A New Approach for the Estimation of the Aerodynamic Damping Characteristics of the ETF Demonstrator 2011-01-2649
Nautilus S.p.A. and the Polytechnic of Turin, in cooperation with Blue Engineering, have developed a very versatile product, the ELETTRA Twin Flyers  (ETF), which consists in a very innovative remotely-piloted airship equipped with high precision sensors and communication devices. This multipurpose platform is particularly suitable for border and maritime surveillance missions and for telecommunication, both in military and civil area.
To assess the actual maneuver capabilities of the airship , a prototype of reduced size and complexity has been assembled . Before the flight tests a further assessment on the flight simulator is needed, because the first version of the software is tuned on the full scale prototype.
Steady state performance and static stability of the demonstrator have been evaluated with CFD analysis. The dynamic stability have been evaluated using CFD as well, because the classical methods to calculate dynamic derivatives, using USAF Datcom or wind tunnel tests, are not accurate enough, for unconventional shaped aircrafts in particular. Moreover, these methods refer to body pitch and plunge motion: it follows that derivatives are affected to a great extent by the frequency  and these derivatives are not suitable for aircraft model. To overcome all of these shortcomings, an innovative approach, based on looping and heaving motion has been used to calculate the dynamic derivative in order to update the flight simulator and thus to train the pilot with a realistic mathematical model.