hill into the air. If there is any
wind, one should face it at starting; to try to start with a side wind
is most unpleasant. It is possible after a great deal of practice to
turn in the air, and fairly quickly. This is accomplished by throwing
one’s weight to one side, and thus lowering the machine on that side
towards which one wants to turn. Birds do the same thing--crows and
gulls show it very clearly. Last year Lilienthal chiefly experimented
with double-surfaced machines. These were very much like the old
machines with awnings spread above them.
‘The object of making these double-surfaced machines was to get more
surface without increasing the length and width of the machine. This,
of course, it does, but I personally object to any machine in which
the wing surface is high above the weight. I consider that it makes
the machine very difficult to handle in bad weather, as a puff of wind
striking the surface, high above one, has a great tendency to heel the
machine over.
‘Herr Lilienthal kindly allowed me to sail down his hill in one of
these double-surfaced machines last June. With the great facility
afforded by his conical hill the machine was handy enough; but I am
afraid I should not be able to manage one at all in the squally
districts I have had to practise in over here.
‘Herr Lilienthal came to grief through deserting his old method of
balancing. In order to control his tipping movements more rapidly he
attached a line from his horizontal rudder to his head, so that when he
moved his head forward it would lift the rudder and tip the machine up
in front, and vice versa. He was practising this on some natural hills
outside Berlin, and he apparently got muddled with the two motions,
and, in trying to regain speed after he had, through a lull in the
wind, come to rest in the air, let the machine get too far down in
front, came down head first and was killed.’
Then in another passage Pilcher enunciates what is the true value of
such experiments as Lilienthal--and, subsequently, he himself--made:
‘The object of experimenting with soaring machines,’ he says, ‘is to
enable one to have practice in starting and alighting and controlling
a machine in the air. They cannot possibly float horizontally in the
air for any length of time, but to keep going must necessarily lose in
elevation. They are excellent schooling machines, and that is all they
are meant to be, until power, in the shape of an engine working a screw
propeller, or an engine working wings to drive the machine forward, is
added; then a person who is used to soaring down a hill with a simple
soaring machine will be able to fly with comparative safety. One can
best compare them to bicycles having no cranks, but on which one could
learn to balance by coming down an incline.’
It was in 1895 that Lilienthal passed from experiment with the
monoplane type of glider to the construction of a biplane glider
which, according to his own account, gave better results than his
previous machines. ‘Six or seven metres velocity of wind,’ he says,
‘sufficed to enable the sailing surface of 18 square metres to carry me
almost horizontally against the wind from the top of my hill without
any starting jump. If the wind is stronger I allow myself to be simply
lifted from the point of the hill and to sail slowly towards the wind.
The direction of the flight has, with strong wind, a strong upwards
tendency. I often reach positions in the air which are much higher than
my starting point. At the climax of such a line of flight I sometimes
come to a standstill for some time, so that I am enabled while floating
to speak with the gentlemen who wish to photograph me, regarding the
best position for the photographing.’
Lilienthal’s work did not end with simple gliding, though he did not
live to achieve machine-driven flight. Having, as he considered, gained
sufficient experience with gliders, he constructed a power-driven
machine which weighed altogether about 90 lbs., and this was thoroughly
tested. The extremities of its wings were made to flap, and the driving
power was obtained from a cylinder of compressed carbonic acid gas,
released through a hand-operated valve which, Lilienthal anticipated,
would keep the machine in the air for four minutes. There were certain
minor accidents to the mechanism, which delayed the trial flights,
and on the day that Lilienthal had determined to make his trial he
made a long gliding flight with a view to testing a new form of rudder
that--as Pilcher relates--was worked by movements of his head. His
death came about through the causes that Pilcher states; he fell from
a height of 50 feet, breaking his spine, and the next day he died.
It may be said that Lilienthal accomplished as much as any one of the
great pioneers of flying. As brilliant in his conceptions as da Vinci
had been in his, and as conscientious a worker as Borelli, he laid the
foundations on which Pilcher, Chanute, and Professor Montgomery were
able to build to such good purpose. His book on bird flight, published
in 1889, with the authorship credited both to Otto and his brother
Gustav, is regarded as epoch-making; his gliding experiments are no
less entitled to this description.
In England Lilienthal’s work was carried on by Percy Sinclair Pilcher,
who, born in 1866, completed six years’ service in the British Navy
by the time that he was nineteen, and then went through a course of
engineering, subsequently joining Maxim in his experimental work. It
was not until 1895 that he began to build the first of the series of
gliders with which he earned his plane among the pioneers of flight.
Probably the best account of Pilcher’s work is that given in the
_Aeronautical Classics_ issued by the Royal Aeronautical Society, from
which the following account of Pilcher’s work is mainly abstracted.[2]
The ‘Bat,’ as Pilcher named his first glider, was a monoplane which he
completed before he paid his visit to Lilienthal in 1895. Concerning
this Pilcher stated that he purposely finished his own machine before
going to see Lilienthal, so as to get the greatest advantage from any
original ideas he might have; he was not able to make any trials with
this machine, however, until after witnessing Lilienthal’s experiments
and making several glides in the biplane glider which Lilienthal
constructed.
The wings of the ‘Bat’ formed a pronounced dihedral angle; the tips
being raised 4 feet above the body. The spars forming the entering
edges of the wings crossed each other in the centre and were lashed to
opposite sides of the triangle that served as a mast for the stay-wires
that guyed the wings. The four ribs of each wing, enclosed in pockets
in the fabric, radiated fanwise from the centre, and were each stayed
by three steel piano-wires to the top of the triangular mast, and
similarly to its base. These ribs were bolted down to the triangle at
their roots, and could be easily folded back on to the body when the
glider was not in use. A small fixed vertical surface was carried in
the rear. The framework and ribs were made entirely of Riga pine; the
surface fabric was nainsook. The area of the machine was 150 square
feet; its weight 45 lbs.; so that in flight, with Pilcher’s weight of
145 lbs. added, it carried one and a half pounds to the square foot.
[Illustration: Rear view of Pilcher’s ‘Beetle.’]
[Illustration: The ‘Beetle.’ side view.]
[Illustration: Pilcher starting on glide with the ‘Bat.’]
Pilcher’s first glides, which he carried out on a grass hill on
the banks of the Clyde near Cardross, gave little result, owing to
the exaggerated dihedral angle of the wings, and the absence of a
horizontal tail. The ‘Bat’ was consequently reconstructed with a
horizontal tail-plane added to the vertical one, and with the wings
lowered so that the tips were only six inches above the level of the
body. The machine now gave far better results; on the first glide into
a head wind Pilcher rose to a height of twelve feet and remained in
the air for a third of a minute; in the second attempt a rope was used
to tow the glider, which rose to twenty feet and did not come to earth
again until nearly a minute had passed. With experience Pilcher was
able to lengthen his glide and improve his balance, but the dropped
wing tips made landing difficult, and there were many breakages.
