page_title: GE Evolution Series
section_title: ET44AC/ET44C4
hierarchical_section_title: GE Evolution Series / Models / ET44AC/ET44C4
caption_attribution_description: English: General Electric ET44AH locomotive of the Union Pacific Railroad.
context_page_description: The Evolution Series is a line of diesel locomotives built by GE Transportation Systems, initially designed to meet the U.S. EPA's Tier 2 locomotive emissions standards that took effect in 2005. The first pre-production units were built in 2003. Evolution Series locomotives are equipped with either AC or DC traction motors, depending on the customer's preference. All are powered by the GE GEVO engine.
  The Evolution Series was named as one of the "10 Locomotives That Changed Railroading" in the January 2009 issue of Trains Magazine. It was the only locomotive introduced after 1972 to be included in that list.
  The Evolution Series, mainly the ES44DC, ES44AC, and ET44AC, are some of the best-selling and most successful freight locomotives in United States history.
context_section_description: The ET44AC (Evolution Series Tier 4, 4400 HP, AC traction) replaces the ES44AC model.  These locomotives have been ordered by most of the Class I railroads in North America, including Union Pacific, CSX Transportation, Norfolk Southern and Canadian National Railway. BNSF Railway will be receiving similar ET44C4 locomotives, which have no traction motor on the middle axle of each truck. CSX designates their ET44ACs as ET44AH, due to their locomotives being Heavy-ballasted.
  In the summer of 2012, GE unveiled its first Tier 4 emissions-compliant locomotive, now officially named the ET44AC. The prototype demonstrators, as well as current production units, are visually quite different from previous models. First, the "ET" is 74 feet 6 inches (22.71 m) long - an increase of 16 inches (0.41 m) from the 73-foot-2-inch (22.30 m) length of all previous GE 6-axle models beginning with the "DASH 9" series in 1993. While the front third of the locomotive, including the control cab, is unchanged, the rear two-thirds is noticeably different. On Tier 4 demonstrator units the entire midsection above the prime mover is raised to accommodate an advanced exhaust treatment system; it is seen as a "hump" that rises above the rest of the locomotive considerably. Production units have this hump only over the exhaust manifold directly ahead of the radiator, rather than encompassing the entire midsection. Also, the radiator section is much larger than that of earlier "ES" units, featuring a two-fan split-cooling system located inside a very large, angular compartment. Grilles under the radiator section have been smoothed out, and there are two extra air intakes on the rear of the locomotive hood. ET44ACs are all equipped with Graham-White electronic bells (E-bells). Tier 4 demonstrator units are equipped with two airhorns: a three-chime horn – facing forward – located behind the cab and a rear-facing two-chime horn protruding from the back of the radiator. Production units feature the now-standard Nathan-Airchime model K5HL-R2 "Evolution" airhorn mounted on the hood slightly forward of the placement location used on previous models.
  A DC variant of the ET44AC has not been cataloged by General Electric.
caption: Union Pacific 2668 ET44AC (C45AH designation)
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