Nagler-Rolz NR 54 V2

During World War II, Bruno Nagler designed this sole prototype as a “backpack” portable helicopter. Although intended for sport or commercial courier duties, the German Air Ministry funded the project for military purposes with specifications for one-hour endurance and a 50-kilometer (31-mile) operational radius. The blade-mounted engines proved unreliable because the tremendous centrifugal forces of rotation interfered with carburation. The NR 54 V2 underwent ground testing at the end of the war, but it never flew.