Quelltext der Seite Aeronautics History Vivian 1920 05 Progress in Design

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|Titel=History of Aeronautics
|Autor=Vivian-Charles-E
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|Entstehungsjahr=1920
|Erscheinungsjahr=1920
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|Kurzbeschreibung=Geschichte der Luftfahrt bis 1920.
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:A History of Aeronautics 
:by E. Charles Vivian
:1920

:PART II - 1903-1920:  PROGRESS IN DESIGN
:BY LIEUT.-COL. W. LOCKWOOD MARSH


==I. THE  BEGINNINGS==

Although the first actual flight of an aeroplane was made by the
Wrights on December 17th 1903, it is necessary, in considering
the progress of design between that period and the present day,
to go back to the earlier days of their experiments with
'gliders,' which show the alterations in design made by them in
their step-bystep progress to a flying machine proper, and give
a clear idea of the stage at which they had arrived in the art
of aeroplane design at the time of their first flights.

They started by carefully surveying the work of previous
experimenters, such as Lilienthal and Chanute, and from the
lesson of some of the failures of these pioneers evolved certain
new principles which were embodied in their first glider, built
in 1900.  In the first place, instead of relying upon the
shifting of the operator's body to obtain balance, which had
proved too slow to be reliable, they fitted in front of the main
supporting surfaces what we now call an 'elevator,' which could
be flexed, to control the longitudinal balance, from where the
operator lay prone upon the main supporting surfaces.  The second
main innovation which they incorporated in this first glider, and
the principle of which is still used in every aeroplane in
existence, was the attainment of lateral balance by warping the
extremities of the main planes.  The effect of warping or pulling
down the extremity of the wing on one side was to increase its
lift and so cause that side to rise.  In the first two gliders
this control was also used for steering to right and left.  Both
these methods of control were novel for other than model work, as
previous experimenters, such as Lilienthal and Pilcher, had
relied entirely upon moving the legs or shifting the position of
the body to control the longitudinal and lateral motions of their
gliders.  For the main supporting surfaces of the glider the
biplane system of Chanute's gliders was adopted with certain
modifications, while the curve of the wings was founded upon the
calculations of Lilienthal as to wind pressure and consequent
lift of the plane.

This first glider was tested on the Kill Devil Hill sand-hills
in North Carolina in the summer of 1900 and proved at any
rate the correctness of the principles of the front elevator and
warping wings, though its designers were puzzled by the fact
that the lift was less than they expected; whilst the 'drag'(as
we call it), or resistance, was also considerably lower than
their predictions.  The 1901 machine was, in consequence, nearly
doubled in area--the lifting surface being increased from 165 to
308 square feet--the first trial taking place on July 27th,
1901, again at Kill Devil Hill.  It immediately appeared that
something was wrong, as the machine dived straight to the
ground, and it was only after the operator's position had been
moved nearly a foot back from what had been calculated as the
correct position that the machine would glide--and even then the
elevator had to be used far more strongly than in the previous
year's glider.  After a good deal of thought the apparent
solution of the trouble was finally found. 

This consisted in the fact that with curved surfaces, while at
large angles the centre of pressure moves forward as the angle
decreases, when a certain limit of angle is reached it travels
suddenly backwards and causes the machine to dive.  The Wrights
had known of this tendency from Lilienthal's researches, but had
imagined that the phenomenon would disappear if they used a
fairly lightly cambered--or curved--surface with a very abrupt
curve at the front.  Having discovered what appeared to be the
cause they surmounted the difficulty by 'trussing down' the
camber of the wings, with the result that they at once got back
to the old conditions of the previous year and could control the
machine readily with small movements of the elevator, even being
able to follow undulations in the ground.  They still found,
however, that the lift was not as great as it should have been;
while the drag remained, as in the previous glider, surprisingly
small.  This threw doubt on previous figures as to wind
resistance and pressure on curved surfaces; but at the same time
confirmed (and this was a most important result) Lilienthal's
previously questioned theory that at small angles the pressure
on a curved surface instead of being normal, or at right angles
to, the chord is in fact inclined in front of the perpendicular. 
The result of this is that the pressure actually tends to draw
the machine forward into the wind--hence the small amount of
drag, which had puzzled Wilbur and Orville Wright.

Another lesson which was learnt from these first two years of
experiment, was that where, as in a biplane, two surfaces are
superposed one above the other, each of them has somewhat less
lift than it would have if used alone.  The experimenters were
also still in doubt as to the efficiency of the warping method
of controlling the lateral balance as it gave rise to certain
phenomena which puzzled them, the machine turning towards the
wing having the greater angle, which seemed also to touch the
ground first, contrary to their expectations.  Accordingly, on
returning to Dayton towards the end of 1901, they set
themselves to solve the various problems which had appeared and
started on a lengthy series of experiments to check the previous
figures as to wind resistance and lift of curved surfaces,
besides setting themselves to grapple with the difficulty of
lateral control.  They accordingly constructed for themselves at
their home in Dayton a wind tunnel 16 inches square by 6 feet
long in which they measured the lift and 'drag' of more than two
hundred miniature wings.  In the course of these tests they for
the first time produced comparative results of the lift of
oblong and square surfaces, with the result that they
re-discovered the importance of 'aspect ratio'--the ratio of
length to breadth of planes.  As a result, in the next year's
glider the aspect ration of the wings was increased from the
three to one of the earliest model to about six to one, which is
approximately the same as that used in the machines of to-day. 
Further than that, they discussed the question of lateral
stability, and came to the conclusion that the cause of the
trouble was that the effect of warping down one wing was to
increase the resistance of, and consequently slow down, that
wing to such an extent that its lift was reduced sufficiently to
wipe out the anticipated increase in lift resulting from the
warping. From this they deduced that if the speed of the warped
wing could be controlled the advantage of increasing the angle
by warping could be utilised as they originally intended.  They
therefore decided to fit a vertical fin at the rear which, if the
machine attempted to turn, would be exposed more and more to the
wind and so stop the turning motion by offering increased
resistance.

As a result of this laboratory research work the third Wright
glider, which was taken to Kill Devil Hill in September, 1902,
was far more efficient aerodynamically than either of its two
predecessors, and was fitted with a fixed vertical fin at the
rear in addition to the movable elevator in front.  According to
Mr Griffith Brewer,[*] this third glider contained 305 square
feet of surface; though there may possibly be a mistake here, as
he states[**] the surface of the previous year's glider to have
been only 290 square feet, whereas Wilbur Wright himself[***]
states it to have been 308 square feet.  The matter is not,
perhaps, save historically, of much importance, except that the
gliders are believed to have been progressively larger, and
therefore if we accept Wilbur Wright's own figure of the surface
of the second glider, the third must have had a greater area
than that given by Mr Griffith Brewer.  Unfortunately, no
evidence of the Wright Brothers themselves on this point is
available.

[*] Fourth Wilbur Wright Memorial Lecture, Aeronautical Journal,
Vol. XX, No. 79, page 75.

[**] Ibid. page 73.  

[***] Ibid.  pp. 91 and 102.

