Dutch Roll Identification for an Ultra-Light Airplane

Angelo Lerro, Department of Mechanical and Aerospace Engineering, Politecnico di Torino (Italy)
Luca de Pasquale, Department of Mechanical and Aerospace Engineering, Politecnico di Torino (Italy)
Piero Gili, Department of Mechanical and Aerospace Engineering, Politecnico di Torino (Italy)
Lorenzo Trainelli, Department of Aerospace Science and Technology, Politecnico di Milano (Italy)
Alberto Rolando, PACE Aerospace & IT GmbH (Germany)

Abstract

Dutch Roll characteristics are crucial for acceptable flying and handling qualities. Their prediction can be obtained in multiple ways, one of the simplest being through a mathematical model whose aerodynamic database is built from semi-empirical formulas. Even when dealing with a fairly simple aircraft such as Nando Groppo’s G70, this task can be trickier than expected. Indeed, this work shows that, even for a conventional aft-tail ultra-light aircraft, flight tests are crucial to identify the airplane’s dynamic characteristics.

In this work, Dutch Roll identification is performed in both time and frequency domains for the G70. A flight test campaign was performed using standard certification flight test techniques, including Dutch Roll excitation. Flight data were retrieved using a dedicated flight test instrumentation suite installed on board. By using such data, the time domain approach was used to identify the main aerodynamic coefficients, also considering the inertia coupling due to the propeller’s rotating mass.

Identification in the frequency domain was further explored to verify the investigation of the overall Dutch Roll characteristics. Based on the identified aerodynamic database, simulations are performed to compare the results of the semi-empirical formulas, the identified model and flight test data.