With the contraprops and messed up airflow, I'd say it's the other way round. Back in my uni years we had a very old lecturer - aerodynamicist, who used to come into close touch with russian technology in his younger years. He had a hell of a lot to say, so in really simple terms - the overall propeller efficiency is a product of its mechanical and aerodynamic efficiency. The aerodynamic efficiency is the amount of forward thrust generated from a unit of power. Conventional propellers actually lose quite a lot of this power by turning it into the swirl energy, which rotates behind the propeller with no apparent use, I believe even the most modern ones like the curved ones on the C130J do lose about 30% on the swirl. The second propeller in the contraprop utilizes mainly the swirl energy, turning it back into the direct stream - theoretically. Quoting a book on Tupolev, the aerodynamic efficiency of the contraprops mounted on the NK-12 (Tu-95, An-22) is 96% - compares to 60-80% of a modern conventional prop. the biggest problems of this kind of a design are but significant added weight, complexity and maintenance requirements, since it is all a heavy piece of machinery. Also as you guys mention, the added noise is tremendous - i don't know where this one is generated, but having heard the whine of the mighty Bear myself on an airshow, it really cuts into the bone. There are stories of submarine crews who could hear the whine of a Bear cruising 10 km above.
BAe-146: this was discussed somewhere around here not long ago. Allegedly the initial design from 80s counted on operations to remote airstrips, where an engine out on a twin would ground the craft and have it wait for a replacement unit. On a quad, that would constitute a deferred defect under the MEL and warrant at least a technical non rev flight back to the base.
B777: that's more of an a.net stuff here
