mhi developed and put into operation the 1,200c class m701d gas turbine and the 1,400c class m501f/m701f gas turbines. their high efficiency and reliability for combined cycle applications have been proven in field operat......mhi developed and put into operation the 1,200c class m701d gas turbine and the 1,400c class m501f/m701f gas turbines. their high efficiency and reliability for combined cycle applications have been proven in field operations. based on the fact that combined cycle efficiency is highly dependent on the turbine inlet temperature, mhi newly developed the 1,500c class m501g/m701g gas turbines, which mhi calls its g-series. development of the g-series gas turbine was started in the early 1990s, and the design was based on the following concepts. first, proven features from the f-series were maintained. second, the most advanced technologies in aerodynamic design, heat transfer design and new materials were introduced into the g-series. third, our conventional design, critical for industrial gas turbines, was applied. fourth, the turbine inlet temperature was increased to the extent where the nox level and the metal temperature could be maintained at the same level as the f-series. m501g rotor finally, verification tests were carried out prior to the production of the m501g gas turbine to ensure its high reliability. the trial operation of the m501g was conducted in 1997 in the combined cycle verification plant in mhi takasago, japan. after its successful trial operation was completed, commercial operation of the m501g started in june 1997. m501g combined cycle verifacition plant of mhl takasago machinery works