The first glide of the 1902, season was made on September 17th
of that year, and the new machine at once showed itself an
improvement on its predecessors, though subsequent trials showed
that the difficulty of lateral balance had not been entirely
overcome.  It was decided, therefore, to turn the vertical fin
at the rear into a rudder by making it movable.  At the same
time it was realised that there was a definite relation between
lateral balance and directional control, and the rudder controls
and wing-warping wires were accordingly connected This ended the
pioneer gliding experiments of Wilbur and Orville Wright--though
further glides were made in subsequent years--as the following
year, 1903, saw the first power-driven machine leave the ground.

To recapitulate--in the course of these original experiments the
Wrights confirmed Lilienthal's theory of the reversal of the
centre of pressure on cambered surfaces at small angles of
incidence:  they confirmed the importance of high aspect ratio
in respect to lift:  they had evolved new and more accurate
tables of lift and pressure on cambered surfaces:  they were the
first to use a movable horizontal elevator for controlling
height:  they were the first to adjust the wings to different
angles of incidence to maintain lateral balance:  and they were
the first to use the movable rudder and adjustable wings in
combination.

They now considered that they had gone far enough to justify
them in building a power-driven 'flier,' as they called their
first aeroplane.  They could find no suitable engine and so
proceeded to build for themselves an internal combustion engine,
which was designed to give 8 horse-power, but when completed
actually developed about 12-15 horse-power and weighed 240 lbs. 
The complete machine weighed about 750 lbs.  Further details of
the first Wright aeroplane are difficult to obtain, and even
those here given should be received with some caution.  The
first flight was made on December 17th 1903, and lasted 12
seconds.  Others followed immediately, and the fourth lasted 59
seconds, a distance of 852 feet being covered against a 20-mile
wind.

The following year they transferred operations to a field
outside Dayton, Ohio (their home), and there they flew a
somewhat larger and heavier machine with which on September 20th
1904, they completed the first circle in the air.  In this
machine for the first time the pilot had a seat; all the
previous experiments having been carried out with the operator
lying prone on the lower wing.  This was followed next year by
another still larger machine, and on it they carried out many
flights.  During the course of these flights they satisfied
themselves as to the cause of a phenomenon which had puzzled
them during the previous year and caused them to fear that they
had not solved the problem of lateral control.  They found that
on occasions--always when on a turn--the machine began to slide
down towards the ground and that no amount of warping could stop
it.  Finally it was found that if the nose of the machine was
tilted down a recovery could be effected; from which they
concluded that what actually happened was that the machine,
'owing to the increased load caused by centrifugal force,' had
insufficient power to maintain itself in the air and therefore
lost speed until a point was reached at which the controls
became inoperative.  In other words, this was the first
experience of 'stalling on a turn,' which is a danger against
which all embryo pilots have to guard in the early stages of
their training.

The 1905 machine was, like its predecessors, a biplane with a
biplane elevator in front and a double vertical rudder in rear. 
The span was 40 feet, the chord of the wings being 6 feet and
the gap between them about the same.  The total area was about
600 square feet which supported a total weight of 925 lbs.;
while the motor was 12 to 15 horse-power driving two propellers
on each side behind the main planes through chains and giving
the machine a speed of about 30 m.p.h. one of these chains was
crossed so that the propellers revolved in opposite directions
to avoid the torque which it was feared would be set up if they
both revolved the same way.  The machine was not fitted with a
wheeled undercarriage but was carried on two skids, which also
acted as outriggers to carry the elevator.  Consequently, a
mechanical method of launching had to be evolved and the machine
received initial velocity from a rail, along which it was drawn
by the impetus provided by the falling of a weight from a wooden
tower or 'pylon.'  As a result of this the Wright aeroplane in
its original form had to be taken back to its starting rail
after each flight, and could not restart from the point of
alighting.  Perhaps, in comparison with French machines of more
or less contemporary date (evolved on independent lines in
ignorance of the Americans' work), the chief feature of the
Wright biplane of 1905 was that it relied entirely upon the
skill of the operator for its stability; whereas in France some
attempt was being made, although perhaps not very successfully,
to make the machine automatically stable laterally.  The
performance of the Wrights in carrying a loading of some 60 lbs. 
per horse-power is one which should not be overlooked.  The wing
loading was about 1 1/2 lbs.  per square foot.

About the same time that the Wrights were carrying out their
power-driven experiments, a band of pioneers was quite
independently beginning to approach success in France.  In
practically every case, however, they started from a somewhat
different standpoint and took as their basic idea the cellular
(or box) kite.  This form of kite, consisting of two superposed
surfaces connected at each end by a vertical panel or curtain of
fabric, had proved extremely successful for man-carrying
purposes, and, therefore, it was little wonder that several minds
conceived the idea of attempting to fly by fitting a series of
box-kites with an engine.  The first to achieve success was M.
Santos-Dumont, the famous Brazilian pioneer-designer of airships,
who, on November 12th, 1906, made several flights, the last of
which covered a little over 700 feet.  Santos-Dumont's machine
consisted essentially of two box-kites, forming the main wings,
one on each side of the body, in which the pilot stood, and at
the front extremity of which was another movable box-kite to act
as elevator and rudder.  The curtains at the ends were intended
to give lateral stability, which was further ensured by setting
the wings slightly inclined upwards from the centre, so that when
seen from the front they formed a wide V.  This feature is still
to be found in many aeroplanes to-day and has come to be known
as the 'dihedral.'  The motor was at first of 24 horse-power, for
which later a 50 horse-power Antoinette engine was substituted;
whilst a three-wheeled undercarriage was provided, so that the
machine could start without external mechanical aid.  The
machine was constructed of bamboo and steel, the weight being as
low as 352 lbs.  The span was 40 feet, the length being 33 feet,
with a total surface of main planes of 860 square feet.  It will
thus be seen--for comparison with the Wright machine--that the
weight per horse-power (with the 50 horse-power engine) was only
7 lbs., while the wing loading was equally low at 1/2 lb. per
square foot.

The main features of the Santos-Dumont machine were the box-kite
form of construction, with a dihedral angle on the main planes,
and the forward elevator which could be moved in any direction
and therefore acted in the same way as the rudder at the rear of
the Wright biplane.  It had a single propeller revolving in the
centre behind the wings and was fitted with an undercarriage
incorporated in the machine.

