BUILDING A BLERIOT MONOPLANE
As mentioned in connection with the description of its construction, the
Curtiss biplane was selected as a standard of this type of aeroplane
after which the student could safely pattern for a number of reasons. It
is not only remarkably simple in construction, easily built by anyone
with moderate facilities and at a slight outlay, but it is likewise the
easiest machine to learn to drive. The monoplane is far more _difficult_
and _expensive_ to build.
The Bleriot may be regarded as the most typical example in this field,
in view of its great success and the very large numbers which have been
turned out. In fact, the Bleriot monoplane is the product of a factory
which would compare favorably with some of the large automobile plants.
Its construction requires skillful workmanship both in wood and metal,
and a great many special castings, forgings, and stampings are
necessary. Although some concerns in this country advertise that they
carry these fittings as stock parts, they are not always correct in
design and, in any case, are expensive. Wherever it is possible to avoid
the use of such parts by any expedient, both forms of construction are
described, so that the builder may take his choice.
Bleriot monoplanes are made in a number of different models, the
principal ones being the 30-horse-power "runabout," Figs. 23 and 24, the
50- and 70-horse-power passenger-carrying machines, and the 50-, 70-,
and 100-horse-power racing machines. Of these the first has been chosen
as best adapted to the purpose. Its construction is typical of the
higher-power monoplanes of the same make, and it is more suitable for
the beginner to fly as well as to build. It is employed exclusively by
the Bleriot schools.
[Illustration: Fig. 23. Details of Bleriot Monoplane]
*Motor*. The motor regularly employed is the 30-horse-power,
three-cylinder Anzani, a two-cylinder type of which is shown in
"Aeronautical Motors" Fig. 40. From the amateur’s standpoint, a
disadvantage of the Bleriot is the very short space allowed for the
installation of the motor. For this reason, the power plant must be fan
shaped, like the Anzani; star form, like the Gnome; or of the
two-cylinder opposed type. It must likewise be air-cooled, as there is
no space available for a radiator.
[Illustration: Fig. 24. Side Elevation of Bleriot Monoplane]
[Illustration: Fig. 25. Top and Side View of Bleriot Fuselage on Which
Machine Is Assembled]
*Fuselage*. Like most monoplanes, the Bleriot has a long central body,
usually termed "fuselage," to which the wings, running gear, and
controls are all attached. A drawing of the fuselage with all dimensions
is reproduced in Fig. 25, and as the machine is, to a large extent,
built up around this essential, its construction is taken up first. It
consists of four long beams united by 35 crosspieces. The beams are of
ash, 1 3/16 inches square for the first third of their length and
tapering to 7/8 inch square at the rear ends. Owing to the difficulty of
securing good pieces of wood the full length, and also to facilitate
packing for shipment, the beams are made in halves, the abutting ends
being joined by sleeves of 1 1/8-inch, 20-gauge steel tubing, each held
on by two 1/8-inch bolts. Although the length of the fuselage is 21 feet
11 1/4 inches, the beams must be made of two 11-foot halves to allow for
the curve at the rear ends.
[Illustration: Fig. 26. Details of U-bolt Which is a Feature of Bleriot
Construction]
The struts are also of ash, the majority of them being 7/8 by 1 1/4
inches, and oval in section except for an inch and a half at each end.
But the first, second, and third struts (counting from the forward end)
on each side, the first and second on the top, and the first strut on
the bottom are 1 3/16 inches square, of the same stock as the main
beams. Practically all of the struts are joined to the main beams by
U-bolts, as shown by the detail drawing, Fig. 26, this being one of
Louis Bleriot’s inventions. The small struts are held by 1/8-inch bolts
and the larger ones by 3/16-inch bolts. The ends of the struts must be
slotted for these bolts, this being done by drilling three holes in a
row with a 5/32- or 7/32-inch drill, according to whether the slot is
for the smaller or larger size bolt. The wood between the holes is cut
out with a sharp knife and the slot finished with a coarse, flat file.
All of the U-bolts measure 2 inches between the ends. The vertical
struts are set 1 inch forward of the corresponding horizontal struts, so
that the four holes through the beam at each joint are spaced 1 inch
apart, alternately horizontal and vertical. To the projecting angles of
the U-bolts are attached the diagonal truss wires, which cross all the
rectangles of the fuselage, except that in which the driver sits. This
trussing should be of 20-gauge piano wire (music-wire gauge) or
1/10-inch cable, except in the rectangles bounded by the large struts,
where it should be 25-gauge piano wire or 3/32-inch cable. Each wire, of
course, should have a turnbuckle. About 100 of these will be required,
either of the spoke type or the regular type, with two screw eyes—the
latter preferred.
Transverse squares, formed by the two horizontal and two vertical struts
at each point, are also trussed with diagonal wires. Although
turnbuckles are sometimes omitted on these wires, it takes considerable
skill to get accurate adjustments without them. The extreme rear strut
to which the rudder is attached, is not fastened in the usual way. It
should be cut with tongues at top and bottom, fitting into notches in
the ends of the beams, and the whole bound with straps of 20-gauge sheet
steel, bolted through the beams with 1/8-inch bolts.
Continuing forward, the struts have no peculiarity until the upper
horizontal one is reached, just behind the driver’s seat. As it is
impossible to truss the quadrangle forward of this strut, owing to the
position of the driver’s body, the strut is braced with a U-shaped
half-round strip of 1/2 by 1 inch of ash or hickory bolted to the beams
at the sides and to the strut at the rear, with two 1/8-inch bolts at
each point. The front side of the strut should be left square where this
brace is in contact with it. The brace should be steam bent with the
curves on a 9-inch radius, and the half-round side on the inside of the
curve.
The vertical struts just forward of the driver’s seat carry the inner
ends of the rear wing beams. Each beam is attached with a single bolt,
giving the necessary freedom to rock up and down in warping the wings.
The upper 6 inches of each of these struts fits into a socket designed
to reinforce it. In the genuine Bleriot, this socket is an aluminum
casting. However, a socket which many would regard as even better can be
made from a 7-inch length of 20-gauge 1 1/8-inch square tubing. One end
of the tube is sawed one inch through the corners; two opposite sides
are then bent down at right angles to form flanges, and the other two
sides sawed off. A 1- by 3-inch strip of 20-gauge sheet steel, brazed
across the top and flanges completes the socket. With a little care, a
very creditable socket can be made in this way. Finally, with the strut
in place, a 3/8-inch hole is drilled through 4 inches from the top of
the socket for the bolt securing the wing beam.
The upper horizontal strut at this point should be arched about six
inches to give plenty of elbow room over the steering wheel. The bending
should be done in a steam press. The strut should be 1 3/16 inches
square, cut sufficiently long to allow for the curve, and fitted at the
ends with sockets as described above, but set at an angle by sawing the
square tube down further on one side than on the other.
On the two lower beams, is laid a floor of half-inch boards, extending
one foot forward and one foot back of the center line of the horizontal
strut. This floor may be of spruce, if it is desired to save a little
weight, or of ordinary tongue-and-grooved floor boards, fastened to the
beams with wood screws or bolts. The horizontal strut under this floor
may be omitted, but its presence adds but little weight and completes
the trussing. Across the top of the fuselage above the first upper
horizontal strut, lies a steel tube which forms the sockets for the
inner end of the front wing beams. This tube is 1 3/4 inches diameter,
18 gauge, and 26 3/4 inches long. It is held fast by two steel straps,
16 gauge and 1 inch wide, clamped down by the nuts of the vertical strut
U-bolts. The center of the tube is, therefore, in line with the center
of the vertical struts, not the horizontal ones. The U-bolts which make
this attachment are, of course, the 3/16-inch size, and one inch longer
on each end than usual. To make a neat job, the tube may be seated in
wood blocks, suitably shaped, but these must not raise it more than a
small fraction of an inch above the top of the fuselage, as this would
increase the angle of incidence of the wings.
The first vertical struts on each side are extras, without corresponding
horizontal ones; they serve only to support the engine. When the Gnome
motor is used, its central shaft is carried at the centers of two
*X*-shaped, pressed-steel frames, one on the front side, flush with the
end of the fuselage and one on the rear.
