Chapter VII: Part II: Building a Bleriot Monoplane (3)

*Causes*. _Lack of Experience_. It will be at once noticeable by Table III that out of a total of 28, no less than 16, or considerably more than half of the accidents, were due in one way or another to lack of experience. In other words, the aviators had not fully complied with the cardinal principle for success in flying upon which the Wright Brothers have always laid so much stress, _i.e._, you must first learn to fly before you can attempt to go aloft safely. Nothing short of a thorough mastery of the machine can suffice to give the aviator the ability to do the right thing at the right moment, in the great majority of cases. There will always be occasions when even the most skilled aviator will make errors of judgment and frequently they cost him his life. But this is equally true of every dangerous calling, whether it be running an automobile, driving a locomotive, or doing any of the thousand and one things where the responsibility for his own and other lives is placed in one man’s hands and depends to a large extent on his discretion and judgment in cases of emergency, so that there will be fatalities from this cause as long as man continues to fly. This involves the personal equation that must always be reckoned with. Just how many of the accidents that have resulted in the fatalities set forth, have been due to the fallibility of the operator and for how much the design of the current types of machines is responsible, would be hard to say. Fig. 45, for example, which shows H. V. Roe in the act of striking the ground in his triplane, illustrates an accident due to bad design. Methods of control will be improved and simplified and made as nearly "fool-proof" as human ingenuity can accomplish, but experience in other fields has demonstrated unmistakably that they can never be developed to a point where it is impossible to do the wrong thing. With skill at such a premium in callings of responsibility which involve only conditions that have been familiar for years, how much more so must it be in the air about which so little is known? Consequently, the real danger is to be found in the personal equation, just as it is in every other mode of conveyance, despite the fact that it has been perfected to a point which apparently admits of little further development where safe-guarding it is concerned.

*Obstructions*. Obstructions are bound to play a prominent part in accidents to any method of conveyance, but less so in aviation than in any other, as it is only in rising and alighting that this danger is present. Of the two fatal accidents ascribed to this cause, one resulted from colliding with an obstruction while running along the ground preparatory to rising, and the other from striking an obstruction in flight, Fig. 46. In view of the numerous cross-country flights that have been made, trips across cities and the like, it is to be marveled at that up to the present writing no fatalities have been caused by what the aviator most dreads when leaving the safety of the open field, that is, being compelled to make a landing through stoppage of the motor, whether from a defection or lack of fuel. While no fatalities have as yet to be put down to this ever-present danger in extended flights, an accident that might have had a fatal termination, occurred to Le Blanc during the competition for the Gordon-Bennett trophy, which was the chief event of the International Meet in October, 1010, at Belmont Park, near New York. Le Blanc and his fellow compatriots who were eligible were all experienced cross-country flyers, the former having won the _Circuit de L’Est_, a race around France, and by far the most ambitious of its kind which had been attempted up to that time. They accordingly protested most vigorously against flying over the American course to compete for the cup which Curtiss had captured at Rheims the year before, owing to the fact that it presented numerous dangerous obstructions in the form of trees and telegraph poles. But as it was impossible to provide any other convenient five-kilometer circuit (3.11 miles) as called for by the conditions, the protest was of no avail. After having covered 19 of the 20 laps necessary to complete the distance of 100 kilometers in time that had never been approached before, Le Blanc was compelled to descend through lack of fuel, and as he had not risen more than 80 to 100 feet at any time during the race, this meant coming down the moment the motor stopped. The result was a collision with a telegraph pole, breaking it off and wrecking the monoplane, the aviator fortunately escaping any serious injury. During the same meet Moisant demolished his Bleriot monoplane by trying to start in the face of a high wind, Figs. 47 and 48.

*Stopping of Motor*. The mere fact that the motor stops does not necessarily mean a disastrous ending to a flight, as is very commonly believed, this having been strikingly illustrated by Brookins’ glide to earth from an altitude of 5,000 feet with the motor dead, and Moisant’s glide from an even greater height in France. But it does mean a wreck unless a suitable landing place can be reached with the limited ability to control the machine that the aviator has when he can no longer command its power. Motors will undoubtedly become more and more reliable as development progresses, but the human equation—the partly-filled fuel tank, the loose adjustment that is overlooked before starting, and a hundred and one things of a similar nature—will always play their role, so that compulsory landing in unsuitable places will always constitute a source of danger as flights become more and more extended.

*Breakage of Parts of Aeroplanes*. In studying the foregoing table, it can only be a source of satisfaction to the intelligent student and believer in aerial navigation, to note how large a proportion of the accidents is due to the breakage of parts of the machine. This implies a fault in construction, but not in principle. It reveals the fact that, in the attempt to secure lightness, strength has sometimes been sacrificed, chiefly through lack of appreciation of the stresses to which the machine is subjected in operation. At a time when weight is regarded almost as the paramount factor by so many builders, it is inevitable that some should err by shaving things too fine. Lightness is an absolute necessity and failure to achieve it in every instance without eliminating the factor of safety has been due more to the crude methods of construction and lack of suitable materials, than any other cause—conditions that are bound to obtain in the early days of any art. Construction is improving rapidly, but progress is bound to be attended with accidents of this nature. The fact that their proportion is greatly diminishing despite the rapidly increasing number of aviators is the best evidence of what is being accomplished. When machines are built with such a high factor of safety in every part that breakage is an almost unheard-of thing, failures from this cause will have been reduced to an unsurpassable minimum.

