It is a mistaken idea that flying machines must be operated at extreme altitudes. True, under the impetus of handsome prizes, and the incentive to advance scientific knowledge, professional aviators have ascended to considerable heights, flights at from 500 to 1,500 feet being now common with such experts as Farman, Bleriot, Latham, Paulhan, Wright and Curtiss. The altitude record at this time is about 4,165 feet, held by Paulhan.
One of the instructions given by experienced aviators to pupils, and for which they insist upon implicit obeyance, is: "If your machine gets more than 30 feet high, or comes closer to the ground than 6 feet, descend at once." Such men as Wright and Curtiss will not tolerate a violation of this rule. If their instructions are not strictly complied with they decline to give the offender further lessons.
Why This Rule Prevails.
There is good reason for this precaution. The higher the altitude the more rarefied (thinner) becomes the air, and the less sustaining power it has. Consequently the more difficult it becomes to keep in suspension a given weight. When sailing within 30 feet of the ground sustentation is comparatively easy and, should a fall occur, the results are not likely to be serious. On the other hand, sailing too near the ground is almost as objectionable in many ways as getting up too high. If the craft is navigated too close to the ground trees, shrubs, fences and other obstructions are liable to be encountered. There is also the handicap of contrary air currents diverted by the obstructions referred to, and which will be explained more fully further on.
How to Make a Start.
Taking it for granted that the beginner has familiarized himself with the manipulation of the machine, and especially the control mechanism, the next thing in order is an actual flight. It is probable that his machine will be equipped with a wheeled alighting gear, as the skids used by the Wrights necessitate the use of a special starting track. In this respect the wheeled machine is much easier to handle so far as novices are concerned as it may be easily rolled to the trial grounds. This, as in the case of the initial experiments, should be a clear, reasonably level place, free from trees, fences, rocks and similar obstructions with which there may be danger of colliding.
The beginner will need the assistance of three men. One of these should take his position in the rear of the machine, and one at each end. On reaching the trial ground the aviator takes his seat in the machine and, while the men at the ends hold it steady the one in the rear assists in retaining it until the operator is ready. In the meantime the aviator has started his motor. Like the glider the flying machine, in order to accomplish the desired results, should be headed into the wind.
When the Machine Rises.
Under the impulse of the pushing movement, and assisted by the motor action, the machine will gradually rise from the ground—provided it has been properly proportioned and put together, and everything is in working order. This is the time when the aviator requires a cool head, At a modest distance from the ground use the control lever to bring the machine on a horizontal level and overcome the tendency to rise. The exact manipulation of this lever depends upon the method of control adopted, and with this the aviator is supposed to have thoroughly familiarized himself as previously advised in Chapter XI.
It is at this juncture that the operator must act promptly, but with the perfect composure begotten of confidence. One of the great drawbacks in aviation by novices is the tendency to become rattled, and this is much more prevalent than one might suppose, even among men who, under other conditions, are cool and confident in their actions.
There is something in the sensation of being suddenly lifted from the ground, and suspended in the air that is disconcerting at the start, but this will soon wear off if the experimenter will keep cool. A few successful flights no matter how short they may be, will put a lot of confidence into him.
Make Your Flights Short.
Be modest in your initial flights. Don't attempt to match the records of experienced men who have devoted years to mastering the details of aviation. Paulhan, Farman, Bleriot, Wright, Curtiss, and all the rest of them began, and practiced for years, in the manner here described, being content to make just a little advancement at each attempt. A flight of 150 feet, cleanly and safely made, is better as a beginning than one of 400 yards full of bungling mishaps.
And yet these latter have their uses, provided the operator is of a discerning mind and can take advantage of them as object lessons. But, it is not well to invite them. They will occur frequently enough under the most favorable conditions, and it is best to have them come later when the feeling of trepidation and uncertainty as to what to do has worn off.
Above all, don't attempt to fly too high. Keep within a reasonable distance from the ground—about 25 or 30 feet. This advice is not given solely to lessen the risk of serious accident in case of collapse, but mainly because it will assist to instill confidence in the operator.
It is comparatively easy to learn to swim in shallow water, but the knowledge that one is tempting death in deep water begets timidity.
Preserving the Equilibrium.
After learning how to start and stop, to ascend and descend, the next thing to master is the art of preserving equilibrium, the knack of keeping the machine perfectly level in the air—on an "even keel," as a sailor would say. This simile is particularly appropriate as all aviators are in reality sailors, and much more daring ones than those who course the seas. The latter are in craft which are kept afloat by the buoyancy of the water, whether in motion or otherwise and, so long as normal conditions prevail, will not sink. Aviators sail the air in craft in which constant motion must be maintained in order to ensure flotation.