*Truss Frame Built on Fuselage*. In connection with the fuselage may be
considered the overhead truss frame and the warping frame. The former
consists of two inverted *V*’s of 20-gauge, 1- by 3/8-inch oval tubing,
joined at their apexes by a 20-gauge, 3/4-inch tube. Each *V* is formed
of a single piece of the oval tubing about 5 feet long. The flattened
ends of the horizontal tube are fastened by a bolt in the angles of the
*V*’s. The center of the horizontal tube should be 2 feet above the top
of the fuselage. The flattened lower ends of the rear *V* should be
riveted and brazed to strips of 18-gauge steel, which will fit over the
bolts attaching the vertical fuselage struts at this point. The legs of
the front *V* should be slightly shorter, as they rest on top of the
wing socket tube. Each should be held down by a single 3/16-inch bolt,
passing through the upper wall of the tube and its retaining strap;
these bolts also serve the purpose of preventing the tube from sliding
out from under the strap. Each side of the frame is now braced by
diagonal wires (No. 20 piano wire, or 1/14-inch cable) with turnbuckles.
At the upper corners of this frame are attached the wires which truss
the upper sides of the wings. The front wires are simply fastened under
the head and nut of the bolt which holds the frame together at this
corner. The attachment of the rear wires, however, is more complex, as
these wires must run over pulleys to allow for the rocking of the rear
wing beams when the wings are warped. To provide a suitable place for
the pulleys, the angle of the rear *V* is enclosed by two plates of
20-gauge sheet steel, one on the front and one on the rear, forming a
triangular box 1 inch thick fore and aft, and about 2 inches on each
side, only the bottom side being open. These plates are clamped together
by a 3/16-inch steel bolt, on which are mounted the pulleys. There
should be sufficient clearance for pulleys 1 inch in diameter. The wires
running over these pulleys must then pass through holes drilled in the
tube. The holes should not be drilled until the wings are on, when the
proper angle for them can be seen. The cutting and bending of the steel
plates is a matter of some difficulty, and should not be done until the
frame is otherwise assembled, so that paper patterns can be cut for
them. They should have flanges bent around the tube, secured by the
bolts which hold the frame together, to keep them from slipping off.
The oval tubing is used in the vertical parts of this frame, principally
to reduce the wind resistance, being placed with the narrow side to the
front. However, if this tubing be difficult to obtain, or if price is a
consideration, no harm will be done by using 3/4-inch round tubing.
Beneath the floor of the driver’s cockpit in the fuselage is the warping
frame, the support for the wires which truss the rear wing beams and
also control the warping.
This frame is built up of four 3/4-inch, 20-gauge steel tubes, each
about 3 feet long, forming an inverted, 4-sided pyramid. The front and
back pairs of tubes are fastened to the lower fuselage beams with
3/16-inch bolts at points 15 inches front and back of the horizontal
strut. At their lower ends the tubes are joined by a fixture which
carries the pulleys for the warping wires and the lever by which the
pulleys are turned. In the genuine Bleriot, this fixture is a special
casting. However, a very neat connection can be made with a piece of
1/16-inch steel stock, 1 1/4 by 6 inches, bent into a *U*-shape with the
legs 1 inch apart inside. The flattened ends of the tubes are riveted
and brazed to the outside upper corners of the *U*, and a bolt to carry
the pulleys passes through the lower part, high enough to give clearance
for 2-inch pulleys. This frame needs no diagonal wires.
*Running Gear*. Passing now to the running gear, the builder will
encounter the most difficult part of the entire machine, and it is
impossible to avoid the use of a few special castings. The general plan
of the running gear is shown in the drawing of the complete machine.
Figs. 23 and 24, while some of the details are illustrated in Fig. 27,
and the remainder are given in the detail sheet, Fig. 28. It will be
seen that each of the two wheels is carried in a double fork, the lower
fork acting simply as a radius rod, while the upper fork is attached to
a slide which is free to move up and down on a 2-inch steel tube. This
slide is held down by two tension springs, consisting of either rubber
tubes or steel coil springs, which absorb the shocks of landing. The
whole construction is such that the wheels are free to pivot sideways
around the tubes, so that when landing in a quartering wind the wheels
automatically adjust themselves to the direction of the machine.
[Illustration: A FRENCH DEVELOPMENT OF THE WRIGHT MACHINE BUILT UNDER
THE WRIGHT PATENTS
There is Little Resemblance to the Original Except in Wing Form and
Warping]
_Framework_. The main framework of the running gear consists of two
horizontal beams, two vertical struts, and two vertical tubes. The beams
are of ash, 4 3/4 inches wide in the middle half, tapering to 3 3/4
inches at the ends, and 5 feet 2 3/4 inches long overall. The upper beam
is H inch thick and the lower 1 inch. The edges of the beams are rounded
off except at the points where they are drilled for bolt holes for the
attachment of other parts. The two upper beams of the fuselage rest on
these beams and are secured to them by two 3/16-inch bolts each.
The vertical struts are also of ash, 1 3/16 inch by 3 inches and 4 feet
2 inches long overall. They have tenons at each end which fit into
corresponding square holes in the horizontal beams. The two lower
fuselage beams are fastened to these struts by two 3/16-inch through
bolts and steel angle plates formed from 1/16-inch sheet steel. The
channel section member across the front sides of these struts is for the
attachment of the motor, and will be taken up later. The general
arrangement at this point depends largely on what motor is to be used,
and the struts should not be rounded or drilled for bolt holes until
this has been decided.
From the lower ends of these struts _CC_, Fig. 27, diagonal struts _DD_
run back to the fuselage. These are of ash, 1 3/16 by 2 1/2 inches and 2
feet inches long. The rear ends of the struts _DD_ are fastened to the
fuselage beams by the projecting ends of the *U*-bolts of the horizontal
fuselage struts, and also by angle plates of sheet steel. At the lower
front ends the struts _DD_ are fastened to the struts _CC_ and the beam
_E_ by steel angle plates, and the beam is reinforced by other plates on
its under side.
_Trussing_. In the genuine Bleriot, the framework is trussed by a single
length of steel tape, 1 1/8 by 1/16 inch and about 11 feet long,
fastened to U-bolts in the beam _A_, Fig. 27. This tape runs down one
side, under the beam _E_, and up the other side, passing through the
beam in two places, where suitable slots must be cut. The tape is not
made in this country, but must be imported at considerable expense.
Ordinary sheet steel will not do. If the tape can not be obtained, a
good substitute is 1/8-inch cable, which then would be made in two
pieces and fastened to eye bolts at each end.
[Illustration: Fig. 27. Details of Bleriot Running Gear]
[Illustration: Fig. 28. Details of Various Fittings for Bleriot
Monoplane]
The two steel tubes are 2 inches in diameter, 18-gauge, and about 4 feet
10 inches long. At their lower ends they are flattened, but cut away so
that a 2-inch ring will pass over them. To these flattened ends are
attached springs and wires which run from each tube across to the hub of
the opposite wheel. The purpose of these is simply to keep the wheels
normally in position behind the tubes. The tubes, it will be noticed,
pass through the lower beam, but are sunk only 1/8 inch into the upper
beam. They are held in place by sheet-steel sockets on the lower side of
the upper beam and the upper side of the lower beam. The other sides of
the beams are provided with flat plates of sheet steel. The genuine
Bleriot has these sockets stamped out of sheet steel, but as the amateur
builder will not have the facilities for doing this, an alternative
construction is given here.
In this method, the plates are cut out to pattern, the material being
sheet steel 1/16 inch thick, and a 1/2-inch hole drilled through the
center, a 2-inch circle then being drawn around this. Then, with a cold
chisel a half dozen radial cuts are made between the hole and the
circle. Finally this part of the plate is heated with a blow-torch and a
2-inch piece of pipe driven through, bending up the triangular corners.
These bent up corners are then brazed to the tubes, and a strip of light
sheet steel is brazed on to cover up the sharp edges. Of course, the
brazing should not be done until the slides _GG_, Figs. 27 and 28, have
been put on. When these are once in place, they have to stay on and a
breakage of one of them, means the replacement of the tube as well. This
is a fault of the Bleriot design that can not well be avoided. It should
be noticed that the socket at the upper end, as well as its
corresponding plate on the other side of the beam, has extensions which
reinforce the beam where the eye bolts or *U*-bolts for the attachment
of the steel tape pass through.
