OCTAVE CHANUTE'S GLIDING EXPERIMENTS.
An ADDRESS* by OCTAVE CHANUTE, C. E., Mem. W. S. E.
(* Illustrated by lantern slides.)
Delivered 20th of October, 1897.
With remarks by Augustus Herring.
Published in the
Journal of the Western Society of Engineers, Vol.2, 1897. XX.
(This page contains a number of images - please allow them to load.)
Click on the images for a larger picture.
Mr. Chanute stated in beginning that when, in 1891, Professor Langley, the eminent
astronomer, and the Secretary of the Smithsonian Institution, published his important
work, "Experiments in Aerodynamics," the closing paragraph of the summary
was as follows: "I wish, however, to put on record my belief, that the time
has come for these questions (i. e., those of aerodynamics and aerial navigation)
to engage the serious attention not only of engineers, but of all interested in
the possibly near practical solution of a problem, one of the most important in
its consequences of any which has ever presented itself in mechanics; for this solution,
it is here shown, cannot longer be considered beyond our capacity to reach."
Mr. Chanute continued that it did not seem to the general public then, and it possibly
might not seem now, as if a commercial and practical flying machine was an achievement
to be expected in the near future; yet it did seem opportune for an engineer approaching
the end of his professional career to devote some of his leisure to the investigation
of the laws which must be here after observed by other engineers in compassing the
navigation of the air. He therefore took up the question; and believing that the
surest method is first to study past failures in a novel undertaking, he made an
investigation of the records of all the experiments, which had been tried during
the last two or three hundred years, in the endeavor to imitate the birds. This
resulted in a number of technical articles which swelled into a book, in which the
attempt was made to eliminate the causes of each failure; for up to that time there
had been nothing but failures.
He said he had hitherto abstained from addressing his fellow engineers on the subject,
as some might deem it premature, but he had become gradually convinced, not only
through investigation but through practical experiment, that it was not only possible
but almost certain that man will eventually be enabled to make his way through and
on the air by dynamic means, although it might require a considerable and long process
of evolution to do so. This evolution was now in progress, and very great advance
has recently been accomplished. It chanced that about the year 1888, a number of
able men, in various parts of the world, simultaneously took up the question, and
the progress which they have made is already greater than that previously achieved
during the past two or three centuries. Those men were Mr. Maxim, an American in
England, Professor Langley in this country, Mr. Hargrave in New South Wales, and
Mr. Lilienthal in Germany. They investigated afresh the laws which underlie the
possible solution of the problem of flight, and the results of their labors will
probably best appear from a discussion of the various elements of that problem.
These elements number ten at least, and may be considered as so many subsidiary
problems, each to be solved separately, perhaps in more ways than one, and those
solutions then to be combined into a harmonious whole. They may be stated as follows:
1st. THE SUPPORTING POWER AND RESISTANCE OF AIR
This first problem is the foundation of the whole subject, and, singularly enough,
it is only within the last six years that it has been settled beyond question what
is the true measure of those properties of air when meeting a surface at an oblique
angle of incidence. Sir Isaac Newton gave by implication from his proposition XXXIV,
Book 2 of the Principia, a law which has variously been interpreted as meaning that
normal fluid pressures vary as the sine, or the square of the sine of oblique incidence.
These formulae are today still taught in the schools, and found in text books, although
experiments have shown that at very acute angles they give from one-tenth to one-twentieth
of the true results. Engineers make current use of them in calculating pressures
upon roofs, and upon parts of bridges struck obliquely by the wind, while with later
knowledge it can be shown that a wind gust deflected upward under the floor of a
bridge, even so little as 5 or 10 degrees, produces such a lifting effect as to
account for the blowing off of superstructures hitherto accounted as inexplicable.
In point of fact, Professor Langley's experiments showed that oblique air pressures
varied not as the sine, or the square of the sine of incidence, but, approximately
as indicated in the empirical formula proposed by Col. Duchemin about 1828, in which
the relation between the rectangular normal pressure and the oblique normal pressure
is represented by:
2 Sine a
P = P' x -------------
In which P = the oblique pressure,
P' = The rectangular pressure,
a = The angle of incidence.
This applies exclusively to planes or flat surfaces, while Lilienthal has shown
by experiment that curved surfaces presented with their concave side to the wind
afford still greater pressures, these being from twelve times to four times the
normal pressures obtaining upon planes at angles between 1 and 5 degrees, which
are those most favorable for flight. Thus it is that we are now enabled to calculate
with some confidence the support which may be obtained by gliding at any given speed
upon the air, and the power required to overcome the resistance. An eminent French
mathematician, at the beginning of this century, calculated that a swallow, weighing
six-tenths ounces, expended in full flight no less than one-thirteenth of a horse-power.
This calculation was evidently erroneous. It would have implied that the weight
of a man, say 150 pounds, would require the expenditure of something like 300 horse-power
to sustain it in the air, but calculations of the power really required could not
be made with confidence until the recent labors of Professor Langley, confirmed
as they have been by those of Mr. Maxim, and the still more encouraging coefficients
for concave surfaces obtained by Lilienthal and in the experiments which were to
be presently described.
2d. THE MOTOR, ITS CHARACTER AND ITS ENERGY.
This second problem, now nearly solved, was thought until five years ago to be still
more difficult than the obtaining of supporting power from the air. It was known
that the motor muscles of birds, though possessing but little more tensile strength
than those of land animals, gave out energy at a much more rapid rate, so that it
was variously estimated that bird machinery (muscles) weighed from 5 to 20 pounds
for one horse-power exerted. Upon investigation in 1890, it was found that the lightest
steam engines then in use were those in launches and weighed 60 pounds per horse-power,
that the lightest petroleum engines weighed 88 pounds per horse-power, while the
lightest electric motor weighed 130 pounds, and the lightest storage battery and
dynamo weighed some 200 pounds per horse-power hour. Since then the advance has
been very great. Mr. Maxim has produced a steamplant of 360 horse-power which weighs
about 8 pounds per horse-power. Professor Langley has built an engine and boiler
which weighs 7 pounds and exerts one horse-power, while Mr. Hargrave has constructed
a steam engine weighing about 10 pounds to the horse-power. Almost as great advances
have been accomplished with petroleum motors, which possess the great merit of dispensing
with a boiler, so that for the first time the realization of a sufficiently light
motor for a dynamic flying machine seems to be within sight. It now seems probable
that this will be accomplished with a petroleum engine when the eccentricities now
inherent to that class of unperfected motors have been over come in practice.
