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aeroplanes-第7章

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angle of the supporting surfaces should be movable;

and not controllable by the body。



The bird; in initiating flight from a perch; darts

downwardly; and changes the angle of the body to

correspond with the direction of the flying start。

When it alights the body is thrown so that its

breast banks against the air; but in ordinary flight

its wings only are used to change the angle of

flight。



ANGLE AND DIRECTION OF FLIGHT。In order to

become familiar with terms which will be frequently

used throughout the book; care should be

taken to distinguish between the terms angle and

direction of flight。 The former has reference to

the up and down movement of an aeroplane;

whereas the latter is used to designate a turning

movement to the right or to the left。



WHY SHOULD THE ANGLE OF THE BODY CHANGE?

The first question that presents itself is; why

should the angle of the aeroplane body change?

Why should it be made to dart up and down and

produce a sinuous motion? Why should its nose

tilt toward the earth; when it is descending; and

raise the forward part of the structure while ascending?



The ready answer on the part of the bird…form

advocate is; that nature has so designed a flying

structure。 The argument is not consistent; because

in this respect; as in every other; it is not

made to conform to the structure which they seek

to copy。



CHANGING ANGLE OF BODY NOT SAFE。Furthermore;

there is not a single argument which can be

advanced in behalf of that method of building;

which proves it to be correct。 Contrariwise; an

analysis of the flying movement will show that it is

the one feature which has militated against safety;

and that machines will never be safe so long as

the angle of the body must be depended upon to

control the angle of flying。



_Fig。 11a Monoplane in Flight。_



In Fig。 11a three positions of a monoplane are

shown; each in horizontal flight。 Let us say that

the first figure A is going at 40 miles per hour;

the second; B; at 50; and the third; C; at 60 miles。

The body in A is nearly horizontal; the angle of

the plane D being such that; with the tail E also

horizontal; an even flight is maintained。



When the speed increases to 50 miles an hour;

the angle of incidence in the plane D must be

decreased; so that the rear end of the frame must

be raised; which is done by giving the tail an angle

of incidence; otherwise; as the upper side of the

tail should meet the air it would drive the rear

end of the frame down; and thus defeat the attempt

to elevate that part。



_Fig。 12。 Angles of Flight。_



As the speed increases ten miles more; the tail

is swung down still further and the rear end of

the frame is now actually above the plane of flight。

In order; now; to change the angle of flight; without

altering the speed of the machine; the tail is

used to effect the control。



Examine the first diagram in Fig。 12。 This

shows the tail E still further depressed; and the

air striking its lower side; causes an upward movement

of the frame at that end; which so much decreases

the angle of incidence that the aeroplane

darts downwardly。



In order to ascend; the tail; as shown in the second

diagram; is elevated so as to depress the rear

end; and now the sustaining surface shoots upwardly。



Suppose that in either of the positions 1 or 2;

thus described; the aviator should lose control of

the mechanism; or it should become deranged or

〃stick;〃 conditions which have existed in the history

of the art; what is there to prevent an accident?



In the first case; if there is room; the machine

will loop the loop; and in the second case the machine

will move upwardly until it is vertical; and

then; in all probability; as its propelling power is

not sufficient to hold it in that position; like a

helicopter; and having absolutely no wing supporting

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 it the

frame; thus setti

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