aeroplanes-第9节
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_Fig。 15。 Utilizing Momentum。_
CUTTING OFF THE POWER。This curve； A； may
reach that point where momentum has ceased as
a forwardly…propelling factor； and the machine
now begins to travel rearwardly。 （Fig。 16。） It
has still the entire supporting surfaces of the
planes。 It cannot loop…the…loop； as in the instance
where the planes are fixed immovably to the body。
Carefully study the foregoing arrangement； and
it will be seen that it is more nearly in accord with
the true flying principle as given by nature than
the vaunted theories and practices now indulged
in and so persistently adhered to。
The body of a flying machine should not be oscillated
like a lever。 The support of the aeroplane
should never be taken from it。 While it may be
impossible to prevent a machine from coming
down； it can be prevented from overturning； and
this can be done without in the least detracting
from it structurally。
_Fig。 16。 Reversing Motion。_
The plan suggested has one great fault； however。
It will be impossible with such a structure
to cause it to fly upside down。 It does not present
any means whereby dare…devil stunts can be performed
to edify the grandstand。 In this respect
it is not in the same class with the present types。
THE STARTING MOVEMENT。Examine this plan
from the position of starting； and see the advantages
it possesses。 In these illustrations we
have used； for convenience only； the monoplane
type； and it is obvious that the same remarks apply
to the bi…plane。
Fig。 17 shows the starting position of the stock
monoplane； in position 1； while it is being initially
run over the ground； preparatory to launching。
Position 2 represents the negative angle at which
the tail is thrown； which movement depresses the
rear end of the frame and thus gives the supporting
planes the proper angle to raise the machine；
through a positive angle of incidence； of the plane。
_Fig。 17。 Showing changing angle of body。_
THE SUGGESTED TYPE。In Fig。 18 the suggested
type is shown with the body normally in a horizontal
position； and the planes in a neutral position；
as represented in position 1。 When sufficient
speed had been attained both planes are
turned to the same angle； as in position 2； and
flight is initiated without the abnormal oscillating
motion of the body。
But now let us see what takes place the moment
the present type is launched。 If； by any error on
the part of the aviator； he should fail to readjust
the tail to a neutral or to a proper angle of incidence；
after leaving the ground； the machine would
try to perform an over…head loop。
The suggested plan does not require this caution。
The machine may rise too rapidly； or its
planes may be at too great an angle for the power
or the speed； or the planes may be at too small an
angle； but in either case； neglect would not turn
the machine to a dangerous position。
These suggestions are offered to the novice； because
they go to the very foundation of a correct
understanding of the principles involved in the
building and in the manipulation of flying machines
and while they are counter to the beliefs of
aviators； as is shown by the persistency in adhering
to the old methods； are believed to be mechanically
correct； and worthy of consideration。
THE LOW CENTER OF GRAVITY。But we have still
to examine another feature which shows the wrong
principle in the fixed planes。 The question is
often asked； why do the builders of aeroplanes
place most of the weight up close to the planes？
It must be obvious to the novice that the lower
the weight the less liability of overturning。
FORE AND AFT OSCILLATIONS。The answer is；
that when the weight is placed below the planes it
acts like a pendulum。 When the machine is traveling
forward； and the propeller ceases its motion；
as it usually does instantaneously； the weight； being
below； and having a certain momentum； continues
to move on； and the plane surface meeting
the resistance just the same； and having no means
to push it forward； a greater angle of resistance is
formed。
In Fig。 19 this action of the two forces is illustrated。 The
plane at the speed of 30 miles is at
an angle of 15 degrees； the body B of the machine
being horizontal； and the weight C suspended directly
below the supporting surfaces。
The moment the power ceases the weight continues
moving forwardly； and it swings the forward
end of the frame upwardly； Fig。 20； and we now
have； as in the second figure； a new angle of incidence；
which is 30 degrees； instead of 12。 It will
be understood that in order to effect a change in
the position of the machine； the forward end ascends；
as shown by the dotted line A。
_Fig。 20。 Action when Propeller ceases to pull。_
The weight a having now ascended as far as
possible forward in its swing； and its motion
checked by the banking action of the plan it will
again swing back； and again carry with it the
frame； thus setting up an oscillation； which is extremely
dangerous。
The tail E； with its unchanged angle； does not；
in any degree； aid in maintaining the frame on
an even keel。 Being nearly horizontal while in
flight； if not at a negative angle； it actually assists
the forward end of the frame to ascend。
APPLICATION OF THE NEW PRINCIPLE。Extending
the application of the suggested form； let us see
wherein it will prevent this pendulous motion at
the moment the power ceases to exert a forwardly…
propelling force。
_Fig。 21。 Synchronously moving Planes。_
In Fig。 21 the body A is shown to be equipped
with the supporting plane B and the tail a； so
they are adjustable simultaneously at the same
angle； and the weight D is placed below； similar to
the other structure。
At every moment during the forward movement
of this type of structure； the rear end of
the machine has a tendency to move upwardly；
the same as the forward end； hence； when the
weight seeks； in this case to go on； it acts on the
rear plane； or tail； and causes that end to raise；
and thus by mutual action； prevents any pendulous
swing。
LOW WEIGHT NOT NECESSARY WITH SYNCHRONOUSLY…MOVING WINGS。
A little reflection will convince
any one that if the two wings move in harmony；
the weight does not have to be placed low；
and thus still further aid in making a compact
machine。 By increasing the area of the tail； and
making that a true supporting surface； instead of
a mere idler； the weight can be moved further
back； the distance transversely across the planes
may be shortened； and in that way still further
increase the lateral stability。
CHAPTER V
DIFFERENT MACHINE TYPES AND THEIR CHARACTERISTICS
THERE are three distinct types of heavier…than…
air machines； which are widely separated in all
their characteristics； so that there is scarcely a
single feature in common。
Two of them； the aeroplane； and the orthopter；
have prototypes in nature； and are distinguished
by their respective similarities to the soaring
birds； and those with flapping wings。
The Helicopter； on the other hand； has no antecedent
type； but is dependent for its raising
powers on the pull of a propeller； or a plurality
of them； constructed； as will be pointed out hereinafter。
AEROPLANES。The only form which has met
with any success is the aeroplane； which； in
practice； is made in two distinct forms； one with
a single set of supporting planes； in imitation of
birds； and called a monoplane； and the other having
two wings； one above the other； and called
the bi…plane； or two…planes。
All machines now on the market which do not
depend on wing oscillations come under those
types。
THE MONOPLANE。The single plane type has
some strong claims for support。 First of these
is the comparatively small head resistance； due
to the entire absence of vertical supporting posts；
which latter are necessary with the biplane type。
The bracing supports which hold the outer ends
of the planes are composed of wires； which offer
but little resistance； comparatively； in flight。
ITS ADVANTAGES。Then the vertical height of
the machine is much less than in the biplane。 As
a result the weight； which is farther below the
supporting surface than in the biplane； aids in
maintaining the lateral stability； particularly
since the supporting frame is higher。
Usually； for the same wing spread； the monoplane
is narrower； laterally； which is a further
aid to prevent tilting。
ITS DISADVANTAGES。But it also has disadvantages
which must be apparent from its structure。
As all the supporting surface is concentrated
in half the number of planes； they must
be made of greater width fore and aft； and this；
as we shall see； later on； proves to be a disadvantage。
It is also doubted whether the monoplane can
be made as strong st
