10fi SMITHSONIAN CONTBIBUTIONS TO KNOWLEDGE VOL. 27 



It will be recalled thai in the more recoil trials the apparent causes of fail 

 urc had been the inability to provide sufficiently rigid wings, the great difficulty 

 of properly adjusting the relative positions of the centers of pressure and grav- 

 ity, and the lack of any means of regaining equilibrium when the balance of the 

 aerodrome had in any way been disturbed. In the fall of 1895, accordingly, it 

 was finally decided to employ a second. pair of wings equal in size to the lirsl or 

 leading pair. This not only added greatly to the stability of the aerodrome, but 

 also made it possible, without any alteration in the plan of the frame, to brim;' 

 the center of pressure into the proper position relative to the center of gravity. 

 In addition the plan of constructing the wings was modified by the introduc- 

 tion of a second main rib, which, placed at approximately the center of pres- 

 sure of the wings, made them much stiffer, both against bending and torsion. 

 The two pairs of wings now became the sole means of support, and the tail 

 which had hitherto been made to bear part of the weight of the aerodrome, as 

 well as assist in preserving the longitudinal equilibrium, was now intended to 

 perform only the latter function. It was placed in the rear of the wings and 

 was combined with the vertical rudder, further, in adjusting it on the aero- 

 drome, it was set at a small negative angle and given a certain degree of elas 

 ticity, as described above. This device proved to be a most efficient means of 

 maintaining and restoring the equilibrium, when it was disturbed, and its value 

 was apparent iu all future tests of the models. 



1896 



The important changes in the steam-driven models which had been begun 

 in the previous fall, and which in the case of No. 4 had been so extensive as to 

 convert it into a new aerodrome, No. 6, were continued during the early spring, 

 ami it was not until the last of April thai the models Nos. 5 and (i were ready 

 for actual test in free flight. 



The condition of No. 5, which made the first successful flight, is given ill 

 the .lata sheet for May (i, 1S!)6, and its general form at this time may be seen 

 in the photograph of May 11, Plate 27A. Although the changes described above, 

 as well as the modifications in the boilers ami burners of both aerodromes had 

 undoubtedly effected a greal improvement in every detail of the machines, the 

 disappointments experienced in the preceding years prevented any great feeling 

 of confidence that the trials which were now to be made would be entirely suc- 

 cessful. On May 4, however, the two mechanics, Mr. Reed and Mr. Maltby, were 

 sent down to Quantico with Aerodromes Nos. •"> and b\ and Mr. Langley, accom- 

 panied by Dr. Graham Bell, who had been invited to witness the tests, followed 

 on the afternoon of the 5th. On May (I the wind was so very high all the morn 

 ing that a test was found impracticable. During the forenoon, however, the 

 wind gradually died down, and by 1 p. in. was blowing from six to ten miles an 



