A History of Aeronautics
by
E. Charles Vivian
Part 2 out of 8
least those were my ideas at the time, but little did I think
how soon it was to be realised. I soon found, before I had time
to introduce the spark, a drooping in the wings, a flagging in
all the parts. In less than ten minutes the machine was
saturated with wet from a deposit of dew, so that anything like
a trial was impossible by night. I did not consider we could get
the silk tight and rigid enough. Indeed, the framework
altogether was too weak. The steam-engine was the best part.
Our want of success was not for want of power or sustaining
surface, but for want of proper adaptation of the means to the
end of the various parts.'
Henson, who had spent a considerable amount of money in these
experimental constructions, consoled himself for failure by
venturing into matrimony; in 1849 he went to America, leaving
Stringfellow to continue experimenting alone. From 1846 to 1848
Stringfellow worked on what is really an epoch-making item in
the history of aeronautics--the first engine-driven aeroplane
which actually flew. The machine in question had a 10 foot
span, and was 2 ft. across in the widest part of the wing; the
length of tail was 3 ft. 6 ins., and the span of tail in the
widest part 22 ins., the total sustaining area being about 14
sq. ft. The motive power consisted of an engine with a cylinder
of three-quarter inch diameter and a two-inch stroke; between
this and the crank shaft was a bevelled gear giving three
revolutions of the propellers to every stroke of the engine; the
propellers, right and left screw, were four-bladed and 16 inches
in diameter. The total weight of the model with engine was 8
lbs. Its successful flight is ascribed to the fact that
Stringfellow curved the wings, giving them rigid front edges and
flexible trailing edges, as suggested long before both by Da
Vinci and Borelli, but never before put into practice.
Mr F. J. Stringfellow, in the pamphlet quoted above, gives the
best account of the flight of this model: 'My father had
constructed another small model which was finished early in
1848, and having the loan of a long room in a disused lace
factory, early in June the small model was moved there for
experiments. The room was about 22 yards long and from 10 to 12
ft. high.... The inclined wire for starting the machine occupied
less than half the length of the room and left space at the end
for the machine to clear the floor. In the first experiment the
tail was set at too high an angle, and the machine rose too
rapidly on leaving the wire. After going a few yards it slid
back as if coming down an inclined plane, at such an angle that
the point of the tail struck the ground and was broken. The
tail was repaired and set at a smaller angle. The steam was
again got up, and the machine started down the wire, and, upon
reaching the point of self-detachment, it gradually rose until
it reached the farther end of the room, striking a hole in the
canvas placed to stop it. In experiments the machine flew well,
when rising as much as one in seven. The late Rev. J. Riste,
Esq., lace manufacturer, Northcote Spicer, Esq., J. Toms, Esq.,
and others witnessed experiments. Mr Marriatt, late of the San
Francisco News Letter brought down from London Mr Ellis, the
then lessee of Cremorne Gardens, Mr Partridge, and Lieutenant
Gale, the aeronaut, to witness experiments. Mr Ellis offered to
construct a covered way at Cremorne for experiments. Mr
Stringfellow repaired to Cremorne, but not much better
accommodations than he had at home were provided, owing to
unfulfilled engagement as to room. Mr Stringfellow was
preparing for departure when a party of gentlemen unconnected
with the Gardens begged to see an experiment, and finding them
able to appreciate his endeavours, he got up steam and started
the model down the wire. When it arrived at the spot where it
should leave the wire it appeared to meet with some obstruction,
and threatened to come to the ground, but it soon recovered
itself and darted off in as fair a flight as it was possible to
make at a distance of about 40 yards, where it was stopped by
the canvas.
'Having now demonstrated the practicability of making a
steam-engine fly, and finding nothing but a pecuniary loss and
little honour, this experimenter rested for a long time,
satisfied with what he had effected. The subject, however, had
to him special charms, and he still contemplated the renewal of
his experiments.'
It appears that Stringfellow's interest did not revive
sufficiently for the continuance of the experiments until the
founding of the Aeronautical Society of Great Britain in 1866.
Wenham's paper on Aerial Locomotion read at the first meeting of
the Society, which was held at the Society of Arts under the
Presidency of the Duke of Argyll, was the means of bringing
Stringfellow back into the field. It was Wenham's suggestion,
in the first place, that monoplane design should be abandoned
for the superposition of planes; acting on this suggestion
Stringfellow constructed a model triplane, and also designed a
steam engine of slightly over one horse-power, and a one
horse-power copper boiler and fire box which, although capable
of sustaining a pressure of 500 lbs. to the square inch, weighed
only about 40 lbs.
Both the engine and the triplane model were exhibited at the
first Aeronautical Exhibition held at the Crystal Palace in
1868. The triplane had a supporting surface of 28 sq. ft.;
inclusive of engine, boiler, fuel, and water its total weight
was under 12 lbs. The engine worked two 21 in. propellers at
600 revolutions per minute, and developed 100 lbs. steam
pressure in five minutes, yielding one-third horse-power. Since
no free flight was allowed in the Exhibition, owing to danger
from fire, the triplane was suspended from a wire in the nave of
the building, and it was noted that, when running along the
wire, the model made a perceptible lift.
A prize of L100 was awarded to the steam engine as the lightest
steam engine in proportion to its power. The engine and model
together may be reckoned as Stringfellow's best achievement. He
used his L100 in preparation for further experiments, but he
was now an old man, and his work was practically done. Both the
triplane and the engine were eventually bought for the
Washington Museum; Stringfellow's earlier models, together with
those constructed by him in conjunction with Henson, remain in
this country in the Victoria and Albert Museum.
John Stringfellow died on December 13th, 1883. His place in the
history of aeronautics is at least equal to that of Cayley, and
it may be said that he laid the foundation of such work as was
subsequently accomplished by Maxim, Langley, and their fellows.
It was the coming of the internal combustion engine that
rendered flight practicable, and had this prime mover been
available in John Stringfellow's day the Wright brothers'
achievement might have been antedated by half a century.
V. WENHAM, LE BRIS, AND SOME OTHERS
There are few outstanding events in the development of
aeronautics 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 I
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 13 1/2 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
practice 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 recipro-cating 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 aero-dynamic
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 Aerienne,
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.
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 Lilenthal (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
practice 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,' [*] gives an excellent short summary of
Lilienthal's experiments, from which the following extracts are
taken:--
[*] Aeronautical Classes, No. 5. Royal Aeronautical Society's
publications.
'At first Lilienthal used to experiment by jumping off a
springboard with a good run. Then he took to practicing 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 practicing ground;
for practicing 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 practice 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
practicing 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.[*]
[*] Aeronautical Classes, No. 5. Royal Aeronautical Society
publications.
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.
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 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.
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 e 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.
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,
Oaklands, 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 wingspread 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 practiced
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
deserve--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 under-carriage 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.
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.
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.
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
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