THE AUTOQIRO PITCAIRN 271 



other phases. For instance, modifying the rotor for higher for- 

 ward speed may be so handled as to decrease rate of vertical descent. 



Without the theoiy worked out and developed by Cierva, all this 

 would be impossible, liecently he has put this theory into written 

 form for the use of engineers. He has also developed a series of 

 graphs with accompanying explanation which will enable the engi- 

 neer to calculate performance and design Autogiros of various sizes 

 and types. This theoretical work alone would in itself be a monu- 

 mental achievement for many a lesser engineer. 



80 far, as I have said, the Autogiro is the work of one man only. 

 Think what the Autogiro will be when the same effort is put on it 

 that has been applied to the airplane. Also, the engineers now con- 

 centrating upon the Autogiro have many more factors with which 

 to deal than those who took the airplane in hand, and they have 

 extensive knowledge of aerodynamics to work with, gained from 

 wind-tunnel tests and airplane experience. 



In conclusion, I may say that the Autogiro is now a practical 

 machine, and within a reasonable time many will be produced com- 

 mercially. The Autogiro is free from many of the inherent limita- 

 tions of the tixed-wing aircraft, and while its performance is even 

 now superior to the airplane in many respects, all considerations of 

 performance are subordinated to the one feature which it affords 

 in large measure: that feature is safety. 