The man who has ridden a bicycle or motorcycle around curves at anything like high speed, will have a very good idea as to the principle of maintaining equilibrium in an airship. He knows that in rounding curves rapidly there is a marked tendency to change the direction of the motion which will result in an upset unless he overcomes it by an inclination of his body in an opposite direction. This is why we see racers lean well over when taking the curves. It simply must be done to preserve the equilibrium and avoid a spill.
How It Works In the Air.
If the equilibrium of an airship is disturbed to an extent which completely overcomes the center of gravity it falls according to the location of the displacement. If this displacement, for instance, is at either end the apparatus falls endways; if it is to the front or rear, the fall is in the corresponding direction.
Owing to uncertain air currents—the air is continually shifting and eddying, especially within a hundred feet or so of the earth—the equilibrium of an airship is almost constantly being disturbed to some extent. Even if this disturbance is not serious enough to bring on a fall it interferes with the progress of the machine, and should be overcome at once. This is one of the things connected with aerial navigation which calls for prompt, intelligent action.
Frequently, when the displacement is very slight, it may be overcome, and the craft immediately righted by a mere shifting of the operator's body. Take, for illustration, a case in which the extreme right end of the machine becomes lowered a trifle from the normal level. It is possible to bring it back into proper position by leaning over to the left far enough to shift the weight to the counter-balancing point. The same holds good as to minor front or rear displacements.
When Planes Must Be Used.
There are other displacements, however, and these are the most frequent, which can be only overcome by manipulation of the stabilizing planes. The method of procedure depends upon the form of machine in use. The Wright machine, as previously explained, is equipped with plane ends which are so contrived as to admit of their being warped (position changed) by means of the lever control. These flexible tip planes move simultaneously, but in opposite directions. As those on one end rise, those on the other end fall below the level of the main plane. By this means air is displaced at one point, and an increased amount secured in another.
This may seem like a complicated system, but its workings are simple when once understood. It is by the manipulation or warping of these flexible tips that transverse stability is maintained, and any tendency to displacement endways is overcome. Longitudinal stability is governed by means of the front rudder.
Stabilizing planes of some form are a feature, and a necessary feature, on all flying machines, but the methods of application and manipulation vary according to the individual ideas of the inventors. They all tend, however, toward the same end—the keeping of the machine perfectly level when being navigated in the air.
When to Make a Flight.
A beginner should never attempt to make a flight when a strong wind is blowing. The fiercer the wind, the more likely it is to be gusty and uncertain, and the more difficult it will be to control the machine. Even the most experienced and daring of aviators find there is a limit to wind speed against which they dare not compete. This is not because they lack courage, but have the sense to realize that it would be silly and useless.
The novice will find a comparatively still day, or one when the wind is blowing at not to exceed 15 miles an hour, the best for his experiments. The machine will be more easily controlled, the trip will be safer, and also cheaper as the consumption of fuel increases with the speed of the wind against which the aeroplane is forced.
As a general proposition it takes much more power to propel an airship a given number of miles in a certain time than it does an automobile carrying a far heavier load. Automobiles with a gross load of 4,000 pounds, and equipped with engines of 30 horsepower, have travelled considerable distances at the rate of 50 miles an hour. This is an equivalent of about 134 pounds per horsepower. For an average modern flying machine, with a total load, machine and passengers, of 1,200 pounds, and equipped with a 50-horsepower engine, 50 miles an hour is the maximum. Here we have the equivalent of exactly 24 pounds per horsepower. Why this great difference?
No less an authority than Mr. Octave Chanute answers the question in a plain, easily understood manner. He says:
"In the case of an automobile the ground furnishes a stable support; in the case of a flying machine the engine must furnish the support and also velocity by which the apparatus is sustained in the air."
Pressure of the Wind.
Air pressure is a big factor in the matter of aeroplane horsepower. Allowing that a dead calm exists, a body moving in the atmosphere creates more or less resistance. The faster it moves, the greater is this resistance. Moving at the rate of 60 miles an hour the resistance, or wind pressure, is approximately 50 pounds to the square foot of surface presented. If the moving object is advancing at a right angle to the wind the following table will give the horsepower effect of the resistance per square foot of surface at various speeds.
Horse PowerMiles per Hour per sq. foot10 0.01315 0 04420 0.10525 0.20530 0.35440 0.8450 1.6460 2.8380 6.72100 13.12
While the pressure per square foot at 60 miles an hour, is only 1.64 horsepower, at 100 miles, less than double the speed, it has increased to 13.12 horsepower, or exactly eight times as much. In other words the pressure of the wind increases with the square of the velocity. Wind at 10 miles an hour has four times more pressure than wind at 5 miles an hour.
