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
A model of this project worked out at Karlin was shown at Brussels in July 1947. It had two intermeshing two-bladed rotors, the hubs of which were very close together.
Also provided was a tricycle landing gear with the rear wheels directly below the twin vertical fins.
P.Lambermont "Helicopters and Autogyros of the World", 1958