3d. THE INSTRUMENT FOR OBTAINING PROPULSION.
The third question relates to the device through which adequate thrust shall be
obtained by action upon the air. All sorts of contrivances have been proposed; reaction
jets of steam or of compressed air, the explosion of gunpowder or even nitro-glycerine,
feathering paddle wheels of varied design, oscillating fins acting like the tails
of fishes, flapping elastic wings like the pinions of birds, and the rotating screw.
Mr. Maxim and Professor Langley have made many experiments to determine the best
form, speed and pitch of the screw to obtain thrust from the air, and have materially
improved that instrument, which, to reason from analogy in land and water transportation,
seems likely to prove the best device, but both Mr. Hargrave and Mr. Lilienthal
have obtained very favorable results with the flapping pinion, which requires no
intervening machinery to change the reciprocating action of a piston into a rotary
motion, and it seems perhaps possible that success in artificial flight may be obtained
with either or both devices.
4th. THE FORM AND KIND OF THE APPARATUS.
This fourth question has elicited great divergence of views among the designers
of flying machines. Almost numberless projects have been advanced, but they can
all be classified under three heads. 1st. Wings to sustain and propel. 2d. Rotating
screws to lift and propel, and 3d, aeroplanes or aerocurves, to consist of fixed
surfaces driven by some kind of propelling instrument. The first two have been the
first to be proposed and experimented with. They have many warm advocates at the
present time, but the practical experiments made within the last five years seem
to indicate that success will first be achieved with aeroplanes, or to state it
more accurately, by coining a new word, with aerocurves, which have been shown by
Lilienthal to furnish much greater lifting reactions. The following table, in which
the weight of the operator of a one-man machine is included with the weight of the
apparatus, approximately indicates the comparative merit which our present knowledge
enables us to assign theoretically to these three varieties of flying machines.
Comparative efficiency of various forms.
Kind of Apparatus
available for motor.
weight of motor per
17 per cent
10 per cent
17 per cent
It will be noticed that this involves motors which shall be very light in proportion
to their output of energy, and that the fuel and other supplies must also be included
in the weights above given, but yet that the desired results for aerocurves at least
are now almost in sight.
5th THE EXTENT OF THE SUSTAINING SURFACES.
The fifth problem, relating to the extent of surface required to support the weight
of a man, has caused in the past active controversy and gathering of data. It was
perceived that in consequence of the law inherent to solids, the surfaces will increase
as the squares, and the weights as the cubes of the homologous dimensions; it might
well be that the additional relative weight due to the greater leverage should make
it impossible to compass any larger flying machine than existing birds. Indeed,
it is not so long ago that a distinguished scientist published an article in which
he flatly took the ground that an artificial flying machine was impossible for three
reasons: 1. That Nature, with her utmost effort, had failed to produce a flying
animal of more than fifty pounds in weight. 2. That the animal machine was far more
effective than any that man may hope to make. 3. That the weight of any artificial
flying machine could not be less, including fuel and engineer, than 300 or 400 pounds.
These assertions have since been modified, but the author still holds that the possible
limit of weight cannot be pushed much, if at all, beyond 100 pounds of machine and
In point of fact, flying creatures vary in extent of supporting surface from about
40 square feet to the pound in the butterfly, to an area of 44-100 square feet to
the pound in the duck. The amount required depends upon the speed of the creature's
flight, the larger soaring birds generally spreading about one square foot or less
to the pound, while the experiments of Lilienthal, as well as those to be hereafter
described, have demonstrated that a man's weight can be well sustained, at 22 to
25 miles an hour, by an apparatus spreading three-quarters of a square foot to the
pound, and that this apparatus need not weigh more than from 23 to 36 pounds, without
motor or propeller, so that if the latter weigh some 60 pounds more, we may fairly
expect to compass a dynamic machine with a weight of about 100 pounds, carrying
a man of about 150 pounds, upon sustaining surfaces of rather less than 200 square
feet in area.
6th. THE MATERIAL AND TEXTURE OF THE APPARATUS.
- The sixth question relates to
the material to be selected for the framing of the machine, for the motor, and to
the texture of the sustaining surfaces. Nature accomplishes her purposes with bone,
flesh and feathers, but man has at his command metals, fuel and textile fabrics.
Many hopes were expressed some years ago, when aluminum first became a commercial
metal, that it was about to solve the problem of aerial navigation. Later investigations
have developed the fact that aluminum is as yet inferior to steel per unit of weight.
It is lighter, but it is also weaker. For a beginning wood will do very well. It
is a fact, realized by few engineers, that the best woods, so long as they remain
undecayed, are actually stronger in proportion to their weight than the ordinary
grades of steel. Wood is easily and cheaply procured and shaped, and whatever success
has hitherto been had in gliding flight has been accomplished with wooden frames
covered with textile fabrics. The latter are probably inferior in efficiency to
the ribbed surface of feathers, as quite recent experiments tend to show, but they
will answer for a beginning.
Thus we see that six out of the ten subsidiary problems involved in the general
question have been approximately solved. Not all, but most of this has been accomplished
within the last few years. The remaining four problems are more difficult of solution,
but even towards this, gratifying advance has been made.
7th. THE MAINTENANCE OF THE EQUILIBRIUM.
The seventh problem relates to the stability of the apparatus in the air, and especially
in a wind. This equilibrium must be maintained at all angles of incidence and under
all conditions of flight and of wind, in rising, in sailing and in coming down.
