AIR TRANSPORT — ^DURAND 531 



the Goodyear Zeppelin Corporation in Akron have helped to bridge 

 the gap between the loads which the elements of the structure must 

 sustain and the dimensions of these elements in order that such loads 

 may be carried with a suitable margin of safety. 



The story is too long and the subject is too complex for any dis- 

 cussion in detail. I believe, however, that a fair conclusion is that 

 with the full utilization of recent advances in both the science and 

 art of airship design and construction, we can now design and build 

 airships with a margin of structural safety and security at least 

 equal to that for the airplane. So far as further comparison goes, 

 the airship is relieved of two possible hazards affecting the airplane — 

 propulsive failure followed by a forced landing, and control failure, 

 followed by the too often fatal spin. 



On the whole, there seems to be no reason why our future air- 

 ships — in case any such be built — should not show an excellent record 

 as regards safety and security in operation. 



With regard to the field for successful commercial service, present 

 opinion in the United States is divided. I shall not take the time 

 to discuss the pros and cons but will only venture my own opinion 

 that for transocean service on relatively long nonstop runs (3,000 

 to 6,000 miles) with relatively heavy loads at speeds three times 

 those of surface ships though perhaps only one-half to one-third 

 those of the airplane, but with greater passenger freedom and com- 

 fort than for the airplane, there may well be found a useful and 

 effective place for the airship in our complex system of modern 

 transport. 



Something might also be said regarding the possible use of the 

 airship in naval warfare ; but here again the question is highly con- 

 troversial and I shall not venture into this domain. 



Perhaps, also, if you will bear with me, I should say a word about 

 the autogyro and the helicopter. The former is sustained by rotat- 

 ing wings or vanes, maintained in rotation by the motion of the 

 structure under the pull of an air propeller, driven by an engine 

 much as in the conventional airplane. 



The latter is, in effect, simply a flying propeller. The shaft, 

 nearly vertical, is tilted so that the upward component of the total 

 pull provides sustenation, while the horizontal component provides 

 transport. 



The autogiro, now some 10 years old, seems to be in the way 

 of acquiring a fairly well-assured place among the varied forms 

 of aircraft available for air transport. I^t appears to have special 

 qualities which go far to adapt it to individual use: take-off from, 

 and landing in, confined areas, and relative safety against casualty 

 from loss of control as may occur with conventional airplane forms. 



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