In consequence of this Pilcher built a second glider which he named
the ‘Beetle,’ because, as he said, it looked like one. In this the
square-cut wings formed almost a continuous plane, rigidly fixed to
the central body, which consisted of a shaped girder. These wings were
built up of five transverse bamboo spars, with two shaped ribs running
from fore to aft of each wing, and were stayed overhead to a couple
of masts. The tail, consisting of two discs placed crosswise (the
horizontal one alone being movable), was carried high up in the rear.
With the exception of the wing-spars, the whole framework was built of
white pine. The wings in this machine were actually on a higher level
than the operator’s head; the centre of gravity was, consequently, very
low, a fact which, according to Pilcher’s own account, made the glider
very difficult to handle. Moreover, the weight of the ‘Beetle,’ 80
lbs., was considerable; the body had been very solidly built to enable
it to carry the engine which Pilcher was then contemplating; so that
the glider carried some 225 lbs. with its area of 170 square feet-too
great a mass for a single man to handle with comfort.
It was in the spring of 1896 that Pilcher built his third glider,
the ‘Gull,’ with 300 square feet of area and a weight of 55 lbs. The
size of this machine rendered it unsuitable for experiment in any but
very calm weather, and it incurred such damage when experiments were
made in a breeze that Pilcher found it necessary to build a fourth,
which he named the ‘Hawk.’ This machine was very soundly built, being
constructed of bamboo, with the exception of the two main transverse
beams. The wings were attached to two vertical masts, 7 feet high, and
8 feet apart, joined at their summits and their centres by two wooden
beams. Each wing had nine bamboo ribs, radiating from its mast, which
was situated at a distance of 2 feet 6 inches from the forward edge
of the wing. Each rib was rigidly stayed at the top of the mast by
three tie-wires, and by a similar number to the bottom of the mast, by
which means the curve of each wing was maintained uniformly. The tail
was formed of a triangular horizontal surface to which was affixed a
triangular vertical surface, and was carried from the body on a high
bamboo mast, which was also stayed from the masts by means of steel
wires, but only on its upper surface, and it was the snapping of one
of these guy wires which caused the collapse of the tail support and
brought about the fatal end of Pilcher s experiments. In flight,
Pilcher’s head, shoulders, and the greater part of his chest projected
above the wings. He took up his position by passing his head and
shoulders through the top aperture formed between the two wings, and
resting his forearms on the longitudinal body members. A very simple
form of undercarriage, which took the weight off the glider on the
ground, was fitted, consisting of two bamboo rods with wheels suspended
on steel springs.
Balance and steering were effected, apart from the high degree of
inherent stability afforded by the tail, as in the case of Lilienthal’s
glider, by altering the position of the body. With this machine Pilcher
made some twelve glides at Eynsford in Kent in the summer of 1896,
and as he progressed he increased the length of his glides, and also
handled the machine more easily, both in the air and in landing. He was
occupied with plans for fitting an engine and propeller to the ‘Hawk,’
but, in these early days of the internal combustion engine, was unable
to get one light enough for his purpose. There were rumours of an
engine weighing 15 lbs. which gave 1 horse-power, and was reported to
be in existence in America, but it could not be traced.
In the spring of 1897 Pilcher took up his gliding experiments again,
obtaining what was probably the best of his glides on June 19th, when
he alighted after a perfectly balanced glide of over 250 yards in
length, having crossed a valley at a considerable height. From his
various experiments he concluded that once the machine was launched
in the air an engine of, at most, 3 horse-power would suffice for
the maintenance of horizontal flight, but he had to allow for the
additional weight of the engine and propeller, and taking into account
the comparative inefficiency of the propeller, he planned for an engine
of 4 horse-power. Engine and propeller together were estimated at under
44 lbs. weight, the engine was to be fitted in front of the operator,
and by means of an overhead shaft was to operate the propeller
situated in rear of the wings. 1898 went by while this engine was
under construction. Then in 1899 Pilcher became interested in Lawrence
Hargrave’s soaring kites, with which he carried out experiments during
the summer of 1899. It is believed that he intended to incorporate
a number of these kites in a new machine, a triplane, of which the
fragments remaining are hardly sufficient to reconstitute the complete
glider. This new machine was never given a trial, for on September
30th, 1899, at Stamford Hall, Market Harborough, Pilcher agreed to
give a demonstration of gliding flight, but owing to the unfavourable
weather he decided to postpone the trial of the new machine and to
experiment with the ‘Hawk,’ which was intended to rise from a level
field, towed by a line passing over a tackle drawn by two horses. At
the first trial the machine rose easily, but the tow-line snapped when
it was well clear of the ground, and the glider descended, weighed down
through being sodden with rain. Pilcher resolved on a second trial, in
which the glider again rose easily to about thirty feet, when one of
the guy wires of the tail broke, and the tail collapsed; the machine
fell to the ground, turning over, and Pilcher was unconscious when he
was freed from the wreckage.
Hopes were entertained of his recovery, but he died on Monday, October
2nd, 1899, aged only thirty-four. His work in the cause of flying
lasted only four years, but in that time his actual accomplishments
were sufficient to place his name beside that of Lilienthal, with whom
he ranks as one of the greatest exponents of gliding flight.
[Illustration: ‘The Hawk’--front view.]
[Illustration: ‘The Hawk’--rear view.]
[Illustration: ‘The Hawk’--in flight with Pilcher.]
VIII
AMERICAN GLIDING EXPERIMENTS
While Pilcher was carrying on Lilienthal’s work in England, the great
German had also a follower in America; one Octave Chanute, who, in one
of the statements which he has left on the subject of his experiments
acknowledges forty years’ interest in the problem of flight, did more
to develop the glider in America than--with the possible exception
of Montgomery--any other man. Chanute had all the practicality of an
American; he began his work, so far as actual gliding was concerned,
with a full-sized glider of the Lilienthal type, just before Lilienthal
was killed. In a rather rare monograph, entitled _Experiments in
Flying_, Chanute states that he found the Lilienthal glider hazardous
and decided to test the value of an idea of his own; in this he
followed the same general method, but reversed the principle upon
which Lilienthal had depended for maintaining his equilibrium in the
air. Lilienthal had shifted the weight of his body, under immovable
wings, as fast and as far as the sustaining pressure varied under his
surfaces; this shifting was mainly done by moving the feet, as the
actions required were small except when alighting. Chanute’s idea was
to have the operator remain seated in the machine in the air, and to
intervene only to steer or to alight; moving mechanism was provided
to adjust the wings automatically, in order to restore balance when
necessary.
