The closest that I have seen was a DC-3 that had a winch mounted right behind the cockpit door. It was a Butler turbine conversion with the large door that could take LD3's in the cabin. A lot of Herks and other tailloaders also can be equipt a winch to help move pallets in the cabin.
The neatest system that I have seen was on an IL-76. Basicly it was a traveling gatry that ran along the roof of the cabin. we would just pull up with the flat. This crane would grab it and then carry it down to the cabin where it would go. Really neat. I under stand that a number of russian cargo aircraft use this system.
The closest I have used it that on the Metros that the flight service that I work for use just standard unpowered rollers. When we convert them to a freighter conversion they are placed into the floor walkway that runs down the center of that aircraft. This makes the floor nice and flat and very easy to slide boxes all the way down the center of the aircraft.
What kind of weight penalty does the powered cargo systems place on the payload??
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.