THE builder of model aeroplanes will do well to keep in touch with the
development of the passenger-carrying air craft. The development of both
types of machines will always be more or less parallel. It is especially
important that you watch the design and position of wings, and the
modeling of propellers, since here the problem confronting both classes
of builders is practically the same. The use of ailerons and vertical
surfaces and all improvement in steering the large machines again may
have a direct application on model aeroplane buildings.
The photographs of the new models of the large machines published in the
newspapers will often give valuable hints, while the technical
aeronautical papers will, of course, give more detailed information. In
a few years, at the present rate of model aeroplane development, the
designers and pilots of large machines may be looking to the new designs
of model aeroplanes with much the same interest.
There is at present but one passenger-carrying monoplane, the Valkyrie,
flown "tail first." It is built in two sizes, the smaller, fitted with
high-powered engines, being intended for racing. The general lines of
the Valkyrie resemble those of many of the model aeroplanes, but there
are some features which deserve careful study. The main plane of the
Valkyrie is set at a pronounced elevation, and has a high aspect ratio.
The front and rear planes are separated by a distance equal to about
five times their width. Both planes have a slight camber. One of the
most novel features of this model is that the forward plane is tilted
upward at a positive angle, while the rear plane is elevated
considerably less, thus giving the machine a longitudinal dihedral
angle. This arrangement makes for fore and aft stability much the same
as the dihedral angle of the wings makes for lateral stability, and
suggests an interesting field of experiment.
The new type of Bleriot XI follows the general lines of the famous
machine which first crossed the Channel. The fuselage of the new
machine, however, is completely covered, tapering to a broad flat
surface at the rear. This plan of gaining more surface by covering the
frame is becoming general. In model building, it is unsafe to follow
this plan, unless the motor base be comparatively small. The new Bleriot
carries a larger horizontal rudder than formerly, placed aft, while the
vertical rudder above it has been increased in size. The general design
of the main plane, which is placed forward, remains unchanged. A single
tractor screw is carried in front as usual.
In the new Blackburn aeroplane, the fuselage is covered with wood as far
back as the pilot’s seat, and with cloth to its extreme end. The use of
thin board for this purpose suggests interesting possibilities. One of
the most novel features of this model is the light skid attached to the
outer ends of the main plane. The skid is very light, adding little to
the weight or head resistance, and prevents the end of the plane from
digging into the ground on landing. Such an attachment may readily be
added to model aeroplanes when they will save many a broken wing.
A novelty in plane-designing is shown in the Handley Page monoplane. The
main plane, carried forward, as in the Bleriot, is cambered just back of
the entering edge, flows back to a flat surface at the middle and then
tilts upward toward the rear edge. The two sides, in turn, are set at a
slight dihedral angle to the horizontal. This modeling is believed to
secure automatic stability in two dimensions, both longitudinal and
transverse. The planes are unusually broad in their fore and aft
dimension, extending back nearly one-half the length of the motor base.
The horizontal and vertical rudders are very small. The design should
work well in models.
Builders of biplane models will find some interesting suggestions in the
new Bristol biplane. The forward planes are of the biplane form, the
lower surface being much narrower than the superimposed plane, the
comparative width being one-third wider. Another original feature of
this machine is that the planes are connected by only four struts
instead of by rows of struts along both the front and rear edges. The
planes are held rigid by a series of braces. It is believed that this
arrangement decreases the head resistance, at the same time insuring
considerable lateral automatic stability. The rear plane is of the
monoplane type.
The friends of the Dunn monoplane believe that the question of automatic
stability has been practically solved in this ingenious machine. The
Dunn machine has flown on an even keel for five miles without the pilot
once touching the controlling levers. The trick is in the design of the
main wings.
The greater part of the wing, extending out from the central stick, has
a slight camber and is slightly elevated, besides being set at a
dihedral angle. Near the outer edge the wings are bent sharply down,
much as the wings of a swallow are bent, and are given a considerable
negative angle both forward and outward. The tips, therefore, form
pockets at either end under the arched tips.
