Penny-farthing also refers to the "traditional" rotor arrangement found on most helicopters: a large horizontal rotor for lift, and a smaller vertical tail rotor to counteract the effects of torque. The derivation of the term, from the relative sizes of the two discs, is apparently the same as for the bicycle.
This was the configuration that Igor Sikorsky finally perfected in 1947 with his VS-300 model, which has been the blueprint for most (but not all) rotorcraft since then. Some competing arrangements include tandem rotors (such as on the CH-47 Chinook), coaxial rotors (used most notably by Kamov in Russia), the Aerospatiale fenestron fan-in-fin design, and more recently the NOTAR tail-rotor-less system.
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