Comparison of Damping Estimation Techniques for Flight Tests

Abstract

Damping estimation plays a very critical role in flutter flight testing of an aircraft. Highly damped structures are more stable than lightly damped structures. Different techniques are used in aerospace community for the computation of damping. This paper describes and compares two damping estimation techniques which are Random Decrement & Half Power method. Half power method was further evaluated with output only and transfer function based computation. Random decrement method (RDD) was used for the time domain data analysis whereas half power method was used for frequency domain analysis. Each technique has its own merits and demerits. These techniques have been analyzed and discussed based on the actual flight test data. Both techniques provided comparable results for the data at similar test conditions. However, RDD technique gives better damping estimation for closely spaced modes and poor signal to noise ratios.