[1] The original Hoppi-Copter consisted of two contra-rotating rotors on a pole attached to a motorized backpack.

[2] Although it was capable of flight, it was extremely hard to control.

[3] Later prototypes of the Hoppi-Copter included versions with the pilot in a sitting position, and were in effect miniature one-man helicopters of a more conventional design, though retaining the contra-rotating rotors and thus obviating a tail rotor.

[1][4] Despite interest from the British Ministry of Supply in the 102 and 104 models,[5] none were adopted commercially.

[3] Data from Jane's All the World's Aircraft 1948[4]General characteristics Performance