[2][3][4] Emile Berliner, an inventor famous for his invention of the flat gramophone record, had experimented with intermeshing helicopters as early as 1907.

The Berliner Helicopter was successfully demonstrated throughout the 1920s, but interest was lost due to its limited controllability and engine-out abilities compared to the autogyro and conventional aircraft.

Emile initially intended his helicopter to have floats and to be used at low levels over water in case of an engine failure that would cause a forced landing.

[6] A Popular Mechanics article of the time supposed that his invention would be used as a "flying torpedo" more capable than an aeroplane at holding rich cities for ransom.

He followed on with a 570 lb, 80 hp Le Rhône engine powered, test rig that required assistants for stabilization.

His test rig, with two wheels and handlebars, resembled a wheelbarrow with an engine mounted in it, with a tall vertical shaft driving two counter-rotating propellers.

[9] In 1922, Henry Berliner developed a helicopter based on a surplus Nieuport 23 fuselage with a 220 hp radial engine driving two wing mounted counter-rotating rotors.

There it was flown by Air Service test pilot Harold R. Harris among others, achieving stable hovers of up to 15 feet.