Assertion: helicopter | /r/HasProperty | designed by igor sikorsky
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Source sentences:
text: Some helicopters reached limited production, but it was not until 1942 that a helicopter designed by Igor Sikorsky reached full-scale production, with 131 aircraft built.
text: Designed by Igor Sikorsky and built by the Vought-Sikorsky Aircraft Division of the United Aircraft Corporation, the helicopter was the first to incorporate a single main rotor and tail rotor design.