The Rotec R3600 is a nine-cylinder radial engine built by Rotec Engineering PTY LTD in Australia. Initially released in 2005, it was a followup of the 7-cylinder Rotec R2800 released five years earlier. Both this engine and its smaller cousin have been frequently used as both replacement engines for vintage World War 1 aircraft, and replica aircraft from the same vintage. Some notable aircraft this engine has been used in are the Fokker Triplane, Sopwith Camel and the Nieuport 17.
Note that these engines are not limited to only aircraft applications, JRL Cycles has converted an R3600 for use in a motorcycle.