*Failure of the Control Mechanism*. Under the general classification B, are included not alone those accidents directly due to breakage of some vital part, but also those instances in which some element of the control, such as the elevator, has become inoperative through jamming. When an accident happens in the air, it takes place so quickly and the machine is so totally wrecked by falling to the ground, that it is usually difficult to determine the exact nature of the cause through a subsequent examination of the parts, so that it can seldom be stated with certainty just what the initial defection consisted of, though it may be regarded as a foregone conclusion that, in the case of experienced aviators who have previously demonstrated their ability to cope with all ordinary emergencies, nothing short of the failure of some vital part could have caused their fall.

This was the case with Johnstone’s accident at Denver—an occurrence illustrating another phase of the personal equation that must be taken into consideration when noting the lessons to be learned from a study of accidents and their causes. It is simply the old, old story of familiarity breeding contempt—the miner thawing out sticks of dynamite before an open fire. Due to the rarefied air of Denver, which is at an elevation of more than 5,000 feet, Johnstone had underestimated the braking powers of the air on the machine in landing the day previous and had crashed into a fence, breaking one of the right outermost struts between the supporting planes.

Proper regard for safety should naturally have called for its replacement by an entirely new strut, but conditions at flying meets as at present conducted make quick repairs to damaged machines imperative. The damaged upright was accordingly glued and braced by placing iron rings around it, the rings themselves being held in place by ordinary nails passing through holes in the iron large enough to let the nail head slip through. The vibration of the motor and the straining of the strut in warping the wings caused the nails to work out of the holes, permitting the rings to slide out of place as well. Johnstone was an accomplished aviator, much given to the execution of aerial maneuvers only possible to the skilled flyer of quick and ready judgment. But such performances impose excessive stresses on the supporting planes and their braces, and one of Johnstone’s quick turns caused the repaired struts to collapse through the strain of sharply warping the wing tips on that side. He immediately attempted to restore the balance of the machine by bringing the left wing down with the control, then tried to force the twisting on the right side, succeeding momentarily, and a few seconds later losing all control and crashing to the ground. It appeared to demonstrate that even when disabled an aeroplane is not entirely without support, but has more or less buoyancy—something which is really more of an optical illusion than anything else due to underestimating the speed at which a body falls from any great height. Johnstone’s accident was the first of its kind, in that he fell from a height of about 800 feet, during the first 500 of which he struggled to regain control of the machine, finally dropping the remaining 300 feet apparently as so much dead weight. It showed in a most striking manner the vital importance of the struts connecting the supporting surfaces of the biplane, any damage to them resulting in the crippling of the balancing devices and the end of all aerial support.

*Biplane vs. Monoplane*. It requires only a glance at Table III to show that the greater number of accidents have happened to the biplane, yet the latter is generally regarded as the safer of the two. Prior to Delagrange’s fatal fall in January, 1910, there had been only four fatalities with modern flying machines: Selfridge and Lefebre were killed in Wright machines, the latter of French manufacture, Ferber lost control of his Voisin biplane, and Fernandez was killed flying a biplane of his own design. In one case at least, that of Lieutenant Selfridge, the accident appears to have been due to the failure of a vital part—the propeller. It has since become customary to cover the tips of propellers for at least a foot or so with fabric tightly fitted and varnished so as to become practically an integral part of the wood. This prevents splintering as well as avoiding the danger of the laminations succumbing to centrifugal force and flying apart. At the extremely high speeds, particularly at which direct-driven propellers are run, the stress imposed on the outer portion of the blades by this force is tremendous. In making any attempt to compare the number of accidents to the biplane and the monoplane, it must also be borne in mind that the former has been in the majority.

Delagrange’s accident offers two special features of technical interest. It was the first fatality to happen with the monoplane and was likewise the first fatal accident which appeared to be distinctly due to a failure of the main structure of the machine. For obvious reasons, it is usually difficult to definitely fix the cause of an accident, but in this case there seemed good reason to suppose that the main framing of one of the wings gave way altogether. Curiously enough, Santos-Dumont had an accident the day following from an exactly similar cause, the machine plunging to the ground. But with the good fortune that has attended the experimenter throughout his long aerial career, he was uninjured. It was definitely established that the cause was the fracture of one of the wires taking the upward thrust of the wing. In the case of the biplane, the top and bottom members are both of wood, with wooden struts, the whole being braced with numerous ties of wire. In the monoplane, however, the main spars are trussed to a strut below by a comparatively small number of wires. The structure of each wing is, in fact, very much like the rigging of a sailboat, the main spars taking the place of the mast while the wire stays take that of the shrouds, with this very important difference, that the mast of the boat is provided with a forestay to take the longitudinal pressure when going head to the wind, while the wing of an aeroplane often has no such provision, the longitudinal pressure due to air resistance being taken entirely by the spar.