The first requisite for this is that the center of gravity shall constantly be in
a vertical line with the center of pressure, and unfortunately the latter is almost
constantly varying with the relative wind, with the speed and with the angle of
incidence. It is a peculiarity of air pressures, ascertained by experiment, that
as the angle of incidence changes, the position of the resultant center of pressure
also changes. When air meets a surface at right angles, the center of pressure coincides
with the center of that surface, but when the angle becomes more acute, the center
of pressure moves forward until it approaches a position about one-fifth of the
distance back of the front edge on a plane. This movement is approximately expressed
by what is known as Joessel's formula for square planes:
C = (0.2 +0.3 Sin a) L.
C= The distance from the front edge.
L= The whole length fore and aft.
a = The angle of incidence.
This formula is found not to be accurate for oblong planes, and even not strictly
true for square planes, but it is understood that recent experiments are likely
to produce a more accurate formula for planes. The great need, however, is for a
formula which shall accurately express the movements of the center of pressure on
concavo-convex surfaces. They are known to present some curious anomalies, but no
physicist, so far as is known, has yet reduced them to the reign of law. The problem
of stability may be said to have been very considerably advanced. The experiments
hereinafter to be described were undertaken with the sole view of evolving the solution
of this question, for it is held to be of the very first importance. Far more so
than seems to be realized by experimenters; for until automatic equilibrium is secured,
and safety is ensured thereby, under all circumstances, it will be exceedingly dangerous
to proceed to apply a motor and a propeller. Birds preserve their balance by instinct,
by skill acquired through long evolution and tentative practice. Man will have to
work out this problem thoroughly, even to the temporary disregard of the others,
if he is ever to make his way safely upon the air.
8th. THE GUIDANCE IN ANY DESIRED DIRECTION.
The eighth problem relates to the steering. It has been generally supposed that
this would be best effected by horizontal and vertical rudders, but the experiments
of Lilienthal, and those to be here described, have shown that slight changes in
the position of the center of gravity are more immediate and effective. This problem
cannot be said to be fully worked out, but it is not that a good deal of experimenting
will be required, and that such experiments will be fraught with danger. He had
nevertheless advised in his writings, and in an article in the Engineering Magazine
for April, 1896, that experiments be carried on preferably with full sized machines,
carrying a man, as the more fruitful and instructive method. This was good advice,
but it might prove dangerous for others to follow. He therefore deemed it desirable
that he should ascertain himself how much of risk this involved, if made with due
care and precaution.
It was not the intention, in these experiments, to seek to invent a flying machine,
although that impression may have been conveyed by some of the newspaper notices
of them. The intention was mainly to study the seventh problem-the maintenance of
the equilibrium-which it was hoped to gain automatically. This it was expected to
do by reversing the method of Lilienthal, who moved his bodily weight to bring back
the center of gravity under the center of pressure, as fast as the latter shifted
from any cause. It had occurred to Mr. Chanute that it might be preferable to provide
moving mechanism within the apparatus itself, to shift the surfaces so as to bring
back the varying center of pressure over a fixed center of gravity, and that in
such care the operator need not move at all, except for the purpose of steering.
The results have been exceedingly gratifying. Two forms of apparatus have been evolved,
each equipped with a different device, which are now believed to be materially safer
than any heretofore produced. With them several hundred flights have been made,
extending over two seasons, without the slightest personal accident.
In December, 1895, Mr. Chanute secured the services of Mr. A. M. Herring, a civil
and mechanical engineer, who had for some years been making experiments in Aviation,
this being the recent name given to attempts to imitate the birds. The first thing
done, after some groping with models, was to build a kite, in order to test the
stability of the proposed gliding machine. This was called the "ladder kite,"
from its resemblance to a step-ladder in one of its postures, for it was so constructed
as to admit of grouping its surfaces in various ways. This kite proved exceedingly
stable, flying in gusty winds without the eccentricities common to that class of
apparatus. Then the construction of a similar machine was begun. which was capable
of carrying a man, but first Mr. Herring rebuilt a machine, previously tested by
him in New York, somewhat similar to that of Lilienthal, so that the known should
be tested before passing to the unknown. With these two machines Mr. Chanute and
Mr. Herring, and two assistants (Mr. Avery and Mr. Butusov), went in June, 1896,
to the desert sand dunes at the south end of Lake Michigan, north of Miller Station,
about thirty miles from Chicago. The Lilienthal-like machine was the first tested.
FIG. 222. Modified Lilienthal
The Figure 222 represents Mr. Herring in the Lilienthal type of apparatus, poised
in a wind at the top of a sand hill about thirty feet high, preparatory to making
a glide. The machine spread 168 square feet of sustaining surface, was equipped
with a double rudder, and weighed thirty-six pounds. With this about 100 glides
were made, the longest being 116 feet. It proved from the outset an awkward machine
to handle. Lilienthal, whose skill had been developed by four or five years of practice,
obtained valuable and safe results with it, but it was otherwise with novices. Its
operation involved a struggle with the wind before it could be brought under control,
and this continued after the flight had begun.
In Fig. 223 this machine is shown gliding a short height over the ground. This was
practiced to avoid untoward accidents, for the winds experimented in, of 12 to 17
miles per hour, constantly varied the position of the center of pressure so far
and so rapidly through their fluctuations, that the operator had to shift his position
as actively as a tight-rope dancer, but to greater distances, to avoid being overturned.
The body had to be moved at times some 15 or 18 inches, and not infrequently in
landing the apparatus was broken. This involved less personal risk than might be
supposed because the radiating ribs curve downward, as shown,
FIG. 223. Lilienthal Type Under Way.
so that they first come into contact with the ground when an awkward landing is
made, and save the operator from harm. Similar experience seems to have obtained
with an acrobat in a public garden in Vienna, with Professor Fitzgerald in Dublin,
with Mr. Lamson in Maine, and with the Journal newspaper in New York, although Mr.