Chanute realised that experiments with models were of little use; in
order to be fully instructive, these experiments should be made with a
full-sized machine which carried its operator, for models seldom fly
twice alike in the open air, and no relation can be gained from them
of the divergent air currents which they have experienced. Chanute’s
idea was that any flying machine which might be constructed must
be able to operate in a wind; hence the necessity for an operator
to report upon what occurred in flight, and to acquire practical
experience of the work of the human factor in imitation of bird
flight. From this point of view he conducted his own experiments;
it must be noted that he was over sixty years of age when he began,
and, being no longer sufficiently young and active to perform any but
short and insignificant glides, the courage of the man becomes all the
more noteworthy; he set to work to evolve the state required by the
problem of stability, and without any expectation of advancing to the
construction of a flying machine which might be of commercial value.
His main idea was the testing of devices to secure equilibrium; for
this purpose he employed assistants to carry out the practical work,
where he himself was unable to supply the necessary physical energy.
Together with his assistants he found a suitable place for experiments
among the sandhills on the shore of Lake Michigan, about thirty miles
eastward from Chicago. Here a hill about ninety-five feet high was
selected as a point from which Chanute’s gliders could set off; in
practice, it was found that the best observation was to be obtained
from short glides at low speed, and, consequently, a hill which was
only sixty-one feet above the shore of the lake was employed for the
experimental work done by the party.
In the years 1896 and 1897, with parties of from four to six persons,
five full-sized gliders were tried out, and from these two distinct
types were evolved: of these one was a machine consisting of five tiers
of wings and a steering tail, and the other was of the biplane type;
Chanute believed these to be safer than any other machine previously
evolved, solving, as he states in his monograph, the problem of
inherent equilibrium as fully as this could be done. Unfortunately,
very few photographs were taken of the work in the first year, but one
view of a multiple wing-glider survives, showing the machine in flight.
In 1897 a series of photographs was taken exhibiting the consecutive
phases of a single flight; this series of photographs represents the
experience gained in a total of about one thousand glides, but the
point of view was varied so as to exhibit the consecutive phases of one
single flight.
The experience gained is best told in Chanute’s own words. ‘The first
thing,’ he says, ‘which we discovered practically was that the wind
flowing up a hill-side is not a steadily-flowing current like that
of a river. It comes as a rolling mass, full of tumultuous whirls
and eddies, like those issuing from a chimney; and they strike the
apparatus with constantly varying force and direction, sometimes
withdrawing support when most needed. It has long been known, through
instrumental observations, that the wind is constantly changing in
force and direction; but it needed the experience of an operator afloat
on a gliding machine to realise that this all proceeded from cyclonic
action; so that more was learned in this respect in a week than had
previously been acquired by several years of experiments with models.
There was a pair of eagles, living in the top of a dead tree about two
miles from our tent, that came almost daily to show us how such wind
effects are overcome and utilised. The birds swept in circles overhead
on pulseless wings, and rose high up in the air. Occasionally there
was a side-rocking motion, as of a ship rolling at sea, and then the
birds rocked back to an even keel; but although we thought the action
was clearly automatic, and were willing to learn, our teachers were too
far off to show us just how it was done, and we had to experiment for
ourselves.’
Chanute provided his multiple glider with a seat, but, since each
glide only occupied between eight and twelve seconds, there was
little possibility of the operator seating himself. With the multiple
glider a pair of horizontal bars provided rest for the arms, and
beyond these was a pair of vertical bars which the operator grasped
with his hands; beyond this, the operator was in no way attached to
the machine. He took, at the most, four running steps into the wind,
which launched him in the air, and thereupon he sailed into the wind
on a generally descending course. In the matter of descent Chanute
observed the sparrow and decided to imitate it. ‘When the latter,’
he says, ‘approaches the street, he throws his body back, tilts his
outspread wings nearly square to the course, and on the cushion of air
thus encountered he stops his speed and drops lightly to the ground.
So do all birds. We tried it with misgivings, but found it perfectly
effective. The soft sand was a great advantage, and even when the
experts were racing there was not a single sprained ankle.’
With the multiple winged glider some two to three hundred glides were
made without any accident either to the man or to the machine, and the
action was found so effective, the principle so sound, that full plans
were published for the benefit of any experimenters who might wish to
improve on this apparatus. The American _Aeronautical Annual_ for 1897
contains these plans; Chanute confessed that some movement on the part
of the operator was still required to control the machine, but it was
only a seventh or a sixth part of the movement required for control of
the Lilienthal type.
Chanute waxed enthusiastic over the possibilities of gliding,
concerning which he remarks that ‘There is no more delightful sensation
than that of gliding through the air. All the faculties are on the
alert, and the motion is astonishingly smooth and elastic. The machine
responds instantly to the slightest movement of the operator; the air
rushes by one’s ears; the trees and bushes flit away underneath, and
the landing comes all too quickly. Skating, sliding, and bicycling
are not to be compared for a moment to aerial conveyance, in which,
perhaps, zest is added by the spice of danger. For it must be
distinctly understood that there is constant danger in such preliminary
experiments. When this hazard has been eliminated by further evolution,
gliding will become a most popular sport.’
Later experiments proved that the biplane type of glider gave better
results than the rather cumbrous model consisting of five tiers of
planes. Longer and more numerous glides, to the number of seven to
eight hundred, were obtained, the rate of descent being about one in
six. The longest distance traversed was about 120 yards, but Chanute
had dreams of starting from a hill about 200 feet high, which would
have given him gliding flights of 1,200 feet. He remarked that ‘In
consequence of the speed gained by running, the initial stage of the
flight is nearly horizontal, and it is thrilling to see the operator
pass from thirty to forty feet overhead, steering his machine,
undulating his course, and struggling with the wind-gusts which whistle
through the guy wires. The automatic mechanism restores the angle of
advance when compromised by variations of the breeze; but when these
come from one side and tilt the apparatus, the weight has to be shifted
to right the machine ... these gusts sometimes raise the machine from
ten to twenty feet vertically, and sometimes they strike the apparatus
from above, causing it to descend suddenly. When sailing near the
ground, these vicissitudes can be counteracted by movements of the
body from three to four inches; but this has to be done instantly,
for neither wings nor gravity will wait on meditation. At a height
of three hundred or four hundred feet the regulating mechanism would
probably take care of these wind-gusts, as it does, in fact, for their
minor variations. The speed of the machine is generally about seventeen
miles an hour over the ground, and from twenty-two to thirty miles an
hour relative to the air. Constant effort was directed to keep down
the velocity, which was at times fifty-two miles an hour. This is
the purpose of the starting and gliding against the wind, which thus
furnishes an initial velocity without there being undue speed at the
landing. The highest wind we dared to experiment in blew at thirty-one
miles an hour; when the wind was stronger, we waited and watched the
birds.’
Chanute details an amusing little incident which occurred in the course
of experiment with the biplane glider. He says that ‘We had taken one
of the machines to the top of the hill, and loaded its lower wings
with sand to hold it while we went to lunch. A gull came strolling
inland, and flapped full-winged to inspect. He swept several circles
above the machine, stretched his neck, gave a squawk and went off.
