What was the first successful aircraft designed by the aviation pioneer who built the Sikorsky S-6?
Sikorsky S-6: The Sikorsky S-6 was a Russian single engine experimental aircraft similar to the S-5, built in 1911 by Igor Sikorsky. Igor Sikorsky: Igor Ivanovich Sikorsky (Russian: И́горь Ива́нович Сико́рский ; ] , "Ígor' Ivánovič Sikórskij"; , "Ihor Ivanovych Sikorskyi"; May 25, 1889 – October 26, 1972), was a Russian-American aviation pioneer in both helicopters and fixed-wing aircraft. Igor Sikorsky:  First success came with the S-2, the second aircraft of his design and construction.
S-2