September 26, 1912] 



NATURE 



attention should be given to the question of 

 balancing', not only of the actual propeller torque 

 by the use of two propellers, but also of the gyro- 

 static couples due to both the propeller and the 

 rotary engine. Why do not the makers try an 

 eiigine rotating about a horizontal axis perpen- 

 dicular to the line of flight, driving a pair of pro- 

 pellers rotating in opposite directions by means of 

 bevelled cogs? The arrangement would be per- 

 fectly symmetrical, and the gyrostatic couple of 

 the engine mii^ht be used to assist in lateral 

 steering. 



Another disadvantageous feature of many mono- 

 planes, though not an essential feature of them, 

 is that the wings are usually of considerable 

 breadth, and, of course, are cambered. The 

 result is that when such a machine pitches, effects 

 may occur the nature of which will remain 

 entirely unknown until some experimental know- 

 ledge has been obtained regarding air pressures 

 on rotating planes. To assume that these effects 

 are negligible, or even that they may not be the 

 cause of accidents, is, in the circumstances, 

 scarcely justifiable. 



It will be interesting to see whether any ques- 

 tions of stability are considered in connection with 

 the present inquir}-. The tendency which has 

 existed up to the present time of shelving the 

 problem of inherent stability, and attempting to 

 attribute accidents to other causes, is, after all, 

 very natural. If stability could be ignored alto- 

 gether, the problem of aviation would be greatly 

 simplified, and much laborious work, both 

 theoretical and experimental, would be saved. 

 Those of us who have spent much time in studying 

 the theory of stability \\ould have been glad to 

 give our attention to other subjects instead, had 

 we believed that a final solution of the problem of 

 flight was possible which should make aviation 

 independent of stability considerations. At the 

 present time, no experimental information exists 

 regarding inherent stability, and a comparison of 

 theory with practice is urgently needed. Under 

 theoretically assumed conditions, stability, both 

 longitudinal and lateral, is greatly affected by 

 variations in the inclination of the flight path to 

 the horizon, and this is a point on which experi- 

 mental tests would be of particular interest. The 

 fact that so many accidents have occurred the 

 causes of which are unknown shows that aviators 

 have not yet been altogether successful in their 

 attempts to dispense with theories of, and experi- 

 ments on, stability. The accounts of manv acci- 

 dents are strangely suggestive of what would 

 happen under theoretical conditions if an aeroplane 

 should be flying at an inclination to the horizon 

 consistent with inherent instability. 



As regards the monoplane and biplane, these 

 limits are probably very different in existing 

 machines of the two types, but there is no 

 essential difference between the " single- " and 

 "double-decker" in regard to stability. Many 

 monoplanes are of the Antoinette type, and can 

 be made laterally stable by making the tail of 

 sufficient length ; many existing biplanes do not 

 possess suflRcient auxiliary surfaces for lateral 

 NO. 2239, VOL. 90] 



stability, though this defect is probably remedied 

 when the planes are bent up; on the other hand, 

 the auxiliary planes in them are as a rule more 

 favourable to longitudinal stability. These are, 

 however, details of construction which do not 

 depend on whether the machine is a monoplane 

 or biplane. It is probable that most existing 

 aeroplanes satisfy the condition that lateral, like 

 longitudinal, instability increases when rising in 

 the air. 



It is necessary to repudiate any suggestion 

 that a so-called " theory " of stability (which is 

 really an experimental study of the results of cer- 

 tain assumed hypotheses, the apparatus for which 

 are the methods of mathematical analysis] should 

 be applied to actual aeroplanes without first being 

 subjected to a second experimental test performed 

 with the actual aeroplanes or models of them. 

 But would not even this course be better than 

 continuing to use aeroplanes about the stability of 

 which nothing is known? And admitting that most 

 flights have to be performed in gusty winds, is 

 this any reason for being satisfied with a flying 

 machine which would not fly straight in still 

 air? Some people appear to think so. But is it 

 not probable that the problem of stability pre- 

 sented by an actual aeroplane is more complex 

 and not less complex than that presented bv a 

 system of narrow planes moving at small angles 

 through a resisting medium? If this be so, the 

 complexities of the simpler problem may afford 

 some clue to those existing in the more diflScult 

 and at present unsolved problem. 



It is hoped that no suggestions made in the 

 present article will be regarded as authoritative 

 statements except so far as they may be confirmed 

 by experiments conducted with the aid of mathe- 

 matical or physical apparatus. If any conclusions 

 are to be drawn from these remarks, they should 

 be to the effect that it is far less important to try 

 to decide whether a biplane is better than a mono- 

 plane than to investigate the relative merits of 

 flying machines on a perfectly broad basis. It 

 is, therefore, to be hoped that the staff of the 

 National Physical Laboratory will not only be 

 given a very free hand in the Investigations that 

 are placed in their hands, but that they will pro- 

 duce a powerful and thorough report, and — if a 

 small criticism is permissible — give a little more 

 attention to formulating broad general principles, 

 and confine themselves a little less exclusively to 

 the tabulation of minute experimental details than 

 they have done on some previous occasions 



G. H. B. 



THE INTERNATIONAL METEOROLOGICAL 

 COMMITTEE. 



Weather Telegr.\phv and Maritime 

 Meteorology. 



MEETINGS were held in London during the 

 week ending on Friday, September 20, of 

 two Commissions constituted by the International 

 Meteorological Committee to deal with questions 

 concerning international weather telegraphy on 

 the one hand, and with those concerning mari- 