How to Determine Upon Power.
This element of air resistance must be taken into consideration in determining the engine horsepower required. When the machine is under headway sufficient to raise it from the ground (about 20 miles an hour), each square foot of surface resistance, will require nearly nine-tenths of a horsepower to overcome the wind pressure, and propel the machine through the air. As shown in the table the ratio of power required increases rapidly as the speed increases until at 60 miles an hour approximately 3 horsepower is needed.
In a machine like the Curtiss the area of wind-exposed surface is about 15 square feet. On the basis of this resistance moving the machine at 40 miles an hour would require 12 horsepower. This computation covers only the machine's power to overcome resistance. It does not cover the power exerted in propelling the machine forward after the air pressure is overcome. To meet this important requirement Mr. Curtiss finds it necessary to use a 50-horsepower engine. Of this power, as has been already stated, 12 horsepower is consumed in meeting the wind pressure, leaving 38 horsepower for the purpose of making progress.
The flying machine must move faster than the air to which it is opposed. Unless it does this there can be no direct progress. If the two forces are equal there is no straight-ahead advancement. Take, for sake of illustration, a case in which an aeroplane, which has developed a speed of 30 miles an hour, meets a wind velocity of equal force moving in an opposite direction. What is the result? There can be no advance because it is a contest between two evenly matched forces. The aeroplane stands still. The only way to get out of the difficulty is for the operator to wait for more favorable conditions, or bring his machine to the ground in the usual manner by manipulation of the control system.
Take another case. An aeroplane, capable of making 50 miles an hour in a calm, is met by a head wind of 25 miles an hour. How much progress does the aeroplane make? Obviously it is 25 miles an hour over the ground.
Put the proposition in still another way. If the wind is blowing harder than it is possible for the engine power to overcome, the machine will be forced backward.
Wind Pressure a Necessity.
While all this is true, the fact remains that wind pressure, up to a certain stage, is an absolute necessity in aerial navigation. The atmosphere itself has very little real supporting power, especially if inactive. If a body heavier than air is to remain afloat it must move rapidly while in suspension.
One of the best illustrations of this is to be found in skating over thin ice. Every school boy knows that if he moves with speed he may skate or glide in safety across a thin sheet of ice that would not begin to bear his weight if he were standing still. Exactly the same proposition obtains in the case of the flying machine.
The non-technical reason why the support of the machine becomes easier as the speed increases is that the sustaining power of the atmosphere increases with the resistance, and the speed with which the object is moving increases this resistance. With a velocity of 12 miles an hour the weight of the machine is practically reduced by 230 pounds. Thus, if under a condition of absolute calm it were possible to sustain a weight of 770 pounds, the same atmosphere would sustain a weight of 1,000 pounds moving at a speed of 12 miles an hour. This sustaining power increases rapidly as the speed increases. While at 12 miles the sustaining power is figured at 230 pounds, at 24 miles it is four times as great, or 920 pounds.
Supporting Area of Birds.
One of the things which all producing aviators seek to copy is the motive power of birds, particularly in their relation to the area of support. Close investigation has established the fact that the larger the bird the less is the relative area of support required to secure a given result. This is shown in the following table:
SupportingWeight Surface Horse areaBird in lbs. in sq. feet power per lb.Pigeon 1.00 0.7 0.012 0.7Wild Goose 9.00 2.65 0.026 0.2833Buzzard 5.00 5.03 0.015 1.06Condor 17.00 9.85 0.043 0.57
So far as known the condor is the largest of modern birds. It has a wing stretch of 10 feet from tip to tip, a supporting area of about 10 square feet, and weighs 17 pounds. It. is capable of exerting perhaps 1-30 horsepower. (These figures are, of course, approximate.) Comparing the condor with the buzzard with a wing stretch of 6 feet, supporting area of 5 square feet, and a little over 1-100 horsepower, it may be seen that, broadly speaking, the larger the bird the less surface area (relatively) is needed for its support in the air.
Comparison With Aeroplanes.
If we compare the bird figures with those made possible by the development of the aeroplane it will be readily seen that man has made a wonderful advance in imitating the results produced by nature. Here are the figures:
SupportingWeight Surface Horse areaMachine in lbs. in sq. feet power per lb.Santos-Dumont.. 350 110.00 30 0.314Bleriot..... 700 150.00 25 0.214Antoinette.... 1,200 538.00 50 0.448Curtiss..... 700 258.00 60 0.368Wright.....41,100 538.00 25 0.489Farman...... 1,200 430.00 50 0.358Voisin...... 1,200 538.00 50 0.448
While the average supporting surface is in favor of the aeroplane, this is more than overbalanced by the greater amount of horsepower required for the weight lifted. The average supporting surface in birds is about three-quarters of a square foot per pound. In the average aeroplane it is about one-half square foot per pound. On the other hand the average aeroplane has a lifting capacity of 24 pounds per horsepower, while the buzzard, for instance, lifts 5 pounds with 15-100 of a horsepower. If the Wright machine—which has a lifting power of 50 pounds per horsepower—should be alone considered the showing would be much more favorable to the aeroplane, but it would not be a fair comparison.