_Forks_. Next in order are the forks which carry the wheels. The short
forks _JJ_, Figs. 27 and 28, which act simply as radius rods, are made
of 1- by 3/8-inch oval tubing, a stock size which was specified for the
overhead truss frame. It will be noticed that these are in two parts,
fastened together with a bolt at the front end. The regular Bleriot
construction calls for forged steel eyes to go in the ends of tubes, but
these will be hard to obtain. The construction shown in the drawings is
much simpler. The ends of the tubes are heated and flattened until the
walls are about 1/16 inch apart inside. Then a strip of 1/16-inch sheet
steel is cut the right width to fit in the flattened end of the tube,
and brazed in place. The bolt holes then pass through the combined
thickness of the tube and the steel strip, giving a better bearing
surface, which may be further increased by brazing on a washer.
The long forks _FF_, which transmit the landing shocks to the springs,
are naturally made of heavier material. The proper size tubing for them
is 1 1/8 by 5/8 inches, this being the nearest equivalent to the 14 by
28 mm French tubing. However, this is not a stock size in this country
and can only be procured by order, or it can be made by rolling out
15/16-inch round tubing. If the oval tubing can not be secured, the
round can be employed instead, other parts being modified to correspond.
The ends are reinforced in the same way as described for the small
forks.
These forks are strengthened by aluminum clamps _H_, Figs. 27 and 28,
which keep the tubes from spreading apart. Here, of course, is another
call for special castings, but a handy workman may be able to improvise
a satisfactory substitute from sheet steel. On each tube there are four
fittings: At the bottom, the collar _M_ to which the fork _J_ is
attached, and above, the slide _G_ and the clamps _K_ and _L_, which
limit its movement. The collar and slide should be forged, but as this
may be impossible, the drawings have been proportioned for castings. The
work is simple and may be done by the amateur with little experience.
The projecting studs are pieces of 3/4-inch, 14-gauge steel tubing
screwed in tight and pinned, though if these parts be forged, the studs
should be integral.
The clamps which limit the movement of the slides are to be whittled out
of ash or some other hard wood. The upper clamp is held in place by four
bolts, which are screwed up tight; but when the machine makes a hard
landing the clamp will yield a little and slip up the tube, thus
deadening the shock. After such a landing, the clamps should be
inspected and again moved down a bit, if necessary. The lower clamps,
which, of course, only keep the wheels from hanging down too far, have
bolts passing clear through the tubes.
To the projecting lugs on the slides _GG_ are attached the rubber tube
springs, the lower ends connecting with eye bolts through the beam _E_.
These rubber tubes, of which four will be needed, are being made by
several companies in this country and are sold by supply houses. They
should be about 14 inches long, unstretched, and 1 1/4 inches in
diameter, with steel tips at the ends for attachment.
_Hub Attachments_. The hubs of the two wheels are connected with the
link _P_, with universal joints _N N_ at each end. In case the machine
lands while drifting sidewise, the wheel which touches the ground first
will swing around to head in the direction in which the machine is
actually moving, and the link will cause the other wheel to assume a
parallel position; thus the machine can run diagonally on the ground
without any tendency to upset.
This link is made of the same 1- by 3/8-inch oval tubing used elsewhere
in the machine. In the original Bleriot, the joints are carefully made
up with steel forgings. But joints which will serve the purpose can be
improvised from a 1-inch cube of hard wood and three steel straps, as
shown in the sketch, Fig. 27. From each of these joints a wire runs
diagonally to the bottom of the tube on the other side, with a spring
which holds the wheel in its normal position. This spring should be
either a rubber tube, like those described above, but smaller, or a
steel coil spring. In the latter case, it should be of twenty 3/4-inch
coils of No. 25 piano wire.
_Wheels_. The wheels are regularly 28 by 2 inches, corresponding to the
700 by 50 mm French size, with 30 spokes of 12-gauge wire. The hub
should be 5 1/4 inches wide, with a 5/8-inch bolt. Of course, these
sizes need not be followed exactly, but any variations will involve
corresponding changes in the dimensions of the forks. The long fork goes
on the hub inside of the short fork, so that the inside measurement of
the end of the big fork should correspond to the width of the hub, and
the inside measurement of the small fork should equal the outside
measurement of the large fork.
_Rear Skid_. Several methods are employed for supporting the rear end of
the fuselage when the machine is on the ground. The first Bleriot
carried a small wheel in a fork provided with rubber springs, the same
as the front wheels. The later models, however, have a double *U*-shaped
skid, as shown in Figs. 23 and 24. This skid is made of two 8-foot
strips of ash or hickory 1/2 by 3/4 inches, steamed and bent to the
*U*-shape as shown in the drawing of the complete machine.
[Illustration: Fig. 29. Details of Framework of Bleriot Main Supporting
Planes]
*Wings*. Having completed the fuselage and running gear, the wings are
next in order. These are constructed in a manner which may seem
unnecessarily complicated, but which gives great strength for
comparatively little weight. Each wing contains two stout ash beams
which carry their share of the weight of the machine, and 12 ribs which
give the proper curvature to the surfaces and at the same time reinforce
the beams. These ribs in turn are tied together and reinforced by light
strips running parallel to the main beams.
[Illustration: Fig. 30. Complete Rib of Bleriot Wing and Pattern from
Which Web Is Cut]
In the drawing of the complete wing. Fig. 29, the beams are designated
by the letters _B_ and _E_. _A_ is a sheet aluminum member intended to
hold the cloth covering in shape on the front edge. _C_, _D_, and _F_
are pairs of strips (one strip on top, the other underneath) which tie
the ribs together. _G_ is a strip along the rear edge, and _H_ is a bent
strip which gives the rounded shape to the end of the wing. The ribs are
designated by the numbers 1 to 12 inclusive.
_Ribs_. The first and most difficult operation is to make the ribs.
These are built up of a spruce board 3/16 inch thick, cut to shape on a
jig saw, with 3/16- by 5/8-inch spruce strip stacked and glued to the
upper and lower edges. Each rib thus has an I-beam section, such as is
used in structural steel work and automobile front axles. Each of the
boards, or webs as they are usually called, is divided into three parts
by the main beams which pass through it. Builders sometimes make the
mistake of cutting out each web in three pieces, but this makes it very
difficult to put the rib together accurately. Each web should be cut out
of a single piece, as shown in the detail drawing. Fig. 30, and the
holes for the beams should be cut in after the top and bottom strips
have been glued on.
The detail drawing, Fig. 30, gives the dimensions of a typical rib. This
should be drawn out full size on a strip of tough paper, and then a
margin of 3/16 inch should be taken off all round except at the front
end where the sheet aluminum member _A_ goes on. This allows for the
thickness of the top and bottom strips. In preparing the pattern for the
jig saw, the notches for strips _C_, _D_, and _F_ should be disregarded;
neither should it be expected that the jig-saw operator will cut out the
oval holes along the center of the web, which are simply to lighten it.
The notches for the front ends of the top and bottom strips should also
be smoothed over in the pattern.
When the pattern is ready, a saw or planing mill provided with a saw
suitable for the work, should cut out the 40 ribs (allowing a sufficient
number for defective pieces and breakage) for about $2. The builder then
cuts the notches and makes the oval openings with an auger and keyhole
saw. Of course, these holes need not be absolutely accurate, but at
least 3/4 inch of wood should be left all around them.
Nine of the twelve ribs in each wing are exactly alike. No. 1, which
forms the inner end of the wing, does not have any holes cut in the web,
and instead of the slot for the main beam _B_, has a 1 3/4-inch round
hole, as the stub end of the beam is rounded to fit the socket tube.
(See Fig. 23.) Rib No. 11 is 5 feet 10 1/2 inches long, and No. 12 is 3
feet long. These can be whittled out by hand, and the shape for them
will be obvious as soon as the main part of the wing is put together.
