03.31.08
Posted in Uncategorized at 10:32 am by admin
Tissandiers, weighing altogether 1,174 lbs., and developing 9
horsepower. A speed of 14 miles an hour was attained with this
dirigible, which had a length of 165 feet, diameter of 27 feet,
and capacity of 65,836 cubic feet of gas.
Reverting to the petrol-fed type again, it is to be noted that
Santos-Dumont was practically the first to develop the use of
the ordinary automobile engine for air work–his work is of such
importance that it has been considered best to treat of it as
one whole, and details of the power plants are included in the
account of his experiments. Coming to the Lebaudy brothers and
their work, their engine of 1902 was a 40 horse-power Daimler,
four-cylindered; it was virtually a large edition of the Daimler
car engine, the arrangement of the various details being on the
lines usually adopted for the standard Daimler type of that
period. The cylinders were fully water-jacketed, and no special
attempt toward securing lightness for air work appears to have
been made.
The fining down of detail that brought weight to such limits as
would fit the engine for work with heavier-than-air craft
appears to have waited for the brothers Wright. Toward the end
of 1903 they fitted to their first practicable flying machine the
engine which made the historic first aeroplane flight; this
engine developed 30 horse-power, and weighed only about 7 lbs.
per horse-power developed, its design and workmanship being far
ahead of any previous design in this respect, with the exception
of the remarkable engine, designed by Manly, installed in
Langleys ill-fated aeroplane–or aerodrome, as he preferred to
call it–tried in 1903.
The light weight of the Wright brothers engine did not
necessitate a high number of revolutions per minute to get the
requisite power; the speed was only 1,300 revolutions per
minute, which, with a piston stroke of 3.94 inches, was quite
moderate. Four cylinders were used, the cylinder diameter being
4.42 inches; the engine was of the vertical type, arranged to
drive two propellers at a rate of about 350 revolutions per
minute, gearing being accomplished by means of chain drive from
crank-shaft end to propeller spindle.
The methods adopted by the Wrights for obtaining a light-weight
engine were of considerable interest, in view of the fact that
the honour of first achieving flight by means of the driven plane
belongs to them–unless Ader actually flew as he claimed. The
cylinders of this first Wright engine were separate castings of
steel, and only the barrels were jacketed, this being done by
fixing loose, thin aluminium covers round the outside of each
cylinder. The combustion head and valve pockets were cast
together with the cylinder barrel, and were not water cooled.
The inlet valves were of the automatic type, arranged on the tops
of the cylinders, while the exhaust valves were also overhead,
operated by rockers and push-rods. The pistons and piston rings
were of the ordinary type, made of cast-iron, and the connecting
rods were circular in form, with a hole drilled down the middle
of each to reduce the weight.
Necessity for increasing power and ever lighter weight in
relation to the power produced has led to the evolution of a
number of different designs of internal combustion engines. It
was quickly realised that increasing the number of cylinders on
an engine was a better way of getting more power than that of
increasing the cylinder diameter, as the greater number of
cylinders gives better torque-even turning effect–as well as
keeping down the weight–this latter because the bigger
cylinders must be more stoutly constructed than the small sizes;
this fact has led to the construction of engines having as many
as eighteen cylinders, arranged in three parallel rows in order
to keep the length of crankshaft within reasonable limits. The
aero engine of to-day may, roughly, be divided into four
classes: these are the V type, in which two rows of cylinders
are set parallel at a certain angle to each other; the radial
type, which consists of cylinders arranged radially and
remaining stationary while the crankshaft revolves; the rotary,
where the cylinders are disposed round a common centre and
revolve round a stationary shaft, and the vertical type, of four
or six cylinders–seldom more than this–arranged in one row. A
modification of the V type is the eighteen-cylindered engine–
the Sunbeam is one of the best examples–in which three rows of
cylinders are set parallel to each other, working on a common
crankshaft. The development these four types started with that
of the vertical–the simplest of all; the V, radial, and rotary
types came after the vertical, in the order given.
Permalink
03.29.08
Posted in Uncategorized at 12:11 pm by admin
CHAPTER XLIX
The Future in the Air
Three years before the outbreak of the Great War, the
Master-General of Ordnance, who was in charge of Aeronautics at
the War Office, declared: “We are not yet convinced that either
aeroplanes or air-ships will be of any utility in war”.
