Samuel Pierpont Langley
Manly helped Smithsonian Institution Secretary Samuel Pierpont Langley build The Great Aerodrome, which was intended to be a manned, powered, winged flying machine. Manly made major contributions to the development of the aircraft's revolutionary 52 hp gasoline-fueled radial engine, called the Manly-Balzer engine. Manly attempted to pilot the Aerodrome in its only two tests, October and December 1903. The machine failed to fly both times, plunging into the Potomac River after its launch from a houseboat. Manly was rescued unhurt, although he was briefly trapped underwater after the second test.