In the large machines as well as in the models there seems to be a general tendency to increase the aspect ratio of the main planes. The Bleriot XI still retains its broad deep plane, but in several of the models the depth of the model has been greatly reduced. In the new Voisin monoplane the main wing has a width of thirty-seven feet and a depth of but five feet, thus giving it an aspect ratio of nearly one to eight. The machine flies with great ease, its resistance is very low and it answers well to its stabilizing devices. The Cody biplane again has supporting planes measuring fifty-two feet by only seven feet six inches.
The same tendency to reduce the size of the planes is noticeable in the recent Wright models. The Wright machines (model R), are the smallest yet used on an aeroplane. They have a spread of but twenty-six feet six inches and a chord of only three feet seven inches, giving them an exceedingly high aspect ratio. In the racing machines the spread has been cut down to twenty-one feet six inches. Attention has been called in an earlier chapter to this same tendency to reduce the wing area in model aeroplanes. It is interesting to find our amateur aviators increasing the aspect ratio of their planes although working independently.
In many of the large machines the front and rear planes are brought much closer together in the more recent models. It would seem that as the front and rear planes are brought closer together there would be a loss in fore and aft stability, but on the other hand the reduction in weight made possible by shortening the frame is very important.
A careful report has been prepared in France recently of all the serious accidents to aeroplanes with the idea of classifying them. The record of fatal accidents shows a total of thirty-one up to the beginning of the present year, resulting in thirty-four deaths. Although these figures taken alone are appalling, they are found on analysis to indicate that aviation is nevertheless growing safer and not more dangerous. In 1910 there were twice as many fatal accidents as in the previous year, but on the other hand there were more than five times as many flights made, so that the percentage of accidents, as a matter of fact, was but forty per cent. as great as for the preceding year.
The commonest cause of accidents according to these tables has been faulty construction. Next in turn came the accidents due to the errors of the pilots. Atmospheric conditions rank third in the list and fourth the carelessness of the spectators. There were in all some forty-seven accidents in 1909, and 101 in 1910. An increase is to be noticed last year in the accidents due to atmospheric conditions. This was caused in most cases by the unusual daring, even foolhardiness of the pilots. In their attempts to amaze their audience by performing hazardous dives and volplanes from great heights many machines were wrecked and several aviators met their death.
Since the main cause of fatal accidents has not been structural weakness or the carelessness of the pilots, it is clear that the science of aviation itself cannot be blamed. It is of course a comparatively easy matter to build machines sufficiently strong to fly without breaking down. The number of accidents, especially fatal accidents, due to the inherent danger of flying, to dangers which cannot be overcome, has been very trifling, and is steadily diminishing.
CHAPTER XIII SELECTED QUESTIONS FOR BEGINNERS
How can I find the center of pressure of my model aeroplane? The simplest plan is to adjust the planes so that the model flies on a perfectly even keel, and then balance the machine. Since the center of pressure and the center of gravity must coincide to produce horizontal flight, this point of balance will be the center of pressure. As a rule, the center of pressure will be found to be near the front edge of the main plane, perhaps slightly back of this forward edge.
What is the best position for the propeller?
In the case of a model driven by a single motor, the propeller shaft should pass through the center of gravity and center of pressure of the machine. It is very important that the alignment should be perfect or you will have great difficulty in securing a horizontal flight. In case of a double propeller machine, the line midway between the two propeller shafts must pass between the center of gravity.