Neyen - Screw plane, German Patent 222868 of 1910
German patent specification drawings filed by Emil Neyen in 1910 for a multi-rotor screw plane, prepared as legal documents for the imperial patent office and examiners. Pen-and-ink plan, elevation and section views in thin uniform line, with numbered callouts, dotted hidden edges, ruled airflow hatching over a wing profile, and handwritten patent numbers on aged paper.
