The British Rail Class 56 is a type of diesel locomotive designed for heavy freight work. It is a Type 5 locomotive, with a Ruston-Paxman power unit developing 3,250 bhp (2,423 kW), and has a Co-Co wheel arrangement. Enthusiasts nicknamed them "Gridirons" (or "Grids" for short), due to the heavy grid-like cab air conditioning unit guard under the buffer beams. Under its Romanian railway factory nomenclature, the locomotive was named "Electroputere LDE 3500", with LDE coming from "Locomotivă Diesel-Electrică" (Diesel-Electric Locomotive) and the 3500 being the planned horsepower output.