Pilcher, in England, has succeeded well with a modified Lilienthal apparatus of
his own building. At last, the machine shown on Figs. 222 and 223, after having
been broken and mended a number of times, was finally discarded altogether, and
within six weeks thereafter Lilienthal's sad death occurred while experimenting
with his double-decked apparatus.
After abandoning this first form of machine, the experimenters in the sand dunes
next tested the machine built after the fashion of the ladder kite which had proven
so steady in the air.
Fig. 224 exhibits a front view of this arrangement. It consisted of six pairs of
wings, superimposed and trussed together, pivoted at their roots upon a central
frame, the lower chord of which was spread open to receive the man at the center.
Here he was expected only to move for the purpose of steering, the stability to
be maintained by the movements of the wings above him, which swung on their pivots
back and forth, restrained by rubber springs, when the wind struck one side more
than the other, or changed the center of pressure fore and aft. It will be seen
that this is just the reverse of the first method tested, in which the man moved
and the wings remained fixed. This wing movement took place as expected, but it
was very soon found that there was an essential difference between the support from
the wind derived from the same arrangement when flown as a kite, at an angle of
incidence of 30 to 40 degrees,
FIG. 224. First Form Multiple-Wing Machine.
and when flown as a gliding machine, at an angle with the wind of three or four
degrees, which is the most favorable for reducing the total resistance to a minimum.
It was found that at very acute angles the moving air was deflected downward by
the front wings, so that the support under all the following wings was greatly diminished,
and that the apparatus was inefficient when its surface was considered. This had
been expected, from prior experiments, and the frame had been designed so that the
grouping of the wings could be readily changed. Then began an interesting and instructive
evolution. The grouping of the wings was gradually changed, through six permutations,
each being guided by gliding flights and by releasing bits of featherdown in front
of the machine, and watching the paths of the air currents which swept past the
wings. The result of this evolution was to change greatly the outward appearance
of the apparatus while retaining the same general principle.
Fig. 225 shows the improved arrangement as seen from one side in flight. It will
be noticed that no less than five of the six pairs of wings have been superimposed
at the front, and trussed together. That the operator is within and under them,
and that a single pair of wings remains at the rear to serve as a tail. This tail
was flexible and vibrated up all down in flight when the angle of incidence varied
in consequence of the back and forth movements of the pivoted front wings.
FIG. 225. Sixth Form Multiple-Wing Machine.
Fig. 226 shows a front view of the same machine in flight. About two hundred glides
were made, in winds of 13 to 22 miles an hour, on a descending course of about 1
in 4 (14o), the longest flight being 82 feet from a height of about 20
feet. There was, however, undue friction in the wing pivots, thus retarding their
automatic action, so that the operator had to move two or three inches, as against
some 15 or 18 inches on the previous machine, and there being some further defects
in the spacing of the wings, both vertically and horizontally, it was determined
to rebuild the machine with the practical information thus obtained.
FIG. 226. Front View Multiple-Wing Machine in Flight.
Camp was accordingly broken up early in July, with the conviction that more had
been learned during this two weeks of experiment with full-sized machines than had
previously been acquired during about seven years of theoretical study and experiments
with models. The equipment was returned to Chicago, where three machines were constructed,
and towards the end of August they were taken out to the wilderness of sand dunes,
north of Dune Park, about five miles from Miller.
FIG. 227. Seventh Form Multiple-Wing Machine.
Fig. 227 shows the multiple-wing machine as reconstructed. This consisted of the
same wings and of a new frame, and instead of ordinary pivots, there were ball bearings
at the ends of vertical wooden posts to which the roots of the wings were attached,
the latter being all trussed together, with vertical posts and diagonal wire ties,
this being probably the first application which has been made of the Pratt truss
to flying machine design. The frame was all made of spruce, the surfaces were of
Japanese silk varnished with pyroxelene; the complete machine weighed 33 1/2 pounds,
the supporting surface at the front was 143 1/2 square feet, including a concave
aerocurve over the top, added when the front wings were cut down to four pairs,
and the rear wings or tail measured 29 1/2 square feet in area. With this arrangement
a great many glides were made, with the result of more than doubling the lengths
previously attained, of reducing the angle of flight to 1 in 5, or 10o
to 11o, and of diminishing the required movements of the operator to
one or two inches in preserving the equilibrium.
FIG. 228. Multiple-Wing Machine in Flight.-(From a drawing.)
Fig. 228, reproduced from a drawing, shows this apparatus as it appeared in flight.
It might have been preferable to omit the aerocurve over the top, and to have placed
all the supporting surface in the pivoted wings at the front. This aerocurve was
added to save the expense of rebuilding the old wings, and this saving proved to
be a mistake. The wings were so far racked and distorted by their prior service
that they did not support alike and did not balance the weight properly, and thus
the results obtained with that machine were inferior to those to be hereafter described.
Yet the principles deemed to be sound, and it is believed that the apparatus can
be further improved.
FIG. 229. Two-Surfaced Machine with Side Keels.
Fig. 229 exhibits the next full-sized machine which was built. It is seen to be
very simple in construction, and to consist in a single intersection Pratt truss
carrying the surfaces, to which was applied a regulating mechanism designed by Mr.
Herring. This truss will safely support 300 or 400 pounds applied to the arm bars
at the center. In calculating its proportions a basis has to be adopted which is
the reverse of that which obtains in the calculation of bridges, for the support,
or air pressure, has to be considered as uniformly distributed, and the load has
to be figured out as concentrated at the center. It may be mentioned in this connection
that one practical difficulty found has been in devising some method of adjustable
connection between the vertical posts and the diagonal ties. The latter are from
two to five hundredths of an inch in diameter, and it is not practicable either
to cut a screw upon them for a nut, nor to apply a sleeve nut or a turn buckle.
Perhaps some engineer will suggest a better device than the loop heretofore used,
which is made by twisting the wire back upon itself, and which is not adjustable.
