N 4-6-6-4 Union Pacific #3997 Steam Locomotive (ATH25545)

Union Pacific 4-6-6-4 Challenger steam locomotive, UP #3997, in N scale, is a fully assembled, ready-to-run model designed to faithfully reproduce the Challenger class’s wartime-era appearance and performance on modern layouts.

Road-number specific features for #3997 include coal burner, dual smokestack, and tender bunker coal extensions, reflecting the 1940s–1959 era. The model features DCC-ready Quick Plug plug-and-play technology, a heavy die-cast frame, LED lighting, see-through running boards and cab windows, a full cab interior with boiler backhead and printed gauges, and individually applied piping and valves for authentic detailing. It uses a five-pole motor with a flywheel for smooth power delivery and includes McHenry scale knuckle couplers for authentic operation, along with pivoting front and rear engines that let the locomotive negotiate 11-inch radius curves, with a minimum radius of 15 inches on typical layouts. Some versions are sound-equipped, featuring a tender-mounted DCC decoder with SoundTraxx Tsunami2 sound for engine, whistle, and bell sounds, full DCC functionality, NMRA compatibility, and enhanced slow-speed control.