It is quite possible that this had something to do with Delagrange’s accident, as, in the effort to make a new record, his Bleriot had just been fitted with a very much more powerful motor. In fact, double that for which the machine was originally designed, and this was given by the maker as the probable cause of the mishap. As the new motor was of a very light type, the extra weight, if any, was quite a negligible proportion of the total weight of the machine. The vertical stresses on the wings and their supporting wires would, therefore, not be materially increased. But as the more powerful engine drove the wings through the air a great deal faster, the stresses brought upon them by the increased resistance would be substantially augmented and, unless provision were made for this, the factor of safety would be much reduced. Whether the failure of the wing was actually from longitudinal stress or the breaking of a supporting wire, as in Santos-Dumont’s case, will never be known, but it is quite clear that the question of ample strength to resist longitudinal stresses should be carefully considered, especially when increasing the power of an existing machine.

The question of the most suitable materials and fastenings for the supporting wires is, moreover, a matter which requires very careful consideration. In the case of the biplane, the wires are so numerous that the failure of one, or even more, may not endanger the whole structure, but those of the monoplane are so few that the breaking of but one may mean the loss of the wing. In this respect, as in others, the conditions are parallel to the mast of the sailboat. It is only reasonable to expect, therefore, that similar materials would be best adapted to the purpose. At present, however, the stays of aeroplane wings are almost invariably solid steel wire, or ribbon, while marine shrouds are always of stranded wire rope, solid wire not having been found satisfactory. Weight for weight, the solid wire will stand a greater strain when tried in a testing machine than will the stranded rope, but practice has always demonstrated that it is not so reliable. The stranded rope never breaks without warning, and sometimes several of its wires may go before the whole gives way. As the breakage of the strands can be easily seen, it is possible to replace a damaged stay before it becomes unsafe. In the case of a single wire, there is nothing to show whether it has deteriorated or not. It seems a doubtful policy to use in an aeroplane what experience has shown not to be good enough for a boat, and stranded wire cables particularly designed for aeronautic use are now being placed on the market in this country.

*Record Breaking*. Striving after records has undoubtedly proved one of the most prolific causes of accident. What is wanted to make the aeroplane of the greatest practical use is that it should be safe and reliable. The tendency of record-breaking machines is the exact opposite of this, as the weights of all the most essential parts must be cut down to the finest limits possible in order to provide sufficient power and fuel-carrying capacity for the record flight. It is, in fact, generally the case in engineering that the design and materials which will give the best results for a short time are essentially different from those which are the most reliable, and striving after speed records consists simply in disregarding safety and reliability to the greatest extent to which the pilots are willing to risk their necks, and there is no difficulty in getting men to take practically any risk for the substantial rewards offered.

The performance of specially sensational feats in the air is likewise a fertile source of accidents. One noted aviator who has the reputation of being a most conservative and expert operator, while endeavoring to land within a set space, made too sudden a turn, which resulted in the tail of the machine giving way, precipitating him to the ground. In fact, the number of failures resulting from abrupt turns shows conclusively that there is too small a factor of safety in the construction, not because the added weight could not be carried, but because the extreme lightness alone made possible the stunts for which there is always applause or financial reward. It may seem strange to the man whose only interest in aeronautics is that of an observer, that so many should be willing to take such unheard-of chances; that an aeronaut will rise to great heights, knowing in advance that a vital part of his machine has been deranged, or is only temporarily repaired; and that many others will attempt ambitious flights with engines or other parts that have never been tested previously in operation in the air. Many young and inexperienced aviators are not content to thoroughly test out each new part on the ground, or close to it, but must go aloft at once to do their experimenting, with the usual result of such foolhardiness. If in other sports safe conditions were absolutely disregarded in this manner—take football as an instance—the resulting fatalities would not be charged against the sport itself. But aviation is so extremely novel and likewise so mysterious to the uninitiated that this is never taken into consideration.

*Excessive Lightness of Machines*. If, even at the present early stage of aviation, machines are being made excessively light for purposes of competition, it is time that the contest committees of organizations in charge of meetings formulate rules as to the size of engines, weight of machines, and similar factors, so that accidents will not only be reduced to a minimum, but competition along proper lines will develop types of machines which are useful and not merely racing freaks, as has already been done in the automobile field. Hair-raising performances also should be prohibited, at least until such time as improvements in the construction of machines make it reasonably certain that they are able, to withstand the terrific strains imposed upon them in this manner. Suddenly attempting to bring the machine to a horizontal plane after a long dip at an appalling angle is an extremely dangerous maneuver, whether it be taken in the upper air or is one of the now familiar long glides to earth, which require pulling up short when within a few feet of the ground and after the dropping machine has acquired considerable inertia. The aviator is simply staking his life against the ability of the struts and stays to withstand the terrific stresses imposed upon them every time this is done.¹

As at present constructed, many of the machines are not sufficiently strong to withstand the utmost in the way of speed and sudden turns which the skilled operator is likely to put on them. They should be made heavier, or of materials providing greatly increased strength with the same weight. That they can be made heavier without seriously damaging their flying ability has been clearly demonstrated by the numerous flights with one and two passengers, and on one occasion in which three passengers besides the driver were taken up on an ordinary machine. This was likewise tempting fate by overloading, but it served to show the possibilities.