The other chief French experimenters at this period were the
Voisin Freres, whose first two machines--identical in
form--were sold to Delagrange and H. Farman, which has sometimes
caused confusion, the two purchasers being credited with the
design they bought.  The Voisins, like the Wrights, based their
designs largely on the experimental work of Lilienthal, Langley,
Chanute, and others, though they also carried out tests on the
lifting properties of aerofoils in a wind tunnel of their own.
Their first machines, like those of Santos-Dumont, showed the
effects of experimenting with box-kites, some of which they had
built for M. Ernest Archdeacon in 1904.  In their case the
machine, which was again a biplane, had, like both the others
previously mentioned, an elevator in front--though in this case
of monoplane form--and, as in the Wright, a rudder was fitted in
rear of the main planes. The Voisins, however, fitted a fixed
biplane horizontal 'tail'--in an effort to obtain a measure of
automatic longitudinal stability--between the two surfaces of
which the single rudder worked.  For lateral stability they
depended entirely on end curtains between the upper and lower
surfaces of both the main planes and biplane tail surfaces. 
They, like Santos-Dumont, fitted a wheeled undercarriage, so
that the machine was self-contained. The Voisin machine, then,
was intended to be automatically stable in both senses; whereas
the Wrights deliberately produced a machine which was entirely
dependent upon the pilot's skill for its stability.  The
dimensions of the Voisin may be given for comparative purposes,
and were as follows:  Span 33 feet with a chord (width from back
to front) of main planes of 6 1/2 feet, giving a total area of
430 square feet.  The 50 horse-power Antoinette engine, which was
enclosed in the body (or 'nacelle ') in the front of which the
pilot sat, drove a propeller behind, revolving between the
outriggers carrying the tail.  The total weight, including Farman
as pilot, is given as 1,540 lbs., so that the machine was much
heavier than either of the others; the weight per horse-power
being midway between the Santos-Dumont and the Wright at 31 lbs. 
per square foot, while the wing loading was considerably greater
than either at 3 1/2 lbs. per square foot.  The Voisin machine
was
experimented with by Farman and Delagrange from about June 1907
onwards, and was in the subsequent years developed by Farman; and
right up to the commencement of the War upheld the principles of
the box-kite method of construction for training purposes.  The
chief modification of the original design was the addition of
flaps (or ailerons) at the rear extremities of the main planes to
give lateral control, in a manner analogous to the wing-warping
method invented by the Wrights, as a result of which the end
curtains between the planes were abolished.  An additional
elevator was fitted at the rear of the fixed biplane tail, which
eventually led to the discarding of the front elevator
altogether.  During the same period the Wright machine came into
line with the others by the fitting of a wheeled undercarriage
integral with the machine.  A fixed horizontal tail was also
added to the rear rudder, to which a movable elevator was later
attached; and, finally, the front elevator was done away with. 
It will thus be seen that having started from the very different
standpoints of automatic stability and complete control by the
pilot, the Voisin (as developed in the Farman) and Wright
machines, through gradual evolution finally resulted in
aeroplanes of similar characteristics embodying a modicum of
both features.

Before proceeding to the next stage of progress mention should
be made of the experimental work of Captain Ferber in France. 
This officer carried out a large number of experiments with
gliders contemporarily with the Wrights, adopting--like
them--the Chanute biplane principle.  He adopted the front
elevator from the Wrights, but immediately went a step farther
by also fitting a fixed tail in rear, which did not become a
feature of the Wright machine until some seven or eight years
later.  He built and appeared to have flown a machine fitted
with a motor in 1905, and was commissioned to go to America by
the French War Office on a secret mission to the Wrights.
Unfortunately, no complete account of his experiments appears to
exist, though it can be said that his work was at least as
important as that of any of the other pioneers mentioned.



==II. MULTIPLICITY OF IDEAS==

In a review of progress such as this, it is obviously
impossible, when a certain stage of development has been
reached, owing to the very multiplicity of experimenters, to
continue dealing in anything approaching detail with all the
different types of machines; and it is proposed, therefore, from
this point to deal only with tendencies, and to mention
individuals merely as examples of a class of thought rather than
as personalities, as it is often difficult fairly to allocate
the responsibility for any particular innovation.

During 1907 and 1908 a new type of machine, in the monoplane,
began to appear from the workshops of Louis Bleriot, Robert
Esnault-Pelterie, and others, which was destined to give rise to
long and bitter controversies on the relative advantages of the
two types, into which it is not proposed to enter here; though
the rumblings of the conflict are still to be heard by
discerning ears.  Bleriot's early monoplanes had certain new
features, such as the location of the pilot, and in some cases
the engine, below the wing; but in general his monoplanes,
particularly the famous No. XI on which the first Channel
crossing was made on July 25th, 1909, embodied the main
principles of the Wright and Voisin types, except that the
propeller was in front of instead of behind the supporting
surfaces, and was, therefore, what is called a 'tractor' in
place of the then more conventional 'pusher.'  Bleriot aimed at
lateral balance by having the tip of each wing pivoted, though he
soon fell into line with the Wrights and adopted the warping
system.  The main features of the design of Esnault-Pelterie's
monoplane was the inverted dihedral (or kathedral as this was
called in Mr S. F. Cody's British Army Biplane of 1907) on the
wings, whereby the tips were considerably lower than the roots at
the body.  This was designed to give automatic lateral stability,
but, here again, conventional practice was soon adopted and the
R.E.P. monoplanes, which became well-known in this country
through their adoption in the early days by Messrs Vickers, were
of the ordinary monoplane design, consisting of a tractor
propeller with wire-stayed wings, the pilot being in an enclosed
fuselage containing the engine in front and carrying at its rear
extremity fixed horizontal and vertical surfaces combined with
movable elevators and rudder.  Constructionally, the R.E.P.
monoplane was of extreme interest as the body was constructed of
steel.  The Antoinette monoplane, so ably flown by Latham, was
another very famous machine of the 1909-1910 period, though its
performance were frequently marred by engine failure; which was
indeed the bugbear of all these early experimenters, and it is
difficult to say, after this lapse of time, how far in many cases
the failures which occurred, both in performances and even in the
actual ability to rise from the ground, were due to defects in
design or merely faults in the primitive engines available.  The
Antoinette aroused admiration chiefly through its graceful,
birdlike lines, which have probably never been equalled; but its
chief interest for our present purpose lies in the novel method
of wing-staying which was employed.  Contemporary monoplanes
practically all had their  wings stayed by wires to a post in the
centre above the fuselage, and, usually, to the undercarriage
below.  In the Antoinette, however, a king post was introduced
half-way along the wing, from which wires were carried to the
ends of the wings and the body.  This was intended to give
increased strength and permitted of a greater wing-spread and
consequently improved aspect ratio.  The same system of
construction was adopted in the British Martinsyde monoplanes of
two or three years later.

This period also saw the production of the first triplane, which
was built by A. V. Roe in England and was fitted with a J.A.P. 
engine of only 9 horse-power--an amazing performance which
remains to this day unequalled.  Mr Roe's triplane was chiefly
interesting otherwise for the method of maintaining longitudinal
control, which was achieved by pivoting the whole of the three
main planes so that their angle of incidence could be altered. 
This was the direct converse of the universal practice of
elevating by means of a subsidiary surface either in front or
rear of the main planes.

