HO 4-6-6-4 Union Pacific #3997 Steam Locomotive (ATHG97975)

This HO-scale Union Pacific 4-6-6-4 Challenger steam locomotive reproduces UP’s iconic Challenger for HO layouts, delivering authentic late-1940s to 1950s mainline power with period-correct detailing. The model reflects variations seen on UP Challengers, including the coal-burner and dual-stack configurations with tender coal extensions, and it represents road number 3997 in era-appropriate styling. Some Challengers wore UP’s two-tone gray passenger-service livery with yellow lettering, adding an extra layer of realism for layout enthusiasts.

Beyond its looks, the locomotive packs scale-accurate features: illuminated number boards and headlights that dim in reverse, a tender back-up light, and adjustable cab vents and windows. Front and rear engines pivot to negotiate 18" radius curves, and current pickup runs on all wheels for steady performance on both DC and DCC layouts. A detailed boiler backhead with printed gauges, plus synchronized sounds (chuff, whistle, bell, blow-down, air compressor, and more) and user-controlled effects, bring operation to life. New features include dual cube speakers for richer sound, a see-through firebox with a flicker effect, brighter LED headlights, and a sturdier loco-to-tender harness. Sound-equipped variants use a tender-mounted DCC decoder with SoundTraxx Tsunami2, offering full DCC functionality and NMRA compatibility, with CV tuning options and a CV chart included.