NO. 3 LANGLEY MEMOIB ON MECHANICAL FLIGHT 139 



JUNE 22 AEKODROME No. <> 



After several days ' delay, due to numerous small hut exceedingly annoying 

 troubles, — such as the leaking of boilers because of defects in the copper tubing, 

 and the bursting of the air tank, due to its being pumped up to an excessive 

 pressure, which a defective pressure gauge bad tailed to indicate, — Aerodrome 

 No. 6 was made ready for another trial, and it was decided to test il again with 

 the superposed wings which had been used in the second experiment of June 13. 

 The aerodrome was mounted on the " overhead " launching apparatus, which 

 it will be remembered had been used in all the previous tests, and after 90 sec- 

 onds had been consumed in raising a steam pressure of 110 pounds, it was 

 launched directly into the wind, which was due south. After leaving the launch- 

 ing car, the aerodrome flew straight ahead for about 75 feet, when it suddenly 

 turned its bow up into the air at an angle of about 15 degrees, and it seemed 

 that the machine would be blown back onto the house hoat. However, when the 

 rear end of the tail was within about 10 feet of the hoat, and only about 10 feet 

 above the water, it suddenly regained its equilibrium and went straight ahead 

 again in the face of the wind with the guy-posts only about 4 feet above the sur- 

 face of the water, flying almost exactly horizontally for a distance of about 1U0 

 feet, when the bow again suddenly hecame elevated. As the aerodrome was so 

 close to the water, the wind forced it down until the burners were extinguished 

 by coming in contact with the water. This broughl the aerodrome to a stand- 

 still absolutely uninjured, the propellers being several inches above the water 

 when they quit turning. The aerodrome was brought into the house-boat and 

 thoroughly dried out, and another trial would have been made with it imme- 

 diately but the wind which had been steadily increasing was now blowing some- 

 thing more than 12 miles an hour, and it was considered best not to attempt ex- 

 periments in so strong and gusty a wind, for fear of the wings being broken 

 by the wind suddenly veering and striking them on the side or rear while the 

 aerodrome was still on the launching apparatus. The peculiar action of the 

 aerodrome in the air appeared to be due to the fact that the propellers inter- 

 fered more with the lifting power of the rear superposed wings, as they were 

 then constructed, than they did with the " single-tier " ones. The data on the 

 setting of the wings, tail, etc., are shown on Data Sheet No. 5 (Appendix). 



It was also found after the experiment that one of the workmen, in assem- 

 bling the machine on the launching car, had secretly increased the stiffness of 

 the spring which controls the elasticity of the Penaud tail. The effect of this 

 increase in the stiffness of the Penaud tail might at first thought appear to be 

 similar to that of moving the center of pressure forward. Upon a closer analy- 

 sis, however, it will be seen that the effect is very much greater, as excessive 

 stiffness of the Penaud tail not only causes the aerodrome to elevate its bow, 