After four years of war, with its ceaseless struggle between the
Allies and the Central Powers for supremacy in the air, such a
statement makes us rub our eyes as though we had been dreaming.
Seven years–and in its passage the air encircling the globe has
become one gigantic battle area, the British Isles have lost the
age-long security which the seas gave them, and to regain the old
proud unassailable position must build a gigantic aerial fleet–
as greatly superior to that of their neighbours as was, and is,
the British Navy.
Seven years–and the monoplane is on the scrap-heap; the Zeppelin
has come as a giant destroyer–and gone, flying rather
ridiculously before the onslaughts of its tiny foes. In a
recent article the editor of The Aeroplane referred to the
erstwhile terror of the air as follows: “The best of air-ships
is at the mercy of a second-rate aeroplane”. Enough to make
Count Zeppelin turn in his grave!
To-day in aerial warfare the air-ship is relegated to the task of
observer. As the “Blimp”, the kite-balloon, the coast patrol,
it scouts and takes copious notes; but it leaves the fighting to
a tiny, heavier-than-air machine armed with a Lewis gun, and
destructive attacks to those big bomb-droppers, the British
Handley Page, the German Gotha, the Italian Morane tri-plane.
The war in the air has been fought with varying fortunes. But,
looking back upon four years of war, we may say that, in spite of
a slow start, we have managed to catch up our adversaries, and of
late we have certainly dealt as hard knocks as we have received.
A great spurt of aerial activity marked the opening of the year
1918. From all quarters of the globe came reports, moderate and
almost bald in style, but between the lines of which the average
man could read word-pictures of the skill, prowess, and ceaseless
bravery of the men of the Royal Flying Corps and Royal Naval Air
Service. Recently there have appeared two official publications
[1], profusely illustrated with photographs, which give an
excellent idea of the work and training of members of the two
corps. Forewords have been contributed respectively by Lord Hugh
Cecil and Sir Eric Geddes, First Lord of the Admiralty. These
publications lift a curtain upon not only the activities of the
two Corps, but the tremendous organization now demanded by war in
the air.
[1] The Work and Training of the Royal Flying Corps and The Work
and Training of the Royal Naval Air Service.
All this to-day. To-morrow the Handley Page and Gotha may be
occupying their respective niches in the museum of aerial
antiquities, and we may be all agog over the aerial passenger
service to the United States of America.
For truly, in the science of aviation a day is a generation, and
three months an eon. When the coming of peace turns mens
thoughts to the development of aeroplanes for commerce and
pleasure voyages, no one can foretell what the future may bring
forth.
At the time of writing, air attacks are still being directed upon
London. But the enemy find it more and more difficult to
penetrate the barrage. Sometimes a solitary machine gets
through. Frequently the whole squadron of raiding aeroplanes is
turned back at the coast.
As for the military advantage the Germans have derived, after
nearly four years of attacks by air, it may be set down as
practically nil. In raid after raid they missed their so-called
objectives and succeeded only in killing noncombatants. Far
different were the aim and scope of the British air offensives
into Germany and into country occupied by German troops. Railway
junctions, ammunition dumps, enemy billets, submarine bases,
aerodromes–these were the targets for our airmen, who scored
hits by the simple but dangerous plan of flying so low that
misses were almost out of the question.
“Make sure of your objective, even if you have to sit upon it.”
Permalink
03.28.08
Posted in Uncategorized at 12:11 am by admin
Scientists estimate that to raise a man of about 12 stone in the
air and enable him to fly there would be required an immense pair
of wings over 20 feet in span. In comparison with the weight of
a man a birds weight is remarkably small–the largest bird does
not weigh much more than 20 pounds–but its wing muscles are
infinitely stronger in proportion than the shoulder and arm
muscles of a man.
As we shall see in a succeeding chapter, the “wing” theory was
persevered with for many years some two or three centuries ago,
and later on it was of much use in providing data for the gradual
development of the modern aeroplane.
CHAPTER XV
A Pioneer in Aviation
Hitherto we have traced the gradual development of the balloon
right from the early days of aeronautics, when the brothers
Montgolfier constructed their hot-air balloon, down to the most
modern dirigible. It is now our purpose, in this and subsequent
chapters, to follow the course of the pioneers of aviation.