Presently he returned with eleven other gulls, and they seemed to hold
a conclave about one hundred feet above the big new white bird which
they had discovered on the sand. They circled round after round, and
once in a while there was a series of loud peeps, like those of a rusty
gate, as if in conference, with sudden flutterings, as if a terrifying
suggestion had been made. The bolder birds occasionally swooped
downwards to inspect the monster more closely; they twisted their heads
around to bring first one eye and then the other to bear, and then they
rose again. After some seven or eight minutes of this performance,
they evidently concluded either that the stranger was too formidable
to tackle, if alive, or that he was not good to eat, if dead, and they
flew off to resume fishing, for the weak point about a bird is his
stomach.’
The gliders were found so stable, more especially the biplane form,
that in the end Chanute permitted amateurs to make trials under
guidance, and throughout the whole series of experiments not a single
accident occurred. Chanute came to the conclusion that any young,
quick, and handy man could master a gliding machine almost as soon
as he could get the hang of a bicycle, although the penalty for any
mistake would be much more severe.
At the conclusion of his experiments he decided that neither the
multiple plane nor the biplane type of glider was sufficiently
perfected for the application of motive power. In spite of the amount
of automatic stability that he had obtained he considered that there
was yet more to be done, and he therefore advised that every possible
method of securing stability and safety should be tested, first with
models, and then with full-sized machines; designers, he said, should
make a point of practice in order to make sure of the action, to
proportion and adjust the parts of their machine, and to eliminate
hidden defects. Experimental flight, he suggested, should be tried
over water, in order to break any accidental fall; when a series of
experiments had proved the stability of a glider, it would then be time
to apply motive power. He admitted that such a process would be both
costly and slow, but, he said, that ‘it greatly diminished the chance
of those accidents which bring a whole line of investigation into
contempt.’ He saw the flying machine as what it has, in fact, been; a
child of evolution, carried on step by step by one investigator after
another, through the stages of doubt and perplexity which lie behind
the realm of possibility, beyond which is the present day stage of
actual performance and promise of ultimate success and triumph over the
earlier, more cumbrous, and slower forms of the transport that we know.
[Illustration: Chanute biplane glider.]
Chanute’s monograph, from which the foregoing notes have been
comprised, was written soon after the conclusion of his series of
experiments. He does not appear to have gone in for further practical
work, but to have studied the subject from a theoretical view-point
and with great attention to the work done by others. In a paper
contributed in 1900 to the American _Independent_, he remarks that
‘Flying machines promise better results as to speed, but yet will be of
limited commercial application. They may carry mails and reach other
inaccessible places, but they cannot compete with railroads as carriers
of passengers or freight. They will not fill the heavens with commerce,
abolish custom houses, or revolutionise the world, for they will be
expensive for the loads which they can carry, and subject to too many
weather contingencies. Success is, however, probable. Each experimenter
has added something to previous knowledge which his successors can
avail of. It now seems likely that two forms of flying machines, a
sporting type and an exploration type, will be gradually evolved within
one or two generations, but the evolution will be costly and slow, and
must be carried on by well-equipped and thoroughly informed scientific
men; for the casual inventor, who relies upon one or two happy
inspirations, will have no chance of success whatever.’
Follows Professor John J. Montgomery, who, in the true American spirit,
describes his own experiments so well that nobody can possibly do it
better. His account of his work was given first of all in the American
Journal, _Aeronautics_, in January, 1909, and thence transcribed in
the English paper of the same name in May, 1910, and that account is
here copied word for word. It may, however, be noted first that as
far back as 1860, when Montgomery was only a boy, he was attracted to
the study of aeronautical problems, and in 1883 he built his first
machine, which was of the flapping-wing ornithopter type, and which
showed its designer, with only one experiment, that he must design some
other form of machine if he wished to attain to a successful flight.
Chanute details how, in 1884 and 1885, Montgomery built three gliders,
demonstrating the value of curved surfaces. With the first of these
gliders Montgomery copied the wing of a seagull; with the second he
proved that a flat surface was virtually useless, and with the third
he pivoted his wings as in the Antoinette type of power-propelled
aeroplane, proving to his own satisfaction that success lay in this
direction. His own account of the gliding flights carried out under his
direction is here set forth, being the best description of his work
that can be obtained:--
‘When I commenced practical demonstration in my work with aeroplanes
I had before me three points; first, equilibrium; second, complete
control; and third, long continued or soaring flight. In starting I
constructed and tested three sets of models, each in advance of the
other in regard to the continuance of their soaring powers, but all
equally perfect as to equilibrium and control. These models were tested
by dropping them from a cable stretched between two mountain tops, with
various loads, adjustments and positions. And it made no difference
whether the models were dropped upside down or any other conceivable
position, they always found their equilibrium immediately and glided
safely to earth.
‘Then I constructed a large machine patterned after the first model,
and with the assistance of three cowboy friends personally made a
number of flights in the steep mountains near San Juan (a hundred
miles distant). In making these flights I simply took the aeroplane
and made a running jump. These tests were discontinued after I put my
foot into a squirrel hole in landing and hurt my leg.
The following year I commenced the work on a larger scale, by engaging
aeronauts to ride my aeroplane dropped from balloons. During this
work I used five hot-air balloons and one gas balloon, five or six
aeroplanes, three riders--Maloney, Wilkie, and Defolco--and had sixteen
applicants on my list, and had a training station to prepare any when I
needed them.
‘Exhibitions were given in Santa Cruz, San Jose, Santa Clara, Oakland,
and Sacramento. The flights that were made, instead of being haphazard
affairs, were in the order of safety and development. In the first
flight of an aeronaut the aeroplane was so arranged that the rider had
little liberty of action, consequently he could make only a limited
flight. In some of the first flights, the aeroplane did little more
than settle in the air. But as the rider gained experience in each
successive flight I changed the adjustments, giving him more liberty of
action, so he could obtain longer flights and more varied movements in
the flights. But in none of the flights did I have the adjustments so
that the riders had full liberty, as I did not consider that they had
the requisite knowledge and experience necessary for their safety; and
hence, none of my aeroplanes were launched so arranged that the rider
could make adjustments necessary for a full flight.
‘This line of action caused a good deal of trouble with aeronauts or
riders, who had unbounded confidence and wanted to make long flights
after the first few trials; but I found it necessary, as they seemed
slow in comprehending the important elements and were willing to
take risks. To give them the full knowledge in these matters I was
formulating plans for a large starting station on the Mount Hamilton
Range from which I could launch an aeroplane capable of carrying two,
one of my aeronauts and myself, so I could teach him by demonstration.
But the disasters consequent on the great earthquake completely stopped
all my work on these lines. The flights that were given were only the
first of the series with aeroplanes patterned after the first model.