With this apparatus as shown in Fig. 230, several hundred glides were made, varying
in length from 150 to 360 feet, at angles of descent of 7 1/2 to 10 degrees, and
during the six weeks occupied with the experiments, not the slightest accident occurred
either to the operators or to the machines.
FIG. 230. Two-Surfaced Machine Just Starting.
The regulating mechanism took care of the equilibrium fore and aft and diminished
the effect of the side wind gusts which were then easily overcome by slight side
movements of the operator. Towards the last amateurs were permitted to try it under
instructions. They made fair glides in safety. One or two cruises by newspaper reporters,
and another by a novice, who was picked up by the wind and raised some forty feet
into the air, but who landed almost in his tracks as gently as if he had only fallen
from the height of a chair.
Fig 231 shows a side view of this apparatus in flight. On this occasion a glide
was made of about 300 feet at a height of ten to twenty feet above the ground, but
it was not uncommon for the machine to sail forty or fifty feet above the ground,
and to pass over the heads of the spectators. The whole apparatus spread 134 square
feet of supporting surface, weighed 23 pounds, and thoroughly supported the weight
of a man at speeds of about 23 miles an hour. A piece of trestle work will be observed
in the background. This was used to launch the machine which is next to be described.
Fig. 232 exhibits the fifth full-sized apparatus which was experimented with in
1896. It was the invention of a Russian, who claimed that he had already attained
success in soaring flight with it, and as this closely resembled the machine of
Captain Le Bris, who was said to have sailed with such a machine in France, in 1867,
it was determined to give the design a trial.
FIG. 231. Under Way and Level with the Starting Point.
FIG. 232. The Albatross Machine.
It was a somewhat complicated apparatus. Over the top was an aeroplane, below which
two great wings extended, 40 feet across, and beneath which again there was a boat-like
frame which could be transformed into a skiff by enclosing it with oiled canvas.
The whole spread of supporting surface was 266 square feet and it weighed 190 pounds.
As this could not, like the other machines, be carried about on a man's shoulders,
special appliances were required to launch it.
FIG. 233. The Albatross on the Ways.
This appliance is exhibited by Fig. 233, and consisted of trestle work built down
the slope of the hill. It involved the great disadvantage that it could only be
used when the wind blew straight up the trestle, a rare occurrence. Nevertheless
two launches were made, but in ballast, as there was no absolute certainty about
the equilibrium. On the first occasion, with 130 pounds of ballast, it went off
very well indeed, but did not sail very far. In alighting, some of the ribs of the
boat-frame were cracked but were replaced in an hour. On the second trial, with
90 pounds of ballast, but in a quartering, unfavorable wind, the latter swung the
machine around, after it left the ways, and upon one of the wings striking a tree,
the apparatus fell and was broken. On neither occasion would the operator have been
hurt had he been in the machine, but it was evidently much too heavy and too cumbrous
to be successfully used in experiments designed solely to work out the problem of
This ended the experiments of 1896. A fuller account will be found in the "Aeronautical
Annual" .for 1897, edited by Mr. James Means, of Boston, whose publications
during the last three years have done very much towards advancing the study and
solution of the problem of Aviation. Detailed plans of the multiple-wing machine
will be found in the 1897 issue.
The results of these experiments in 1896 were to develop two machines which are
believed to be safer than any others previously tried. To advance materially the
solution of the problem of equilibrium. To learn much about the management of flying
apparatus in the wind, and to determine with some accuracy the power required. For
this purpose the lengths and heights of some of the flights were measured. They
were also timed, and it was found that the power expended was from 619 to 789 foot-pounds
per second, or 1.13 to 1.43 horse-power to sustain 178 pounds in the air. This,
however, was in a rising trend of wind. In nearly calm air, the power expended was
found to be 2 horse-power, or at the rate of 89 pounds sustained per horse-power.
FIG .234. Getting Ready.
This represented the actual thrust required to be exerted by a propeller. If we
assume the latter to possess only an efficiency of 70 per cent, then we should require
2.85 actual horse-power on the shaft, and if the internal friction of the engine
diminished its efficiency to 70 per cent of its indicated horse-power, then a motor
of about five indicated horse-power might be expected to maintain an apparatus of
the above type, carrying a man, in horizontal flight through the air. A result which
is surely encouraging.
Mr. Chanute continued by saying that in 1897 he had inaugurated
experiments with models for the purpose of testing still a third method of obtaining
automatic equilibrium, but that these had not proceeded very far. That Mr. Herring,
having been requested by an amateur to supply him with a gliding machine, had built
a new one with his regulating mechanism, and that the pictures next to be shown
had all been taken from flights made with that apparatus, it having been tested
at Dune Park in September, 1897.
Fig. 234 exhibits the machine at the top of the hill, preparatory to making a glide.
lt is a common saying that a child must creep before he learns to walk, and something
of the same required training obtains with a flying machine. The operator (Mr. Herring
in this instance) is seen creeping under the machine in order to rise with it, when
lifted up by the two assistants, and to place himself within the arm bars.
FIG. 235. Poised for Flight.
Fig. 235 shows the apparatus poised in the wind. This involves generally a struggle
with the breeze, which buffets the surfaces either from one side or the other, or
fore and aft. A skillful operator resists this by bracing the machine against his
back and keeping the front edge depressed, facing the wind accurately. As soon as
this poise has been obtained, two or three running steps are taken, the front edge
is slightly raised, and a leap is taken forward.
FIG. 236. The Flight Begun.
Fig. 236 shows the result, which is that the man is lifted up and supported by the
air, and then sails forward at a slightly descending angle, the motive power being
furnished by gravity, and the supporting power, which is due to the speed, being
assisted by the adverse wind.
Fig. 237 exhibits the machine as thoroughly under way, the regulating mechanism
providing for the fore and aft equilibrium, which is the most precarious and productive
of accidents. If the wind be steady, and the operator has placed himself at just
the right point within the arm bars, the glide might continue without any movement
on the man's part, but there are incidents which are apt to occur in consequence
of the irregularity of the wind, such as that shown in the next picture.
