258 ANNUAL REPORT SMITHSONIAN INSTITUTION, 195 5 



has added to human knowledge; but he is always gratified when his 

 work is recognized as good by those competent to judge." 



A second important benefit accruing from work in the PE.T was 

 more positive information about the best location of engine nacelles. 

 The engines of the Ford Tri-motor, and similar aircraft of the twen- 

 ties, were hung below the wing. As a consequence of research reported 

 confidentially in 1930, multiengine aircraft designed thereafter had 

 their engines faired into the leading edge of the wing with an impor- 

 tant gain in speed. 



The systematic work accomplished in the PUT led to other practical 

 design changes. For example, it was possible to obtain an accurate 

 estimate of the drag caused by such apparently insignificant details as 

 the location of a gasoline filler cap. Similarly, engineers studied the 

 aerodynamic interference of wings and fuselage, and the use of fillets 

 to reduce the interference was proposed. (In 1928 the NACA pub- 

 lished its first Technical Note on this subject, by Melvin N. Gough.) 



That the fixed landing gear represented a large amount of drag had 

 long been appreciated, but it was not until the PE.T became operative 

 that the drag penalties of fixed landing gear could be determined pre- 

 cisely. The higher speeds made possible by use of the NACA cowling, 

 the wing positioning of the engine nacelles, the filleting of wing- 

 fuselage junctures, and other aerodynamic refhiements now made 

 attractive the investment of added cost and weight implicit in retract- 

 able landing gear. 



In 1933, looking at the gains from the research at its Langley Lab- 

 oratory, the Committee said: "No money estimate can be placed on 

 the value of superior performance of aircraft in warfare . . . nor can 

 a money estimate be placed on . . . improved safety. . . . The value 

 in dollars and cents of improved efficiency in aircraft resulting from 

 the Committee's work can, however, be fairly estimated. For example, 

 the results of . . . researches completed by the Committee within the 

 last few years, show that savings in money alone will be made possible 

 in excess annually of the total appropriations for the Committee since 

 its establishment in 1915." 



The economic depression that began with the stock-market crash of 

 1929 was not an unmixed evil for the NACA. Although there were 

 strong pressures to reduce operating expenditures, these were success- 

 fully resisted, in the main, by such impressive evidence of the money 

 value of the Committee's work as that just cited. On the favorable side 

 was the opportunity for the NACA to construct at depression costs 

 new research equipment with funds already appropriated, and the 

 availability of engineers, from whom many of its future leaders have 

 developed. 



The 30- by 60-foot, "full-scale" wind tunnel and the 2,000- foot tow- 

 ing tank (for study of hydrodynamic characteristics of water-based 