More Surface, Less Power.
Broadly speaking, the larger the supporting area the less will be the power required. Wright, by the use of 538 square feet of supporting surface, gets along with an engine of 25 horsepower. Curtiss, who uses only 258 square feet of surface, finds an engine of 50 horsepower is needed. Other things, such as frame, etc., being equal, it stands to reason that a reduction in the area of supporting surface will correspondingly reduce the weight of the machine. Thus we have the Curtiss machine with its 258 square feet of surface, weighing only 600 pounds (without operator), but requiring double the horsepower of the Wright machine with 538 square feet of surface and weighing 1,100 pounds. This demonstrates in a forceful way the proposition that the larger the surface the less power will be needed.
But there is a limit, on account of its bulk and awkwardness in handling, beyond which the surface area cannot be enlarged. Otherwise it might be possible to equip and operate aeroplanes satisfactorily with engines of 15 horsepower, or even less.
The Fuel Consumption Problem.
Fuel consumption is a prime factor in the production of engine power. The veriest mechanical tyro knows in a general way that the more power is secured the more fuel must be consumed, allowing that there is no difference in the power-producing qualities of the material used. But few of us understand just what the ratio of increase is, or how it is caused. This proposition is one of keen interest in connection with aviation.
Let us cite a problem which will illustrate the point quoted: Allowing that it takes a given amount of gasolene to propel a flying machine a given distance, half the way with the wind, and half against it, the wind blowing at one-half the speed of the machine, what will be the increase in fuel consumption?
Increase of Thirty Per Cent.
On the face of it there would seem to be no call for an increase as the resistance met when going against the wind is apparently offset by the propulsive force of the wind when the machine is travelling with it. This, however, is called faulty reasoning. The increase in fuel consumption, as figured by Mr. F. W. Lanchester, of the Royal Society of Arts, will be fully 30 per cent over the amount required for a similar operation of the machine in still air. If the journey should be made at right angles to the wind under the same conditions the increase would be 15 per cent.
In other words Mr. Lanchester maintains that the work done by the motor in making headway against the wind for a certain distance calls for more engine energy, and consequently more fuel by 30 per cent, than is saved by the helping force of the wind on the return journey.
One of the first difficulties which the novice will encounter is the uncertainty of the wind currents. With a low velocity the wind, some distance away from the ground, is ordinarily steady. As the velocity increases, however, the wind generally becomes gusty and fitful in its action. This, it should be remembered, does not refer to the velocity of the machine, but to that of the air itself.
In this connection Mr. Arthur T. Atherholt, president of the Aero Club of Pennsylvania, in addressing the Boston Society of Scientific Research, said:
"Probably the whirlpools of Niagara contain no more erratic currents than the strata of air which is now immediately above us, a fact hard to realize on account of its invisibility."
Changes In Wind Currents.
While Mr. Atherholt's experience has been mainly with balloons it is all the more valuable on this account, as the balloons were at the mercy of the wind and their varying directions afforded an indisputable guide as to the changing course of the air currents. In speaking of this he said:
"In the many trips taken, varying in distance traversed from twenty-five to 900 miles, it was never possible except in one instance to maintain a straight course. These uncertain currents were most noticeable in the Gordon-Bennett race from St. Louis in 1907. Of the nine aerostats competing in that event, eight covered a more or less direct course due east and southeast, whereas the writer, with Major Henry B. Hersey, first started northwest, then north, northeast, east, east by south, and when over the center of Lake Erie were again blown northwest notwithstanding that more favorable winds were sought for at altitudes varying from 100 to 3,000 meters, necessitating a finish in Canada nearly northeast of the starting point.
"These nine balloons, making landings extending from Lake Ontario, Canada, to Virginia, all started from one point within the same hour.
"The single exception to these roving currents occurred on October 21st, of last year (1909) when, starting from Philadelphia, the wind shifted more than eight degrees, the greatest variation being at the lowest altitudes, yet at no time was a height of over a mile reached.
"Throughout the entire day the sky was overcast, with a thermometer varying from fifty-seven degrees at 300 feet to forty-four degrees, Fahrenheit at 5,000 feet, at which altitude the wind had a velocity of 43 miles an hour, in clouds of a cirro-cumulus nature, a landing finally being made near Tannersville, New York, in the Catskill mountains, after a voyage of five and one-half hours.