There were no aeroplanes constructed according to the two other models,
as I had not given the full demonstration of the workings of the first,
though some remarkable and startling work was done. On one occasion
Maloney, in trying to make a very short turn in rapid flight, pressed
very hard on the stirrup which gives a screw-shape to the wings, and
made a side somersault. The course of the machine was very much like
one turn of a corkscrew. After this movement the machine continued
on its regular course. And afterwards Wilkie, not to be outdone by
Maloney, told his friends he would do the same, and in a subsequent
flight made two side somersaults, one in one direction and the other in
an opposite, then made a deep dive and a long glide, and, when about
three hundred feet in the air, brought the aeroplane to a sudden stop
and settled to the earth. After these antics, I decreased the extent of
the possible change in the form of wing-surface, so as to allow only
straight sailing or only long curves in turning.
‘During my work I had a few carping critics that I silenced by this
standing offer: If they would deposit a thousand dollars I would cover
it on this proposition. I would fasten a 150 pound sack of sand in the
rider’s seat, make the necessary adjustments, and send up an aeroplane
upside down with a balloon, the aeroplane to be liberated by a time
fuse. If the aeroplane did not immediately right itself, make a flight,
and come safely to the ground, the money was theirs.
‘Now a word in regard to the fatal accident. The circumstances are
these: The ascension was given to entertain a military company in which
were many of Maloney’s friends, and he had told them he would give the
most sensational flight they ever heard of. As the balloon was rising
with the aeroplane, a guy rope dropping switched around the right wing
and broke the tower that braced the two rear wings and which also gave
control over the tail. We shouted Maloney that the machine was broken,
but he probably did not hear us, as he was at the same time saying,
“Hurrah for Montgomery’s airship,” and as the break was behind him,
he may not have detected it. Now did he know of the breakage or not,
and if he knew of it did he take a risk so as not to disappoint his
friends? At all events, when the machine started on its flight the rear
wings commenced to flap (thus indicating they were loose), the machine
turned on its back, and settled a little faster than a parachute. When
we reached Maloney he was unconscious and lived only thirty minutes.
The only mark of any kind on him was a scratch from a wire on the side
of his neck. The six attending physicians were puzzled at the cause
of his death. This is remarkable for a vertical descent of over 2,000
feet.’
The flights were brought to an end by the San Francisco earthquake in
April, 1906, which, Montgomery states, ‘Wrought such a disaster that
I had to turn my attention to other subjects and let the aeroplane
rest for a time.’ Montgomery resumed experiments in 1911 in California,
and in October of that year an accident brought his work to an end.
The report in the American _Aeronautics_ says that ‘a little whirlwind
caught the machine and dashed it head on to the ground; Professor
Montgomery landed on his head and right hip. He did not believe himself
seriously hurt, and talked with his year-old bride in the tent. He
complained of pains in his back, and continued to grow worse until he
died.’
IX
NOT PROVEN
The early history of flying, like that of most sciences, is replete
with tragedies; in addition to these it contains one mystery concerning
Clement Ader, who was well known among European pioneers in the
development of the telephone, and first turned his attention to the
problems of mechanical flight in 1872. At the outset he favoured the
ornithopter principle, constructing a machine in the form of a bird
with a wing-spread of twenty-six feet; this, according to Ader’s
conception, was to fly through the efforts of the operator. The result
of such an attempt was past question and naturally the machine never
left the ground.
A pause of nineteen years ensued, and then in 1886 Ader turned his
mind to the development of the aeroplane, constructing a machine of
bat-like form with a wing-spread of about forty-six feet, a weight of
eleven hundred pounds, and a steam-power plant of between twenty and
thirty horse-power driving a four-bladed tractor screw. On October 9th,
1890, the first trials of this machine were made, and it was alleged
to have flown a distance of one hundred and sixty-four feet. Whatever
truth there may be in the allegation, the machine was wrecked through
deficient equilibrium at the end of the trial. Ader repeated the
construction, and on October 14th, 1897, tried out his third machine
at the military establishment at Satory in the presence of the French
military authorities, on a circular track specially prepared for the
experiment. Ader and his friends alleged that a flight of nearly a
thousand feet was made; again the machine was wrecked at the end of the
trial, and there Ader’s practical work may be said to have ended, since
no more funds were forthcoming for the subsidy of experiments.
There is the bald narrative, but it is worthy of some amplification. If
Ader actually did what he claimed, then the position which the Wright
Brothers hold as first to navigate the air in a power-driven plane is
nullified. Although at this time of writing it is not a quarter of a
century since Ader’s experiment in the presence of witnesses competent
to judge on his accomplishment, there is no proof either way, and
whether he was or was not the first man to fly remains a mystery in the
story of the conquest of the air.
The full story of Ader’s work reveals a persistence and determination
to solve the problem that faced him which was equal to that of
Lilienthal. He began by penetrating into the interior of Algeria after
having disguised himself as an Arab, and there he spent some months in
studying flight as practised by the vultures of the district. Returning
to France in 1886 he began to construct the ‘Eole,’ modelling it, not
on the vulture, but in the shape of a bat. Like the Lilienthal and
Pilcher gliders this machine was fitted with wings which could be
folded; the first flight made, as already noted, on October 9th, 1890,
took place in the grounds of the chateau d’Amainvilliers, near Bretz;
two fellow-enthusiasts named Espinosa and Vallier stated that a flight
was actually made; no statement in the history of aeronautics has been
subject of so much question, and the claim remains unproved.
It was in September of 1891 that Ader, by permission of the Minister of
War, moved the ‘Eole’ to the military establishment at Satory for the
purpose of further trial. By this time, whether he had flown or not,
his nineteen years of work in connection with the problems attendant
on mechanical flight had attracted so much attention that henceforth
his work was subject to the approval of the military authorities, for
already it was recognised that an efficient flying machine would confer
an inestimable advantage on the power that possessed it in the event
of war. At Satory the ‘Eole’ was alleged to have made a flight of 109
yards, or, according to another account, 164 feet, as stated above, in
the trial in which the machine wrecked itself through colliding with
some carts which had been placed near the track--the root cause of this
accident, however, was given as deficient equilibrium.
Whatever the sceptics may say, there is reason for belief in the
accomplishment of actual flight by Ader with his first machine in the
fact that, after the inevitable official delay of some months, the
French War Ministry granted funds for further experiment. Ader named
his second machine, which he began to build in May, 1892, the ‘Avion,’
and--an honour which he well deserves--that name remains in French
aeronautics as descriptive of the power-driven aeroplane up to this day.
This second machine, however, was not a success, and it was not
until 1897 that the second ‘Avion,’ which was the third power-driven
aeroplane of Ader’s construction, was ready for trial. This was
fitted with two steam motors of twenty horse-power each, driving two
four-bladed propellers; the wings warped automatically: that is to say,
if it were necessary to raise the trailing edge of one wing on the
turn, the trailing edge of the opposite wing was also lowered by the
same movement; an undercarriage was also fitted, the machine running on
three small wheels, and levers controlled by the feet of the aviator
actuated the movement of the tail planes.
