An overall design plan for an indigenously developed large passenger-jet engine is expected to be released by the end of the year, the Commercial Aircraft Corporation of China (COMAC) confirmed Thursday. Trials of prototype components of the engine had already taken place, said Li Jibao, Deputy General Manager with the COMAC. A metal model of the engine went on public display in Shanghai Wednesday, arousing the curiosity of many enthusiasts. \"The model shown to public is a symbol of the accomplishments made in the first stage of developing the engine,\" said Li. A research and design team of 500 professionals is working on developing the engine. China\'s first self-developed jumbo jet, the C919, which will be equipped with the engine, is expected take off in 2014 after being rolled off the assemble line between the end of 2013 and the first half of 2014. It is expected to be put into service in 2016.