It must not be supposed that the invention of the steerable
balloon was greatly in advance of that of the heavier-than-air
machine. Indeed, developments in both the dirigible airship and
the aeroplane have taken place side by side. In some cases men
like Santos Dumont have given earnest attention to both forms of
air-craft, and produced practical results with both. Thus, after
the famous Brazilian aeronaut had won the Deutsch prize for a
flight in an air-ship round the Eiffel tower, he immediately set
to work to construct an aeroplane which he subsequently piloted
at Bagatelle and was awarded the first “Deutsch prize” for
aviation.
It is generally agreed that the undoubted inventor of the
aeroplane, practically in the form in which it now appears, was
an English engineer, Sir George Cayley. Just over a hundred
years ago this clever Englishman worked out complete plans for an
aeroplane, which in many vital respects embodied the principal
parts of the monoplane as it exists to-day.
There were wings which were inclined so that they formed a
lifting plane; moreover, the wings were curved, or “cambered”,
similar to the wing of a bird, and, as we shall see in a later
chapter, this curve is one of the salient features of the plane
of a modern heavier-than-air machine. Sir George also advocated
the screw propeller worked by some form of “explosion” motor,
which at that time had not arrived. Indeed, if there had been a
motor available it is quite possible that England would have led
the way in aviation. But, unfortunately, owing to the absence of
a powerful motor engine, Sir Georges ideas could not be
practically carried out till nearly a century later, and then
Englishmen were forestalled by the Wright brothers, of America,
as well as by several French inventors.
The distinguished French writer, Alphonse Berget, in his book,
The Conquest of the Air, pays a striking tribute to our English
inventor, and this, coming from a gentleman who is writing from a
French point of view, makes the praise of great value. In
alluding to Sir George, M. Berget says: “The inventor, the
incontestable forerunner of aviation, was an Englishman, Sir
George Cayley, and it was in 1809 that he described his project
in detail in Nicholsons Journal. . . . His idea embodied
everything–the wings forming an oblique sail, the empennage,
the spindle forms to diminish resistance, the screw-propeller,
the explosion motor, . . . he even described a means of
securing automatic stability. Is not all that marvellous, and
does it not constitute a complete specification for everything in
aviation?
“Thus it is necessary to inscribe the name of Sir George Cayley
in letters of gold, in the first page of the aeroplanes history.
Besides, the learned Englishman did not confine himself to
drawing-paper: he built the first apparatus (without a motor)
which gave him results highly promising. Then he built a second
machine, this time with a motor, but unfortunately during the
trials it was smashed to pieces.”
Permalink
03.25.08
Posted in Uncategorized at 1:21 am by admin
Brabazon, who made a flight of 17 miles.
Some of Colonel Codys achievements in aviation were made with
the Green engine. In 1910 he succeeded in winning both the
duration and cross-country Michelin competitions, and in 1911 he
again accomplished similar feats. In this year he also finished
fourth in the all-round-Britain race. This was a most
meritorious performance when it is remembered that his Cathedral
weighed nearly a ton and ahalf, and that the 60-horse-power Green
was practically “untouched”, to use an engineering expression,
during the whole of the 1010-mile flight.
The following year saw Cody winning another Michelin prize for a
cross-country competition. Here he made a flight of over 200
miles, and his high opinion of the engine may be best described
in the letter he wrote to the company, saying: “If you kept the
engine supplied from without with petrol and oil, what was within
would carry you through”.
But the pinnacle of Mr. Greens fame as an inventor was reached
in 1913, when Mr. Harry Hawker made his memorable waterplane
flight from Cowes to Lough Shinny, an account of which appears in
a later chapter. His machine was fitted with a 100-horse-power
Green, and with it he flew 1043 miles of the 1540-miles course.
Though the complete course was not covered, neither Mr. Sopwith–
who built the machine and bore the expenses of the flight–nor
Mr. Hawker attached any blame to the engine. At a dinner of the
Aero Club, given in 1914, Mr. Sopwith was most enthusiastic in
discussing the merits of the “Green”, and after Harry Hawker had
recovered from the effects of his fall in Lough Shinny he
remarked in reference to the engine: “It is the best I have ever
met. I do not know any other that would have done anything like
the work.”