*Landings*. Then there is a class of accidents for which neither the aviator nor the machine is responsible, as where spectators have crowded on the field, causing the flyers to make altogether too sudden or impromptu landings at angles which would otherwise not be considered for a moment. This, of course, refers solely to exhibition meets, and the comparative immunity of cross-country flights from fatal accidents as compared with the latter, speaks for itself in this respect. In the open, even the novice seems to be able to pick a safe landing, especially if high enough to glide some distance before reaching the ground. This brings out the fact that, as a rule, the machines are safer in the air—a large part of the danger lies in making a landing. Starting places are usually smooth, but landing places may be the reverse. When alighting directly against the wind, which is the only safe practice, most of the machines will remain on an even keel until they come to a stop, but the slightest bump or depression, in connection with a side gust of wind, may swerve it around and capsize it, as demonstrated by the illustration of a bad landing by De Lesseps, Fig. 49. This was emphasized by some of the minor accidents at the International Meet near New York. There is no precision or accuracy in the movements of a flying machine when rolling slowly over the ground after the engine has been shut off, and the aviator is, to a certain extent, helpless. The wheels on most machines are placed too near the center and too close together. When an attempt is made to land with the wind on the quarter or side, although the machine may strike the ground safely, owing to the accuracy with which it may be controlled in the air while at speed, it is apt to turn after rolling a short distance and the wind will then easily capsize it, breaking a wing, smashing a propeller, and sometimes injuring the motor or the aviator. Accidents from this cause have been common.

These accidents and collisions with obstructions make plain the fact that brakes are quite as necessary on an aeroplane as on any other vehicle intended to run on the ground. Practically all aeroplanes are fitted with pneumatic tires and ball-bearing wheels and, as there is very little head resistance, they will run a considerable distance after alighting at a speed of 20 to 30 miles an hour. The employment of a brake on the wheels would have averted one of the fatal accidents abroad, as noted in Table III. They would have enabled Johnstone to stop his machine before colliding with the fence surrounding the aviation grounds at Denver, and they would have prevented several minor accidents at various meets, which, though not endangering the aviator in every instance, have often seriously damaged his machine. Every exhibition field is obstructed by fences, posts, buildings, and the like, and to avoid coming in contact with these, as well as with the irrepressible spectator, the aviator should certainly have an effective means of bringing the machine to a standstill when it is running along the ground. How much more so is this necessary for cross-country flying when the choice of a landing place is a difficult matter at best. Ability to come to a stop quickly would make it possible to land in restricted places where only a very limited run along the ground could be had.

*Lack of Sufficient Motor Control*. Another class of accidents that take place on the ground suggests the necessity for improving the motor control. In alighting, the motor is usually stopped by cutting off the ignition—ordinarily by grounding or short-circuiting. Throttling to stop appears to be seldom resorted to, but as several instances have occurred in which the aviator found it impossible to cut off the ignition, resulting in a collision with another machine or a building, it is evident that the control should be arranged so that both methods could be employed. With the increasing use of air-cooled motors that may continue to run through self-ignition after the spark has been cut off, this is more necessary than ever.

While it has been demonstrated that the stoppage of the motor does not necessarily involve a fall, most aviators will naturally prefer to command the assistance of the motor at all times, and in the case of motors using a carbureter this should be jacketed either from the cooling water or the exhaust, and means provided for increasing the air supply to prevent the motor stopping at a great height owing to the cold and the rarefied air. The reasons for this have been gone into more at length under the heading of "Altitude." With these and similar improvements that will be suggested by experience and further accidents, there appears to be no reason why aviation can not be made as safe as the personal equation will permit it to be. There will always be reckless flyers. Ignorance and incompetence can not be altogether eliminated any more than they can in sailing, hunting, or any other sport. The annual hunting fatalities from these causes in this country alone make a total beside which the aggregate of four years in aviation the world over, is but an insignificant fraction.

*Parachute Garment as a Safeguard*. To save as many as possible of these reckless ones from themselves, so to speak, a parachute garment has been devised to ease the shock of the fall. It will be recalled that Voisin would not fly in his biplane until he had provided himself with a heavily-padded helmet, somewhat on the order of the football headpiece. But neither a padded headpiece nor padded clothing would avail much against a fall of any kind from an aeroplane; hence, the parachute garment. Its object is not to take the shock of a fall, as are the pads, nor is it to prevent a fall, but to reduce the rate of drop by interposing sufficient air resistance to make the fall safe. This new parachute is in the form of a loose flowing garment, securely fastened to the body and fitted over a framework carried on the aviator’s back. The lower ends of the garment are secured to the ankles. The arrangement is such that when the aviator throws out his arms, the garment is extended somewhat in umbrella or parachute form, thus creating sufficient resistance to prevent too rapid a descent. Experiments have been made with this parachute dress in which the wearer has jumped from buildings, cliffs, and other heights, and the garment has assumed its role of parachute at once, permitting a safe and easy descent.

