AIR TRANSPORT — DURAND 517 



wing area 2,320 square feet, wing loading 22.5, power, 4 engines devel- 

 oping 3,600 horsepower, cruising speed 130 miles per hour, range 

 2,400 miles, and pay load 2,600 pounds including 8 passengers. The 

 new Douglas 4 of 65,000 pounds has wing area 2,130, wing spread 

 138 feet, wing loading 30.5, power, 4 engines developing 5,600 horse- 

 power, cruising speed 170 miles per hour, range 1,000 miles with a 

 pay load of 9,400 pounds including 40 passengers. The new Boeing 

 flying boat, with a total lift of 82,500 pounds, has a wing area 2,880 

 square feet, wing spread 152 feet, wing loading 28.8 pounds, 4 

 engines developing 5,950 horsepower, cruising speed 150 miles per 

 hour, range 2,400 miles with a pay load of 10,000 pounds including 

 40 passengers. 



The recent Boeing 307, intended especially for stratosphere flight, 

 with a total lift of 42,000 pounds, has a wing area of 1,390 square 

 feet, a wing spread of 107 feet, wing loading 30.3 pounds, 4 engines 

 developing 4,150 horsepower, cruising speed 175 miles per hour, range 

 1,000 miles with a pay load of 9,200 pounds including 33 passengers. 



Then passing to the future, the new designs, referred to above, 

 proposed for trans-Atlantic flight, with a total life of 200,000 pounds, 

 will have a wing area approximately of 4,450 square feet, a wing 

 loading of 45 pounds, engines developing 11,750 horsepower, cruising 

 speed 250 miles per hour, range 3,700 miles with a pay load of 25,000 

 pounds including 100 passengers. 



In these figures for horsepower and speed, it should be noted that 

 the power is the maximum developed by the engines, used normally 

 only when taking off. The cruising power usually varies from 50 to 

 60 percent of this. With full power, the top speed would be some 

 25 to 30 percent higher than the cruising speed. 



These illustrations are all of American design and manufacture. 

 It must not be supposed, however, that we stand alone in this march 

 of progress. England, France, Germany, Italy, and Russia are 

 all thinking and designing along these same general lines. I shall 

 attempt no comparisons since my purpose is simply to indicate the 

 trend of progress, and for this purpose the American designs will 

 serve as well as, or perhaps better than, those from abroad. I may, 

 however, go so far as to say that no foreign design actually built 

 appears to have the promise of the Boeing boat No. 314, and no 

 designs, especially for trans- Atlantic service, appear to be in the class 

 with those submitted in competition for the contemplated 200,000- 

 pound type, to which I have just referred. 



In summarizing the characteristics of these modern airplanes, the 

 wing loading was noted as one of the significant features. This, 

 we remember, is the total lift or total weight divided by the wing 

 area — that is, the lift per square foot of area. Perhaps no character- 