At the same time that this race was being held the French had a
competition from Paris to Deauville, a distance of about 160
miles. When compared with the time and distance covered by Mr.
Hawker, the results achieved by the French pilots, flying
machines fitted with French engines, were quite insignificant;
thus proving how the British industry had caught up, and even
passed, its closest rivals.
In 1913 Mr. Grahame White, with one of the 100-horse-power
“Greens” succeeded in winning the duration Michelin with a flight
of over 300 miles, carrying a mechanic and pilot, 85 gallons of
petrol, and 12 gallons of lubricating oil. Compulsory landings
were made every 63 miles, and the engine was stopped. In spite
of these trying conditions, the engine ran, from start to finish,
nearly nine hours without the slightest trouble.
Sufficient has been said to prove conclusively that the thought
and labour expended in the perfecting of the Green engine have
not been fruitless.
CHAPTER XXIV
The Wright Biplane (Camber of Planes)
Now that the internal-combustion engine had arrived, the Wrights
at once commenced the construction of an aeroplane which could be
driven by mechanical power. Hitherto, as we have seen, they had
made numerous tests with motorless gliders; but though these
tests gave them much valuable information concerning the best
methods of keeping their craft on an even keel while in the air,
they could never hope to make much progress in practical flight
until they adopted motor power which would propel the machine
through the air.
Permalink
03.22.08
Posted in Uncategorized at 8:41 pm by admin
Should a strand become broken, then the cable should be
replaced at once by another one.
Control cables have a way of wearing out and fraying
wherever they pass round pulleys. Every time an aeroplane
comes down from flight the rigger should carefully examine
the cables, especially where they pass round pulleys. If
he finds a strand broken, he should replace the cable.
The ailerons balance cable on the top of the top plane
is often forgotten, since it is necessary to fetch a high pair
of steps in order to examine it. Dont slack this, or some
gusty day the pilot may unexpectedly find himself minus the
aileron control.
CONTROLLING SURFACES.–The greatest care should be
exercised in rigging the aileron, rudder, and elevator properly,
for the pilot entirely depends upon them in managing the
aeroplane.
The ailerons and elevator should be rigged so that, when
the aeroplane is in flight, they are in a fair true line with the
surface in front and to which they are hinged.
If the surface to which they are hinged is not a lifting
surface, then they should be rigged to be in a fair true line
with it as illustrated above.
If the controlling surface is, as illustrated, hinged to the
back of a lifting surface, then it should be rigged a little below
the position it would occupy if in a fair true line with the
surface in front. This is because, in such a case, it is set
at an angle of incidence. This angle will, during flight,
cause it to lift a little above the position in which it has been
rigged. It is able to lift owing to a certain amount of slack
in the control wire holding it–and one cannot adjust the
control wire to have no slack, because that would cause it
to bind against the pulleys and make the operation of it too
hard for the pilot. It is therefore necessary to rig it a little
below the position it would occupy if it was rigged in a fair
true line with the surface in front. Remember that this
only applies when it is hinged to a lifting surface. The
greater the angle of incidence (and therefore the lift) of the
surface in front, then the more the controlling surface will
have to be rigged down.
As a general rule it is safe to rig it down so that its trailing
edge is 1/2 to 3/4 inch below the position it would occupy if in
a fair line with the surface in front; or about 1/2 inch down for
every 18 inches of chord of the controlling surface.
When making these adjustments the pilots control levers
should be in their neutral positions. It is not sufficient
to lash them. They should be rigidly blocked into position
with wood packing.
The surfaces must not be distorted in any way. If
they are held true by bracing wires, then such wires must be
carefully adjusted. If they are distorted and there are no
bracing wires with which to true them, then some of the
internal framework will probably have to be replaced.
The controlling surfaces should never be adjusted with
a view to altering the stability of the aeroplane. Nothing
can be accomplished in that way. The only result will be
to spoil the control of the aeroplane.
FABRIC-COVERED SURFACES.–First of all make sure
that there is no distortion of spars or ribs, and that they are
perfectly sound. Then adjust the internal bracing wires
so that the ribs are parallel to the direction of flight. The
ribs usually cause the fabric to make a ridge where they occur,
and, if such ridge is not parallel to the direction of flight,
it will produce excessive drift. As a rule the ribs are at
right angles to both main and rear spars.