On October the 12th, 1897, the first trials of this ‘Avion’ were made
in the presence of General Mensier, who admitted that the machine made
several hops above the ground, but did not consider the performance as
one of actual flight. The result was so encouraging, in spite of the
partial failure, that, two days later, General Mensier, accompanied by
General Grillon, a certain Lieutenant Binet, and two civilians named
respectively Sarrau and Leaute, attended for the purpose of giving the
machine an official trial, over which the great controversy regarding
Ader’s success or otherwise may be said to have arisen.
[Illustration: Course of the Avion’s Flight, October 14, 1897.]
We will take first Ader’s own statement as set out in a very competent
account of his work published in Paris in 1910. Here are Ader’s own
words: ‘After some turns of the propellers, and after travelling a few
metres, we started off at a lively pace; the pressure-gauge registered
about seven atmospheres; almost immediately the vibrations of the rear
wheel ceased; a little later we only experienced those of the front
wheels at intervals. Unhappily, the wind became suddenly strong, and
we had some difficulty in keeping the “Avion” on the white line. We
increased the pressure to between eight and nine atmospheres, and
immediately the speed increased considerably, and the vibrations of the
wheels were no longer sensible; we were at that moment at the point
marked G in the sketch; the “Avion” then found itself freely supported
by its wings; under the impulse of the wind it continually tended to
go outside the (prepared) area to the right, in spite of the action of
the rudder. On reaching the point V it found itself in a very critical
position; the wind blew strongly and across the direction of the white
line which it ought to follow; the machine then, although still going
forward, drifted quickly out of the area; we immediately put over the
rudder to the left as far as it would go; at the same time increasing
the pressure still more, in order to try to regain the course. The
“Avion” obeyed, recovered a little, and remained for some seconds
headed towards its intended course, but it could not struggle against
the wind; instead of going back, on the contrary it drifted farther and
farther away. And ill-luck had it that the drift took the direction
towards part of the School of Musketry, which was guarded by posts and
barriers. Frightened at the prospect of breaking ourselves against
these obstacles, surprised at seeing the earth getting farther away
from under the “Avion,” and very much impressed by seeing it rushing
sideways at a sickening speed, instinctively we stopped everything.
What passed through our thoughts at this moment which threatened a
tragic turn would be difficult to set down. All at once came a great
shock, splintering, a heavy concussion: we had landed.’
Thus speaks the inventor; the cold official mind gives out a different
account, crediting the ‘Avion’ with merely a few hops, and to-day,
among those who consider the problem at all, there is a little group
which persists in asserting that to Ader belongs the credit of the
first power-driven flight, while a larger group is equally persistent
in stating that, save for a few ineffectual hops, all three wheels of
the machine never left the ground. It is past question that the ‘Avion’
was capable of power-driven flight; whether it achieved it or no
remains an unsettled problem.
[Illustration: Clement Ader’s ‘Avion,’ with wings partly folded.]
Ader’s work is negative proof of the value of such experiments as
Lilienthal, Pilcher, Chanute, and Montgomery conducted; these four set
to work to master the eccentricities of the air before attempting to
use it as a supporting medium for continuous flight under power; Ader
attacked the problem from the other end; like many other experimenters
he regarded the air as a stable fluid capable of giving such support to
his machine as still water might give to a fish, and he reckoned that
he had only to produce the machine in order to achieve flight. The
wrecked ‘Avion’ and the refusal of the French War Ministry to grant any
more funds for further experiment are sufficient evidence of the need
for working along the lines taken by the pioneers of gliding rather
than on those which Ader himself adopted.
Let it not be thought that in this comment there is any desire to
derogate from the position which Ader should occupy in any study of
the pioneers of aeronautical enterprise. If he failed, he failed
magnificently, and if he succeeded, then the student of aeronautics
does him an injustice and confers on the Brothers Wright an honour
which, in spite of the value of their work, they do not deserve. There
was one earlier than Ader, Alphonse Penaud, who, in the face of a
lesser disappointment than that which Ader must have felt in gazing on
the wreckage of his machine, committed suicide; Ader himself, rendered
unable to do more, remained content with his achievement, and with the
knowledge that he had played a good part in the long search which must
eventually end in triumph. Whatever the world might say, he himself was
certain that he had achieved flight. This, for him, was perforce enough.
Before turning to consideration of the work accomplished by the
Brothers Wright, and their proved conquest of the air, it is necessary
first to sketch as briefly as may be the experimental work of Sir (then
Mr) Hiram Maxim, who, in his book, _Artificial and Natural Flight_, has
given a fairly complete account of his various experiments. He began by
experimenting with models, with screw-propelled planes so attached to a
horizontal movable arm that when the screw was set in motion the plane
described a circle round a central point, and, eventually, he built a
giant aeroplane having a total supporting area of 1,500 square feet,
and a wing-span of fifty feet. It has been thought advisable to give
a fairly full description of the power plant used to the propulsion
of this machine in the section devoted to engine development. The
aeroplane, as Maxim describes it, had five long and narrow planes
projecting from each side, and a main or central plane of pterygoid
aspect. A fore and aft rudder was provided, and had all the auxiliary
planes been put in position for experimental work a total lifting
surface of 6,000 square feet could have been obtained. Maxim, however,
did not use more than 4,000 square feet of lifting surface even in his
later experiments; with this he judged the machine capable of lifting
slightly under 8,000 lbs. weight, made up of 600 lbs. water in the
boiler and tank, a crew of three men, a supply of naphtha fuel, and the
weight of the machine itself.
Maxim’s intention was, before attempting free flight, to get as much
data as possible regarding the conditions under which flight must
be obtained, by what is known in these days as ‘taxi-ing’--that is,
running the propellers at sufficient speed to drive the machine along
the ground without actually mounting into the air. He knew that he had
an immense lifting surface and a tremendous amount of power in his
engine even when the total weight of the experimental plant was taken
into consideration, and thus he set about to devise some means of
keeping the machine on the nine foot gauge rail track which had been
constructed for the trials. At the outset he had a set of very heavy
cast-iron wheels made on which to mount the machine, the total weight
of wheels, axles, and connections being about one and a half tons.
These were so constructed that the light flanged wheels which supported
the machine on the steel rails could be lifted six inches above the
track, still leaving the heavy wheels on the rails for guidance of
the machine. ‘This arrangement,’ Maxim states, ‘was tried on several
occasions, the machine being run fast enough to lift the forward end
off the track. However, I found considerable difficulty in starting
and stopping quickly on account of the great weight, and the amount of
energy necessary to set such heavy wheels spinning at a high velocity.
The last experiment with these wheels was made when a head wind was
blowing at the rate of about ten miles an hour. It was rather unsteady,
and when the machine was running at its greatest velocity, a sudden
gust lifted not only the front end, but also the heavy front wheels
completely off the track, and the machine falling on soft ground was
soon blown over by the wind.’
