LEARNING TO FLY.

Don't be too ambitious at the start. Go slow, and

avoid unnecessary risks. At its best there is an element

of danger in aviation which cannot be entirely eliminated, but it

may be greatly reduced and minimized by

the use of common sense.



Theoretically, the proper way to begin a glide is from

the top of an incline, facing against the wind, so that

the machine will soar until the attraction of ravitation

draws it gradually to the ground. This is the manner in

which experienced aviators operate, but it must be kept

in mind that these men are experts. They understand

air currents, know how to control the action and direction

of their machines by shifting the position of their

bodies, and by so doing avoid accidents which would be

unavoidable by a novice.



Begin on Level Ground.



Make your first flights on level ground, having a couple

of men to assist you in getting the apparatus under

headway. Take your position in the center rectangle,

back far enough to give the forward edges of the glider

an inclination to tilt upward very slightly. Now start

and run forward at a moderately rapid gait, one man at

each end of the glider assisting you. As the glider cuts

into the air the wind will catch under the uplifted edges

of the curved planes, and buoy it up so that it will rise

in the air and take you with it. This rise will not be

great, just enough to keep you well clear of the ground.

Now project your legs a little to the front so as to shift

the center of gravity a trifle and bring the edges of the

glider on an exact level with the atmosphere. This, with

the momentum acquired in the start, will keep the machine

moving forward for some distance.



Effect of Body Movements.



When the weight of the body is slightly back of the

center of gravity the edges of the advancing planes are

tilted slightly upward. The glider in this position acts

as a scoop, taking in the air which, in turn, lifts it off the

ground. When a certain altitude is reached--this varies

with the force of the wind--the tendency to a forward

movement is lost and the glider comes to the ground.

It is to prolong the forward movement as much as possible

that the operator shifts the center of gravity slightly,

bringing the apparatus on an even keel as it were by

lowering the advancing edges. This done, so long as

there is momentum enough to keep the glider moving, it

will remain afloat.



If you shift your body well forward it will bring the

front edges of the glider down, and elevate the rear ones.

In this way the air will be "spilled" out at the rear, and,

having lost the air support or buoyancy, the glider comes

down to the ground. A few flights will make any ordinary

man proficient in the control of his apparatus by his

body movements, not only as concerns the elevating and

depressing of the advancing edges, but also actual steering. You

will quickly learn, for instance, that, as the

shifting of the bodily weight backwards and forwards

affects the upward and downward trend of the planes, so

a movement sideways--to the left or the right--affects

the direction in which the glider travels.



Ascends at an Angle.



In ascending, the glider and flying machine, like the

bird, makes an angular, not a vertical flight. Just what

this angle of ascension may be is difficult to determine.

It is probable and in fact altogether likely, that it varies

with the force of the wind, weight of the rising body,

power of propulsion, etc. This, in the language of physicists,

is the angle of inclination, and, as a general thing,

under normal conditions (still air) should be put down as

about one in ten, or 5 3/4 degrees. This would be an ideal

condition, but it has not, as vet been reached. The force

of the wind affects the angle considerably, as does also

the weight and velocity of the apparatus. In general

practice the angle varies from 23 to 45 degrees. At

more than 45 degrees the supporting effort is overcome

by the resistance to forward motion.



Increasing the speed or propulsive force, tends to

lessen the angle at which the machine may be successfully

operated because it reduces the wind pressure.

Most of the modern flying machines are operated at an

angle of 23 degrees, or less.



Maintaining an Equilibrium.



Stable equilibrium is one of the main essentials to

successful flight, and this cannot be preserved in an

uncertain, gusty wind, especially by an amateur. The

novice should not attempt a glide unless the conditions

are just right. These conditions are: A clear, level

space, without obstructions, such as trees, etc., and a

steady wind of not exceeding twelve miles an hour. Always

fly against the wind.



When a reasonable amount of proficiency in the handling

of the machine on level ground has been acquired

the field of practice may be changed to some gentle

slope. In starting from a slope it will be found easier

to keep the machine afloat, but the experience at first is

likely to be very disconcerting to a man of less than iron

nerve. As the glider sails away from the top of the

slope the distance between him and the ground increases

rapidly until the aviator thinks he is up a hundred miles

in the air. If he will keep cool, manipulate his apparatus

so as to preserve its equilibrium, and "let nature take its

course," he will come down gradually and safely to the

ground at a considerable distance from the starting place.

This is one advantage of starting from an elevation--

your machine will go further.



But, if the aviator becomes "rattled"; if he loses control

of his machine, serious results, including a bad fall

with risk of death, are almost certain. And yet this

practice is just as necessary as the initial lessons on

level ground. When judgment is used, and "haste made

slowly," there is very little real danger. While experimenting

with gliders the Wrights made flights innumerable

under all sorts of conditions and never had an accident

of any kind.



Effects of Wind Currents.



