This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Vortex ring helicopter. The straight arrows indicate airflow circulation about the rotor disc The helicopter shown is the RAH Comanche en El Grafo Xmnemonic en Xmnemonic original upload log page en Vringrah Xmnemonic bytes no ring diagram revised modeling and rendering done by myself Xmnemonic bytes no ring diagram