The next step is to glue on the top and bottom strips. The front ends
should be put on first and held, during the drying, in a screw clamp,
the ends setting close up into the notches provided for them. Thin
1/2-inch brads should be driven in along the top and bottom at 1- to
2-inch intervals. The rear ends of the strips should be cut off to the
proper length and whittled off a little on the inside, so that there
will be room between them for the strip _G_, 1/4 inch thick. Finally,
cut the slots for the main beams, using a bit and brace and the keyhole
saw, and the ribs will be ready to assemble.
_Beams and Strips_. The main beams are of ash, the front beam in each
wing being 3 1/4 by 3/4 inches and the rear beam 2 1/2 by 5/8 inches.
They are not exactly rectangular but must be planed down slightly on the
top and bottom edges, so that they will fit into the irregularly-shaped
slots left for them in the ribs. The front beams, as mentioned above,
have round stubs which fit into the socket tube on the fuselage. These
stubs may be made by bolting short pieces of ash board on each side of
the end of the beam and rounding down the whole.
To give the wings their slight inclination, or dihedral angle, which
will be apparent in the front view of the machine, the stubs must lie at
an angle of 2 1/2 degrees with the beam itself. This angle should be
laid out very carefully, as a slight inaccuracy at this point will
result in a much larger error at the tips. The rear beams project about
2 inches from the inner ribs. The ends should be reinforced with bands
of sheet steel to prevent splitting, and each drilled with a 3/8-inch
hole for the bolt which attaches to the fuselage strut. A strip of heavy
sheet steel should be bent to make an angle washer to fill up the
triangular space between the beam and the strut; the bolt hole should be
drilled perpendicularly to the beam, and not to the strut. The outer
ends of the beams, beyond rib No. 10, taper down to 1 inch deep at the
ends.
The aluminum member _A_, Fig. 29, which holds the front edge of the wing
in shape, is made of a 4-inch strip of fairly heavy sheet aluminum,
rolled into shape round a piece of half-round wood, 2 1/4 inches in
diameter. As sheet aluminum usually comes in 6-foot lengths, each of
these members will have to be made in two sections, joined either by
soldering (if the builder has mastered this difficult process) or by a
number of small copper rivets.
No especial difficulties are presented by the strips, _C_, _D_, and _F_,
which are of spruce 3/16 by 5/8 inch, or by the rear edge strip _G_, of
spruce 1/4 by 1 1/2 inches. Each piece _H_ should be 1 by 1/2 inch
half-round spruce, bent into shape, fitted into the aluminum piece at
the front, and at the rear flattened down to 1/4 inch and reinforced by
a small strip glued to the back, finally running into the strip _G_. The
exact curve of this piece does not matter, provided it is the same on
both wings.
_Assembling the Wings_. Assembling the wings is an operation which
demands considerable care. The main beams should first be laid across
two horses, set level so that there will be no strain on the framework
as it is put together. Then the 12 ribs should be slipped over the beams
and evenly spaced 13 inches apart to centers, care being taken to see
that each rib stands square with the beams, Fig. 31. The ribs are not
glued to the beams, as this would make repairs difficult, but are
fastened with small nails.
Strips _C_, _D_, and _F_, Fig, 29, are next put in place, simply being
strung through the rows of holes provided for them in the ribs, and
fastened with brads. Then spacers of 3/16-inch spruce, 2 or 3 inches
long, are placed between each pair of strips halfway between each rib,
and fastened with glue and brads. This can be seen in the broken-off
view of the wing in the front view drawing, Fig. 23. The rear edge strip
fits between the ends of the top and bottom strips of the ribs, as
mentioned above, fastened with brads or with strips of sheet-aluminum
tacked on.
[Illustration: Fig. 31. Assembling the Main Planes of a Bleriot
Monoplane]
Each wing is trussed by eight wires, half above and half below; half
attached to the front and half to the rear beam. In the genuine Bleriot
steel tape is used for the lower trussing of the main beams, similar to
the tape employed in the running gear, but American builders prefer to
use 1/8-inch cable. The lower rear trussing should be 3/32- or 7/64-inch
cable, and the upper trussing 3/32-inch.
The beams are provided with sheet-steel fixtures for the attachment of
the cables, as shown in the broken-off wing view, Fig. 23. These are cut
from fairly-heavy metal, and go in pairs, one on each side of the end
beam, fasten with three 3/16-inch bolts. They have lugs top and bottom.
They are placed between the fifth and sixth and ninth and tenth ribs on
each side.
To resist the backward pressure of the air, the wings are trussed with
struts of 1-inch spruce and 1/16-inch cable, as shown in Fig. 23. The
struts are placed between the cable attachments, being provided with
ferrules of flattened steel tubing arranged to allow the rear beam
freedom to swing up and down. The diagonal cables are provided with
turnbuckles and run through the open spaces in the ribs.
*Control System*. The steering gear and tail construction of the Bleriot
are as distinctive as the swiveling wheels and the *U*-bolts, and the
word "cloche" applied to the bell-like attachment for the control wires,
has been adopted into the international vocabulary of aeroplaning. The
driver has between his knees a small steering wheel mounted on a short
vertical post. This wheel does not turn, but instead the post has a
universal joint at the bottom which allows it to be swung backward and
forward or to either side. The post is really a lever, and the wheel a
handle. Encircling the lower part of the post is a hemispherical
bell—the cloche—with its bottom edge on the same level as the universal
joint.
Four wires are attached to the edge of the cloche. Those at the front
and back are connected with the elevator, and those at the sides with
the wing-warping lever. The connections are so arranged that pulling the
wheel back starts the machine upward, while pushing it forward causes it
to descend, and pulling to either side lowers that side and raises the
other. The machine can be kept on a level keel by the use of the wheel
and cloche alone; the aviator uses them just as if they were rigidly
attached to the machine, and by them he could move the machine bodily
into the desired position.
In practice, however, it has been found that lateral stability can be
maintained more easily by the use of the vertical rudder than by
warping. This is because the machine naturally tips inward on a turn,
and, consequently, a tip can be corrected by a partial turn in the other
direction. If, for example, the machine tips to the right, the aviator
steers slightly to the left, and the machine comes back to a level keel
without any noticeable change in direction. Under ordinary circumstances
this plan is used altogether, and the warping is used only on turns and
in bad weather.
It will be noticed that the Bleriot control system is almost identical
with that of the Henri Farman biplane, the only difference being that in
the Farman the cloche and wheel are replaced by a long lever. The
movements, however, remain the same, and as there are probably more
Bleriot and Farman machines in use than all other makes together, this
control may be regarded almost as a standard. It is not as universal as
the steering wheel, gear shift, and brake levers of the automobile, but
still it is a step in the right direction.
[Illustration: Fig. 32. Control Device of Steel Tubing instead of
Bleriot "Cloche"]
In the genuine Bleriot, the cloche is built up of two bells, one inside
the other, both of sheet aluminum about 1/16 inch thick. The outer bell
is 11 inches in diameter and 3 1/2 inches deep, and the inner one 10
inches in diameter and 2 inches deep. A ring of hard wood is clamped
between their edges and the steering column, an aluminum casting passing
through their centers. This construction is so complicated and requires
so many special castings and parts that it is almost impossible for the
amateur.
_Steering Gear_. While not so neat, the optional construction shown in
the accompanying drawing, Fig. 32, is equally effective. In this plan,
the cloche is replaced by four *V*-shaped pieces of 1/2-inch, 20-gauge
steel tubing, attached to a steering post of 1-inch, 20-gauge tubing. At
the lower end, the post has a fork, made of pieces of smaller tubing
bent and brazed into place, and this fork forms part of the universal
joint on which the post is mounted. The cross of the universal joint,
which is somewhat similar to those employed on automobiles, can best be
made of two pieces of heavy tubing, 1/2 inch by 12 gauge, each cut half
away at the middle. The two pieces are then fastened together by a small
bolt and brazed for greater security. The ends which are to go into the
fork of the steering post must then be tapped for 3/8-inch machine
screws. The two other ends of the cross are carried on *V*’s of
1/2-inch, 20-gauge tubing, spread far enough apart at the bottom to make
a firm base, and bolted to the floor of the cockpit.
