Assertion: rotor helicopter | /r/HasProperty | designated as the vertol model
Facets:
Source sentences:
text: The Chinook was originally designed by Vertol, which had begun work in 1957 on a new tandem-rotor helicopter, designated as the Vertol Model 107 or V-107.
text: During 1957, Vertol commenced work upon a new tandem-rotor helicopter, designated as the Vertol Model 107 or V-107.