Recollection of the various flying meetings and exhibitions
which one attended during the years from 1909 to 1911, or even
1912 are chiefly notable for the fact that the first thought on
seeing any new type of machine was not as to what its
'performance'--in speed, lift, or what not--would be; but
speculation as to whether it would leave the ground at all when
eventually tried.  This is perhaps the best indication of the
outstanding characteristic of that interim period between the
time of the first actual flights and the later period,
commencing about 1912, when ideas had become settled and it
was at last becoming possible to forecast on the drawing-board
the performance of the completed machine in the air.  Without
going into details, for which there is no space here, it is
difficult to convey the correct impression of the chaotic state
which existed as to even the elementary principles of aeroplane
design.  All the exhibitions contained large numbers--one had
almost written a majority--of machines which embodied the most
unusual features and which never could, and in practice never
did, leave the ground.  At the same time, there were few who
were sufficiently hardy to say certainly that this or that
innovation was wrong; and consequently dozens of inventors in
every country were conducting isolated experiments on both good
and bad lines.  All kinds of devices, mechanical and otherwise,
were claimed as the solution of the problem of stability, and
there was even controversy as to whether any measure of
stability was not undesirable; one school maintaining that the
only safety lay in the pilot having the sole say in the attitude
of the machine at any given moment, and fearing danger from the
machine having any mind of its own, so to speak.  There was, as
in most controversies, some right on both sides, and when we
come to consider the more settled period from 1912 to the
outbreak of the War in 1914 we shall find how a compromise was
gradually effected.

At the same time, however, though it was at the time difficult
to pick out, there was very real progress being made, and,
though a number of 'freak' machines fell out by the wayside, the
pioneer designers of those days learnt by a process of trial and
error the right principles to follow and gradually succeeded in
getting their ideas crystallised.

In connection with stability mention must be made of a machine
which was evolved in the utmost secrecy by Mr J. W. Dunne in a
remote part of Scotland under subsidy from the War office.  This
type, which was constructed in both monoplane and biplane form,
showed that it was in fact possible in 1910 and 1911 to design an
aeroplane which could definitely be left to fly itself in the
air.  One of the Dunne machines was, for example flown from
Farnborough to Salisbury Plain without any control other than the
rudder being touched; and on another occasion it flew a complete
circle with all controls locked automatically assuming the
correct bank for the radius of turn.  The peculiar form of wing
used, the camber of which varied from the root to the tip, gave
rise however, to a certain loss in efficiency, and there was also
a difficulty in the pilot assuming adequate control when desired.
Other machines designed to be stable--such as the German Etrich
and the British Weiss gliders and Handley-Page monoplanes--were
based on the analogy of a wing attached to a certain seed found
in Nature (the 'Zanonia' leaf), on the righting effect of
back-sloped wings combined with upturned (or 'negative') tips. 
Generally speaking, however, the machines of the 1909-1912 period
relied for what automatic stability they had on the principle of
the dihedral angle, or flat V, both longitudinally and laterally.
Longitudinally this was obtained by setting the tail at a
slightly smaller angle than the main planes.

The question of reducing the resistance by adopting 'stream-line'
forms, along which the air could flow uninterruptedly without the
formation of eddies, was not at first properly realised, though
credit should be given to Edouard Nieuport, who in 1909 produced
a monoplane with a very large body which almost completely
enclosed the pilot and made the machine very fast, for those
days, with low horse-power.  On one of these machines C. T.
Weyman won the Gordon-Bennett Cup for America in 1911 and
another put up a fine performance in the same race with only a 30
horse-power engine.  The subject, was however, early taken up by
the British Advisory Committee for Aeronautics, which was
established by the Government in 1909, and designers began to
realise the importance of streamline struts and fuselages towards
the end of this transition period.  These efforts were at first
not always successful and showed at times a lack of understanding
of the problems involved, but there was a very marked improvement
during the year 1912.  At the Paris Aero Salon held early in that
year there was a notable variety of ideas on the subject; whereas
by the time of the one held in October designs had considerably
settled down, more than one exhibitor showing what were called
'monocoque' fuselages completely circular in shape and having
very low resistance, while the same show saw the introduction of
rotating cowls over the propeller bosses, or 'spinners,' as they
came to be called during the War.  A particularly fine example of
stream-lining was to be found in the Deperdussin monoplane on
which Vedrines won back the Gordon-Bennett Aviation Cup from
America at a speed of 105.5 m.p.h.--a considerable improvement on
the 78 m.p.h. of the preceding year, which was by no means
accounted for by the mere increase in engine power from 100
horse-power to 140 horse-power.  This machine was the first in
which the refinement of 'stream-lining' the pilot's head, which
became a feature of subsequent racing machines, was introduced. 
This consisted of a circular padded excresence above the cockpit
immediately behind the pilot's head, which gradually tapered off
into the top surface of the fuselage.  The object was to give the
air an uninterrupted flow instead of allowing it to be broken up
into eddies behind the head of the pilot, and it also provided a
support against the enormous wind-pressure encountered.  This
true stream-line form of fuselage owed its introduction to the
Paulhan-Tatin 'Torpille' monoplane of the Paris Salon of early
1917.  Altogether the end of the year 1912 began to see the
disappearance of 'freak' machines with all sorts of original
ideas for the increase of stability and performance.  Designs had
by then gradually become to a considerable extent standardised,
and it had become unusual to find a machine built which would
fail to fly.  The Gnome engine held the field owing to its
advantages, as the first of the rotary type, in lightness and
ease of fitting into the nose of a fuselage.  The majority of
machines were tractors (propeller in front) although a
preference, which died down subsequently, was still shown for the
monoplane over the biplane.  This year also saw a great increase
in the number of seaplanes, although the 'flying boat' type had
only appeared at intervals and the vast majority were of the
ordinary aeroplane type fitted with floats in place of the land
undercarriage; which type was at that time commonly called
'hydro-aeroplane.'  The usual horse power was 50--that of the
smallest Gnome engine--although engines of 100 to 140 horse-power
were also fitted occasionally.  The average weight per
horse-power varied from 18 to 25 lbs., while the wing-loading was
usually in the neighbourhood of 5 to 6 lbs. per square foot.  The
average speed ranged from 65-75 miles per hour.



==III. PROGRESS ON STANDARDISED LINES==

In the last section an attempt has been made to show how, during
what was from the design standpoint perhaps the most critical
period, order gradually became evident out of chaos,
ill-considered ideas dropped out through failure to make good,
and, though there was still plenty of room for improvement in
details, the bulk of the aeroplanes showed a general similarity
in form and conception.  There was still a great deal to be
learnt in finding the best form of wing section, and performances
were still low; but it had become definitely possible to say that
flying had emerged from the chrysalis stage and had become a
science.  The period which now began was one of scientific
development and improvement--in performance, manoeuvrability,
and general airworthiness and stability.

The British Military Aeroplane Competition held in the summer of
1912 had done much to show the requirements in design by giving
possibly the first opportunity for a definite comparison of the
performance of different machines as measured by impartial
observers on standard lines--albeit the methods of measuring were
crude.  These showed that a high speed--for those days--of 75
miles an hour or so was attended by disadvantages in the form of
an equally fast low speed, of 50 miles per hour or more, and
generally may be said to have given designers an idea what to aim
for and in what direction improvements were required.  In fact,
the most noticeable point perhaps of the machines of this time
was the marked manner in which a machine that was good in one
respect would be found to be wanting in others.  It had not yet
been possible to combine several desirable attributes in one
machine.   The nearest approach to this was perhaps to be found
in the much discussed Government B.E.2 machine, which was
produced from the Royal Aircraft Factory at Farnborough, in the
summer of 1912.  Though considerably criticized from many points
of view it was perhaps the nearest approach to a machine of
all-round efficiency that had up to that date appeared.  The
climbing rate, which subsequently proved so important for
military purposes, was still low, seldom, if ever, exceeding 400
feet per minute; while gliding angles (ratio of descent to
forward travel over the ground with engine stopped) little
exceeded 1 in 8.