The steering wheel itself is comparatively unimportant. On the genuine
Bleriot it is a solid piece of wood 8 inches in diameter, with two holes
cut in it for hand grips. On the post just under the wheel are usually
placed the spark and throttle levers. It is rather difficult, however,
to arrange the connections for these levers in such a way that they will
not be affected by the movements of the post, and for this reason many
amateur builders place the levers at one side on one of the fuselage
beams.
From the sides of the cloche, or from the tubing triangles which may be
substituted for it, two heavy wires run straight down to the ends of the
warping lever. This lever, together with two pulleys, is mounted at the
lower point of the warping frame already described. The lever is 12
inches long, 11 inches between the holes at its ends, and 2 inches wide
in the middle; it should be cut from a piece of sheet steel about 1/16
inch thick. The pulleys should be 2 1/2 inches in diameter, one of them
bolted to the lever, the other one running free. The wires from the
outer ends of the rear wing beams are joined by a piece of flexible
control cable, which is given a single turn over the free pulley. The
inner wires, however, each have a piece of flexible cable attached to
their ends, and these pieces of cable, after being given a turn round
the other pulley, are made fast to the opposite ends of the warping
lever. These cables should be run over the pulleys, not under, so that
when the cloche is pulled to the right, the left wing will be warped
downward.
It is a common mistake to assume that both pulleys are fastened to the
warping lever; but when this is done the outer wire slackens off and
does not move in accord with the inner wire, on account of the different
angles at which they work.
_Foot Levers_. The foot lever for steering is cut from a piece of wood
22 inches long, hollowed out at the ends to form convenient rests for
the feet. The wires connecting the lever to the rudder may either be
attached to this lever direct, or, if a neater construction is desired,
they may be attached to another lever under the floor of the cockpit. In
the latter case, a short piece of 1-inch steel tubing serves as a
vertical shaft to connect the two levers, which are fastened to the
shaft by means of aluminum sockets such as may be obtained from any
supply house. The lower lever is 12 inches long and 2 inches wide, cut
from 1/16-inch steel similar to the warping lever.
Amateur builders often cross the rudder wires so that pressing the lever
to the right will cause the machine to steer to the left. This may seem
more natural at first glance, but it is not the Bleriot way. In the
latter, the wires are not crossed, the idea being to facilitate the use
of the vertical rudder for maintaining lateral equilibrium. With this
arrangement, pressing the lever with the foot on the high side of the
machine tends to bring it back to an even keel.
_Tail and Elevator_. The tail and elevator planes are built up with ribs
and tie strips in much the same manner as the wings. However, it will
hardly pay to have these ribs cut out on a jig saw unless the builder
can have this work done very cheaply. It serves the purpose just as well
to clamp together a number of strips of 3/16-inch spruce and plane them
down by hand. The ribs when finished should be 24 1/4 inches long. The
greatest depth of the curve is 1 1/4 inches, at a point one-third of the
way back from the front edge, and the greatest depth of the ribs
themselves 2 1/4 inches, at the same point. Sixteen ribs are required.
A steel tube 1 inch by 20 gauge, _C_, Fig. 33, runs through both tail
and elevators, and is the means of moving the latter. Each rib at the
point where the tube passes through, is provided with an aluminum
socket. Those on the tail ribs act merely as bearings for the tube, but
those on the elevator ribs are bolted fast, so that the elevators must
turn with the tube. At its center the tube carries a lever _G_, of
1/16-inch steel 12 by 2 inches, fastened on by two aluminum sockets, one
on each side. From the top of the lever a wire runs to the front side of
the cloche, and from the bottom a second wire runs to the rear side of
the cloche.
[Illustration: Fig. 33. Construction Details of Bleriot Tail, Elevators,
and Rudder]
[Illustration: AN OLD DUTCH WINDMILL AND A MODERN FRENCH AEROPLANE
_This Photograph Protected By International Copyright_]
[Illustration: VIEW OF THE R. E. P. MOTOR AND LANDING GEAR
This Machine is the Work of One of the Cleverest Aeroplane Designers in
Europe]
The tube is carried in two bearings _HH_, attached to the lower beams of
the fuselage. These are simply blocks of hard wood, fastened by steel
strips and bolts. The angle of incidence of the tail is adjustable, the
tail itself being held in place by two vertical strips of steel rising
from the rear edge and bolted to the fuselage, as shown in the drawing,
Fig. 33. To prevent the tail from folding up under the air pressure to
which it is subjected, it is reinforced by two 3/4-inch, 20-gauge steel
tubes running down from the upper sides of the fuselage, as shown in the
drawing of the complete machine, Fig. 23.
The tail and elevators have two pairs of tie strips, _B_ and _D_, Fig.
33, made of 3/16- by 5/8-inch spruce. The front edge _A_ is half round,
1- by 1/2-inch spruce, and the rear edge _E_ is a spruce strip 1/4- by 1
1/2-inches. The end pieces are curved.
_Rudder_. The rudder is built up on a piece of 1-inch round spruce _M_,
corresponding in a way to the steel tube used for the elevators. On this
are mounted two long ribs _KK_, and a short rib _J_, made of spruce 3/8
inch thick and 1 3/8 inches wide at the point where _M_ passes through
them. They are fastened to _M_ with 1/8-inch through bolts. The rudder
lever _N_, of 1/16-inch steel, 12 by 2 inches, is laid flat on _J_ and
bolted in place; it is then trussed by wires running from each end to
the rear ends of _KK_. From the lever other wires also run forward to
the foot lever which controls the rudder.
The wires to the elevator and rudder should be of the flexible cable
specially made for this purpose, and should be supported by fairleaders
attached to the fuselage struts. Fairleaders of different designs may be
procured from supply houses, or may be improvised. Ordinary screw eyes
are often used, or pieces of copper tubing, bound to the struts with
friction tape.
*Covering the Planes*. Covering the main planes, tail, elevators, and
rudder may well be left until the machine is otherwise ready for its
trial trip, as the cloth will not then be soiled by the dust and grime
of the shop. The cloth may be any of the standard brands which are on
the market, preferably in a rather light weight made specially for
double-surfaced machines of this type; or light-weight sail cloth may be
used, costing only 25 or 30 cents a yard. About 80 yards will be
required, assuming a width of 36 inches.
[Illustration: Fig. 34. Method of Mounting Fabric on Main Supporting
Frame]
Except on the rudder, the cloth is applied on the bias, the idea being
that with this arrangement the threads act like diagonal truss wires,
thus strengthening and bracing the framework. When the cloth is to be
put on in this way it must first be sewed together in sheets large
enough to cover the entire plane. Each wing will require a sheet about
14 feet square, and two sheets each 6 feet square will be required for
the elevators and tail. The strips of cloth run diagonally across the
sheets, the longest strips in the wing sheets being 20 feet long.
Application of the cloth to the wings, Fig. 34, is best begun by
fastening one edge of a sheet to the rear edge of the wing, stretching
the cloth as tight as can be done conveniently with one hand. The cloth
is then spread forward over the upper surface of the wing and is made
fast along the inner end rib. Small copper tacks are used, spaced 2
inches apart on the upper side and 1 inch on the lower side. After the
cloth has been tacked to the upper sides of all the ribs, the wing is
turned over and the cloth stretched over the lower side. Finally the raw
edges are trimmed off and covered with light tape glued down, tape also
being glued over all the rows of tacks along the ribs, making a neat
finish and at the same time preventing the cloth from tearing off over
the tack heads.
*Installation of Motor*. As stated previously, the ideal motor for a
Bleriot-type machine is short along the crank shaft, as the available
space in the fuselage is limited, and air-cooled for the same reason.
Genuine Bleriots are always fitted with one of the special types of
radial or rotary aeronautic motors, which are always air-cooled. Next in
popularity to these is the two-cylinder, horizontal-opposed motor,
either air- or water-cooled. However, successful machines have been
built with standard automobile-type, four-cylinder, water-cooled motors,
and with four-cylinder, two-cycle, aeronautic motors.
When the motor is water-cooled, there will inevitably be some difficulty
in finding room for a radiator of sufficient size. One scheme is to use
twin radiators, one on each side of the fuselage, inside of the main
frame of the running gear. Another plan is to place the radiator
underneath the fuselage, using a supplementary water tank above the
cylinders to facilitate circulation. These two seem to be about the only
practicable arrangements, as behind the motor the radiator would not get
enough air, and above it would obstruct the view of the operator.
