Model Validation and Simulation of a Light Twin Engine Aircraft

 

Mazzoni S.*, Penati M.E.*, Rossi V.°

*University of  Bologna, Department of Electronics Computer Science and Systems

°University of  Bologna, Department of Aerospace Engineering

Viale Risorgimento 2  Bologna, Italy

Ph. +39-051-2093036 / email: smazzoni@deis.unibo.it – Fax: +39-051-2093073

 

 

 

 

 

 

At the Aerospace Department of the Forlì Campus of University of Bologna a DGNSS Instrumental Approach System called FO-DIAS (Bertoni, 1998, Chiarini, et al., 1999, 2000, Castaldi, et al., 2001) is being developed.

The aim of this work is to provide the model of the aircraft and its autopilot for the approach flight condition, that will be integrated in the overall simulation system: the aircraft considered is a light twin engine aircraft (Piper PA-30 B Turbo). 

The research has been divided into three parts: the determination of the aircraft dynamics mathematical model, its validation and the aircraft autopilot project.

The aircraft dynamic model, defined in the body-fixed reference frame, uses the flight-path variables (flight velocity module, angle of attack and sideslip angle) instead of the velocity components along the reference frame axes, in order to simplify the aerodynamic loads determination and to improve the numerical solution accuracy. The aerodynamic and thrust forces and moments have been modeled following the classical approach, based on the aircraft stability and control derivatives.

The aircraft dynamic model is made up by the general force and mo­ment equations for a rigid body in the body-fixed reference frame: the motion system equations are non­-linear and the longitudinal and the lateral-directional dynamics are coupled. The modified dyna­mic models turn out to be implicit, because the aero­­dy­na­mic forces and moments depend upon the time-deriva­tives of some state variables.

The validation model method has been obtained com­paring the dynamic model here analysed with an old model of the same aircraft developed by the NASA in a RPV application. The latter is a nonlinear model, using the small perturbation theory, and is based on the forces and moments equations partially simplified. The analysis of these two systems is based on the lateral and longitu­dinal dynamics linearization and decoupling, in the same trim condition, and it shows that the dy­na­mics characteristics of the two models are very similar.

Up to now the autopilot which has been developed concerns only the approach phase, but also the autopilot for the holding phase will be developed.