The year 1912 and 1913 saw the subsequently all-conquering
tractor biplane begin to come into its own.  This type, which
probably originated in England, and at any rate attained to its
greatest excellence prior to the War from the drawing offices of
the Avro Bristol and Sopwith firms, dealt a blow at the monoplane
from which the latter never recovered. 

The two-seater tractor biplane produced by Sopwith and piloted
by H. G. Hawker, showed that it was possible to produce a
biplane with at least equal speed to the best monoplanes, whilst
having the advantage of greater strength and lower landing
speeds.  The Sopwith machine had a top speed of over 80 miles an
hour while landing as slowly as little more than 30 miles an
hour; and also proved that it was possible to carry 3 passengers
with fuel for 4 hours' flight with a motive power of only 80
horse-power.  This increase in efficiency was due to careful
attention to detail in every part, improved wing sections, clean
fuselage-lines, and simplified undercarriages.  At the same
time, in the early part of 1913 a tendency manifested itself
towards the four-wheeled undercarriage, a pair of smaller wheels
being added in front of the main wheels to prevent overturning
while running on the ground; and several designs of
oleo-pneumatic and steel-spring undercarriages were produced in
place of the rubber shock-absorber type which had up till then
been almost universal.

These two statements as to undercarriage designs may appear to
be contradictory, but in reality they do not conflict as they
both showed a greater attention to the importance of good
springing, combined with a desire to avoid complication and a
mass of struts and wires which increased head resistance.

The Olympia Aero Show of March, 1913, also produced a machine
which, although the type was not destined to prove the best for
the purpose for which it was designed, was of interest as being
the first to be designed specially for war purposes.  This was
the Vickers 'Gun-bus,' a 'pusher' machine, with the propeller
revolving behind the main planes between the outriggers carrying
the tail, with a seat right in front for a gunner who was
provided with a machine gun on a swivelling mount which had a
free field of fire in every direction forward.  The device which
proved the death-blow for this type of aircraft during the war
will be dealt with in the appropriate place later, but the
machine should not go unrecorded.

As a result of a number of accidents to monoplanes the
Government appointed a Committee at the end of 1912 to inquire
into the causes of these.  The report which was presented in
March, 1913, exonerated the monoplane by coming to the
conclusion that the accidents were not caused by conditions
peculiar to monoplanes, but pointed out certain desiderata in
aeroplane design generally which are worth recording.  They
recommended that the wings of aeroplanes should be so internally
braced as to have sufficient strength in themselves not to
collapse if the external bracing wires should give way.  The
practice, more common in monoplanes than biplanes, of carrying
important bracing wires from the wings to the undercarriage was
condemned owing to the liability of damage from frequent
landings.  They also pointed out the desirability of duplicating
all main wires and their attachments, and of using stranded
cable for control wires.  Owing to the suspicion that one
accident at least had been caused through the tearing of the
fabric away from the wing, it was recommended that fabric should
be more securely fastened to the ribs of the wings, and that
devices for preventing the spreading of tears should be
considered.  In the last connection it is interesting to note
that the French Deperdussin firm produced a fabric wing-covering
with extra strong threads run at right-angles through the fabric
at intervals in order to limit the tearing to a defined area.

In spite, however, of the whitewashing of the monoplane by the
Government Committee just mentioned, considerable stir was
occasioned later in the year by the decision of the War office
not to order any more monoplanes; and from this time forward
until the War period the British Army was provided exclusively
with biplanes.  Even prior to this the popularity of the
monoplane had begun to wane.  At the Olympia Aero Show in March,
1913, biplanes for the first time outnumbered the
'single-deckers'(as the Germans call monoplanes); which had the
effect of reducing the wing-loading.  In the case of the
biplanes exhibited this averaged about 4 1/2 lbs. per square
foot, while in the case of the monoplanes in the same exhibition
the lowest was 5 1/2 lbs., and the highest over 8 1/2 lbs. per
square foot of area.  It may here be mentioned that it was not
until the War period that the importance of loading per
horse-power was recognised as the true criterion of aeroplane
efficiency, far greater interest being displayed in the amount
of weight borne per unit area of wing.

An idea of the state of development arrived at about this time
may be gained from the fact that the Commandant of the Military
Wing of the Royal Flying Corps in a lecture before the Royal
Aeronautical Society read in February, 1913, asked for
single-seater scout aeroplanes with a speed of 90 miles an hour
and a landing speed of 45 miles an hour--a performance which
even two years later would have been considered modest in the
extreme.  It serves to show that, although higher performances
were put up by individual machines on occasion, the general
development had not yet reached the stage when such performances
could be obtained in machines suitable for military purposes. 
So far as seaplanes were concerned, up to the beginning of 1913
little attempt had been made to study the novel problems
involved, and the bulk of the machines at the Monaco Meeting in
April, 1913, for instance, consisted of land machines fitted with
floats, in many cases of a most primitive nature, without other
alterations.  Most of those which succeeded in leaving the water
did so through sheer pull of engine power; while practically all
were incapable of getting off except in a fair sea, which enabled
the pilot to jump the machine into the air across the trough
between two waves.  Stability problems had not yet been
considered, and in only one or two cases was fin area added at
the rear high up, to counterbalance the effect of the floats low
down in front.  Both twin and single-float machines were used,
while the flying boat was only just beginning to come into being
from the workshops of Sopwith in Great Britain, Borel-Denhaut in
France, and Curtiss in America.  In view of the approaching
importance of amphibious seaplanes, mention should be made of the
flying boat (or 'bat boat' as it was called, following Rudyard
Kipling) which was built by Sopwith in 1913 with a wheeled
landing-carriage which could be wound up above the bottom surface
of the boat so as to be out of the way when alighting on water.

During 1913 the (at one time almost universal) practice
originated by the Wright Brothers, of warping the wings for
lateral stability, began to die out and the bulk of aeroplanes
began to be fitted with flaps (or 'ailerons') instead.  This
was a distinct change for the better, as continually warping the
wings by bending down the extremities of the rear spars was
bound in time to produce 'fatigue' in that member and lead to
breakage; and the practice became completely obsolete during the
next two or three years.

The Gordon-Bennett race of September, 1913, was again won by
a Deperdussin machine, somewhat similar to that of the previous
year, but with exceedingly small wings, only 107 square feet in
area.  The shape of these wings was instructive as showing how
what, from the general utility point of view, may be
disadvantageous can, for a special purpose, be turned to
account.  With a span of 21 feet, the chord was 5 feet, giving
the inefficient 'aspect ratio' of slightly over 4 to 1 only. 
The object of this was to reduce the lift, and therefore the
resistance, to as low a point as possible.  The total weight was
1,500 lbs., giving a wing-loading of 14 lbs. per square foot--a
hitherto undreamt-of figure.  The result was that the machine
took an enormously long run before starting; and after touching
the ground on landing ran for nearly a mile before stopping; but
she beat all records by attaining a speed of 126 miles per
hour.  Where this performance is mainly interesting is in
contrast to the machines of 1920, which with an even higher
speed capacity would yet be able to land at not more than 40 or
50 miles per hour, and would be thoroughly efficient flying
machines.