It is impossible to generalize to much effect about the method of
supporting the motor in the fuselage, as this must differ with the
motor. Automobile-type motors will be carried on two heavy ash beams,
braced by lengths of steel tubing of about 1 inch diameter and 16 gauge.
When the seven-cylinder rotary Gnome motor is used, the crank shaft
alone is supported; it is carried at the center of two X-shaped frames
of pressed steel, one in front of and the other behind the motor. The
three-cylinder Anzani motors are carried on four lengths of channel
steel bent to fit around the upper and lower portions of the crank case,
which is of the motorcycle type.
Considerable care should be taken to prevent the exhaust from blowing
back into the operator’s face as this sometimes carries with it drops of
burning oil, besides disagreeable smoke and fumes. The usual plan is to
arrange a sloping dashboard of sheet aluminum so as to deflect the gases
down under the fuselage.
The three sections of the fuselage back of the engine section are
usually covered on the sides and bottom with cloth like that used on the
wings. Sometimes sheet aluminum is used to cover the section between the
wing beams. However, those who are just learning to operate machines and
are a little doubtful about their landings often leave off the covering
in order to be able to see the ground immediately beneath their front
wheels.
[Illustration: Fig. 35. Running Gear of Morane Type of Bleriot
Monoplane]
*New Features*. _Morane Landing Gear_. Although the regular Bleriot
landing gear already described, has many advantages and ha.s been in use
with only detail changes for several years, some aviators prefer the
landing gear of the new Morane monoplane, which in other respects
closely resembles the Bleriot. This gear, Fig. 35, is an adaptation of
that long in use on the Henri Farman and Sommer biplanes, combining
skids and wheels with rubber-band springs. In case a wheel or spring
breaks, whether due to a defect or to a rough landing, the skids often
save an upset. Besides, the tension of the springs is usually such that
on a rough landing the wheels jump up and allow the skids to take the
shock; this also prevents the excessive rebound of the Bleriot springs
under similar conditions.
Another advantage which may have some weight with the amateur builder,
is that the Morane running gear is much cheaper and easier to construct.
Instead of the two heavy tubes, the four forks of oval tubing, and the
many slides, collars, and blocks—most of them special forgings or
castings—the Morane gear simply requires two short laminated skids, four
ash struts, and some sheet steel.
The laminated skids are built up of three boards each of 5/8 by 2-inch
ash, 3 1/2 feet long. These must be glued under heavy pressure in forms
giving the proper curve at the front end. When they are taken from the
press, three or four 1/2-inch holes should be bored at equal distances
along the center line and wood pins driven in; these help in retaining
the curve. The finished size of the skids should be 1 3/4 by 1 3/4
inches.
Four ash struts 1 1/4 by 2 1/2 inches support the fuselage. They are
rounded off to an oval shape except at the ends, where they are attached
to the skids and the fuselage beams with clamps of 1/16 inch sheet
steel. The ends of the struts must be beveled off carefully to make a
good fit; they spread out 15 degrees from the vertical, and the rear
pair have a backward slant of 30 degrees from vertical.
Additional fuselage struts must be provided at the front end of the
fuselage to take the place of the struts and beams of the Bleriot
running gear. The two vertical struts at the extreme front end may be of
the same 1 1/4- by 2 1/2-inch ash used in the running gear, planed down
to 1 3/16 inches thick to match the thickness of the fuselage beams. The
horizontal struts should be 1 3/16 by 1 3/4 inches.
The wheels run on the ends of an axle tube, and usually have plain
bearings. The standard size bore of the hub is 15/16 inch, and the axle
tube should be 15/16 inch diameter by 11 gauge. The tube also has
loosely mounted on it two spools to carry the rubber band springs. These
are made of 2 1/4-inch lengths of 1 3/8-inch tubing, with walls of
sufficient thickness to make an easy sliding fit on the axle tube. To
the ends of each length of tube are brazed 2 1/2-inch washers of 3/16
inch steel, completing the spool.
The ends of the rubber bands are carried on rollers of 3/4-inch,
16-gauge tubing, fastened to the skids by fittings bent up from
3/16-inch sheet steel. Each fitting is bolted to the skid with two
3/8-inch bolts.
Some arrangement must now be made to keep the axle centered under the
machine, as the rubber bands will not take any sidewise strain. A clamp
of heavy sheet steel should be made to fit over the axle at its center,
and from this heavy wires or cables run to the bottom ends of the
forward struts. These wires may be provided with stiff coil springs, if
it is desired to allow a little sidewise movement.
[Illustration: Fig. 36. Details of Bleriot Inverse Curve Tail]
_New Bleriot Inverse Curve Tail_. Some of the latest Bleriot machines
have a new tall which seems to add considerable to their speed. It
consists of a fixed tail, Fig. 36, nearly as large as the old-style tail
and elevators combined, with two elevator flaps hinged to its rear edge.
The peculiarity of these elevators, from which the tail gets its name,
is that the curve is concave above and convex below—at first glance
seeming to have been attached upside down. In this construction, the
1-inch, 20-gauge tube, which formerly passed through the center of the
tail, now runs along the rear edge, being held on by strips of 1/2- by
1/16-inch steel bent into *U*-shape and fastened with screws or bolts to
the ribs. Similar strips attach the elevators to the tube, but these
strips are bolted to the tube. The construction is otherwise like that
previously described. It is said that fitting this tail to a Bleriot in
place of the old-style tail adds 5 miles an hour to the speed, without
any other changes being made.
Another slight change which distinguishes the newer Bleriots is in the
overhead frame, which now consists of a single inverted *V* instead of
two *V*’s connected by a horizontal tube. The single *V* is set slightly
back of the main wing beam, and is higher and, of course, of heavier
tubing than in the previous construction. Its top should stand 2 feet 6
inches above the fuselage, and the tubing should be 1 inch 18 gauge. It
also requires four truss wires, two running to the front end of the
fuselage and two to the struts to which the rear wing beams are
attached. All of the wires on the upper side of the wings converge to
one point at the top of this *V*, the wires from the wing beams, of
course, passing over pulleys.
These variations from the form already described may be of interest to
those who wish to have their machines up-to-date in every detail, but
they are by no means essential. Hundreds of the old-style Bleriots are
flying every day and giving perfect satisfaction.
ART OF FLYING
Knowledge of the science of aeronautics and ability to fly are two
totally different things. Long-continued study of the problem from its
scientific side enabled the Wright Brothers to learn how to build a
machine that would fly, but it did not teach them how to fly with it.
That came as the result of persistent attempts at flying itself. A study
of the theoretic laws of balancing does not form a good foundation for
learning how to ride a bicycle—practice with the actual machine is the
only road to success. The best evidence of this is to be found in the
fact that several of the most successful aviators today have but a
slight knowledge of the science of aeronautics. They are not
particularly well versed in what makes flight possible, but they know
how to fly because they have learned it in actual practice.
Reference to the early work of the Wright Brothers shows that during a
period of several years they spent a large part of their time in actual
experiments in the air, and it was not until these had proved entirely
satisfactory that they attempted to build a power-driven machine.
*Methods Used in Aviation Schools*. Aviation schools are springing up
all over this country and there are a number of well-established
institutions of this kind abroad. In the course of instruction, the
student must first learn the use of the various controls on a dummy
machine. In the case of an English school, this dummy, Fig. 37, is a
motorless aeroplane mounted on a universally-jointed support so as to
swing about a pivot as desired. This is employed for the purpose of
familiarizing the beginner with the means of maintaining equilibrium in
the air.
[Illustration: Fig. 37. Monoplane Dummy Used for Practice in Aviation
School]
[Illustration: Fig. 38. Aerocycle with Treadle Power for Practice Work]
A French school, on the other hand, employs a wingless machine, which is
otherwise complete, as it consists of a regulation chassis with motor
and propeller, all steering and elevating controls. On this, the student
may practice what has come to be familiarly known as "grass-cutting," to
his heart’s content, without any danger of the machine taking to the air
unexpectedly, as has frequently been the case where first attempts have
been made on a full-fledged machine. Usually, most of such attempts
result disastrously, often destroying in a moment the result of months
of work in building the machine.
