At the end of the development cycle, a new aircraft is certified by means of in-flight flutter tests. These tests consist of flying the aircraft at different airspeeds and measuring the accelerations at a limited number of locations on the aircraft structure. The scope is to open the flight domain by verifying that the aircraft does not suffer from aero-elastic instabilities such as flutter.
In this paper, some modern frequency-domain modal parameter estimation methods are applied to in-flight data of a large aircraft. Traditional sine sweep excitation was applied at the control surfaces. However, during the test the aircraft passed through a turbulent zone. The sweep excitation was immediately stopped, but the on-board data acquisition system continued to record the aircraft vibration response. After quitting the turbulent zone, the sweep test was reinitiated. The present data thus allows for a comparison between artificial and natural excitation. More specifically, aspects such as data pre-processing, easiness of the parameter extraction process and the accuracy of the results are investigated.