In Fig. 238, the apparatus is shown as struck by a side gust. The illustration in
this particular picture was somewhat exaggerated by the fact that the camera was
not held quite level, but it is clear that the left wing has been raised by the
FIG. 237. Well Up.
FIG.FIG. 238. Struck by a Side Gust
and that the operator has thrown his feet towards that side, in order to bring the
wing down. It may be well here to remark that when in flight the bodily movements
should be just the reverse of those which are instinctively made if standing on
the ground. In the latter case, if one finds himself going over in one direction,
the foot on that side is instinctively thrown out to that side; on a flying machine,
if one willing is found to be depressed, the weight should be thrown to the opposite
side in order to bring the wing down. This requires some practice to become second
nature, but after awhile it is done semi-automatically, and without stopping to
FIG. 239. Righted Again.
In Fig. 239 the machine has been righted up and is gliding forward on an even keel
at a flatter angle of descent than the slope of the hill, so that the next picture
shows increased height.
In Fig. 240 it is seen directly overhead of the camera and thoroughly under control,
the legs having been raised up ready to be thrown in any direction to do the steering.
In Fig. 241 the trees have been passed for some distance, the apparatus is sailing
steadily, and the ground is being gradually approached.
FIG. 240. Passing Overhead.
FIG. 241. Sailing Along
In Fig. 242, the foot of the hill has been nearly reached, and it is time to think
of alighting. This is very easily accomplished by pushing the weight of the body
backward on the supporting bars, through a movement of the fore arms. The effect
of this is to raise the front edge of the machine, thus increasing the angle of
incidence and the consequent air pressure. This stops the speed, and as the diminished
velocity also diminishes the pressure, the apparatus oscillates gently to a level
keel, and the operator alights on the ground with almost no jar.
FIG. 242. Time to Think of Alighting
The curious in such matters will see this manoeuvre performed thousands of times
a day by the sparrows in the street. Mr. Herring and Mr. Avery, who were the experts
who operated this machine at Dune Park, seldom or never struck the ground with greater
force than would have been produced by jumping down one or two feet, and even when
racing no sprained ankles occurred.
Fig. 243 shows the apparatus being carried back preparatory to making another glide.
These were generally 200 or 300 feet long, and occupied 8 to 14 seconds, although
it takes nearly 20 minutes to describe one of them. The sport is so exciting, the
sensation of flying through the air is so delightful, that the operators immediately
desire to make another glide, and they generally alternate in taking such flights.
Each of the pictures shown has been taken from a different glide, but the effort
has been made to have each represent a different phase, so that the sequence of
aerial transit might be followed.
Mr. Chanute further said that the first requisite towards devising an artificial
flying machine was to learn how such machines behaved in the air, and that he therefore
advised constant practice to acquire the science of the birds. That the present
auditors would doubtless like to know in greater detail just how it felt to be riding
on the air, and he therefore begged to introduce Mr. Herring, who would describe
the remainder of the pictures.
[More on the Herring Arnot Experiments.]
Mr. Herring stated that the slides previously described by Mr. Chanute were views
of flights taken toward what was known as the valley or southwest side of the hill.
But those from view 23 onward were from the lake side or northern slope.
FIG. 243. Going Back Again.
Fig. 243, he said, represented very well the method of carrying. the machine in
mild or moderate winds, for in toiling up the slope the operator's feet sank so
deeply in the fine yellow sand that outside aid was sometimes sought from the wind
pressure on the surfaces. This pressure, which was a lifting one, amounted in some
cases to more than 100 pounds, but that there were drawbacks to its use which required
considerable practice of the carrier to overcome. These drawbacks, he said, were
first, those due to the varying direction at which the wind arrived - each variation
producing very wide range of travel of the center of lifting effort, and, consequently,
considerable leverages to contend with - leverages so great that the 25 pounds weight
of machine often became almost a negligible factor beside the forces which had to
be occasionally contended with unless great care and quickness of action were exercised
to always point the front of the apparatus into the momentary direction of the wind;
the accurate judging of the extent of these momentary changes was a matter in itself
which required considerable practice.
FIG. 244. Near the Starting Point.
Another difficulty of handling the machine on the steep slope was, he said, due
to a property peculiar to arched surfaces, namely, to a strong propelling component
which they possessed at small positive, as well as negative, angles of inclination
(to the horizontal), when held in a strongly ascending current of air, such as always
existed in winds at the hillside. This propelling component,which tended to force
the carrier back down the hill against the wind, would frequently be brought about
by gusts, or disturbances in the wind which affected the vertical trend and produced
these propelling components so suddenly and with such force, in winds of 20 miles
an hour or over, that it was generally safer to employ two men to carry what in
a calm would be a comparatively light load for one.
After arriving at the starting point, which, he said, was not at top of the hill
but just a few feet beyond the position shown in the Figure 244, the apparatus was
held with the chord of the surfaces pointed downward at a considerable negative
angle in order that the machine should sustain only its own weight, and at the same
time the apparatus was directed squarely into the momentary wind so that both sides
lifted equally, and, while the machine was thus poised, the operator (in front of
the apparatus), released his hold and slipped quickly underneath, passing his arms
over the longitudinal bars (called arm bars), beneath the lower surface, at the
same time grasping the front pair of diagonal struts which joined these bars to
the framing. This done, the whole machine was lowered until the small cross-piece
in the rear of the operator rested on his hips or the small of his back. In this
position a considerable leverage could be exerted, and with practice even a novice
could soon hold the machine under perfect control until the actual start was made
down the hill.
