1 11 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



voi,. 27 



.11 I. V L9 AERODROME NO. 5 



After several days of exceedinglj bad weather the conditions were more £a 

 rorable on July 1!). Since the Lasl experiment on July 14 the coefficient of elas- 

 ticity of the Penaud tail had been decreased, the rear wings moved bach 5 centi- 

 metres, and the "float " so placed thai the center of gravity of the machine 



was brought to tin- same, position il had had on that day, thai is, 2 centimetres 



bach of the line of thrust. With this arrangement, assuming that the CP is 

 over the CG, we should have an apparent efficiency of the rear wings of 63.6 per 

 cent, since the distance between CPfv and CG is 7!). 7 centimetres, and the dis- 

 tance between <"/',,. and CG is L25.3 centimetres. With the adjustment of duly 

 14, the distance between GPt* and CG was 7!). 7 cent i met res, and the distance be- 

 tween ('/',„ and CG was IIS.;; centimetres, thus allowing for an apparent effi- 

 ciency of (i7..'i7 per cent for the rear wings. It will he recalled thai in the un- 

 successful flight of .July L4themidrod of the aerodrome was inclined at an angle 

 of ahout hd degrees during most of the time that it was in the air, thus indi- 

 cating that the front wings were lifting proportionately more than they should. 



On July 14 the Penaud tail had a negative elevation of 7 .'!<)', and it required 



L240 grammes placed at its center to bring it to the horizontal. On Jul) lit the 



elevation of the tail was changed to 5 and a weaker spring for controlling the 



elasticity was substituted, so that it required only 200 grammes placed at the 



center of the tail to bring it to the horizontal. A rubber hand, of about one 



half the strength of the upper spring, wag attached bj means of a cord to the 



lower guj post and the lower vertical ribs of the tail, so that the tail would be 



elastic both ways. This rubber band was in place and acting to help draw the 



tail down when the above measurement of t he coefficient of elasticity was made. 

 A rubber band connected to the lower side of the tail was also used in the 

 flight of Julj it. but il was so very weak, compared to the upper spring, (hat its 

 effect was negligible. 



The effect of this change in the balancing of the aerodrome, and also the 



more considerable effect which the coefficient of elasticity of the tail bason the 



balancing, will be immediately noticed from the description of the next flight. 

 The data on setting of wings, tail, etc. are given on Data Sheet No. H. 



At 3 p. m., the wind having died down, Aerodrome \o. 5, equipped with its 

 "single-tier" wingg and Penaud tail adjusted ■■> above, was placed on the 

 " overhead " launching apparatus. After lighting the burners, one minute and 

 thirty seconds were required to raise a steam pressure of 120 pounds, [mme 

 diately upon leaving the launching apparatus, the aerodrome started straight 



ahead, dropping about :: feel by the time il had --'one 1(1(1 feel; it then ro '• 



with its midrod at an aic.de of about (J or- 8 degrees, regaining il- level very 



quickly, however, and making three of these undulations by the time it had gone 



