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Aviation History
1909
1909 - 0720.PDF
NOVEMBER 13, 1909. more than novices in management. A thousand glides is equivalent to about four hours of steady practice, far too little to give anyone a complete mastery of the art of flying. Progress is very slow in the preliminary stages, but when once it becomes possible to undertake con- tinuous soaring, advancement should be rapid. Soaring. - . :; Under special conditions, it is possible that this point is not so far away as might be supposed. Since soaring is merely gliding in a rising current it would be easy to soar in front of any hill of suitable slope whenever the wind blew with sufficient force to furnish support, provided the wind were steady. But by reason of changes in wind velocity, there is more support at times than is needed, while at others there is too little, so that a considerable degree of skill, experience, and sound judgment is required in order to keep the machine exactly in the rising current. So far, our only attempts at soaring have been made on the Little Hill, which has a slope of only 70. In a wind blowing from 11 to 16 metres a second, we frequently made glides of 8 to obtain a speed of 12 miles by running required very severe exertion. Consequently, unless the wind blew in our faces with a speed of at least six miles, we did not usually attempt to practise ; but when the wind rose to 20 miles an hour, gliding was real sport, for starting was easy and the labour of carrying the machine back up-hiil was performed by the wind. On the day when the wind rose to over 16 metres a second we made more than a hundred glides with much less physical exhaustion than resulted from twenty or thirty glides on days when the wind was light. No complete record was kept of all the glides made during the season. In the last six days of experiment we made more than 375, but these included our very best days. The total number for the season was probably between 700 and 1,000. The longest glide was 6225 ft., and the time 26 seconds. Lessons of the Trials* The prime object of these experiments was to obtain practice in the management of a man-carrying machine, but an object of scarcely less importance was to obtain data for the study of the scientific problems involved in Starting a flight, showing bow the two assistants run along- side while launching. 15 seconds duration with very little forward motion. As we kept within 5 or 6 ft. of the ground, a momentary lessening of the wind speed, or a slight error in judgment, was sufficient to bring about a landing in a short time. The wind had too little rising trend to make soaring easy. The buzzards themselves were baulked when they attempted to soar on this hill, as we observed more than once. It would be well within the power of the machine to soar on the Big Hill, which has steeper slopes, but we have not felt that our few hours of practice is sufficient to justify ambitious attempts too hastily. Before trying to rise to any dangerous height a man ought to know that in an emergency his mind and muscles will work by instinct rather than by conscious effort. There is no time to think. Suitable "Winds, During a period of five weeks glides were made when- ever the weather conditions were favourable. Many days were lost on account of rain. Still moie were lost on account of light winds. Whenever the breeze fell below six miles an hour, very hard running was required to get the machine started, and the task of carrying it back up the hill was real labour. A relative speed of at least 18 miles an hour was required for gliding, while to At close range, showing very clearly the exact positionoccupied by Wilbur Wright in gliding. The machine illustrated is the 1902 model fitted with a rudder. flight. Observations were almost constantly being made for the purpose of determining the amount and direction of the pressures upon the sustaining wings ; the minimum speed required for support; the speed and angle of incidence at which the horizontal resistance became least; and the minimum angle of descent at which it was possible to glide. To determine any of these points with exactness was found to be very difficult indeed, but by careful observations under test conditions it was possible to obtain reasonably close approximations. It was found that a speed of about 16 miles an hour would produce a pressure sufficient to support machine and operator, but the angle of incidence was too great for general gliding purposes. At 18 miles the angle of incidence was about 8", and the machine would glide on the Little Hill, descending at an angle of a little over 7°. Although the wings were inclined slightly above the horizon the machine continued to glide without loss of velocity. With a speed of 22 miles an hour, the angle of incidence required for support was 40 or 50, and the angle of descent a little less than 70. At this speed the surfaces were inclined several degrees below the horizon. As the speed became greater the angle of incidence continued to grow less, but the angle 722
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