222 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
struction and tests of the large aeroplane up to December 8, 1903, 
reports that he obtained from the propulsion plant a static thrust 
of 450 pounds, and that he once ran the engine under full load for 10 
hours consecutively. This thrust is nearly 100 pounds more than 
that commonly obtamed at Hammondsport with the same plant, 
and 20 pounds more than the static thrust obtained with the Curtiss 
motor on the day when it flew the aeroplane with 1,520 pounds 
ageregate weight. Hence, by restoring the engine and propellers to 
their original normal working condition they should be able to drive 
the aeroplane in successful flight with an aggregate weight of nearly 
1,600 pounds, even when hampered with the floats and their sustain- 
ing truss work. With a thrust of 450 pounds, the Langley aero- 
plane, without floats, restored to its original condition and provided 
with stronger bearings, should be able to carry a man and sufficient 
supplies for a voyage lasting practically the whole day. 
Dr. Langley’s aerotechnic work may be briefly summarized as 
follows: 
1. His aerodynamic experiments, some published and some as yet 
unpublished, were complete enough to form a basis for practical 
pioneer aviation. 
2. He built and launched, in 1896, the first steam model aeroplane 
capable of prolonged free flight, and possessing good inherent sta- 
bility. 
3. He built the first internal-combustion motor suitable for a practi- 
cal man-carrying aeroplane. 
4. He developed and successfully launched the first gasoline model 
aeroplane capable of sustained free flight. 
5. He developed and built the first man-carrying aeroplane capable 
of sustained free flight. 