The tension of the internal bracing wires should be just
sufficient to give rigidity to the framework. They should
not be tensioned above that unless the wires are, at their
ends, bent to form loops. In that case a little extra tension
may be given to offset the probable elongation of the
loops.
Permalink
03.20.08
Posted in Uncategorized at 9:21 am by admin
Henry Farman, who began his flying career with a Voisin machine,
evolved from it the aeroplane which bore his name, following the
main lines of the Voisin type fairly closely, but making
alterations in the controls, and in the design of the
undercarriage, which was somewhat elaborated, even to the
inclusion of shock absorbers. The seven-cylinder 50 horse-power
Gnome rotary engine was fitted to the Farman machine–the
Voisins had fitted an eight-cylinder Antoinette, giving 50
horse-power at 1,100 revolutions per minute, with direct drive
to the propeller. Farman reduced the weight of the machine from
the 1,450 lbs. of the Voisins to some 1,010 lbs. or
thereabouts, and the supporting area to 450 square feet. This
machine won its chief fame with Paulhan as pilot in the famous
London to Manchester flight–it is to be remarked, too, that
Farman himself was the first man in Europe to accomplish a
flight of a mile.
Other notable designs of these early days were the R.E.P.,
Esnault Pelteries machine, and the Curtiss-Herring biplane. Of
these Esnault Pelteries was a monoplane, designed in that form
since Esnault Pelterie had found by experiment that the wire
used in bracing offers far more resistance to the air than its
dimensions would seem to warrant. He built the wings of
sufficient strength to stand the strain of flight without
bracing wires, and dependent only for their support on the
points of attachment to the body of the machine; for the rest,
it carried its propeller in front of the planes, and both
horizontal and vertical rudders at the stern–a distinct
departure from the Wright and similar types. One wheel only was
fixed under the body where the undercarriage exists on a normal
design, but light wheels were fixed, one at the extremity of
each wing, and there was also a wheel under the tail portion of
the machine. A single lever actuated all the controls for
steering. With a supporting surface of 150 square feet the
machine weighed 946 lbs., about 6.4 lbs. per square foot of
lifting surface.
The Curtiss biplane, as flown by Glenn Curtiss at the Rheims
meeting, was built with a bamboo framework, stayed by means of
very fine steel-stranded cables. A–then–novel feature of the
machine was the moving of the ailerons by the pilot leaning to
one side or the other in his seat, a light, tubular arm-rest
being pressed by his body when he leaned to one side or the
other, and thus operating the movement of the ailerons employed
for tilting the plane when turning. A steering-wheel fitted
immediately in front of the pilots seat served to operate a
rear steering-rudder when the wheel was turned in either
direction, while pulling back the wheel altered the inclination
of the front elevating planes, and so gave lifting or depressing
control of the plane.
This machine ran on three wheels before leaving the ground, a
central undercarriage wheel being fitted in front, with two more
in line with a right angle line drawn through the centre of the
engine crank at the rear end of the crank-case. The engine was
a 35 horsepower Vee design, water cooled, with overhead inlet
and exhaust valves, and Bosch high-tension magneto ignition.
The total weight of the plane in flying order was about 700 lbs.
As great a figure in the early days as either Ferber or
Santos-Dumont was Louis Bleriot, who, as early as 1900 built a
flapping-wing model, this before ever he came to experimenting
with the Voisin biplane type of glider on the Seine. Up to 1906
he had built four biplanes of his own design, and in March of
1907 he built his first monoplane, to wreck it only a few days
after completion in an accident from which he had a fortunate
escape. His next machine was a double monoplane, designed after
Langleys precept, to a certain extent, and this was totally
wrecked in September of 1907. His seventh machine, a
monoplane, was built within a month of this accident, and with
this he had a number of mishaps, also achieving some good
flights, including one in which he made a turn. It was wrecked
in December of 1907, whereupon he built another monoplane on
which, on July 6th, 1908, Bleriot made a flight lasting eight
and a half minutes. In October of that year he flew the machine
from Toury to Artenay and returned on it–this was just a day
after Farmans first cross-country flight–but, trying to repeat
the success five days later, Bleriot collided with a tree in a
fog and wrecked the machine past repair. Thereupon he set about
building his eleventh machine, with which he was to achieve the
first flight across the English channel.