Continuing, Mr. Herring said that in view of the small size of the machine, exposing
in the present instance but 131 square feet of surface, one in first handling it
would be surprised at the very great lifting effect, as well as the extent of the
disturbing forces which come into play in comparatively light winds. He explained
that this increased lifting effect was due to the very great superiority of arched
surfaces over plane ones. This superiority had been first discovered and explained
by the late Otto Lilienthal, a German engineer, who pointed out that the lifting
forces which come into play were those due to a considerable thickness of air strata
swinging around the arched profile of the surfaces - producing by their centrifugal
moment (a partial vacuum on the upper or convex side of the surfaces and an added
pressure on the lower or concave side - these together), giving lifting effects
at small angles of inclination, such as from three to four degrees, (the same as
used in flight on the present apparatus) equal to from eight to twelve times as
much as could be produced by perfectly plane surfaces at the same angles and speed.
It was common practice, Mr. Herring said, to designate all these machines as aeroplanes,
although it was probable that if the inventor were limited to flat surfaces man
flight would not be possible with them, and, in view of the wide differences between
the properties of plane and arched surfaces, Mr. Chanute and he used the word aerocurve,
to designate the latter form. Continuing, the speaker said that on account of the
internal irregularities which all winds possessed, it was a great deal more difficult
to control any gliding machine on the ground than when the operator was in the air,
and that this was especially true of the machines, that had been provided with the
automatic regulating devices; on these, he said, the effect of the operator to keep
the balance proper, while in flight, was, except in extreme cases, almost nil; but
that when automatic regulation was absent or momentarily shut off, the flights,
in winds of upwards of fifteen miles an hour, were marked by numerous movements
of the operator requiring great quickness and considerable bodily strength which
tired one almost as much as carrying the machine single handed up the hill. He said,
to gather an idea of what those difficulties were which had to be contended with
by either the operator or the mechanism, one might recall the actions of smoke issuing
from a chimney which, if watched for any two succeeding fractions of a second, would
show that its course was rarely the same, that in moderate or high winds it consisted
of thousands of irregular curves and twists which came with a suddenness and irregularity
greater than any man could intelligently follow, even mentally. He stated that their
experiments had convinced them that similar disturbances existed throughout all
winds, even the most steady, and that as each of these changes or "gusts"
had its disturbing effects any apparatus depending for dynamic support on the air,
it was plain to be seen why Mr. Chanute had placed so much importance on the problem
of securing automatic equilibrium, as the latter was, undoubtedly by far the most
important of all the many difficulties connected with the whole subject. Consequently,
nearly all of their recent experimental work had been directed to a study of these
"gusts," or wind changes, and especially to the counteraction of their
disturbing effects by automatic machinery. For both felt convinced that without
ample provision for automatically overcoming at least the more dangerous of these
gusts a practical aerocurve, or aeroplane flying machine would be out of question.
Mr. Herring said he felt himself to be too much of an enthusiast to express his
own opinion of what had been accomplished by these experiments, but would leave
it to others to form their opinions of the results, which, he said, were substantially
as follows: That, whereas the maximum (natural) wind velocity in which an unregulated
machine was ever controlled by an operator (Lilienthal) was in the neighborhood
of 22 miles an hour, they had been able to experiment on the: machine here shown
in winds of 31 1/2 miles an hour, corresponding to wind energy of about three times
as great, with entire safety, and with another apparatus and more complex regulator
this limit had been raised very much higher. Also, notwithstanding the fact that
neither Mr. Avery nor the speaker, who operated the machines, possessed anywhere
near the skill exhibited by Lilienthal, the latter's best flights had, nevertheless,
been equaled if not exceeded.
He said that before describing the succeeding views, he wished to explain that,
though he had stated that the exertion required in keeping the balance proper of
the present machines was almost nil, he did not wish to convey the impression that
movements of the operator's weight were therefore not resorted to. On the contrary,
they were very necessary in directing both the course and the angle of descent,
and that extreme sensitiveness of the machine to these movements of the operator
was an essential feature to secure success with this type of apparatus, and that
the ability to gauge these movements, as well as the speed and angle of the machine
on the other hand, were the main points of skill required of the operator. Returning
again to the views, he stated that after the machine was poised, as previously explained,
the front edges were brought down until the chord of these surfaces pointed downward
nearly parallel with the slope of the hill. In this position a running start was
made towards the wind; the operator meantime advanced himself on the arm bars until
he reached the proper position for flight, and as the speed in creased, the apparatus
gradually carried more and more of the operator's weight until he was entirely sustained.
From this point the machine carried him the balance of the flight through the air,
at a speed, and an angle of descent, dependent almost wholly upon his position on
the apparatus. This speed varied all the way from 10 to 40 miles an hour in reference
to the ground or from 18 to 57 miles per hour in reference to the air, at the will
of the aviator. A perfect guide, the speaker said, to the speed of the machine in
reference to the air was furnished the operator, as well as to the spectators below,
by the pitch of the note which the wires and framing made in passing through the
air, a note similar to the shrieking of the shrouds of a ship in a storm.
The running start in a calm consisted of about half a dozen steps; in moderate winds,
from two to three; and in high winds (those above 25 miles an hour), it was only
necessary to give a slight positive inclination to the surfaces, when the machine
and operator were raised high in the air, and then commenced their forward journey
against the wind. The advance at a positive angle of inclination was due to the
fact that arched surfaces possessed a strong propelling component, even at .small
positive inclinations (to the horizontal) in strongly ascending currents such as
always existed on the windward slope of the hill. After reaching a certain point
over the hillside (approximately one-third the way down the hill), a sudden decrease
in support was generally experienced, due, in all probability, to a mass of slower
moving air between the base and top of the hill, as measurement with the anemometer
showed very much higher wind at the starting point and at the foot of the hill (or
over the level stretch below) than between the two. The relationship in a 23-mile
wind having been found to be as follows: Velocity at the lake, 20 miles per hour;
at the foot of the hill (distant 300 feet), 16 miles; from first third to middle
of the hill 9 miles per hour; starting point (one third from top), 23 miles; and
top, 231/2 miles per hour. From which it would be seen that from starting in a wind
of somewhat higher velocity than that necessary for support ( 211/2 to 22 miles
per hour), the machine (in the space of from one to one and a half seconds) passed
into a wind capable of exerting but little more than one-sixth of that effect;
FIG. 245. Two Seconds After Start.
the equilibrium, however, remained practically undisturbed; but to prevent losing
headway, he said the operator should, in such a case, move his weight slightly to
bring the surfaces at a greater negative angle than would be produced automatically
by the regulating mechanism, as shown in Fig. 245, so that gravity might add to
the speed during the descent and thus store a large part of the energy of the fall.