The Rheims Aviation Meeting, at which the Gordon-Bennett race
was flown, also saw the first appearance of the Morane 'Parasol'
monoplane.  The Morane monoplane had been for some time an
interesting machine as being the only type which had no fixed
surface in rear to give automatic stability, the movable
elevator being balanced through being hinged about one-third of
the way back from the front edge.  This made the machine
difficult to fly except in the hands of experts, but it was very
quick and handy on the controls and therefore useful for racing
purposes.  In the 'Parasol' the modification was introduced of
raising the wing above the body, the pilot looking out beneath
it, in order to give as good a view as possible.

Before passing to the year 1914 mention should be made of the
feat performed by Nesteroff, a Russian, and Pegoud, a French
pilot, who were the first to demonstrate the possibilities of
flying upside-down and looping the loop.  Though perhaps not
coming strictly within the purview of a chapter on design
(though certain alterations were made to the top wing-bracing of
the machine for this purpose) this performance was of extreme
importance to the development of aviation by showing the
possibility of recovering, given reasonable height, from any
position in the air; which led designers to consider the extra
stresses to which an aeroplane might be subjected and to take
steps to provide for them by increasing strength where
necessary.

When the year 1914 opened a speed of 126 miles per hour had been
attained and a height of 19,600 feet had been reached.  The
Sopwith and Avro (the forerunner of the famous training machine
of the War period) were probably the two leading tractor
biplanes of the world, both two-seaters with a speed variation
from 40 miles per hour up to some 90 miles per hour with 80
horse-power engines.  The French were still pinning their faith
mainly to monoplanes, while the Germans were beginning to come
into prominence with both monoplanes and biplanes of the 'Taube'
type.  These had wings swept backward and also upturned at the
wing-tips which, though it gave a certain measure of automatic
stability, rendered the machine somewhat clumsy in the air, and
their performances were not on the whole as high as those of
either France or Great Britain.

Early in 1914 it became known that the experimental work of
Edward Busk--who was so lamentably killed during an experimental
flight later in the year--following upon the researches of
Bairstow and others had resulted in the production at the Royal
Aircraft Factory at Farnborough of a truly automatically stable
aeroplane. This was the 'R.E.' (Reconnaissance Experimental), a
development of the B.E. which has already been referred to.  The
remarkable feature of this design was that there was no
particular device to which one could point out as the cause of
the stability.  The stable result was attained simply by detailed
design of each part of the aeroplane, with due regard to its
relation to, and effect on, other parts in the air.  Weights and
areas were so nicely arranged that under practically any
conditions the machine tended to right itself.  It did not,
therefore, claim to be a machine which it was impossible to
upset, but one which if left to itself would tend to right itself
from whatever direction a gust might come.  When the principles
were extended to the 'B.E. 2c' type (largely used at the outbreak
of the War) the latter machine, if the engine were switched of f
at a height of not less than 1,000 feet above the ground, would
after a few moments assume its correct gliding angle and glide
down to the ground.

The Paris Aero Salon of December, 1913, had been remarkable
chiefly for the large number of machines of which the chassis and
bodywork had been constructed of steel-tubing; for the excess of
monoplanes over biplanes; and (in the latter) predominance of
'pusher' machines (with propeller in rear of the main planes)
compared with the growing British preference for 'tractors' (with
air screw in front).  Incidentally, the Maurice Farman, the last
relic of the old type box-kite with elevator in front appeared
shorn of this prefix, and became known as the 'short-horn' in
contradistinction to its front-elevatored predecessor which,
owing to its general reliability and easy flying capabilities,
had long been affectionately called the 'mechanical cow.'  The 
1913 Salon also saw some lingering attempts at attaining
automatic stability by pendulum and other freak devices.

Apart from the appearance of 'R.E.1,' perhaps the most notable
development towards the end of 1913 was the appearance of the
Sopwith 'Tabloid 'tractor biplane.  This single-seater machine,
evolved from the two-seater previously referred to, fitted with a
Gnome engine of 80 horse-power, had the, for those days,
remarkable speed of 92 miles an hour; while a still more
notable feature was that it could remain in level flight at not
more than 37 miles per hour.  This machine is of particular
importance because it was the prototype and forerunner of the
successive designs of single-seater scout fighting machines
which were used so extensively from 1914 to 1918.  It was also
probably the first machine to be capable of reaching a height of
1,000 feet within one minute.  It was closely followed by the
'Bristol Bullet,' which was exhibited at the Olympia Aero Show
of March, 1914.  This last pre-war show was mainly remarkable
for the good workmanship displayed--rather than for any distinct
advance in design.  In fact, there was a notable diversity in
the types displayed, but in detailed design considerable
improvements were to be seen, such as the general adoption of
stranded steel cable in place of piano wire for the mail bracing



==IV. THE WAR PERIOD==

Up to this point an attempt has been made to give some idea of
the progress that was made during the eleven years that had
elapsed since the days of the Wrights' first flights.  Much
advance had been made and aeroplanes had settled down,
superficially at any rate, into more or less standardised forms
in three main types--tractor monoplanes, tractor biplanes, and
pusher biplanes.  Through the application of the results of
experiments with models in wind tunnels to full-scale machines,
considerable improvements had been made in the design of wing
sections, which had greatly increased the efficiency of
aeroplanes by raising the amount of 'lift' obtained from the
wing compared with the 'drag' (or resistance to forward motion)
which the same wing would cause.  In the same way the shape of
bodies, interplane struts, etc., had been improved to be of
better stream-line shape, for the further reduction of
resistance; while the problems of stability were beginning to be
tolerably well understood.  Records (for what they are worth)
stood at 21,000 feet as far as height was concerned, 126 miles
per hour for speed, and 24 hours duration. That there was
considerable room for development is, however, evidenced by a
statement made by the late B. C. Hucks (the famous pilot) in
the course of an address delivered before the Royal Aeronautical
Society in July, 1914.  'I consider,' he said, 'that the present
day standard of flying is due far more to the improvement in
piloting than to the improvement in machines.... I consider
those (early 1914) machines are only slight improvements on the
machines of three years ago, and yet they are put through
evolutions which, at that time, were not even dreamed of.  I can
take a good example of the way improvement in piloting has
outdistanced improvement in machines--in the case of myself, my
'looping' Bleriot.  Most of you know that there is very little
difference between that machine and the 50 horse-power Bleriot
of three years ago.'  This statement was, of course, to some
extent an exaggeration and was by no means agreed with by
designers, but there was at the same time a germ of truth in it. 
There is at any rate little doubt that the theory and practice
of aeroplane design made far greater strides towards becoming an
exact science during the four years of War than it had done
during the six or seven years preceding it.

