Abstract: In accordance with the national research project in West Germany "Flight Control" （SFB-58 Flugfuhrung） it is necessary to develop an optimal baro/radio/inertial hybrid altimeter for the research aircraft DO-2S.For this purpose, the random error models for vertical accelerome-ters on inertial platform and a barometric altimeter under the conditions of landing approach are identified and estimated with the aid of two onboard data acquisition systems. The optimal estimate of ARIMA model of the associated random error sources is obtained by the time series analysis. A number of actual problems, such as data preprocessing and effect of measurement noise on error model, are also discussed.