After reaching the lowest point of this descent, which he said in some cases seemed
to be attributable to a current of air curling backward against the mean wind, the
operator again shifted his weight (or if he remained quiet the freshening wind would
perform the same function through the regulating mechanism, but less quickly) and
give the surfaces a slight positive angle as shown in Fig. 246,
FIG. 246. Four Seconds After Start.
when by reason of the increased speed of the machine and the fresher wind over the
level stretch of the beach, the apparatus immediately rose, some times with greater
rapidity than it fell, to almost the same level from which the descent was started,
as shown in Fig. 247, the whole operation between Figs. 245 and 247 rarely occupying
as much as three seconds. After passing the position shown in the last named figure,
the flight as a whole was steady along a gradually descending line of one in six
to one in seven, and occasionally but rarely one in eight. In strong winds, however,
he continued, the gusts in the wind made considerable undulations in the flight,
on a number of occasions raising the machine and operator as much as forty feet
above the starting point, and giving the remainder of the course a number of vertical
undulations departing from eight to fifteen feet from the mean line of the flights.
The sensations produced by these sudden variations being somewhat similar to that
experienced in a quick starting elevator.
FIG. 247. Five Seconds After Start.
One great peculiarity, he said, which distinguished the sensation of riding on the
air from all other modes of locomotion was the exceeding smoothness and elasticity
of the support, and although ascending or descending motions were occasionally imparted
to the machine, which were practically equal to what gravity would produce on a
free moving body in the same time, yet, the application of these forces was always
so elastic that there was never the slightest shock felt.
FIG. 248. Nearly Down.
Continuing, he said the line of flight eventually approached nearer and nearer to
the sand when it became necessary to select a proper landing point, and, at the
same time, to head the machine directly into the wind, as was being done in Fig
248, the landing in which case would be effected some sixty or seventy feet nearer
the camera than the piece of charred wreckage in the foreground (the length of flight
being on an average 268 feet horizontally in a descent of 42 feet in windy weather,
or 254 feet in a calm from the same point, thus showing that in flights against
the wind the ascending trend of the latter (blowing from the lake over the hill)
furnished but little more energy than that necessary to overcome its own horizontal
component and that the length of flight measured on the ground, in gliding against
the wind, was more dependent upon the height from which the flight started than
on the velocity of the wind.
FIG. 249. Quartering.
Continuing, Mr. Herring said that so much had formerly been said relative to the
necessity of starting and stopping against the wind that the impression had gone
abroad that flight in any other direction with the present machines was impossible.
He wished, therefore, to call attention to the Figs. 249, 250 and 251, which represented
the machine facing north but advancing west of northwest in a wind coming from the
northeast. These flights were known as quartering, in that they were made at an
angle or "quartering" with the wind in order to make use of the ascending
current over the slope which furnished in these flights both support and propulsion.
FIG. 250. Quartering Flight Overhead.
Such flights, he said, in a sufficiently strong wind, could, in a suitable locality,
having a long hillside entirely free of obstructions, be prolonged indefinitely,
but that his best attempt in this direction lasted only about 48 seconds. This,
he said, was accomplished with a similar machine with three superimposed surfaces
in covering a distance of 927 feet. There were, however, he said, few localities
among the lakeside sand hills where this length of flight might be made except at
the risk of running into trees or other obstructions, so that no matter how much
longer than the average the level part of any particular flight might be there was
still the same operation (that shown in Fig. 252) to be gone through with at the
end, namely, the winding up of gravity's spring by man-power. This, said Mr. Herring,
was a part of the operation which made one think more of adding the motor than any
other. Whether the time were ripe for this step or not could, perhaps, be best judged
by others; his individual opinion was, however in the affirmative, and that, judging
from the action of power-driven models of the gliding machine, which he had recently
built and tested, it was probable, he said, that the power machinery would add to,
rather than diminish the stability of the glider, and if this conclusion proved
FIG. 251 Turning on Quartering Flight
FIG. 252. Winding Up Gravity Spring
finest mode of travel in the world, he thought, for the few, if not for the many,
would not only be a possibility but a reasonable certainty of the near future.
President Johnston: I am sure we have all listened with a great deal of interest
to Mr. Chanute's very interesting address and Mr. Herring's remarks, and if there
are any others who have anything to say on this subject we will be glad to hear
Mr. L. I.. Summers: I would like to call attention to the fact that Mr.Chanute's
modesty has prevented his calling attention to the particular work he has done.
It is well known that Mr. Maxim in England, has spent a small fortune in perfecting
his machine and his effort has been towards constructing a machine of full size,
and I believe some $40,000 or $50,000 has been spent on it. He has never succeeded
in actually flying, and he has broken his machine several times in getting away
from the tracks. Mr. Chanute has endeavored in every way to avoid dangerous experiments
and has confined his experiments to solving the problem of equilibrium. He has devoted
a number of years to the subject, and I think all those who have read his book and
know the great care he has taken to point out the success and failures of others,
feel indebted to him. I think; it is a source of congratulation to the West that
we have an engineer and a scientist who is willing to devote himself to the subject
in the way he has, and along the line he is working unquestionably must come our
ultimate success. Many fail to appreciate that equilibrium must first be obtained
before we can hope to accomplish successful flight, and to this problem Mr. Chanute's
whole attention has been turned.
Thanks to Ms. Simine Short for providing the images and the text for this page.