Brantly B-1 prototype (1946)
The Brantly B-1 was a 2-seat, coaxial-rotor helicopter designed by Newby O. Brantly and constructed by the Pennsylvania Elastic Company. In 1946, Brantly started flight testing the B-1 prototype (NX69125), which used a 150 hp Franklin O-335 engine in the fabric fuselage and two three-bladed rotors that rotated at 320 rpm and were fitted coaxially. The collective, cyclic, and differential controls were enclosed in the rotor hubs and ran in an oil-bath. Each rotor blade weighed 5.5 kilos. It also had a fixed wheel undercarriage with a tailwheel under the tailfin. Unfortunately, the design was too heavy and complex and was abandoned.