"I have no knowledge of a recorded trip of this distance and duration, maintained in practically a straight line from start to finish."
This wind disturbance is more noticeable and more difficult to contend with in a balloon than in a flying machine, owing to the bulk and unwieldy character of the former. At the same time it is not conducive to pleasant, safe or satisfactory sky-sailing in an aeroplane. This is not stated with the purpose of discouraging aviation, but merely that the operator may know what to expect and be prepared to meet it.
Not only does the wind change its horizontal course abruptly and without notice, but it also shifts in a vertical direction, one second blowing up, and another down. No man has as yet fathomed the why and wherefore of this erratic action; it is only known that it exists.
The most stable currents will be found from 50 to 100 feet from the earth, provided the wind is not diverted by such objects as trees, rocks, etc. That there are equally stable currents higher up is true, but they are generally to be found at excessive altitudes.
How a Bird Meets Currents.
Observe a bird in action on a windy day and you will find it continually changing the position of its wings. This is done to meet the varying gusts and eddies of the air so that sustentation may be maintained and headway made. One second the bird is bending its wings, altering the angle of incidence; the next it is lifting or depressing one wing at a time. Still again it will extend one wing tip in advance of the other, or be spreading or folding, lowering or raising its tail.
All these motions have a meaning, a purpose. They assist the bird in preserving its equilibrium. Without them the bird would be just as helpless in the air as a human being and could not remain afloat.
When the wind is still, or comparatively so, a bird, having secured the desired altitude by flight at an angle, may sail or soar with no wing action beyond an occasional stroke when it desires to advance. But, in a gusty, uncertain wind it must use its wings or alight somewhere.
Trying to Imitate the Bird.
Writing inFly, Mr. William E. White says:
"The bird's flight suggests a number of ways in which the equilibrium of a mechanical bird may be controlled. Each of these methods of control may be effected by several different forms of mechanism.
"Placing the two wings of an aeroplane at an angle of three to five degrees to each other is perhaps the oldest way of securing lateral balance. This way readily occurs to anyone who watches a sea gull soaring. The theory of the dihedral angle is that when one wing is lifted by a gust of wind, the air is spilled from under it; while the other wing, being correspondingly depressed, presents a greater resistance to the gust and is lifted restoring the balance. A fixed angle of three to five degrees, however, will only be sufficient for very light puffs of wind and to mount the wings so that the whole wing may be moved to change the dihedral angle presents mechanical difficulties which would be better avoided.
"The objection of mechanical impracticability applies to any plan to preserve the balance by shifting weight or ballast. The center of gravity should be lower than the center of the supporting surfaces, but cannot be made much lower. It is a common mistake to assume that complete stability will be secured by hanging the center of gravity very low on the principle of the parachute. An aeroplane depends upon rapid horizontal motion for its support, and if the center of gravity be far below the center of support, every change of speed or wind pressure will cause the machine to turn about its center of gravity, pitching forward and backward dangerously.
Preserving Longitudinal Balance.
"The birds maintain longitudinal, or fore and aft balance, by elevating or depressing their tails. Whether this action is secured in an aeroplane by means of a horizontal rudder placed in the rear, or by deflecting planes placed in front of the main planes, the principle is evidently the same. A horizontal rudder placed well to the rear as in the Antoinette, Bleriot or Santos-Dumont monoplanes, will be very much safer and steadier than the deflecting planes in front, as in the Wright or Curtiss biplanes, but not so sensitive or prompt in action.
"The natural fore and aft stability is very much strengthened by placing the load well forward. The center of gravity near the front and a tail or rudder streaming to the rear secures stability as an arrow is balanced by the head and feathering. The adoption of this principle makes it almost impossible for the aeroplane to turn over.
The Matter of Lateral Balance.
"All successful aeroplanes thus far have maintained lateral balance by the principle of changing the angle of incidence of the wings.
"Other ways of maintaining the lateral balance, suggested by observation of the flight of birds are—extending the wing tips and spilling the air through the pinions; or, what is the same thing, varying the area of the wings at their extremities.
"Extending the wing tips seems to be a simple and effective solution of the problem. The tips may be made to swing outward upon a vertical axis placed at the front edge of the main planes; or they may be hinged to the ends of the main plane so as to be elevated or depressed through suitable connections by the aviator; or they may be supported from a horizontal axis parallel with the ends of the main planes so that they may swing outward, the aviator controlling both tips through one lever so that as one tip is extended the other is retracted.
"The elastic wing pinions of a bird bend easily before the wind, permitting the gusts to glance off, but presenting always an even and efficient curvature to the steady currents of the air."
High Winds Threaten Stability.