*Study of Stresses in Fancy Flying*. To sum up, it will be seen that the most prolific cause of fatalities is the personal equation. Of all the many dangers encountered in aeroplaning, one of the most clearly defined, as well as one of the most seductive, results from fancy flying: from wheeling round sharp, horizontal curves; from conic spiraling; from cascading, swooping, and undulating in vertical plane curves, popularly dubbed "stunts." These are forms of flying in which aviators constantly vie with one another. They frequently result in imposing stresses upon the machine which are far beyond its capacity to withstand. The danger is particularly alluring to reckless young aviators engaged in public exhibitions. The death of St. Croix Johnstone, at the Chicago Meet in the summer of 1911, affords a typical illustration of what may be expected as the result of such performances. Nevertheless, partly because they do not adequately appreciate the risk, and largely, no doubt, because of the liberal applause accorded by an admiring throng which also fails to realize the hazardous nature of the fascinating maneuvers, there will doubtless always be aviators to undertake such feats.

Singularly enough, the exact magnitude of such hazards, or more accurately, the extent of the increased stress in the machine, though beyond even the approximate guess of the aviator, is capable of nice computation in terms of the speed and curvature of flight. During an exhibition meet in Washington, D. C, during the summer of 1911, Glenn H. Curtiss found difficulty in restraining one of his young pupils from executing various hair-raising maneuvers. He would plunge from a great elevation to acquire the utmost speed, then suddenly rebound and shoot far aloft. He would undulate about the field, and on turns would bank the machine until the wings appeared to stand vertical. Curtiss solemnly warned the young aviator and earnestly restrained him, pointing out the dangers of sweeping sharp curves at high speed, of swooping at such dangerous angles, and the like. Curtiss then turned to A. F. Zahm and expressed the wish that someone would determine exactly the amount of the added stress in curvilinear flight. The following, published by Zahm, in the _Scientific American_, gives the method of calculating this:

When a body pursues a curvilinear path in space, the centripetal force urging it at any instant may be expressed by the equation

Fn = m(V/R)² (absolute units) = (m/g)(V²/R) (gravitational units)

in which _Fn_ is the centripetal force, _m_ the mass of the body, _V_ its velocity, and _R_ the instantaneous radius of curvature of the path followed by its center of mass. Since the mass may be regarded as constant for any short period, the equation may be expressed by the following simple law:

_The centripetal force varies directly as the square of the velocity of flight and inversely as the instantaneous radius of the curvature of its path._

In applying the above equation to compute the stress in an aeroplane of given mass _m_, we may assume a series of values for _V_ and _R_, compute the corresponding values for _Fn_, and tabulate the results for reference. Table IV has been obtained in this manner. It may be noted that on substituting in the equation, _V_ is taken as representing miles per hour, _R_ as feet, and _g_ as 22 miles an hour, in order to simplify the figuring, this being 32.1 feet per second. The table shows at a glance the centripetal force acting on an aeroplane to be a fractional part of the gravitational force, of weight of the machine and its load. For example, if the aviator is rounding a curve of 300 feet radius at 60 miles per hour, the centripetal force is 0.55 of the total weight. At the excessively high speed of 100 miles per hour and the extremely short radius of 100 feet, the centripetal force would be 4.55 times the weight of the moving mass. The pilot would then feel heavier on his seat than he would sitting still with a man of his own weight on either shoulder. For speeds below 60 miles per hour and radii of curvature above 500 feet, the centripetal force is less than one third of the weight. The table gives values for speeds of 30 to 100 miles per hour, by increments of 10 miles and for radii of curvature of 100 to 500 feet, by increments of 100 feet, so that intermediate speeds and radii may readily be calculated.

The entire stress on the aeroplane in horizontal flight, being substantially the resultant of the total weight and the centripetal force, can readily be figured by compounding them. Thus in horizontal wheeling, the resultant force as shown in the diagram, Fig. 50, is approximately

_F = √(Fn²+W²)_

In swooping, or undulating in a vertical plane, the resultant force at the bottom of the curve has its maximum value

_F = (Fn+W)_

and at any other part of the vertical path, it has a more complex though smaller value, which need not be given in detail.

It is obvious that the greatest stress on the machine occurs at the bottom of a swoop, if the machine be made to rebound on a sharp curve. The total force _(Fn+W)_ sustained at this point may be found from the table, if _V_ and _R_ be known, simply by adding 1 to the figures given, then multiplying by the weight of the machine. For example, if the speed be 90 miles per hour and the radius of curvature 200 feet, the total force on the sustaining surface would be 2.84 times the total weight of the machine. In this case, the stress on all parts of the framing would be 2.84 times its value in level flight, when only the weight has to be sustained. The pilot would feel nearly three times his usual weight.