Wings modeled in this way are remarkably stable even when traveling
across the wind. When a gust of wind strikes the outer edge of the
plane, it tends to thrust it down rather than up, as is the case when a
gust gets under a wing of the ordinary design. The wing quickly rights
itself, however, since the angle of the plane tends to lift it. The
pockets in turn by compressing the air tend to counteract this tipping
tendency. These pockets are besides closed to an extent by ailerons or
flaps, which may be pulled down, thus confining the air still further.
An effective device for securing lateral control appears in the new
Grahame-White machine. Narrow ailerons are placed on the forward edge of
the front plane near the outer tips. The tips at the opposite ends are
hinged and so connected that as one is raised the corresponding tip is
lowered, or the other way about. Now as one of these tips is lowered,
tending to lift the machine, the opposite aileron working in the other
direction tends to depress it.
The increased resistance offered by the lowered flap again tends to keep
the machine from swinging around in the direction of the side on which
the other aileron is lowered. The lateral control is thus much more
quickly applied than in the case of the rear ailerons. In applying this
principle to model construction, it must be borne in mind that the
resistance of these forward tips is tending to retard the machine and
must be used with care when the motive power is limited.
As far as general appearance is concerned, the Piggot monoplane is
probably the greatest novelty of the year. It is the first aeroplane to
carry a cabin, as it were, in which the pilot sits completely enclosed.
In general appearance it suggests a great whale with exaggerated fins.
The pilot looks out through elliptical windows at the sides and bottom,
covered with mica, to protect him from the wind.
The wings of the Piggot aeroplane resemble the Bleriot machine, the
propeller, or rather tractor, being carried forward. It is extremely
interesting, however, since it suggests for the first time what the
appearance of a cabined, passenger-carrying aeroplane of the future may
be.
On the Farman aeroplane, the arrangement for providing stability is very
interesting. The ailerons in this case are attached to the rear of one
of the main planes, the lower one, by hinges. This general plan will be
followed in the case of the model aeroplanes. In a number of successful
model aeroplanes, the Farman ailerons have been closely imitated. The
Curtiss biplane depends for its stability upon ailerons mounted midway
between the two main planes and partly within them. This plan is
scarcely practicable in the case of model aeroplanes, since they
increase air resistance and are difficult to control.
The Baldwin biplane has introduced a new feature for obtaining stability
which may be closely imitated. A large plane is set vertically, directly
above the upper main plane which may be swung from side to side by the
pilot. The theory of this stabilizing surface is that it will restore
equilibrium from side to side, since it works in undisturbed air while
meeting with very little head resistance.
Many builders of model aeroplanes have introduced a similar vertical
plane directly above the main plane, or have placed it well forward at
the extreme front of the motor base. By removing this rudder as far as
possible from the main supporting surface, it exerts a greater leverage,
and a very small plane carried well forward will be more effective than
a larger plane directly above the main supporting surface. It has the
disadvantage of catching any chance side current and thereby knocking
the aeroplane off its course.
[Illustration: Percy Pierce, winner of the distance record]
[Illustration: A well-proportioned model, capable of long flights]
[Illustration: A well designed aeroplane built by James MacPherson]
The same principle has been carried somewhat further in the case of the
new Herring biplane, which carries six triangular stabilizing fins set
vertically above the upper plane. It is believed that these fins offer
considerable resistance to any tipping motion of the planes, and if the
machine slants to one side or the other, for any cause, there is a
tendency, of course, to dart downward at an abrupt angle. The fins
retard this motion as far as the upper plane is concerned, and the lower
plane without such an equipment tends to swing back like a pendulum,
thus bringing the aeroplane to an even keel.
