How did helicopters change from the olden days to the new days?

Answer 1

The first human lifting helicopters were multi rotor craft where two rotors generating lift cancelled out each other's torque.

The earliest man carrying helicopters were flown by Frenchmen Jaques and Lois Breguet and also Paul Cornu. The Breguet craft flew tethered but Cornu's craft lifted off untethered in 1907.

The first military helicopter, the Austro-Hungarian PKZ-2 had contra-rotating blades and flew in 1918, demonstrated in front of military officials and specifically intended as an combat observation platform. Other craft were developed through the 1920s and achieved long flights of many kilometers but the first highly practical Helicopter was the German FockeWulf FW61. It had two main rotors like a Chinook, but mounted side by side rather than fore and aft. It was developed into the Combat Fa223 which was used in WW2 for rescues, Vehicle lifting and crashed aircraft recovery.

The countermeshing Flettner 282 was used for naval reconnaissance and submarine spotting and was used for artillery spotting on the Eastern Front. The flettner 282, the world's first production helicopter still holds the record of most mass lifted per engine horsepower. No helicopter since has surpassed it in efficiency or ease of handling.

Modern Helicopters based on Igor Sikorsky's single main rotor designs are more difficult to fly than the inherently balanced Flettner design that was perfected earlier and flew first. The design that Sikorsky popularised is less efficient as it uses a tail rotor and consumes around 20% of the engine power just to try to stop the craft spinning out of control. Most helicopter fatalities result from failures of this inefficient system. Being the main allied helicopter design of ww2, despite it's inferior capabilities, the aggressive Sikorsky and Bell companies solved most of their control difficulties and large military contracts helped to dominate the last 40 years of helicopter development. Attempts to modernise the helicopter focus on a return to the earlier more efficient system of having two counter-rotating main rotors