[Illustration: Fig. 39. Voisin Biplane with Double Control for Teaching
Beginners]
A French aerocycle, Fig. 38, a comparatively inexpensive machine, is
also useful for practice in balancing and in short, low flights. The
French apparatus in question may accordingly be considered an advance,
not only over the English machine, even of the type shown in Fig. 39,
which has a double control, and is especially designed for the teaching
of beginners, but very much over the practice of attempting to actually
fly for the first time in a strange machine, as it provides the
necessary practice in the handling of the motor and the lateral
steering. The machine can make high speed over the ground, but is
perfectly safe for the beginner, as it is incapable of rising. Having
gone through the stages represented by either of these contrivances, the
best course for the learner to follow is to try gliding, taking short
glides to attain the ability to quickly meet varying conditions of the
atmosphere.
The fact that these glides are of extremely short duration at first need
not be discouraging when it is recalled that, after several years of
work, the Wright Brothers considered that great progress had been made
when, in 1902, they were able to make glides of 26 seconds. During six
days of the practice season of that year, they made 375 gliding flights
of various distances, most of them comparatively short, but each one of
value in familiarizing the glider with the conditions to be met. It is
not material whether gliding or manipulation of the control levers is
taken up first, as both should be mastered as far as possible before
attempting to fly a regular machine.
*Use of the Elevating Plane*. So many things are necessary to the
control of an aeroplane that thinking becomes entirely too slow a
process—the aviator must be endowed with something approaching the
instinct of the bird; he must be so familiar with his machine and its
peculiarities that a large part of the work of controlling it is the
result of subconscious movement. The control levers of many machines are
so arranged that this subconscious movement on the part of the aviator
directly operates the balancing mechanism. There is no time to think.
When a machine rises from the ground, facing the wind as it should, its
path of flight should be a gradual upward inclination, this being
something difficult to accomplish at first, owing to the sensitiveness
of the elevating rudder, the tendency almost invariably being to give
the latter too great an angle of incidence. At this stage, the maximum
velocity of flight has not yet been attained and care must be taken to
keep the angle of ascent small. Otherwise, the power of the engine,
which may not have reached its maximum, would not be sufficient to cause
the machine to ascend an inclined path at the starting speed. If the
speed of flight be reduced by the increased resistance at this point,
the whole machine will slide back in the air, and if a sudden gust of
wind happens to coincide with the attempt to rise at too great an angle,
there is danger of it being blown over backward.
Where the machine is just leaving the ground and the elevator has been
set at an excessive angle, the rear end of the skids or the tail may
slap the ground hard and break off, or they will impose so much
resistance upon its movement by scraping over the turf that the machine
can not attain its soaring speed. It must be borne in mind, of course,
that remarks such as the present can be only of the most general nature,
every type of machine having its own peculiarities—in some instances,
the extreme opposite of those characterizing similar machines. For
example, in the Voisin 1910 type, the very large and powerful light tail
tends to lift before the main planes, and if this be not counteracted,
the whole machine may turn up on its end. In order to offset this
tendency, the elevator must be raised so as to keep sufficient pressure
beneath it; the moment of this pressure about the center of gravity must
be at least equal to the pressure under the tail planes about the center
of gravity of the machine, or the tail will rise unduly in the air. At
least that is the theory of it—naturally, only practice with that
particular machine would suffice to enable an aviator to familiarize
himself with that particular peculiarity. Again, some machines are "tail
heavy." But there is great difficulty in even approximating the degree
of relative motion, for which reason it has been suggested, under
"Accidents and Their Lessons," that a gradometer, or small spirit level,
in plain sight of the aviator, should form part of the equipment of
every machine. The Wrights long ago adopted the expedient of attaching a
strip of ribbon to the elevator to provide an indication of motion
relative to the wind.
*Aeroplane in Flight*. The sensation of motion after the machine leaves
the ground is almost imperceptible, and it is likewise extremely
difficult to tell at just what moment the aeroplane ceases running on
the solid ground and takes to the air. There is a feeling of
exhilaration but very little of motion. Whereas 40 miles an hour over
the ground, particularly in an automobile, brings with it a lively
appreciation of the speed of travel, the same speed in an aeroplane is a
very gentle motion when high above the ground. If there be no objects
close at hand, with which to compare the speed, the sense of motion is
almost entirely lost.
*Center of Gravity*. The static balance of a machine should be carefully
tried before commencing to fly, and particularly that of a biplane of
the Wright type, in which the aviator sits behind the engine. When
provision is made for carrying a passenger, his seat is placed in the
center line of the machine, so that his presence or absence does not
materially affect the question of lateral balance. As men are not all of
the same weight, in cases in which the aviator only partly balances the
engine about the center line, his weight being insufficient for the
purpose, extra weights should be placed on the wing tip at the lightest
end until the true balance is secured, otherwise a permanent warping, or
_gauchissement_ as the French term it, is required at this side in order
to keep the machine on an even keel. In other words, the machine will
carry what sailors term a port helm where the left side of the machine
is lighter than the right, and _vice versa_, and it will be necessary to
keep the rudder over to that side slightly during the entire flight to
counteract this tendency.
In aeroplanes fitted with tails, the center of gravity is usually in the
vicinity of the trailing edge of the main planes and, of course, should
be on the center line of the machine. The center of gravity of the
aviator on a monoplane should approximately coincide with that of the
machine. If this be not the case, the stabilizers or the elevator must
be permanently set to produce longitudinal balance. Much downward set,
or the increase of the angle of incidence of the tail, will create undue
resistance to flight and should be avoided when possible by bringing the
weight farther forward. The center of pressure should coincide with the
center of gravity, and balance will result.
Before even ground work is attempted, the position of the center of
gravity should be determined in the manner shown in Fig. 40, the
approximate location for four types of machines being shown. At what
point the machine must be suspended, so that it can tip only frontward
and backward and be evenly balanced, is a question that must be answered
in order to ascertain the probability of the machine’s pitching forward
whenever mud, grass, or rough ground is encountered in alighting. If the
center of gravity should lie in front of the axles of the ground wheels
in a machine of the Farman type, trouble is sure to follow. Always
consider the relation of the center of gravity to the wheels, in order
that you may gain some idea of the distribution of the weight on the
running gear when the machine is tipped forward 10 degrees. If the
wheels are not forward far enough there will be trouble in running on
the ground. The elevators must correct whatever variance there may be
from the correct center of gravity and position of the wheels, and the
manipulation of the elevators for that purpose requires skill. If the
tail be very heavy, the elevator may not be able to counteract that
defect.
[Illustration: Fig. 40. Method of Determining Center of Gravity of
Different Types of Machines]
The position of the center of gravity of a machine in regard to lateral
stability in flight is a matter of far greater importance than untried
aviators realize. Having it too low is quite as bad as too high, as in
either case there is a tendency to upset. Although the dihedral angle is
considered wasteful of power, it seems to do more to secure inherent
stability than any other device. Devices for maintaining stability
automatically are to be frowned upon in the present state of the art.
The sensitive perception and quick response which come with intimate
knowledge of a machine’s peculiarities, are at present worth more than
gyroscopes and pendulums. To acquire this intimate knowledge, the
aviator must familiarize himself thoroughly with the machine; he must
become so accustomed to controls that he and the machine are literally
one. A practiced bicycle rider does not have to think about balance,
neither does the practiced aviator, yet he must always be prepared to
meet motor stoppages, unusual air disturbances, and breakages. A leap
from the ground directly into the air, without preliminary practice,
means certain accident, to put it mildly.
