The Wright brothers’ 1903 aircraft engine had four cylinders.
The brothers and their mechanic, Charlie Taylor, built the engine for the Wright Flyer after automobile engines available at the time proved too heavy for their aircraft. The water-cooled, inline four-cylinder engine produced roughly 12 horsepower at first, although later measurements and reconstructions have produced somewhat different figures.
Its design was comparatively simple and light. An aluminium crankcase reduced weight, while the engine drove two counter-rotating propellers through chains. The propellers turned in opposite directions to cancel torque and help keep the aircraft stable.
The four-cylinder layout is easy to confuse with later aviation engines, many of which used radial or V-shaped arrangements. The 1903 Flyer’s engine was an inline four-cylinder machine specifically adapted to the brothers’ weight and power requirements.