The Mercedes D.III is a German six-cylinder, liquid-cooled inline aircraft engine designed and built by Daimler. The engine was introduced in 1914 with an initial power output of 160 hp, though later variants in the early 1920s could 200hp with much greater reliability and ease of maintenance. This engine features a large aluminium crankcase as the main structural component, with separate steel cylinders bolted onto it. The cooling jackets cover the top two-thirds of the cylinder, feeding a radiator via connections at the back of the engine. It also features a prominent overhead cam operating the single intake and exhaust valves, powered by a shaft running up from the crankshaft at the rear of the engine. Ignition is provided by two sets of spark plugs, one located on either side of the cylinders, each powered by a separate magneto for redundancy. Fuel is fed into the cylinders via pipes on the left side of the engine, supplied from a twin-barrel carburettor located just above the crankcase. Both the fuel and oil reservoirs are pressurized by an air compressor run off the crank.