576 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1941 



comment here concerns the fact that because of the increase just de- 

 scribed, it has not been possible to increase the useful load in terms of 

 percentages of gross load. In fact, an actual decrease has occurred. 

 From 1929 to 1939, this percentage has decreased from 40 to 33, where 

 it appears to be stabilized. For flying boats, during the same period, 

 it started at 45 percent and increased in certain instances to 50 but 

 now seems to be stabilizing at 42, The fact that it has not gone down 

 still further is only due to improvements in structural efficiency which 

 have been accomplished. 



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Provision for increased space as shown in figure 4 (i?) will be recog- 

 nized at once as a substantial contribution toward passenger comfort. 

 These curves for flying boats give values roughly twice those that main- 

 tain for landplanes. For the latter our modern transport planes pro- 

 vide over 10 square feet and 60 cubic feet per passenger. But from 

 the standpoint of comfort, it is perhaps figure 4 {C) which shows the 

 most important contribution, namely, reduction of noise. The decibel 

 unit (old scale) is used and it may be seen that from the days of the 

 Ford in which noise of 110 decibels existed, we are now in the 70- 

 decibel range. This 40-percent decrease is (as mentioned above) 

 based on the decibel unit which, in turn, is a logarithmic scale measure- 

 ment. The actual sound in our present-day air-transport cabins is 