From the foregoing, it is apparent that in ordinary banking at moderate speeds on moderate curves, the additional stress due to centripetal force is usually well below that due to the weight of the machine, and that in violent flying, the added stress may considerably exceed that due to the weight of the machine and may accordingly be dangerous, unless the aeroplane be constructed with a specially high factor of safety. But there is nothing in the results here obtained that seems to make sharp curving and swooping prohibitive. If the framing of the machine be given an extra factor of safety, at the expense perhaps of endurance and speed, it may be made practically unbreakable by such maneuvers, and still afford to the pilot and spectators alike all the pleasures of fantastic flying.

*Methods of Making Tests*. In order to obtain actual data for the fluctuations of stress in an aeroplane in varied flying, it is suggested that the stress or strain of some tension or compression member of the machine be recorded when in action; or simpler still, perhaps, that a record of the aeroplane’s acceleration be taken and particularly its transverse acceleration. A very simple device to reveal the transverse acceleration of an aeroplane in flight would be a massive index elastically supported. A lath or flat bar stretching lengthwise of the machine, one end fixed, the other free to vibrate, and carrying a pencil along a vertical chronograph drum, would serve the purpose. This could be protected from the wind by a housing as shown in the sketch, Fig. 51.

An adjustable sliding weight could be set to increase or diminish the amplitude of the tracing, and an aerial or liquid damper could be added to smooth the tracing. The zero line would be midway between the tracings made on the drum by the stationary instrument when resting alternately in its normal position and upside down; the distance between this zero line to the actual tracing of the stationary instrument would be proportional to the aeroplane stresses in level, rectilinear flight; while in level flight on a curve, either horizontal or vertical, the deviation of the mean tracing from the zero line would indicate the actual stress during such accelerated flight. Of course, the drum could be omitted and a simple scale put in its place, so that the pilot could observe the mean excursion of the pencil or pointer from instant to instant; also, the damper of such excursion could be adjusted to any amount in the proposed instrument if the vibrating lath fitted its encasing box closely with an adjustable passage for the air as it moved to and fro; or if light damping wings were added to the lath, or flat pencil bar.

Another method would be to obtain by instantaneous photography the position of the centroid of the aeroplane at a number of successive instants, from which could be determined its speed and path, or _V_ and _R_ of the first equation, by which data, therefore, the stress could be read from Table IV.

Perhaps the simplest plan would be to add an acceleration penholder, with its spring and damper, to any recording drum the aeroplane may carry for recording air pressure, temperature, speed, and so forth. Indeed, all such records could be taken on a single drum.

A score of devices, more or less simple, but suitable for revealing the varying stress in an aeroplane, will occur to any engineer who may give the subject attention. And it is desirable in the interests both of aeroplane design and of prudent manipulation that someone obtain roughly accurate data for the stresses developed in actual flight.

*Increment of Speed in Driving*. It is commonly supposed by aviators that the _increment_ of speed due to driving is very prodigious. An easy formula will determine the major limit of such speed increment. If the initial and natural speed of the aeroplane be _v_, and the change of level in diving be _h_, while the speed at the end of the dive be _V_, the minimum change of level necessary to acquire any increment of speed, _V—v_, may be found from the equation

h = (V - v)/2g

If, as before, _g_ be taken as 22 miles per hour, the equation reduces to the convenient formula

h = (V-v)/30

in which _V_ and _v_ are taken in miles per hour. Assuming various values for _V_ and _v_, Table V has been found for the corresponding values of _h_ in feet: For example, if the natural speed of the aeroplane in level flight be 50 miles per hour, and the aviator wishes to increase the speed by 20 miles per hour, he must dive at least 80 feet, assuming that the aeroplane falls freely, like a body in vacuo, or that its propeller overcomes the air resistance completely; otherwise the fall must be rather more than 80 feet.

It has been suggested that a contest be arranged to determine which aviator could dive most swiftly and rebound most suddenly, the prize going to the one who should stress his machine most as indicated by the accelerograph above proposed. But to avoid danger, the contest would have to be supervised by competent experimentalists, and would be best conducted over water. It is safe to say that more than one well-known aeroplane would be denied entry in such a contest because of lack of a sufficient factor of safety in its construction.

*Dirigible Accidents*. Because its wrecks are spectacular and the loss involved tremendous, the dirigible has probably earned an undeserved reputation, though it must be admitted that the big airships have come to grief with surprising regularity. The fact must be noted, however, that when an airplane is wrecked, the aviator seldom escapes with his life, while the spectators’ lives are endangered to an even greater extent, whereas in the case of the dirigible, the loss is simply financial, both the crew and passengers usually escaping without a scratch. This is largely due to the fact that the majority of accidents to dirigibles have happened on the ground, and have been caused by lack of facilities for properly handling or "docking" the huge gas bag. Of course, lack of flotation or an accident to the motors, or both combined, have brought two of the numerous Zeppelins to earth in a very hazardous manner, though no one was killed, while four French army officers lost their lives in the Republique disaster, the exact cause of which was never definitely ascertained. This was likewise the case with Erbsloeh and his companion who were dropped from the sky, their airship having taken fire. It was thought that ignition was caused by atmospheric electricity, in this instance.

