My Dad worked for Kaman Aircraft in the 50's and early 60's as the Chief Rotor Blade technician. He was responsible for blade manufacture, inspection and repair. These were the days when turbine engine technology was still being perfected. Kaman Aircraft was the first to incorporate a turbine engine into helicopters. Kaman Aircraft benefited from WW2 German engineering. After the war, Anton Flettner immigrated to the USA under Operation Paperclip and became Head Design Engineer at Kaman. Flettner designed helicopters using counter rotating intermeshing main rotor blades. This eliminated the need for the torque-cancelling tail rotor which consumes 30% of the engine power.
I remember this altitude record day. When Dad came home from work he was very happy. We always talked about his work and aircraft. This record setting day was celebratory in our house. Almost 30,000 feet in a helicopter using 1959 technology.