Consequently, a safety track was provided, consisting of squared pine
logs, three inches by nine inches, placed about two feet above the
steel way and having a thirty-foot gauge. Four extra wheels were fitted
to the machine on outriggers and so adjusted that, if the machine
should lift one inch clear of the steel rails, the wheels at the ends
of the outriggers would engage the under side of the pine trackway.
The first fully loaded run was made in a dead calm with 150 lbs. steam
pressure to the square inch, and there was no sign of the wheels
leaving the steel track. On a second run, with 230 lbs. steam pressure
the machine seemed to alternate between adherence to the lower and
upper tracks, as many as three of the outrigger wheels engaging at the
same time, and the weight on the steel rails being reduced practically
to nothing. In preparation for a third run, in which it was intended
to use full power, a dynamometer was attached to the machine and
the engines were started at 200 lbs. pressure, which was gradually
increased to 310 lbs per square inch. The incline of the track, added
to the reading of the dynamometer, showed a total screw thrust of 2,164
lbs. After the dynamometer test had been completed, and everything had
been made ready for trial in motion, careful observers were stationed
on each side of the track, and the order was given to release the
machine. What follows is best told in Maxim’s own words:--
‘The enormous screw-thrust started the engine so quickly that it nearly
threw the engineers off their feet, and the machine bounded over
the track at a great rate. Upon noticing a slight diminution in the
steam pressure, I turned on more gas, when almost instantly the steam
commenced to blow a steady blast from the small safety valve, showing
that the pressure was at least 320 lbs. in the pipes supplying the
engines with steam. Before starting on this run, the wheels that were
to engage the upper track were painted, and it was the duty of one of
my assistants to observe these wheels during the run, while another
assistant watched the pressure gauges and dynagraphs. The first part
of the track was up a slight incline, but the machine was lifted clear
of the lower rails and all of the top wheels were fully engaged on the
upper track when about 600 feet had been covered. The speed rapidly
increased, and when 900 feet had been covered, one of the rear axle
trees, which were of two-inch steel tubing, doubled up and set the
rear end of the machine completely free. The pencils ran completely
across the cylinders of the dynagraphs and caught on the underneath
end. The rear end of the machine being set free, raised considerably
above the track and swayed. At about 1,000 feet, the left forward wheel
also got clear of the upper track, and shortly afterwards the right
forward wheel tore up about 100 feet of the upper track. Steam was at
once shut off and the machine sank directly to the earth, embedding
the wheels in the soft turf without leaving any other marks, showing
most conclusively that the machine was completely suspended in the
air before it settled to the earth. In this accident, one of the pine
timbers forming the upper track went completely through the lower
framework of the machine and broke a number of the tubes, but no damage
was done to the machinery except a slight injury to one of the screws.’
It is a pity that the multifarious directions in which Maxim turned
his energies did not include further development of the aeroplane, for
it seems fairly certain that he was as near solution of the problem
as Ader himself, and, but for the holding-down outer track, which was
really the cause of his accident, his machine would certainly have
achieved free flight, though whether it would have risen, flown and
alighted, without accident, is matter for conjecture.
The difference between experiments with models and with full-sized
machines is emphasised by Maxim’s statement to the effect that with
a small apparatus for ascertaining the power required for artificial
flight, an angle of incidence of one in fourteen was most advantageous,
while with a large machine he found it best to increase his angle to
one in eight in order to get the maximum lifting effect on a short
run at a moderate speed. He computed the total lifting effect in the
experiments which led to the accident as not less than 10,000 lbs., in
which is proof that only his rail system prevented free flight.
X
SAMUEL PIERPOINT LANGLEY
Langley was an old man when he began the study of aeronautics, or, as
he himself might have expressed it, the study of aerodromics, since he
persisted in calling the series of machines he built ‘Aerodromes,’ a
word now used only to denote areas devoted to use as landing spaces for
flying machines; the Wright Brothers, on the other hand, had the great
gift of youth to aid them in their work. Even so it was a great race
between Langley, aided by Charles Manly, and Wilbur and Orville Wright,
and only the persistent ill-luck which dogged Langley from the start
to the finish of his experiments gave victory to his rivals. It has
been proved conclusively in these later years of accomplished flight
that the machine which Langley launched on the Potomac River in October
of 1903 was fully capable of sustained flight, and only the accidents
incurred in launching prevented its pilot from being the first man to
navigate the air successfully in a power-driven machine.
The best account of Langley’s work is that diffused throughout a
weighty tome issued by the Smithsonian Institution, entitled the
_Langley Memoir on Mechanical Flight_, of which about one-third was
written by Langley himself, the remainder being compiled by Charles
M. Manly, the engineer responsible for the construction of the first
radial aero engine, and chief assistant to Langley in his experiments.
To give a twentieth of the contents of this volume in the present
short account of the development of mechanical flight would far exceed
the amount of space that can be devoted even to so eminent a man in
aeronautics as S. P. Langley, who, apart from his achievement in the
construction of a power-driven aeroplane really capable of flight,
was a scientist of no mean order, and who brought to the study of
aeronautics the skill of the trained investigator allied to the
inventive resource of the genius.
That genius exemplified the antique saw regarding the infinite capacity
for taking pains, for the Langley Memoir shows that as early as 1891
Langley had completed a set of experiments, lasting through years,
which proved it possible to construct machines giving such a velocity
to inclined surfaces that bodies indefinitely heavier than air could
be sustained upon it and propelled through it at high speed. For full
account (very full) of these experiments, and of a later series leading
up to the construction of a series of ‘model aerodromes’ capable of
flight under power, it is necessary to turn to the bulky memoir of
Smithsonian origin.
[Illustration: Quarter-size model, Langley Aerodrome, in flight, 8th
August, 1903.
Langley Memoir on Mechanical Flight, Smithsonian Institution,
Washington.]
The account of these experiments as given by Langley himself reveals
the humility of the true investigator. Concerning them, Langley remarks
that, ‘Everything here has been done with a view to putting a trial
aerodrome successfully in flight within a few years, and thus giving an
early demonstration of the only kind which is conclusive in the eyes of
the scientific man, as well as of the general public--a demonstration
that mechanical flight is possible--by actually flying. All that has
been done has been with an eye principally to this immediate result,
and all the experiments given in this book are to be considered only
as approximations to exact truth. All were made with a view, not to
some remote future, but to an arrival within the compass of a few years
at some result in actual flight that could not be gainsaid or mistaken.’
With a series of over thirty rubber-driven models Langley demonstrated
the practicability of opposing curved surfaces to the resistance of the
air in such a way as to achieve flight, in the early nineties of last
century; he then set about finding the motive power which should permit
of the construction of larger machines, up to man-carrying size. The
internal combustion engine was then an unknown quantity, and he had to
turn to steam, finally, as the propulsive energy for his power plant.