By far the great majority of later dirigible accidents have been due solely to the crude methods of handling the airships on the ground, and the frequency with which these have occurred should certainly have been responsible for the adoption of improvements in this respect at an earlier day.

For instance, the Morning Post, a big Lebaudy type bought for English use, had the envelope ripped open by an iron girder projecting from its shed. Repairs took several months, and at the end of the first trial thereafter, the ship was again Wrecked in landing. A company of soldiers failed to hold the big craft and it drifted broadside into a clump of trees, hopelessly wrecking it. In attempting to dock the Deutschland I, 200 men were unable to hold it down, a heavy gust of wand catching the big airship and pounding it down on top of a wind break that had been specially erected at the entrance of the shed for protection. A similar accident happened to the big Parseval, a violent gust of wind casting it against the shed and tearing such a hole in the envelope that the gas rushed out and the car dropped 30 feet to the ground. The big British naval dirigible of the rigid type, the Mayfly, was broken in half in attempting to take it out of the shed the first time. A cross wind was blowing and the gas bag of one of the central sections was torn, deflating it and showing in a striking manner that the solidity of a rigid dirigible results chiefly from the aerostatic pressure of the gas in its various compartments. Without the gas lift, a rigid frame is so in reality only for certain limited distances, as was shown by the total collapse of the Mayfly’s frame after having been subjected to the opposed leverage of the parts on either side of the original break. This, of course, was an error in design, as the frame of a rigid dirigible should certainly not be so weak in itself as to collapse upon the deflation of a single one of the central compartments. The incident on the trip of the Zeppelin III to Berlin, in 1909, when the flying blades of a broken propeller pierced the hull without causing an accident, shows how much resistance it may offer.

¹ This is exactly what occured at the Chicago Meet, August 15, 1911,
when Badger’s Baldwin biplane collapsed at the end of a long dive,
causing the death of the aviator.

AMATEUR AVIATORS

It will probably come as a surprise to the average reader to learn that at the end of 1910, there were more than a thousand amateur aviators in this country, though all the flights which form the subject of newspaper reports have been the work of not more than a dozen flyers and doubtless half the population has not as yet seen an aeroplane in flight. The desire to fly, whether it be to satisfy one’s desire to soar above the world in seeming defiance of natural laws, or merely to obtain the financial reward that is won by successful flight, attracts a great many from all stations and walks of life. This is particularly true among older boys who look on aviation as an advanced form of kite-flying. An example of rather serious work along this line may be cited of two high school boys of Chicago, Harold Turner and Fred Croll, who built a monoplane weighing 125 pounds, Fig. 52. This machine, although too small for a motor, was equipped with rudder and other operating planes and levers, the elevating plane and ailerons being automatically operated by an electrical device. On one of its flights the machine, carrying a 120 pound operator, was started and propelled by attaching it to an automobile; it rose to a height of 15 feet, and remained in the air 43 seconds.

Contrary to all precedent, the average amateur is bent upon achieving what the skilled professional considers as beyond even his talent and resources—that of building his own flying machine. With every other mechanical vehicle, the amateur learns to drive first and the majority are content with that achievement—for example, very few chauffeurs have any great ambition to build their own automobiles. With flying machines (one of the most difficult of mechanical contrivances), nearly all amateurs want to construct new types for themselves and all confidently expect to fly with no more knowledge than that gained in constructing them. We all have to be apprentices before becoming masters, so all aviators necessarily have to be learners and "grass cutters" before being professionals. Charles K. Hamilton was an exception, but he was already an expert pilot of dirigible balloons, and he did not try to build his own aeroplane. Willard, Mars, and Ely, all Curtiss pupils, flew after a very short training, but they did not attempt to construct aeroplanes for themselves. This is also true of Clifford B. Harmon, the champion amateur.

*Classes of Amateurs*. _Inventors_. Generally speaking, amateurs are of two classes. Those of the _first class_ believe they have conceived some entirely new system or invention, or an improvement on some machine that has previously proved a failure; they think they have discovered the secret which other inventors who preceded them failed to grasp. They expend their meager capital in trying to realize high hopes. A comparatively small number ever get as far as completing the machine and one trial on the field is usually sufficient to put a quietus on those who do, as it is disappointing, to say the least, to see the result of a number of months’ work undone in a twinkling without the machine having shown the least disposition or ability to get off terra firma.

_Would Be Performers_. _The second class_ finds its chief incentive in the munificent reward to be gained with what appears to be comparatively little effort or expenditure, and the amateur who is seeking financial returns has no alternative except to build his own machine, or enter either the Wright or Curtiss school of flying and secure a berth with one of these companies.