Permalink
03.18.08
Posted in Uncategorized at 5:41 pm by admin
About the time that Mr. Spencer was experimenting with his large
air-ship, Dr. Barton, of Beckenham, was forming plans for an even
larger craft. This he laid down in the spacious grounds of the
Alexandra Park, to the north of London. An enormous shed was
erected on the northern slopes of the park, but visitors to the
Alexandra Palace, intent on a peep at the monster air-ship under
construction, were sorely disappointed, as the utmost secrecy in
the building of the craft was maintained.
The huge balloon was 43 feet in diameter and 176 feet long, with
a gas capacity of 235,000 cubic feet. To maintain the external
form of the envelope a smaller balloon, or compensator, was
placed inside the larger one. The framework was of bamboo, and
the car was attached by about eighty wire-cables. The wooden
deck was about 123 feet in length. Two 50-horse-power engines
drove four propellers, two of which were at either end.
The inventor employed a most ingenious contrivance to preserve
the horizontal balance of the air-ship. Fitted, one at each end
of the carriage, were two 50-gallon tanks. These tanks were
connected with a long pipe, in the centre of which was a
hand-pump. When the bow of the air-ship dipped, the man at the
pump could transfer some of the water from the fore-tank to the
after-tank, and the ship would right itself. The water could
similarly be transferred from the after-tank to the fore-tank
when the stern of the craft pointed downwards.
There were many reports, in the early months of 1905, that the
air-ship was going to be brought out from the shed for its trial
flights, and the writer, in common with many other residents in
the vicinity of the park, made dozens of journeys to the shed in
the expectation of seeing the mighty dirigible sail away. But
for months we were doomed to disappointment; something always
seemed to go wrong at the last minute, and the flight had to be
postponed.
At last, in 1905, the first ascent took place. It was
unsuccessful. The huge balloon, made of tussore silk, cruised
about for some time, then drifted away with the breeze, and came
to grief in landing.
A clever inventor of air-ships, a young Welshman, Mr. E. T.
Willows, designed in 1910, an air-ship in which he flew from
Cardiff to London in the dark–a distance of 139 miles. In the
same craft he crossed the English Channel a little later.
Mr. Willows has a large shed in the London aerodrome at Hendon,
and he is at present working there on a new air-ship. For some
time he has been the only successful private builder of air-ships
in Great Britain. The Navy possess a small Willows air-ship.
Messrs. Vickers, the famous builders of battleships, are giving
attention to the construction of air-ships for the Navy, in their
works at Walney Island, Barrow-in-Furness. This firm has erected
an enormous shed, 540 feet long, 150 feet broad, and 98 feet
high. In this shed two of the largest air-ships can be built
side by side. Close at hand is an extensive factory for the
production of hydrogen gas.
At each end of the roof are towers from which the difficult task
of safely removing an air-ship from the shed can be directed.
At the time of writing, the redoubtable DORA (Defence of the
Realm Act) forbids any but the vaguest references to what is
going forward in the way of additions to our air forces. But it
may be stated that air-ships are included in the great
constructive programme now being carried out. It is not long
since the citizens of Glasgow were treated to the spectacle of a
full-sized British “Zep” circling round the city prior to her
journey south, and so to regions unspecified. And use, too, is
being found by the naval arm for that curious hybrid the “Blimp”,
which may be described as a cross between an aeroplane and an
air-ship.
CHAPTER VIII
The First Attempts to Steer a Balloon
For nearly a century after the invention of the Montgolfier and
Charlier balloons there was not much progress made in the science
of aeronautics. True, inventors such as Charles Green suggested
and carried out new methods of inflating balloons, and scientific
observations of great importance were made by balloonists both in
Permalink
03.17.08
Posted in Uncategorized at 2:21 pm by admin
FLUTTER.–Propeller “flutter, or vibration, may be due
to faulty pitch angle, balance, camber, or surface area. It
causes a condition sometimes mistaken for engine trouble,
and one which may easily lead to the collapse of the propeller.
CARE OF PROPELLERS.–The care of propellers is of the
greatest importance, as they become distorted very easily.
1. Do not store them in a very damp or a very dry place.
2. Do not store them where the sun will shine upon them.
3. Never leave them long in a horizontal position or
leaning up against a wall.
