The CZAL (Aero) factory at Karlin, led by Jaroslav Slechta, developed the XE-1 two-seat helicopter project in 1947, fitted with twin inter-meshing rotors and a 100hp Praga M-197 engine. This led to the XE-II (OK-FYA) which flew on 14 December 1949. It was an open single-seater with a single three-blade main rotor and 75hp Praga D engine.

R.Simpson "Airlife's Helicopter and Rotorcraft", 1998

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