It is impossible in the space at disposal to treat of this
development even with the meagre amount of detail that has been
possible while covering the 'settling down' period from 1911 to
1914, and it is proposed, therefore, to indicate the improvements
by sketching briefly the more noticeable difference in various
respects between the average machine of 1914 and a similar
machine of 1918.

In the first place, it was soon found that it was possible to
obtain greater efficiency and, in particular, higher speeds,
from tractor machines than from pusher machines with the air
screw behind the main planes.  This was for a variety of reasons
connected with the  efficiency of propellers and the possibility
of reducing resistance to a greater extent in tractor machines
by using a 'stream-line' fuselage (or body) to connect the main
planes with the tail.  Full advantage of this could not be
taken, however, owing to the difficulty of fixing a machine-gun
in a forward direction owing to the presence of the propeller. 
This was finally overcome by an ingenious device (known as an
'Interrupter gear') which allowed the gun to fire only when
none of the propeller blades was passing in front of the muzzle. 
The monoplane gradually fell into desuetude, mainly owing to the
difficulty of making that type adequately strong without it
becoming prohibitively heavy, and also because of its high
landing speed and general lack of manoeuvrability.  The triplane
was also little used except in one or two instances, and,
practically speaking, every machine was of the biplane tractor
type.

A careful consideration of the salient features leading to
maximum efficiency in aeroplanes--particularly in regard to
speed and climb, which were the two most important military
requirements--showed that a vital feature was the reduction in
the amount of weight lifted per horse-power employed; which in
1914 averaged from 20 to 25 lbs.  This was effected both by
gradual increase in the power and size of the engines used and
by great improvement in their detailed design (by increasing
compression ratio and saving weight whenever possible); with the
result that the motive power of single-seater aeroplanes rose
from 80 and 100 horse-power in 1914 to an average of 200 to 300
horse-power, while the actual weight of the engine fell from 3
1/2-4 lbs. per horse-power to an average of 2 1/2 lbs. per
horse-power.  This meant that while a pre-war engine of 100
horse-power would weigh some 400 lbs., the 1918 engine developing
three times the power would have less than double the weight. 
The result of this improvement was that a scout aeroplane at the
time of the Armistice would have 1 horse-power for every 8 lbs.
of weight lifted, compared with the 20 or 25 lbs. of its 1914
predecessors.  This produced a considerable increase in the rate
of climb, a good postwar machine being able to reach 10,000 feet
in about 5 minutes and 20,000 feet in under half an hour.  The
loading per square foot was also considerably increased; this
being rendered possible both by improvement in the design of wing
sections and by more scientific construction giving increased
strength.  It will be remembered that in the machine of the very
early period each square foot of surface had only to lift a
weight of some 1 1/2 to 2 lbs., which by 1914 had been increased
to about 4 lbs.  By 1918 aeroplanes habitually had a loading of 8
lbs. or more per square foot of area; which resulted in great
increase in speed.  Although a speed of 126 miles per hour had
been attained by a specially designed racing machine over a short
distance in 1914, the average at that period little exceeded, if
at all, 100 miles per hour; whereas in 1918 speeds of 130 miles
per hour had become a commonplace, and shortly afterwards a speed
of over 166 miles an hour was achieved.

In another direction, also, that of size, great developments
were made.  Before the War a few machines fitted with more than
one engine had been built (the first being a triple
Gnome-engined biplane built by Messrs Short Bros. at Eastchurch
in 1913), but none of large size had been successfully produced,
the total weight probably in no case exceeding about 2 tons.  In
1916, however, the twin engine Handley-Page biplane was
produced, to be followed by others both in this country and
abroad, which represented a very great increase in size and,
consequently, load-carrying capacity.  By the end of the War
period several types were in existence weighing a total of 10
tons when fully loaded, of which some 4 tons or more represented
'useful load' available for crew, fuel, and bombs or passengers. 
This was attained through very careful attention to detailed
design, which showed that the material could be employed more
efficiently as size increased, and was also due to the fact that
a large machine was not liable to be put through the same
evolutions as a small machine, and therefore could safely be
built with a lower factor of safety.  Owing to the fact that a
wing section which is adopted for carrying heavy loads usually
has also a somewhat low lift to drag ratio, and is not therefore
productive of high speed, these machines are not as fast as
light scouts; but, nevertheless, they proved themselves capable
of achieving speeds of 100 miles an hour or more in some cases;
which was faster than the average small machine of 1914.

In one respect the development during the War may perhaps have
proved to be somewhat disappointing, as it might have been
expected that great improvements would be effected in metal
construction, leading almost to the abolition of wooden
structures.  Although, however, a good deal of experimental work
was done which resulted in overcoming at any rate the worst of
the difficulties, metal-built machines were little used (except
to a certain extent in Germany) chiefly on account of the need
for rapid production and the danger of delay resulting from
switching over from known and tried methods to experimental
types of construction.  The Germans constructed some large
machines, such as the giant Siemens-Schukhert machine, entirely
of metal except for the wing covering, while the Fokker and
Junker firms about the time of the Armistice in 1918 both
produced monoplanes with very deep all-metal wings (including
the covering) which were entirely unstayed externally, depending
for their strength on internal bracing.  In Great Britain cable
bracing gave place to a great extent to 'stream-line wires,'
which are steel rods rolled to a more or less oval section,
while tie-rods were also extensively used for the internal
bracing of the wings.  Great developments in the economical use
of material were also made in the direction of using built-up
main spars for the wings and interplane struts; spars composed
of a series of layers (or 'laminations') of different pieces of
wood also being used.

Apart from the metallic construction of aeroplanes an enormous
amount of work was done in the testing of different steels and
light alloys for use in engines, and by the end of the War
period a number of aircraft engines were in use of which the
pistons and other parts were of such alloys; the chief
difficulty having been not so much in the design as in the
successful heat-treatment and casting of the metal.

An important development in connection with the inspection and
testing of aircraft parts, particularly in the case of metal,
was the experimental application of X-ray photography, which
showed up latent defects, both in the material and in
manufacture, which would otherwise have passed unnoticed.  This
method was also used to test the penetration of glue into the
wood on each side of joints, so giving a measure of the
strength;  and for the effect of 'doping' the wings, dope being a
film (of cellulose acetate dissolved in acetone with other
chemicals) applied to the covering of wings and bodies to render
the linen taut and weatherproof, besides giving it a smooth
surface for the lessening of 'skin friction' when passing rapidly
through the air.

An important result of this experimental work was that it in
many cases enabled designers to produce aeroplane parts from
less costly material than had previously been considered
necessary, without impairing the strength.  It may be mentioned
that it was found undesirable to use welded joints on aircraft
in any part where the material is subjectto a tensile or bending
load, owing to the danger resulting from bad workmanship causing
the material to become brittle--an effect which cannot be
discovered except by cutting through the weld, which, of course,
involves a test to destruction.  Written, as it has been, in
August, 1920, it is impossible in this chapter to give any
conception of how the developments of War will be applied to
commercial aeroplanes, as few truly commercial machines have yet
been designed, and even those still show distinct traces of the
survival of war mentality.  When, however, the inevitable
recasting of ideas arrives, it will become evident, whatever the
apparent modification in the relative importance of different
aspects of design, that enormous advances were made under the
impetus of War which have left an indelible mark on progress.

