Although it never progressed beyond the prototype stage, the Mil V-12 remains the largest and heaviest helicopter ever built. This helicopter has an airplane like fuselage, that has an internal volume about the size of an Antonov An-22. Typically, the helicopter has two cockpits on top of each other, with the lower having the largest windows. This fuselage has a regular tail plane with a vertical stabiliser and horizontal stabilisers attached to the rear fuselage. They have trapezium shaped end plates. The V-12 also has a sort of wings, with an inverse taper: to reduce the effects of the rotor downwash the widest chord is at the wing tips (and narrowest near the fuselage joint), where they are attached to the engine/gear box nacelles. Two turboshaft engines on each side power the two counterrotating five blade main rotors. They are in a transverse configuration, not often seen on helicopters. The fixed two wheel main gears, wings and nacelles are braced by a complex set of struts. All-in-all quite a sight!