The larger the machine the more difficult it will be to

control its movements in the air, and yet enlargement is

absolutely necessary as weight, in the form of motor,

rudder, etc., is added.



Air currents near the surface of the ground are diverted

by every obstruction unless the wind is blowing

hard enough to remove the obstruction entirely. Take,

for instance, the case of a tree or shrub, in a moderate

wind of from ten to twelve miles an hour. As the wind

strikes the tree it divides, part going to one side and

part going to the other, while still another part is directed

upward and goes over the top of the obstruction.

This makes the handling of a glider on an obstructed

field difficult and uncertain. To handle a glider successfully

the place of operation should be clear and the wind

moderate and steady. If it is gusty postpone your flight.

In this connection it will be well to understand the velocity

of the wind, and what it means as shown in the

following table:



Miles per hour Feet per second Pressure per sq. foot

10 14.7 .492

25 36.7 3.075

50 73.3 12.300

100 146.6 49.200



Pressure of wind increases in proportion to the square

of the velocity. Thus wind at 10 miles an hour has four

times the pressure of wind at 5 miles an hour. The

greater this pressure the large and heavier the object

which can be raised. Any boy who has had experience

in flying kites can testify to this, High winds, however,

are almost invariably gusty and uncertain as to direction,

and this makes them dangerous for aviators. It

is also a self-evident fact that, beyond a certain stage,

the harder the wind blows the more difficult it is to

make headway against it.



Launching Device for Gliders.



On page 195 will be found a diagram of the various

parts of a launcher for gliders, designed and patented

by Mr. Octave Chanute. In describing this invention

in Aeronautics, Mr. Chanute says:



"In practicing, the track, preferably portable, is

generally laid in the direction of the existing wind and

the car, preferably a light platform-car, is placed on the

track. The truck carrying the winding-drum and its motor

is placed to windward a suitable distance--say from

two hundred to one thousand feet--and is firmly blocked

or anchored in line with the portable track, which is

preferably 80 or 100 feet in length. The flying or gliding

machine to be launched with its operator is placed on

the platform-car at the leeward end of the portable track.

The line, which is preferably a flexible combination

wire-and-cord cable, is stretched between the winding-

drum on the track and detachably secured to the flying

or gliding machine, preferably by means of a trip-hoop,

or else held in the hand of the operator, so that the

operator may readily detach the same from the flying-

machine when the desired height is attained.



How Glider Is Started.



"Then upon a signal given by the operator the engineer

at the motor puts it into operation, gradually increasing

the speed until the line is wound upon the drum

at a maximum speed of, say, thirty miles an hour. The

operator of the flying-machine, whether he stands upright and

carries it on his shoulders, or whether he sits

or lies down prone upon it, adjusts the aeroplane or

carrying surfaces so that the wind shall strike them on

the top and press downward instead of upward until

the platform-car under action of the winding-drum and

line attains the required speed.



"When the operator judges that his speed is sufficient,

and this depends upon the velocity of the wind as well

as that of the car moving against the wind, he quickly

causes the front of the flying-machine to tip upward, so

that the relative wind striking on the under side of the

planes or carrying surfaces shall lift the flying machine

into the air. It then ascends like a kite to such height

as may be desired by the operator, who then trips the

hook and releases the line from the machine.



What the Operator Does.



"The operator being now free in the air has a certain

initial velocity imparted by the winding-drum and line

and also a potential energy corresponding to his height

above the ground. If the flying or gliding machine is

provided with a motor, he can utilize that in his further

flight, and if it is a simple gliding machine without

motor he can make a descending flight through the air

to such distance as corresponds to the velocity acquired

and the height gained, steering meanwhile by the devices

provided for that purpose.



"The simplest operation or maneuver is to continue

the flight straight ahead against the wind; but it is possible

to vary this course to the right or left, or even to

return in downward flight with the wind to the vicinity

of the starting-point. Upon nearing the ground the

operator tips upward his carrying-surfaces and stops his

headway upon the cushion of increased air resistance

so caused. The operator is in no way permanently

fastened to his machine, and the machine and the operator

simply rest upon the light platform-car, so that

the operator is free to rise with the machine from the

car whenever the required initial velocity is attained.



Motor For the Launcher.



"The motor may be of any suitable kind or construction,

but is preferably an electric or gasolene motor.

The winding-drum is furnished with any suitable or customary

reversing-guide to cause the line to wind smoothly

and evenly upon the drum. The line is preferably a

cable composed of flexible wire and having a cotton or

other cord core to increase its flexibility. The line

extends from the drum to the flying or gliding machine.

Its free end may, if desired, be grasped and held by the

operator until the flying-machine ascends to the desired

height, when by simply letting go of the line the operator

may continue his flight free. The line, however, is preferably

connected to the flying or gliding machine

directly by a trip-hook having a handle or trip lever

within reach of the operator, so that when he ascends

to the required height he may readily detach the line

from the flying or gliding machine."