We have, during the seventeen years since aeroplanes first took
the air, seen them grow from tentative experimental structures
of unknown and unknowable performance to highly scientific
products, of which not only the performances (in speed,
load-carrying capacity, and climb) are known, but of which the
precise strength and degree of stability can be forecast with
some accuracy on the drawing board.  For the rest, with the
future lies--apart from some revolutionary change in fundamental
design--the steady development of a now well-tried and well-found
engineering structure.





:Fortsetzung: [[Aeronautics_History_Vivian_1920 06 Aerostatics|I.  BEGINNINGS]]


==CONTENTS==

:Part I--THE EVOLUTION OF THE AEROPLANE
:   [[Aeronautics_History_Vivian_1920 01 Evolution of the Aeroplane Early Phase|I.  THE PERIOD OF LEGEND]]
: [[Aeronautics_History_Vivian_1920 01 Evolution of the Aeroplane Early Phase|II.  EARLY EXPERIMENTS]]
:  [[Aeronautics_History_Vivian_1920 01 Evolution of the Aeroplane Early Phase|III.  SIR GEORGE CAYLEY--THOMAS WALKER]]
:   [[Aeronautics_History_Vivian_1920 01 Evolution of the Aeroplane Early Phase|IV.  THE MIDDLE NINETEENTH CENTURY]]
:    [[Aeronautics_History_Vivian_1920 01 Evolution of the Aeroplane Early Phase|V.  WENHAM, LE BRIS, AND SOME OTHERS]]
:   [[Aeronautics_History_Vivian_1920 02 Evolution of the Aeroplane Age of the Giants|VI.  THE AGE OF THE GIANTS]]
:  [[Aeronautics_History_Vivian_1920 02 Evolution of the Aeroplane Age of the Giants|VII.  LILIENTHAL AND PILCHER]]
: [[Aeronautics_History_Vivian_1920 02 Evolution of the Aeroplane Age of the Giants|VIII.  AMERICAN GLIDING EXPERIMENTS]]
:   [[Aeronautics_History_Vivian_1920 02 Evolution of the Aeroplane Age of the Giants|IX.  NOT PROVEN]]
:    [[Aeronautics_History_Vivian_1920 02 Evolution of the Aeroplane Age of the Giants|X.  SAMUEL PIERPOINT LANGLEY]]
:   [[Aeronautics_History_Vivian_1920 02 Evolution of the Aeroplane Age of the Giants|XI.  THE WRIGHT BROTHERS]]
:  [[Aeronautics_History_Vivian_1920 03 Evolution of the Aeroplane Years of Conquest|XII.  THE FIRST YEARS OF CONQUEST]]
: [[Aeronautics_History_Vivian_1920 03 Evolution of the Aeroplane Years of Conquest|XIII.  FIRST FLIERS IN ENGLAND]]
:  [[Aeronautics_History_Vivian_1920 03 Evolution of the Aeroplane Years of Conquest|XIV.  RHEIMS, AND AFTER]]
:   [[Aeronautics_History_Vivian_1920 03 Evolution of the Aeroplane Years of Conquest|XV.  THE CHANNEL CROSSING]]
:  [[Aeronautics_History_Vivian_1920 03 Evolution of the Aeroplane Years of Conquest|XVI.  LONDON TO MANCHESTER]]
: [[Aeronautics_History_Vivian_1920 03 Evolution of the Aeroplane Years of Conquest|XVII.  A SUMMARY--TO 1911]]
:[[Aeronautics_History_Vivian_1920 04 Evolution of the Aeroplane Pre-war,WW1, Post-war to 1920|XVIII.  A SUMMARY--TO 1914]]
:  [[Aeronautics_History_Vivian_1920 04 Evolution of the Aeroplane Pre-war,WW1, Post-war to 1920|XIX.  THE WAR PERIOD--I]]
:   [[Aeronautics_History_Vivian_1920 04 Evolution of the Aeroplane Pre-war,WW1, Post-war to 1920|XX.  THE WAR PERIOD--II]]
:  [[Aeronautics_History_Vivian_1920 04 Evolution of the Aeroplane Pre-war,WW1, Post-war to 1920|XXI.  RECONSTRUCTION]]
: [[Aeronautics_History_Vivian_1920 04 Evolution of the Aeroplane Pre-war,WW1, Post-war to 1920|XXII.  1919-1920]]

:Part II--1903-1920: PROGRESS IN DESIGN
:    [[Aeronautics_History_Vivian_1920 05 Progress in Design|I.  THE BEGINNINGS]]
:   [[Aeronautics_History_Vivian_1920 05 Progress in Design|II.  MULTIPLICITY OF IDEAS]]
:  [[Aeronautics_History_Vivian_1920 05 Progress in Design|III.  PROGRESS ON STANDARDISED LINES]]
:   [[Aeronautics_History_Vivian_1920 05 Progress in Design|IV.  THE WAR PERIOD]]

:Part III--AEROSTATICS
:    [[Aeronautics_History_Vivian_1920 06 Aerostatics|I.  BEGINNINGS]]
:   [[Aeronautics_History_Vivian_1920 06 Aerostatics|II.  THE FIRST DIRIGIBLES]]
:  [[Aeronautics_History_Vivian_1920 06 Aerostatics|III.  SANTOS-DUMONT]]
:   [[Aeronautics_History_Vivian_1920 06 Aerostatics|IV.  THE MILITARY DIRIGIBLE]]
:    [[Aeronautics_History_Vivian_1920 06 Aerostatics|V.  BRITISH AIRSHIP  DESIGN]]
:   [[Aeronautics_History_Vivian_1920 06 Aerostatics|VI.  THE AIRSHIP  COMMERCIALLY]]
:  [[Aeronautics_History_Vivian_1920 06 Aerostatics|VII.  KITE  BALLOONS]]

:PART IV--ENGINE DEVELOPMENT
:    [[Aeronautics_History_Vivian_1920 07 Engine Development|I.  THE VERTICAL TYPE]]
:   [[Aeronautics_History_Vivian_1920 07 Engine Development|II.  THE VEE TYPE]]
:  [[Aeronautics_History_Vivian_1920 07 Engine Development|III.  THE RADIAL TYPE]]
:   [[Aeronautics_History_Vivian_1920 07 Engine Development|IV.  THE ROTARY TYPE]]
:    [[Aeronautics_History_Vivian_1920 07 Engine Development|V.  THE HORIZONTALLY-OPPOSED ENGINE]]
:   [[Aeronautics_History_Vivian_1920 07 Engine Development|VI.  THE TWO-STROKE CYCLE ENGINE]]
:  [[Aeronautics_History_Vivian_1920 07 Engine Development|VII.  ENGINES OF THE WAR  PERIOD]]

:[[Aeronautics_History_Vivian_1920 08 Appendixes|APPENDICES]]


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