High speed dynamic balance of power turbine rotor which generally runs over the second bending critical speed is a key technique in developing turbine shaft engine.This paper presents an improved multispeed

multiplane and step by step balance precedure developed to balance a power turbine rotor with a long slender hollow shaft

elastic supports and squeeze film dampers

and inherent torque tube.A group of precise balance collars are designed for adding trial masses.A set of balance steps and balance technologies are summarized.Criteria for evaluating the quality are established which involve the limits of both vibration displacement of shaft and vibration acceleration of supports.The procedure is carried out throughout the whole operating speed range and the highest balance speed is over 20

000 rpm.It has been successfully applied to balancing the power turbine rotor in practice.