*Center of Pressure*. But although the center of gravity remains
approximately constant, the center of pressure is continually varying
and is never constant for many seconds. The center of pressure on an
aerocurve constructed to Phillips’ design, Fig. 41, is about one-third
of the chord from the leading edge of the plane under normal conditions,
_i.e._, when the angle of incidence is about 8 degrees between the
direction of motion of the plane and that of the air. At the moment this
angle is increased the center of pressure moves toward the rear, and
_vice versa_. The center of gravity must be moved to coincide with this
new position, or the center of pressure must be artificially restored by
the use of supplementary planes or elevators, moving in a contrary
direction. A forward movement of the center of pressure tends to lower
the tail of the machine, when the intensity of the pressure is
unchanged, and to counterbalance this the rear elevator must have its
angle of incidence increased in order to increase the lift at the rear
of the machine, or it will slide down backward. The alternative to be
adopted in case of temporary lack of engine power is to decrease the
angle of the elevator and allow the aeroplane to sweep downward, thus
gaining momentum. The increase of speed will then be sufficient probably
to enable the machine to continue in a horizontal flight, when the
center of pressure is again restored to its normal position.
[Illustration: Fig. 41. Aerocurve of Phillip’s Design]
*Ground Practice*. First of all, the aviator should familiarize himself
with his seat for it is from that place that he must judge wind effects,
vibration, motor trouble, and the thousand and one little creaks and
hums that will ultimately mean so much to him. Not until he has
thoroughly accustomed himself to his seat, should he try to run along
the ground. This done, hours should be spent running up and down and
around the field to learn the use of the rudder, particularly on rough
ground. The runs should be straight so that when the time comes to leap
into the air, the aviator may be sure that he is on an even keel, and
flying straightaway. In order to prevent the possibility of leaving the
ground unexpectedly in practice, trials should be made only in calm
weather and with the motor well throttled down so that the machine will
be reduced to a speed of not more than 15 miles per hour. After a time
this may be increased to 20, but the latter is the maximum for ground
practice, as the machine will rise at speeds slightly exceeding this. In
these practice rims on the ground, the student should learn to gauge the
rush of air against his face, as when aloft his best gauge will be the
wind pressure on his cheeks, as that will tell him whether he is moving
with sufficient speed to keep up or not. It will also tell him
ultimately whether he is moving along the ground fast enough to leap up.
[Illustration: VEDRINES, ONE OF THE MOST FAMOUS AND SUCCESSFUL OF
EUROPEAN AEROPLANE PILOTS, SEATED
IN A DEPERDUSSIN MONOPLANE]
[Illustration: AIRSHIP CROSSING ONE OF THE NATIONAL ROADS IN RURAL
FRANCE
_This Photograph Protected by International Copyright_]
In this stage of experimenting on the ground, the elevator is kept
neutral as far as possible. With increasing skill its use may be
ventured, but only sparingly, for it takes very little to lift the
machine from the ground with a speed in excess of 20 miles per hour. It
will soon be discovered that the elevator can be used as a brake to
prevent pitching forward. The tail elevators on the Farman or Bleriot
running gear are very effective owing to the blast of the propeller,
even when the main planes are not moving forward at lifting speed. With
the Curtiss type of running gear and a front elevator only, it is often
possible at 18 to 20 miles per hour to raise the front wheel off the
ground for a second or two—facts which indicate that at 25 to 28 miles
per hour, the elevator is far more effective.
*First Flight*. The first actual flight should be confined to a short
trip parallel to the ground and not more than one or two feet above it.
At first, the student should see how close he can fly to the ground
without actually touching it, which he can do by gradually increasing
his forward speed. This must be done in an absolute calm as an
appreciable amount of wind will bring in too many other factors for the
student to master at so early a stage. This practice should be continued
in calm air until short, straight flights can be made a foot or two from
the ground with the motor wide open. If it be found that the machine
barely flies straightaway with the full power of the motor, the latter
is either badly out of adjustment, or a more powerful engine is
required. In an under-powered machine turning would be suicidal.
Moreover, the resistance encountered in the air is greater than on the
ground and may be such that the speed is not sufficient for
sustentation. Fig. 42, (a) and (b), show why it is possible to run along
the ground faster than it is possible to travel in the air, under
certain conditions, and why the ground can be left at low speed. If it
were possible to drive a machine with such enormous projected areas as
_BB_, shown in Fig. 42 (b), a man could fly slowly for an indefinite
period. But the projected area is greater than the air displaced by the
propeller, and it is impossible to fly except with a moderate angle of
incidence, giving projected areas _A A_, Fig. 42 (a). The student, as he
increases in skill, may venture to a height of 10 feet, which should be
maintained as accurately as before, and after making a run of 100 yards,
the machine should be pointed down, but ever so slightly. The wind
pressure on the face immediately becomes greater. Within a foot or two
of the ground the motor should be cut off or throttled. This should be
tried ten or fifteen times, and the height increased to 30 or 40 feet,
in order that the student may familiarize himself with the sensation of
coasting. At the end of each glide the machine will seem to become more
responsive, as indeed it does, for gliding down greatly increases the
efficiency of the elevator and other controls, because of the increased
speed. Gliding down steep angles is often the aviator’s salvation in a
tight place, particularly when the motor fails, a side gust threatens or
an air pocket is encountered.
[Illustration: Fig. 42. Diagrams Showing Greater Projected Area of Main
Plane when
Running along Ground]
*Warping the Wings*. When sufficient confidence has been attained at a
height of 30 to 40 feet, the ailerons or warping devices may be tried
judiciously. Here the intention should be to correct any tendency to
side tipping, and not purposely to incline the machine as far as
possible without actually causing a wreck. The use of the lateral
control may cause the machine to swerve a little, but that may be
ignored. Before landing, a straight course should be taken so that the
machine will always come down on an even keel. With increasing practice,
the student may fly higher, but always with the understanding that there
is a limit to the angle of incidence. An automobile is retarded when it
strikes a short, steep hill; so is an aeroplane. No aeroplane has yet
been built that can take a steep angle and climb right up that grade
continuously. Altitude is reached by a series of small steps and at
comparatively low angles, as unless the course is straightened out at
regular intervals, a machine will lose its speed and tend to plunge tail
first, just as is the case when an attempt is made to rise from the
ground at too sharp an angle.
In warping the wings an increase of lift imparted to one wing of the
machine is produced by increasing the angle of incidence of the whole or
part of the wing, or by an increase of pressure under that wing, and
will tend to cause that side of the machine to rise and the other side
to lower, the result being that the machine will be liable to slide
through the air diagonally. In the majority of aeroplanes there are no
fins or keels to counteract this movement, and lateral stability must be
restored by artificially increasing the lift of the depressed wing. This
can be done by warping, or lowering the trailing edge of the depressed
wing and increasing its lift, and simultaneously raising the trailing
edge of the other wing, thus decreasing the angle of incidence of the
latter and reducing its lifting effect. This applies to flight on a
straight course, whatever the cause may be that tends to upset lateral
stability. It will be seen, therefore, that the center of gravity
remains constant and the center of pressure must be manipulated to
restore stability. This manipulation is much more rapid and positive
than the alteration of the center of gravity by the movement of the
aviator’s body resorted to in the early gliding flights of pioneer
experimenters.
*Making a Turn*. The first turn should be made over a large field and
the diameter of the turn should be at least half a mile. The height
should be not less than 50 feet. After that level has been maintained,
the rudder should be moved very gingerly. The machine will lean in
almost immediately, because the outer end travels at a higher speed than
the inner and therefore has a greater lift. Warping or working the
ailerons should be resorted to as a means of counteracting this
tendency, and the rudder swung to the opposite direction, if necessary.
It is obvious that if the rudder will cause the machine to bank when
swung in one direction, it will right the machine again when swung in
the opposite direction. It is even possible to turn the machine on an
even keel by anticipating the banking, simply by correctly using the
rudder, which was necessary in the old Voisin machine flown by Farman in
1908, because it had no mechanical lateral control. The student should
learn the correct angle of banking, _i.e._ the angle at which the
machine will neither skid nor slide down and which is most economical of
power because it requires less use of the lateral controls. The
necessity of "feeling the air" is greater in turning than in any other
phase of flying. By "feeling the air" is meant the ability to meet any
contingency intuitively and not until this is acquired can the student
become an expert aviator. When it has been acquired, safe flying is
assured and is dependent only upon the integrity of the planes, motor,
and controls. By using the rudder discreetly and by banking simply far
enough to partially offset the centrifugal force of turning, the use of
the lateral control will not be necessary in still air. Even too short a
turn can be corrected by a quick use of the rudder.