4. They should be hung on horizontal pegs, and the
position of the propellers should be vertical.
If the points I have impressed upon you in these notes
are not attended to, you may be sure of the following results:
1. Lack of efficiency, resulting in less aeroplane speed
and climb than would otherwise be the case.
2. Propeller “flutter and possible collapse.
3. A bad stress upon the propeller shaft and its bearings.
TRACTOR.–A propeller mounted in front of the main
surface.
PUSHER.–A propeller mounted behind the main surface.
FOUR-BLADED PROPELLERS.–Four- bladed propellers are
suitable only when the pitch is comparatively large.
For a given pitch, and having regard to “interference,
they are not so efficient as two-bladed propellers.
The smaller the pitch, the less the “gap, i.e., the distance,
measured in the direction of the thrust, between the
spiral courses of the blades.
If the gap is too small, then the following blade will
engage air which the preceding blade has put into motion,
with the result that the following blade will not secure as
good a reaction as would otherwise be the case. It is very
much the same as in the case of the aeroplane gap.
For a given pitch, the gap of a four-bladed propeller is
only half that of a two-bladed one. Therefore the four-
bladed propeller is only suitable for large pitch, as such
pitch produces spirals with a large gap, thus offsetting the
decrease in gap caused by the numerous blades.
The greater the speed of rotation, the less the pitch for
a given aeroplane speed. Then, in order to secure a large
pitch and consequently a good gap, the four-bladed propeller
is usually geared to rotate at a lower speed than would be
the case if directly attached to the engine crank-shaft.
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03.16.08
Posted in Uncategorized at 6:01 am by admin
The Lecture Hall at the Royal Flying Corps School for
Officers was deserted. The pupils had dispersed, and the
Officer Instructor, more fagged than any pupil, was out on
the aerodrome watching the test of a new machine.
Deserted, did I say? But not so. The lecture that day
had been upon the Elementary Principles of Flight, and
they lingered yet. Upon the Blackboard was the illustration
you see in the frontispiece.
“I am the side view of a Surface, it said, mimicking
the tones of the lecturer. “Flight is secured by driving me
through the air at an angle inclined to the direction of
motion.
“Quite right, said the Angle. “Thats me, and Im
the famous Angle of Incidence.
“And, continued the Surface, “my action is to deflect
the air downwards, and also, by fleeing from the air behind,
to create a semi-vacuum or rarefied area over most of the
top of my surface.
“This is where I come in, a thick, gruff voice was
heard, and went on: “Im the Reaction. You cant have
action without me. Im a very considerable force, and my
direction is at right-angles to you, and he looked heavily
at the Surface. “Like this, said he, picking up the chalk
with his Lift, and drifting to the Blackboard.
“I act in the direction of the arrow R, that is, more or
less, for the direction varies somewhat with the Angle of
Incidence and the curvature of the Surface; and, strange
but true, Im stronger on the top of the Surface than at
the bottom of it. The Wind Tunnel has proved that by
exhaustive research–and dont forget how quickly I can
grow! As the speed through the air increases my strength
increases more rapidly than you might think–approximately,
as the Square of the Speed; so you see that if the Speed of
the Surface through the air is, for instance, doubled, then
I am a good deal more than doubled. Thats because I
am the result of not only the mass of air displaced, but also
the result of the Speed with which the Surface engages
the Air. I am a product of those two factors, and at the
speeds at which Aeroplanes fly to-day, and at the altitudes
and consequent density of air they at present experience,
I increase at about the Square of the Speed.
“Oh, Im a most complex and interesting personality, I
assure you–in fact, a dual personality, a sort of aeronautical
Dr. Jekyll and Mr. Hyde. Theres Lift, my vertical part or
COMPONENT, as those who prefer long words would say; he
always acts vertically upwards, and hates Gravity like poison.
Hes the useful and admirable part of me. Then theres Drift,
my horizontal component, sometimes, though rather erroneously,
called Head Resistance; hes a villain of the deepest
dye, and must be overcome before flight can be secured.
“And I, said the Propeller, “I screw through the air and
produce the Thrust. I thrust the Aeroplane through the air
and overcome the Drift; and the Lift increases with the Speed
and when it equals the Gravity of Weight, then–there you
are–Flight! And nothing mysterious about it at all.
