Identification of modal models od helicopters using in-flight measuremants

The paper presents a new methodology of modal model identification based on in-operation system response measurements. This methodology consists in estimation of cross- and auto-correlation of acceleration acquired at all measuring points. The method was applied to helicopter modal model identification basing on in-flight measurement results. The obtained model parameters have been compared with the ground modal test results. This comparison permits evaluating of level of each mode excitation during the operation and can be applied to structure modification and diagnostics.