NO. 3 LANGLEY MEMOIR ON MECHANICAL FLIGHT 135 



These models, Nos. 5 and 6, which had flown so successfully in 189(5, had, 

 during the preceding 1 twelve months, been completely overhauled and thoroughly 

 tested in preparing them for trials in actual flight. Many pendulum tests were 

 made on both aerodromes, and it was found after repeated trial that each could 

 be depended on to show a lift of sixty per cent of its flying weight. 



This was more than sufficient for flight, but in order to insure successful 

 trials and avoid delay no aerodrome was launched until it had shown previously 

 its ability to generate enough power to maintain for at least two minutes a lift 

 of at least fifty per cent of the total flying weight. 



Models Nos. 5 and 6, having thus proved their readiness for trial in flight, 

 were accordingly, in April, 1899, taken to Chopawamsic Island, together with 

 the old " overhead " launching apparatus and the new one above described, and 

 placed on a small house-boat similar to the one which had been used in 1896. 

 Two men were detailed for this special work, and were first employed in mount- 

 ing the old launching apparatus for a few preliminary tests with it, in order to 

 make sure that the aerodromes were in proper working order before trying 

 them on the new " underneath " one. After considerable delay, due to various 

 causes, this apparatus and the aerodromes were got into proper working con- 

 dition, and during June, July and August the following flights were made with 

 these machines, the record being condensed from the reports made by the writer 

 to Mr. Langley while he was abroad. 



Condensed Record of Flights of Aerodromes Nos. 5 and 6 from 

 June 7 to August 3, 1899 



JUNE 7 — aerodrome no. 6 



After making a preliminary test of the engines and boiler, with the aero- 

 drome mounted on benches inside the house-boat, to insure that everything con- 

 nected with the power plant was in proper working order, the aerodrome was 

 mounted on the launching apparatus on top of the house, the various parts 

 were assembled and everything made ready for a flight. As it was calculated 

 that this aerodrome would require a soaring speed of something like twenty-five 

 feet a second, the springs which furnished the motive power for the initial ac- 

 celeration of the car were adjusted to the proper tension to cause it to reach a 

 speed of approximately twenty-three feet a second at the moment of launch- 

 ing. Everything being in readiness the burners were lighted but worked some- 

 what sluggishly at first, so that two minutes were consumed in raising a steam 

 pressure of 110 pounds. Although this pressure should have been reached within 

 one minute after lighting the burners, and the extra minute which had been 

 consumed had made a drain on the supply of fuel and water which should have 