In the case of the Antoinette aeroplane, of a monoplane type, a somewhat
different device is depended upon for stability. The ailerons in this
case are attached to the outer edges of the rear wing and are hinged so
that they may be raised or lowered at will. One of these may be turned
up while the other is turned down. Although these resemble the Farman
ailerons, they are believed to be twice as effective since they may work
in opposite directions, while those of the Farman aeroplane may only be
inclined downward.
It will be noticed in the photographs of many successful model
aeroplanes that the tips of the wings are flexed upward at an angle
often as much as 45 degrees. These planes, it is believed, tend to lower
the center of gravity, and in the case of a turn tend to bring the
aeroplane to an even keel. Their head resistance in a straight flight
is, of course, rather great. It is claimed that the Antoinette aeroplane
is the easiest of all aeroplanes for a beginner, largely because of this
adjustment of ailerons.
One of the most novel devices for gaining stability which has appeared
during the year, is that of the Pfitzner monoplane, which gains lateral
stability by means of an ingenious sliding wing tip which may be pushed
out or drawn back at will. When the aeroplane begins to fall from its
level, one of these wing tips is shot out, while the other is pulled in.
This increased surface tends to throw one plane upward while the shorter
plane, which for the time exerts less lifting power, falls
correspondingly. The Pfitzner monoplane makes many sharp turns with very
little tipping.
A New York aviator has succeeded, it is reported, in building a
practicable aeroplane, which combines the best features of both the
lighter and heavier than air machines. In the earlier stages of the
development of aeronautics many believed that the solution of the
problem was to be found in some such combination. The attempts usually
consisted in adding large planes to dirigible balloons. Gradually,
however, the combination was given up as impossible. The great
dirigibles of to-day carry considerable plane surface, but this is
intended to lend stability for guiding and not support.
The New York aviator, however, reverses matters and retaining the
aeroplane form attempts to gain additional support from gas pockets. He
does this by building his plane after the general Bleriot model but with
a considerable space between the upper and lower surfaces, which he
fills with gas. The machine has not yet been exhibited, but it is
understood that this space is upwards of one foot in thickness and as
wide and long as the planes. The front entering edge is kept sharp so
that the wings, for all their size, meet as little resistance as
possible. Whether the support gained from so small a body of gas is
worth while, and counteracts the increased resistance of the enlarged
wing, is of course an open question. The dirigible aeroplane has been
flown successfully several times, however, with a passenger and is
reported to have behaved well.
The new Paulhan biplane introduces an entirely new form of plane which
is being watched with great interest. The wings have the appearance of
being fluted or corrugated. The frames of the planes consist of a great
number of ribs, running from front to rear, placed but a few inches
apart. These ribs are made very flexible. The canvass covering of the
planes is sewn with a series of pockets, exactly corresponding to the
ribs. The wings are covered by merely pulling the canvass on the ribs
and fastening it rigidly in place. This gives the canvass a tendency to
arch between the ribs so that the planes consist of a series of
corrugations. It is believed by some aviators that the supporting power
of the aeroplane is increased in this way. It has the advantage at least
of being very easy to adjust. A model aeroplane built on these lines
should fly well and have a distinctive appearance.
Another feature of the new Paulhan which should appeal to the builder of
model aeroplanes is its ingenious trussed girder. It is known as the
Fabre girder. It is interesting to note here that the built-up girder
was used in the model aeroplanes even before it was adopted in the
man-carrying machines. The Fabre girder consists of two long strips of
light wood connected by crosspieces of steel running diagonally. This
form of construction gives unusual strength and is very light. It has
its parallel in the beautifully built-up trusses to be found for
instance in the models built by Mr. Mungokee. In this case the girders
are made entirely of wood.
The question is often asked whether the rear edge of the front plane
should be straight or brought back and tipped at either end. A study of
the various models of the standard manufacturers shows that there is
considerable difference of opinion among the experts. The builders of
model aeroplanes in America still retain the straight line, while in
England the tips are brought well back in a great many of the designs.
