Chicago IL.
USA
In 1923 Thomas O Perry / Chicago Helicopters Ltd built a two-place helicopter with coaxial counter-rotating rotors, collective pitch control. A novel approach to power-off descent was used—with a hand crank, the rotors could be moved to a position perpendicular to the direction of flight, transforming the helicopter into a sort-of biplane. A horizontal tail surface mounted on a boom was then used as elevator. A prototype was built by Plamondon Mfg Co of Chicago and flight-tested at Lombard IL. Results were not publicized but apparently were unsatisfactory.
Engine: 110hp LeRhone
Rotor diameter: 47’0″
Rotor blade chord: 4’0″
Useful load: 1020 lb
Seats: 2
All Aero 