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Aviation History
1910
1910 - 0836.PDF
JycRf OCTOBER 15, 1910. NATURAL STABILITY r. IUICKNESS OF CONTROL. inertia will, of course, interfere with the immediate restoration of equilibrium, but practice has not shown that this interference is of a preventative order of magnitude except in some cases of the underhung load. By separating the wings from the body, the advantages and disadvantages of its inertia are both apparently eliminated, but to argue that this is, therefore, the better system, is to suggest that the advantage of inertia in the first place was purely imaginary. It seems to us that this idea of separating the wings from the body is merely transferring the operations of control an octave, so to speak, up the scale. It must, after all, be remembered that the purpose of control is to keep the wings in the proper position of transverse equilibrium. If it were immaterial whether they remained in this position or not, then there would, of course, be much to be said for disconnecting them from rigid attachment to the body. It may perhaps be recollected that there was a peculiar model exhibited at the last Olympia Show in which a series of planes were mounted in a kind of cage surrounding the body of the machine, about which it was free to rotate. The device was so arranged that an equal amount of supporting surface was exposed on either side of the vertical axis for any position of the cage, and indeed the wings could revolve about the body all the time if necessary without destroy ing their normal transverse equilibrium. In some respects such a principle of operation deserves to be regarded as the logical development of the fundamental idea that we are discussing, for if the design is restricted to one pair of wings, it is absolutely essential that these should be maintained in their proper position, since the machine cannot be supported in flight if they are to be canted for any appreciable time. With the inertia of the body eliminated, a given wind gust will presumably cant the wings to a greater degree than would result from the same force if the wings were directly attached to the body itself, and the action would also essentially take place more quickly. True, the restoration of equilibrium could likewise be made more quickly with a given degree of warping, but this factor, taken in conjunction with the initial disturbance, has no claim to be considered as an advantage per se. If a machine with rigid wings once canted could not be righted with a fair degree of certainty under ordinary flying conditions, the situation would be altogether different, but while pilots have this degree of control within their power, progress is rather to be sought along the lines of increased natural stability, which prevents canting, than in means for more quickly restoring an equilibrium that has itself been more readily disturbed thereby. ELSEWHERE in this issue will be found a brief descrip tion of a special form of aeroplane that has, as its principal characteristic, a floating connection for the attachment of the wings to the body so that the wings are capable of canting about the fore and aft axis of the machine, independently of the body. The basic underlying idea of the system is to obtain greater rapidity of control by eliminating the effect of the inertia of the body, which essentially contains the princi pal masses. It necessarily involves the assumption that this is a greater desideratum than any advantage accruing in the way of initial natural stability from this same inertia when the body is, as ordinarily, rigidly attached to the wings. As we have noticed that this idea of disassociating the supporting members of an aeroplane from the load that they carry is one that is prevalent among students of aviation, we take this opportunity of passing a few remarks upon the broader aspects of the principles involved without any pretence of considering the pros and cons of the relative constructional convenience of the two systems. For our own part we find it difficult to accept any validity for the point of view that professes to see a distinct fundamental benefit in quickness of control over natural stability, although we admit that the idea of reducing the effect of inertia has a prima facie claim to consideration in view of the now very generally accepted belief that a minimum moment of inertia is desirable in the design of the machine as a whole. We refer to the pros and cons of the ascentric (or underhung) and concentric positions of the centre of gravity in respect to the centre of pressure. There is a general tendency at the present time to concentrate all the principal masses as far as possible in one spot, which is coincident or nearly coincident with the centre of pressure. This undoubtedly reduces the moment of inertia of the machine about its longitudinal axis, and on first thoughts it might be argued from this that the disconnection of the body from the wings altogether, which would bring about a still further reduction in the moment of inertia, would be even more advantageous. It does not, however, seem to us logical to take this line of reasoning, for the moment of inertia of the machine as a whole is not altered by the separation of the wings from the body although the moment of inertia resisting movement of the wings alone is itself very materially reduced. Other things being equal, however, the inertia of the body surely constitutes a factor of natural stability inasmuch as it increases the resistance of the machine as a whole to initial canting, and that after all is the great desideratum. If the resistance thus offered is inadequate to prevent canting, then the same Aviation Classes at Birmingham. THE authorities of the Birmingham Technical School have . been approached by the Midland Aero Club with a view to classes being instituted to deal with aeronautical subjects. The idea has been favourably received, and the Midland Aero Club are ascertain ing from their members how far they would support such a course. The Council propose, in the event of the classes being held, to encourage members in every way possible by rebating the fees of those who complete the course, and by offering' prizes for general .proficiency and for the best essay on the work done during the session. Aeroplanes for French Colonies. THE French Aerial League has lately brought to the attention of the Minister of the Colonies the great advantages which will accrue from the development of aeroplanes in connection with transport in the French colonies and possessions which include large tracts of desert. The Minister has assured the League that he is fully alive to the possibilities of the new mode of locomotion, and will do all in his power to facilitate its development. With this end in view he has requested the various Governors-General to furnish him with all particulars regarding their territories, which will be useful to designers of aeroplanes, &c. 834
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