The difficulties of design determination of the quantitative characteristics of weight, elas
ticity, damping, critical frequencies of fast revolving rotors are demonstrated. It is suggested to use two
approaches in order to obtain accurate and stable solutions of ill conditioned reverse problems of rotor
dynamics. The first one concerns the reduction of design model size. It is shown that relatively uncom
plicated design rotor models are used as they were considered the most effective and stable, and match
the selected design scheme and parameter values (hardness, weights, deflections, etc.) obtained as a
result of experiments or calculations. The second approach deals with statistical method of the
increase of solution stability. Its efficiency was shown while identifying rotor eccentricity by the exam
ple of five mass rotor model.