Common in aircraft with propellers, a radial engine has its pistons in a circular arrangement around and attached to the crankshaft. This engine is not as widely used today as in the World War II era, but it still has many advantages that make it practical for an airplane. Browse through the large inventory on eBay to find a radial aircraft engine, or look for specific parts such as rocker assemblies and exhaust gaskets. One of the main reasons these engines are good for use in planes is that they are capable of producing a lot of horsepower. A typical model in a B-17 plane, for instance, can produce 1,200 hp with a relatively low rpm. If you do not pilot real planes but find them fascinating anyway, consider a model radial engine kit that allows you to build an authentic-looking replica and gain a clearer understanding of how these engines work. Some models come fully assembled, in case you would prefer to simply display one on your bookshelf rather than take the time to build it. A model radial engine can also make a great gift for a serious airplane enthusiast.