NO. 3 LANGLEY MEMOIR ON MECHANICAL FLIGHT 131 



A brief account has already been give?i of the attempts made by Mr. Lang- 

 ley to secure a suitable gasoline engine for the large aerodrome, but the difficul 

 ties encountered in the search have not perhaps been sufficiently emphasized. 

 At tins time (1898) the automobile industry, through which has come the de- 

 velopment of the gasoline engine, was iu its infancy, and there were few build- 

 ers either in the United States or Europe who were attempting anything but 

 rough and heavy construction. Many of them were enthusiastic over the possi- 

 bilities of the internal combustion engine, and were ready to talk of devising 

 such an engine as the aerodrome would require, but few were willing to guaran- 

 tee any such definite results as were demanded. However, the prospects of se- 

 curing a suitable gasoline engine from a reliable builder within a reasonable 

 time seemed so strong that it was decided early in 1898 to begin the construc- 

 tion of the frame on the general plan which would probably be best adapted for 

 use with a gasoline engine, and in case it finally proved impossible to secure such 

 an engine, to construct later a steam plant which could be adapted to this par- 

 ticular frame. 



Some tentative work on the construction of the frame was accordingly be- 

 gun in the summer of 1898, some months before an engine builder was found 

 who seemed likely to be successful in furnishing the engines. An extensive 

 series of tests on propellers was also made at this time for the immediate pur- 

 pose of determining what form and size would be best, since the dimensions of 

 the transverse frame could not be definitely settled until it was known how large 

 the propellers would need to be. 



Preliminary designs were also begun for the wings, rudders, and launching 

 apparatus, but when the point was reached of actually making the working 

 drawings for these, it was seen that the change in the scale of the work re- 

 quired many important modifications in constructional details. As the models 

 had flown successfully only three times, and in each case under practically the 

 same conditions, it was felt that it would be unwise to make changes in im- 

 portant details without first making a series of tests of the models in flight to 

 determine the effect of such changes. It was therefore decided to completely 

 overhaul Models Nos. 5 and G, strengthening them in many important parts and 

 " timing up " their power plants, which had slightly deteriorated since they 

 were last used in November, 1896. When the work of preparing these models 

 for further experiments was begun it was thought that it would require at most 

 only a few weeks, but as it progressed it was found that certain parts of the 

 mechanical work on the engines had been so poorly executed originally that it 

 would be necessary to practically rebuild the engines. The final result was that 

 the power plants of both aerodromes were entirely rebuilt, and they were not 

 ready for actual test in flight until the spring of 1899. 



