按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
surface when in that position； it will dart
down tail foremost。
A NON…CHANGING BODY。We may contrast the
foregoing instances of flight with a machine having
the sustaining planes hinged to the body in
such a manner as to make the disposition of its
angles synchronous with the tail。 In other words；
see how a machine acts that has the angle of flight
controllable by both planes；that is； the sustaining
planes； as well as the tail。
_Fig。 13。 Planes on Non…changing Body。_
In Fig。 13 let the body of the aeroplane be horizontal；
and the sustaining planes B disposed at
the same angle； which we will assume to be 15
degrees； this being the imaginary angle for illustrative
purposes； with the power of the machine
to drive it along horizontally； as shown in position
1。
In position 2 the angles of both planes are now
at 10 degrees； and the speed 60 miles an hour；
which still drives the machine forward horizontally。
In position 3 the angle is still less； being now
only 5 degrees but the speed is increased to 80
miles per hour； but in each instance the body of
the machine is horizontal。
Now it is obvious that in order to ascend； in
either case； the changing of the planes to a greater
angle would raise the machine； but at the same
time keep the body on an even keel。
_Fig。 14。 Descent with Non…changing Body。_
DESCENDING POSITIONS BY POWER CONTROL。In
Fig。 14 the planes are the same angles in the three
positions respectively； as in Fig。 13； but now the
power has been reduced； and the speeds are 30；
25； and 20 miles per hour； in positions A； B and C。
Suppose that in either position the power should
cease； and the control broken； so that it would be
impossible to move the planes。 When the machine
begins to lose its momentum it will descend on a
curve shown； for instance； in Fig。 15； where position
1 of Fig。 14 is taken as the speed and angles
of the plane when the power ceased。
_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 i