Samuel Pierpont Langley became the third Secretary of the Smithsonian Institution in 1887.  In 1891, he began experiments with large, tandem-winged models powered by small steam and gasoline engines he called aerodromes.  After several failures with designs that were too fragile and under-powered to sustain themselves, Langley had his first genuine success on May 6, 1896, with his Aerodrome Number 5.  It made the world's first successful flight of an unpiloted, engine-driven, heavier-than-air craft of substantial size.