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In the old days about a quarter of the trains operating around the Loop were lite engines dropping down the mountain after helping an eastbound train up to Summit. Engines 7439, 9130, 9236, and 7339 were the helper power from Extra 7518 East. They emerge from tunnel 10 and go around the loop on their way back to the helper spur at Bena on June 9, 1987. Now most of the heavy trains have DPU power and the helper engines stay with the train. Disk 45