“I hope youll excuse me interrupting, said a very
beautiful young lady, “my name is Efficiency, and, while
no doubt, all you have said is quite true, and that, as my
young man the Designer says, `You can make a tea-tray
fly if you slap on Power enough, I can assure you that Im
not to be won quite so easily.
“Well, eagerly replied the Lift and the Thrust, “lets
be friends. Do tell us what we can do to help you to overcome
Gravity and Drift with the least possible Power. That
obviously seems the game to play, for more Power means
heavier engines, and that in a way plays into the hands of
our enemy, Gravity, besides necessitating a larger Surface
or Angle to lift the Weight, and that increases the Drift.
“Very well, from Efficiency, “Ill do my best, though
Permalink
03.13.08
Posted in Uncategorized at 8:21 pm by admin
Large sheets of water form admirable “sign-posts” for an airman;
thus at Kempton Park, one of the turning-points in the course
followed in the “Aerial Derby”, there are large reservoirs, which
enable the airmen to follow the course at this point with the
greatest ease. Railway lines, forests, rivers and canals, large
towns, prominent structures, such as gasholders, chimney-stalks,
and so on, all assist an airman to find his way.
CHAPTER XLIII
The First Airman to Fly Upside Down
Visitors to Brooklands aerodrome on 25th September, 1913, saw one
of the greatest sensations in this or any other century, for on
that date a daring French aviator, M. Pegoud, performed the
hazardous feat of flying upside down.
Before we describe the marvellous somersaults which Pegoud made,
two or three thousand feet above the earth, it would be well to
see what was the practical use of it all. If this amazing airman
had been performing some circus trick in the air simply for the
sake of attracting large crowds of people to witness it, and
therefore being the means of bringing great monetary gain both to
him and his patrons, then this chapter would never have been
written. Indeed, such a risk to ones life, if there had been
nothing to learn from it, would have been foolish.
No; Pegouds thrilling performance must be looked at from an
entirely different standpoint to such feats of daring as the
placing of ones head in the jaws of a lion, the traversing of
Niagara Falls by means of a tight-rope stretched across them, and
other similar senseless acts, which are utterly useless to
mankind.
Let us see what such a celebrated airman as Mr. Gustav Hamel said
of the pioneer of upside-down flying.
“His looping the loop, his upside-down flights, his general
acrobatic feats in the air are all of the utmost value to pilots
throughout the world. We shall have proof of this, I am sure, in
the near future. Pegoud has shown us what it is possible to do
with a modern machine. In his first attempt to fly upside down
he courted death. Like all pioneers, he was taking liberties
with the unknown elements. No man before him had attempted the
feat. It is true that men have been upside down in the air; but
they were turned over by sudden gusts of wind, and in most cases
were killed. Pegoud is all the time rehearsing accidents and
showing how easy it is for a pilot to recover equilibrium
providing he remains perfectly calm and clear-headed. Any one of
his extraordinary positions might be brought about by adverse
elements. It is quite conceivable that a sudden gust of wind
might turn the machine completely over. Hitherto any pilot in
such circumstances would give himself up for lost. Pegoud has
taught us what to do in such a case. . . . his flights have given
us all a new confidence.
“In a gale the machine might be upset at many different angles.
Pegoud has shown us that it is easily possible to recover from
such predicaments. He has dealt with nearly every kind of
awkward position into which one might be driven in a gale of
wind, or in a flight over mountains where air-currents prevail.
“He has thus gained evidence which will be of the utmost value to
present and future pilots, and prove a factor of signal
importance in the preservation of life in the air.”
Such words as these, coming from a man of Mr. Hamels reputation
as an aviator, clearly show us that M. Pegoud has a life-saving
mission for airmen throughout the world.
Let us stand, in imagination, with the enormous crowd of
spectators who invaded the Surrey aerodrome on 25th September,
and the two following days, in 1913.
What an enormous crowd it was! A line of motor-cars bordered the
track for half a mile, and many of the spectators were busy city
men who had taken a hasty lunch and rushed off down to Weybridge
to see a little French airman risk his life in the air.
Thousands of foot passengers toiled along the dusty road from the
paddock to the hangars, and thousands more, who did not care to
pay the shilling entrance fee, stood closely packed on the high
ground outside the aerodrome.
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