Abstract: In a planetary transmission system, all parts' temperature and their fields are important to the system's performance and reliability. With the planetary transmission of a helicopter main gear system as a study object, a power loss model and a heat transfer coefficient model are built up. On the basis of the thermal network method, the steady temperature field is predicted, which offers an effective method for steady thermal analysis of planetary transmission. The basis for its transient thermal analysis is also established.

Key words: p lanetary t ransm ission system, thermal netwo rk analysis, survivability