To ensure perfect stability, without control, either human or automatic, it is asserted that the aeroplane must move faster than the wind is blowing. So long as the wind is blowing at the rate of 30 miles an hour, and the machine is traveling 40 or more, there will be little trouble as regards equilibrium so far as wind disturbance goes, provided the wind blows evenly and does not come in gusts or eddying currents. But when conditions are reversed—when the machine travels only 30 miles an hour and the wind blows at the rate of 50, look out for loss of equilibrium.
One of the main reasons for this is that high winds are rarely steady; they seldom blow for any length of time at the same speed. They are usually "gusty," the gusts being a momentary movement at a higher speed. Tornadic gusts are also formed by the meeting of two opposing currents, causing a whirling motion, which makes stability uncertain. Besides, it is not unusual for wind of high speed to suddenly change its direction without warning.
Trouble With Vertical Columns.
Vertical currents—columns of ascending air—are frequently encountered in unexpected places and have more or less tendency, according to their strength, to make it difficult to keep the machine within a reasonable distance from the ground.
These vertical currents are most generally noticeable in the vicinity of steep cliffs, or deep ravines. In such instances they are usually of considerable strength, being caused by the deflection of strong winds blowing against the face of the cliffs. This deflection exerts a back pressure which is felt quite a distance away from the point of origin, so that the vertical current exerts an influence in forcing the machine upward long before the cliff is reached.
That there is an element of danger in aviation is undeniable, but it is nowhere so great as the public imagines. Men are killed and injured in the operation of flying machines just as they are killed and injured in the operation of railways. Considering the character of aviation the percentage of casualties is surprisingly small.
This is because the results following a collapse in the air are very much different from what might be imagined. Instead of dropping to the ground like a bullet an aeroplane, under ordinary conditions will, when anything goes wrong, sail gently downward like a parachute, particularly if the operator is cool-headed and nervy enough to so manipulate the apparatus as to preserve its equilibrium and keep the machine on an even keel.
Two Fields of Safety.
At least one prominent aviator has declared that there are two fields of safety—one close to the ground, and the other well up in the air. In the first-named the fall will be a slight one with little chance of the operator being seriously hurt. From the field of high altitude the the descent will be gradual, as a rule, the planes of the machine serving to break the force of the fall. With a cool-headed operator in control the aeroplane may be even guided at an angle (about 1 to 8) in its descent so as to touch the ground with a gliding motion and with a minimum of impact.
Such an experience, of course, is far from pleasant, but it is by no means so dangerous as might appear. There is more real danger in falling from an elevation of 75 or 100 feet than there is from 1,000 feet, as in the former case there is no chance for the machine to serve as a parachute—its contact with the ground comes too quickly.
Lesson in Recent Accidents.
Among the more recent fatalities in aviation are the deaths of Antonio Fernandez and Leon Delagrange. The former was thrown to the ground by a sudden stoppage of his motor, the entire machine seeming to collapse. It is evident there were radical defects, not only in the motor, but in the aeroplane framework as well. At the time of the stoppage it is estimated that Fernandez was up about 1,500 feet, but the machine got no opportunity to exert a parachute effect, as it broke up immediately. This would indicate a fatal weakness in the structure which, under proper testing, could probably have been detected before it was used in flight.
It is hard to say it, but Delagrange appears to have been culpable to great degree in overloading his machine with a motor equipment much heavier than it was designed to sustain. He was 65 feet up in the air when the collapse occurred, resulting in his death. As in the case of Fernandez common-sense precaution would doubtless have prevented the fatality.
Aviation Not Extra Hazardous.
All told there have been, up to the time of this writing (April, 1910), just five fatalities in the history of power-driven aviation. This is surprisingly low when the nature of the experiments, and the fact that most of the operators were far from having extended experience, is taken into consideration. Men like the Wrights, Curtiss, Bleriot, Farman, Paulhan and others, are now experts, but there was a time, and it was not long ago, when they were unskilled. That they, with numerous others less widely known, should have come safely through their many experiments would seem to disprove the prevailing idea that aviation is an extra hazardous pursuit.
In the hands of careful, quick-witted, nervy men the sailing of an airship should be no more hazardous than the sailing of a yacht. A vessel captain with common sense will not go to sea in a storm, or navigate a weak, unseaworthy craft. Neither should an aviator attempt to sail when the wind is high and gusty, nor with a machine which has not been thoroughly tested and found to be strong and safe.
Safer Than Railroading.
Statistics show that some 12,000 people are killed and 72,000 injured every year on the railroads of the United States. Come to think it over it is small wonder that the list of fatalities is so large. Trains are run at high speeds, dashing over crossings at which collisions are liable to occur, and over bridges which often collapse or are swept away by floods. Still, while the number of casualties is large, the actual percentage is small considering the immense number of people involved.