The theory of this form is, obviously, that this tip tends to damp out
any lateral motion, and makes for stability. In the most successful
American models the rear line of the plane is kept straight without
apparent loss of stability.
Turning now to the large machines, we find a similar contrast. In none
of the Bleriot models is the rear line broken. The Wright, Curtis and
Antoinette machines, even in their latest form, still retain the
straight line. The Etrich monoplane has had good results with rear wing
tips. The model has been accepted by the Austrian Minister of War who
has ordered a fleet of twenty of these craft for the army.
The rear tip was first suggested by Lilienthal. The friends of this form
claim that it more nearly approaches the form of a bird’s wing than any
of the other planes now in use. The depth of the main plane is nine and
three-quarter feet and at the tips twelve feet. The entire tip is so
adjusted that it may be flexed at will from the pilot’s seat. It will be
seen that this arrangement makes it possible to imitate the flight of a
bird very closely. In adopting this idea in model aeroplanes it will be
well to attach the extension by a hinge so that it may be turned up or
down at will. Since it is placed well out from the main axis of the
machine its leverage is naturally great.
In the large machines as well as in the models there seems to be a
general tendency to increase the aspect ratio of the main planes. The
Bleriot XI still retains its broad deep plane, but in several of the
models the depth of the model has been greatly reduced. In the new
Voisin monoplane the main wing has a width of thirty-seven feet and a
depth of but five feet, thus giving it an aspect ratio of nearly one to
eight. The machine flies with great ease, its resistance is very low and
it answers well to its stabilizing devices. The Cody biplane again has
supporting planes measuring fifty-two feet by only seven feet six
inches.
The same tendency to reduce the size of the planes is noticeable in the
recent Wright models. The Wright machines (model R), are the smallest
yet used on an aeroplane. They have a spread of but twenty-six feet six
inches and a chord of only three feet seven inches, giving them an
exceedingly high aspect ratio. In the racing machines the spread has
been cut down to twenty-one feet six inches. Attention has been called
in an earlier chapter to this same tendency to reduce the wing area in
model aeroplanes. It is interesting to find our amateur aviators
increasing the aspect ratio of their planes although working
independently.
In many of the large machines the front and rear planes are brought much
closer together in the more recent models. It would seem that as the
front and rear planes are brought closer together there would be a loss
in fore and aft stability, but on the other hand the reduction in weight
made possible by shortening the frame is very important.
A careful report has been prepared in France recently of all the serious
accidents to aeroplanes with the idea of classifying them. The record of
fatal accidents shows a total of thirty-one up to the beginning of the
present year, resulting in thirty-four deaths. Although these figures
taken alone are appalling, they are found on analysis to indicate that
aviation is nevertheless growing safer and not more dangerous. In 1910
there were twice as many fatal accidents as in the previous year, but on
the other hand there were more than five times as many flights made, so
that the percentage of accidents, as a matter of fact, was but forty per
cent. as great as for the preceding year.
The commonest cause of accidents according to these tables has been
faulty construction. Next in turn came the accidents due to the errors
of the pilots. Atmospheric conditions rank third in the list and fourth
the carelessness of the spectators. There were in all some forty-seven
accidents in 1909, and 101 in 1910. An increase is to be noticed last
year in the accidents due to atmospheric conditions. This was caused in
most cases by the unusual daring, even foolhardiness of the pilots. In
their attempts to amaze their audience by performing hazardous dives and
volplanes from great heights many machines were wrecked and several
aviators met their death.
Since the main cause of fatal accidents has not been structural weakness
or the carelessness of the pilots, it is clear that the science of
aviation itself cannot be blamed. It is of course a comparatively easy
matter to build machines sufficiently strong to fly without breaking
down. The number of accidents, especially fatal accidents, due to the
inherent danger of flying, to dangers which cannot be overcome, has been
very trifling, and is steadily diminishing.