*Wright and Curtiss Patents*. This is the result of conditions at present obtaining in the field of aviation. The only generally successful types of American aeroplanes are the Wright and Curtiss, and the acquirement of a biplane of either type means the expenditure of at least $5,000 for the machine alone, and they are sold only to individuals on the express condition that the machines are not to be used for exhibition or as a means of profit to the owner. The manufacturers have expert flyers of their own who attend meets and fairs throughout the country. It would make their monopoly impossible to allow outsiders to fly their aeroplanes publicly or to exhibit them. By this restriction the price of the machines is kept up and large returns are gained by exhibitions and flying.

To break this monopoly by importing European machines is not possible. All the successful aeroplanes made abroad such as the Farman, Cody, and Sommer biplanes; and the Bleriot, Antoinette, and Grade monoplanes are fitted with devices of control or stability, or both, covered by the Wright patents and can not be flown in this country without legal trouble. The numerous foreign aviators who brought over their machines in the fall of 1910 to compete at the International Meet, did so only on being granted a concession by the Wright Company to the effect that they would not be considered as infringers and sued. Similar arrangements were made at subsequent meets and this handicap will always be present where foreign machines are used.

_Evasion by Invention of New Types_. But when he thinks of the unprecedented sums paid professionals for simply exhibiting their machines and making short flights, the amateur is anxious to obtain a share of the profits. No thought is given the fact that were he and all his kind permitted to fly, the achievement would soon be commonplace and the aviator’s golden age would be over. There are accordingly hundreds of would-be aviators in this country today who are striving to evade the Wright basic patents by either devising entirely new types of aeroplanes, or by inventing new methods of control and stability that will not infringe. Others, reasoning that the old aeroplanes built before the advent of the Wright machine cannot be held as infringements owing to priority, propose to develop Maxim, Langley, and Ader machines, though the dictum in the New York Court of Appeals decision referred to under the head of "Legal Status of Wright Patent," which states that a prior machine which _had never been known to fly_ would not be considered an anticipation of a modern successful machine, may prove a stumbling block in their case as well. Thus, a round of the workshops of these enthusiasts reveals a host of heavier-than-air machines of every conceivable type and shape, every one of which, according to its builder, is _an aeroplane that will fly_. Mineola and Garden City, Long Island, harbor a score of these little shops the year round, but the same scenes are being enacted on a smaller scale in almost every state in the Union, and particularly in California, Ohio, Kansas, Massachusetts, and Arizona, in addition to which there are many who are carrying their experiments on in secret. Each believes deep in his heart that he will succeed where a master failed.

"Maxim failed with this type of machine," quotes one. "How did he expect to fly when his control was not proportionate to the machine’s lift capacity?" Seemingly, nobody ever thought of that and our friend will make a fortune by going Maxim one better, but he does not. After months of labor and a great deal of expense he finds that some unforeseen difficulty develops which keeps his machine to earth as if it were part and parcel of it. Another has conceived a type of monoplane that is entirely new—different from any existing type—and as the latter are all foreign, he prides himself on having developed a monoplane that will be entirely American—the first and only American monoplane. Theoretically, it is a wonder; mechanically it is correct; and it speeds over the turf with surprising velocity; but when the elevating rudder is operated to make the machine rise, it balks and plunges head first into the ground. Again and again, the propeller and other broken parts are replaced at no small expense; again and again the inventor goes over every part of the machinery and computes the dimensions of the supporting surface to see if it all corresponds with the formula of his special theory. But time after time, the aeroplane acts like a jumping frog and lands head first. At last, its builder becomes convinced that there is something radically wrong and begins to depart from his original plans, involving changes that simply mean a waste of effort and money, since the inventor does not himself know what he is trying to correct and no one else knows better than he what the trouble is.

_Evasion by Acquiring European Types_. Others still, realizing from the foregoing experiences that it is almost impossible to construct an entirely new type of aeroplane off-hand, acquire European types and propose to fit them with new control and stability devices, such as are not covered by the Wright patents. So far, none has succeeded. Somehow, the Wrights seem to have covered all the conceivable working devices for control and stability, and the numerous attempts have accordingly resulted in failure. Undoubtedly, some of these aeroplanes built by amateurs may really be capable of flight; but how is the inventor to know it when he lacks the ability to operate it? To know how to fly an aeroplane is a condition precedent to success in the field of aviation that can not be met by building of a machine. The beginner is thus badly handicapped. Even though his machine may embody the elements essential to successful flight, he may never be able to establish the fact, since his first blundering attempt or two frequently ends by wrecking the machine, and many have neither the means nor the stamina to persevere further after a few bad wrecks, involving weeks and weeks of rebuilding each time. He can not engage an expert to fly his machine for him, as the expert’s time per minute figures out a price that makes him gasp, and even at that the expert professional’s time is pretty much all taken. Furthermore, very few would run the risk of attempting to fly an untried aeroplane—they have more to lose through accidental injury than the builder has through the failure of his theories.