It is so in aviation. The number of casualties is remarkably small in comparison with the number of flights made. In the hands of competent men the sailing of an airship should be, and is, freer from risk of accident than the running of a railway train. There are no rails to spread or break, no bridges to collapse, no crossings at which collisions may occur, no chance for some sleepy or overworked employee to misunderstand the dispatcher's orders and cause a wreck.
Two Main Causes of Trouble.
The two main causes of trouble in an airship leading to disaster may be attributed to the stoppage of the motor, and the aviator becoming rattled so that he loses control of his machine. Modern ingenuity is fast developing motors that almost daily become more and more reliable, and experience is making aviators more and more self-confident in their ability to act wisely and promptly in cases of emergency. Besides this a satisfactory system of automatic control is in a fair way of being perfected.
Occasionally even the most experienced and competent of men in all callings become careless and by foolish action invite disaster. This is true of aviators the same as it is of railroaders, men who work in dynamite mills, etc. But in nearly every instance the responsibility rests with the individual; not with the system. There are some men unfitted by nature for aviation, just as there are others unfitted to be railway engineers.
Changes, many of them extremely radical in their nature, are continually being made by prominent aviators, and particularly those who have won the greatest amount of success. Wonderful as the results have been few of the aviators are really satisfied. Their successes have merely spurred them on to new endeavors, the ultimate end being the development of an absolutely perfect aircraft.
Among the men who have been thus experimenting are the Wright Brothers, who last year (1909) brought out a craft totally different as regards proportions and weight from the one used the preceding year. One marked result was a gain of about 3 1/2 miles an hour in speed.
Dimensions of 1908 Machine.
The 1908 model aeroplane was 40 by 29 feet over all. The carrying surfaces, that is, the two aerocurves, were 40 by 6 feet, having a parabolical curve of one in twelve. With about 70 square feet of surface in the rudders, the total surface given was about 550 square feet. The engine, which is the invention of the Wright brothers, weighed, approximately, 200 pounds, and gave about 25 horsepower at 1,400 revolutions per minute. The total weight of the aeroplane, exclusive of passenger, but inclusive of engine, was about 1,150 pounds. This result showed a lift of a fraction over 2 1/4 pounds to the square foot of carrying surface. The speed desired was 40 miles an hour, but the machine was found to make only a scant 39 miles an hour. The upright struts were about 7/8-inch thick, the skids, 2 1/2 by 1 1/4 inches thick.
Dimensions of 1909 Machine.
The 1909 aeroplane was built primarily for greater speed, and relatively heavier; to be less at the mercy of the wind. This result was obtained as follows: The aerocurves, or carrying surfaces, were reduced in dimensions from 40 by 6 feet to 36 by 5 1/2 feet, the curve remaining the same, one in twelve. The upright struts were cut from seven-eighths inch to five-eighths inch, and the skids from two and one-half by one and one-quarter to two and one-quarter by one and three-eighths inches. This result shows that there were some 81 square feet of carrying surface missing over that of last year's model. and some 25 pounds loss of weight. Relatively, though, the 1909 model aeroplane, while actually 25 pounds lighter, is really some 150 pounds heavier in the air than the 1908 model, owing to the lesser square feet of carrying surface.
Some of the Results Obtained.
Reducing the carrying surfaces from 6 to 5 1/2 feet gave two results—first, less carrying capacity; and, second, less head-on resistance, owing to the fact that the extent of the parabolic curve in the carrying surfaces was shortened. The "head-on" resistance is the retardance the aeroplane meets in passing through the air, and is counted in square feet. In the 1908 model the curve being one in twelve and 6 feet deep, gave 6 inches of head-on resistance. The plane being 40 feet spread, gave 6 inches by 40 feet, or 20 square feet of head-on resistance. Increasing this figure by a like amount for each plane, and adding approximately 10 square feet for struts, skids and wiring, we have a total of approximately, 50 square feet of surface for "head-on" resistance.
In the 1909 aeroplane, shortening the curve 6 inches at the parabolic end of the curve took off 1 inch of head-on resistance. Shortening the spread of the planes took off between 3 and 4 square feet of head-on resistance. Add to this the total of 7 square feet, less curve surface and about 1 square foot, less wire and woodwork resistance, and we have a grand total of, approximately, 12 square feet of less "head-on" resistance over the 1908 model.
Changes in Engine Action.
The engine used in 1909 was the same one used in 1908, though some minor changes were made as improvements; for instance, a make and break spark was used, and a nine-tooth, instead of a ten-tooth magneto gear-wheel was used. This increased the engine revolutions per minute from 1,200 to 1,400, and the propeller revolutions per minute from 350 to 371, giving a propeller thrust of, approximately, 170 foot pounds instead of 153, as was had last year.