The chief problem which faced him was that of the relative weight and
power of his engine; he harked back to the Stringfellow engine of 1868,
which in 1889 came into the possession of the Smithsonian Institution
as a historical curiosity. Rightly or wrongly Langley concluded on
examination that this engine never had developed and never could
develop more than a tenth of the power attributed to it; consequently
he abandoned the idea of copying the Stringfellow design and set about
making his own engine.
How he overcame the various difficulties that faced him and constructed
a steam-engine capable of the task allotted to it forms a story in
itself, too long for recital here. His first power-driven aerodrome of
model size was begun in November of 1891, the scale of construction
being decided with the idea that it should be large enough to carry an
automatic steering apparatus which would render the machine capable of
maintaining a long and steady flight. The actual weight of the first
model far exceeded the theoretical estimate, and Langley found that a
constant increase of weight under the exigencies of construction was
a feature which could never be altogether eliminated. The machine was
made principally of steel, the sustaining surfaces being composed of
silk stretched from a steel tube with wooden attachments. The first
engines were the oscillating type, but were found deficient in power.
This led to the construction of single-acting inverted oscillating
engines with high and low pressure cylinders, and with admission and
exhaust ports to avoid the complication and weight of eccentric and
valves. Boiler and furnace had to be specially designed; an analysis
of sustaining surfaces and the settlement of equilibrium while in
flight had to be overcome, and then it was possible to set about the
construction of the series of model aerodromes and make test of their
‘lift.’
By the time Langley had advanced sufficiently far to consider it
possible to conduct experiments in the open air, even with these
models, he had got to his fifth aerodrome, and to the year 1894.
Certain tests resulted in failure, which in turn resulted in further
modifications of design, mainly of the engines. By February of 1895
Langley reported that under favourable conditions a lift of nearly
sixty per cent of the flying weight was secured, but although this was
much more than was required for flight, it was decided to postpone
trials until two machines were ready for the test. May, 1896, came
before actual trials were made, when one machine proved successful and
another, a later design, failed. The difficulty with these models was
that of securing a correct angle for launching; Langley records how, on
launching one machine, it rose so rapidly that it attained an angle of
sixty degrees and then did a tail slide into the water with its engines
working at full speed, after advancing nearly forty feet and remaining
in the air for about three seconds. Here, Langley found that he had
to obtain greater rigidity in his wings, owing to the distortion of
the form of wing under pressure, and how he overcame this difficulty
constitutes yet another story too long for the telling here.
Field trials were first attempted in 1893, and Langley blamed his
launching apparatus for their total failure. There was a brief, but at
the same time practical, success in model flight in 1894, extending
to between six and seven seconds, but this only proved the need for
strengthening of the wing. In 1895 there was practically no advance
toward the solution of the problem, but the flights of May 6th and
November 28th, 1896, were notably successful. A diagram given in
Langley’s memoir shows the track covered by the aerodrome on these two
flights; in the first of them the machine made three complete circles,
covering a distance of 3,200 feet; in the second, that of November
28th, the distance covered was 4,200 feet, or about three-quarters of a
mile, at a speed of about thirty miles an hour.
These achievements meant a good deal; they proved mechanically
propelled flight possible. The difference between them and such
experiments as were conducted by Clement Ader, Maxim, and others,
lay principally in the fact that these latter either did or did not
succeed in rising into the air once, and then, either willingly or by
compulsion, gave up the quest, while Langley repeated his experiments
and thus attained to actual proof of the possibilities of flight.
Like these others, however, he decided in 1896 that he would not
undertake the construction of a large man-carrying machine. In addition
to a multitude of actual duties, which left him practically no time
available for original research, he had as an adverse factor fully
ten years of disheartening difficulties in connection with his model
machines. It was President McKinley who, by requesting Langley to
undertake the construction and test of a machine which might finally
lead to the development of a flying machine capable of being used in
warfare, egged him on to his final experiment. Langley’s acceptance
of the offer to construct such a machine is contained in a letter
addressed from the Smithsonian Institution on December 12th, 1898,
to the Board of Ordnance and Fortification of the United States War
Department; this letter is of such interest as to render it worthy of
reproduction:--
‘Gentlemen,--In response to your invitation I repeat what I had the
honour to say to the Board--that I am willing, with the consent of
the Regents of this Institution, to undertake for the Government the
further investigation of the subject of the construction of a flying
machine on a scale capable of carrying a man, the investigation to
include the construction, development and test of such a machine under
conditions left as far as practicable in my discretion, it being
understood that my services are given to the Government in such time
as may not be occupied by the business of the Institution, and without
charge.
‘I have reason to believe that the cost of the construction will come
within the sum of $50,000·00, and that not more than one-half of that
will be called for in the coming year.
‘I entirely agree with what I understand to be the wish of the Board
that privacy be observed with regard to the work, and only when it
reaches a successful completion shall I wish to make public the fact of
its success.
‘I attach to this a memorandum of my understanding of some points of
detail in order to be sure that it is also the understanding of the
Board, and I am, gentlemen, with much respect, your obedient servant,
S. P. Langley.’
One of the chief problems in connection with the construction of
a full-sized apparatus was that of the construction of an engine,
for it was realised from the first that a steam power plant for a
full-sized machine could only be constructed in such a way as to make
it a constant menace to the machine which it was to propel. By this
time (1898) the internal combustion engine had so far advanced as
to convince Langley that it formed the best power plant available.
A contract was made for the delivery of a twelve horse-power engine
to weigh not more than a hundred pounds, but this contract was never
completed, and it fell to Charles M. Manly to design the five-cylinder
radial engine, of which a brief account is included in the section of
this work devoted to aero engines, as the power plant for the Langley
machine.
The history of the years 1899 to 1903 in the Langley series of
experiments contains a multitude of detail far beyond the scope of
this present study, and of interest mainly to the designer. There were
frames, engines, and propellers, to be considered, worked out, and
constructed. We are concerned here mainly with the completed machine
and its trials. Of these latter it must be remarked that the only two
actual field trials which took place resulted in accidents due to
the failure of the launching apparatus, and not due to any inherent
defect in the machine. It was intended that these two trials should
be the first of a series, but the unfortunate accidents, and the fact
that no further funds were forthcoming for continuance of experiments,
prevented Langley’s success, which, had he been free to go through as
he intended with his work, would have been certain.
The best brief description of the Langley aerodrome in its final form,
and of the two attempted trials, is contained in the official report of
Major M. M. Macomb of the United States Artillery Corps, which report
is here given in full:--
REPORT
Experiments with working models which were concluded August 8 last
having proved the principles and calculations on which the design
of the Langley aerodrome was based to be correct, the next step
was to apply these principles to the construction of a machine
of sufficient size and power to permit the carrying of a man,
who could control the motive power and guide its flight, thus
pointing the way to attaining the final goal of producing a machine
capable of such extensive and precise aerial flight, under normal
atmospheric conditions, as to prove of military or commercial
utility.