More Speed and Same Capacity.
One unsatisfactory feature of the 1909 model over that of 1908, apparently, was the lack of inherent lateral stability. This was caused by the lesser surface and lesser extent of curvatures at the portions of the aeroplane which were warped. This defect did not show so plainly after Mr. Orville Wright had become fully proficient in the handling of the new machine, and with skillful management, the 1909 model aeroplane will be just as safe and secure as the other though it will take a little more practice to get that same degree of skill.
To sum up: The aeroplane used in 1909 was 25 pounds lighter, but really about 150 pounds heavier in the air, had less head-on resistance, and greater propeller thrust. The speed was increased from about 39 miles per hour to 42 1/2 miles per hour. The lifting capacity remained about the same, about 450 pounds capacity passenger-weight, with the 1908 machine. In this respect, the loss of carrying surface was compensated for by the increased speed.
During the first few flights it was plainly demonstrated that it would need the highest skill to properly handle the aeroplane, as first one end and then the other would dip and strike the ground, and either tear the canvas or slew the aeroplane around and break a skid.
Wrights Adopt Wheeled Gears.
In still another important respect the Wrights, so far as the output of one of their companies goes, have made a radical change. All the aeroplanes turned out by the Deutsch Wright Gesellschaft, according to the German publication,Automobil-Welt, will hereafter be equipped with wheeled running gears and tails. The plan of this new machine is shown in the illustration on page 145. The wheels are three in number, and are attached one to each of the two skids, just under the front edge of the planes, and one forward of these, attached to a cross-member. It is asserted that with these wheels the teaching of purchasers to operate the machines is much simplified, as the beginners can make short flights on their own account without using the starting derrick.
This is a big concession for the Wrights to make, as they have hitherto adhered stoutly to the skid gear. While it is true they do not control the German company producing their aeroplanes, yet the nature of their connection with the enterprise is such that it may be taken for granted no radical changes in construction would be made without their approval and consent.
Only Three Dangerous Rivals.
Official trials with the 1909 model smashed many records and leave the Wright brothers with only three dangerous rivals in the field, and with basic patents which cover the curve, warp and wing-tip devices found on all the other makes of aeroplanes. These three rivals are the Curtiss and Voisin biplane type and the Bleriot monoplane pattern.
The Bleriot monoplane is probably the most dangerous rival, as this make of machine has a record of 54 miles per hour, has crossed the English channel, and has lifted two passengers besides the operator. The latest type of this machine only weighs 771.61 pounds complete, without passengers, and will lift a total passenger weight of 462.97 pounds, which is a lift of 5.21 pounds to the square foot. This is a better result than those published by the Wright brothers, the best noted being 4.25 pounds per square foot.
Other Aviators at Work.
The Wrights, however, are not alone in their efforts to promote the efficiency of the flying machine. Other competent inventive aviators, notably Curtiss, Voisin, Bleriot and Farman, are close after them. The Wrights, as stated, have a marked advantage in the possession of patents covering surface plane devices which have thus far been found indispensable in flying machine construction. Numerous law suits growing out of alleged infringements of these patents have been started, and others are threatened. What effect these actions will have in deterring aviators in general from proceeding with their experiments remains to be seen.
In the meantime the four men named—Curtiss, Voisin, Bleriot and Farman—are going ahead regardless of consequences, and the inventive genius of each is so strong that it is reasonable to expect some remarkable developments in the near future.
Smallest of Flying Machines.
To Santos Dumont must be given the credit of producing the smallest practical flying machine yet constructed. True, he has done nothing remarkable with it in the line of speed, but he has demonstrated the fact that a large supporting surface is not an essential feature.
This machine is named "La Demoiselle." It is a monoplane of the dihedral type, with a main plane on each side of the center. These main planes are of 18 foot spread, and nearly 6 1/2 feet in depth, giving approximately 115 feet of surface area. The total weight is 242 pounds, which is 358 pounds less than any other machine which has been successfully used. The total depth from front to rear is 26 feet.
The framework is of bamboo, strengthened and held taut with wire guys.
Have One Rule in Mind.
In this struggle for mastery in flying machine efficiency all the contestants keep one rule in mind, and this is:
"The carrying capacity of an aeroplane is governed by the peripheral curve of its carrying surfaces, plus the speed; and the speed is governed by the thrust of the propellers, less the 'head-on' resistance."
Their ideas as to the proper means of approaching the proposition may, and undoubtedly are, at variance, but the one rule in solving the problem of obtaining the greatest carrying capacity combined with the greatest speed, obtains in all instances.