Avaliação comparativa de diferentes métodos de análise de estabilidade longitudinal estática aplicados a uma aeronave da competição SAE Brasil aerodesign

Abstract

This work deals with the evaluation of different methods of analysis of static longitudinal stability in order to analyze the differences in the results obtained for an aircraft destined for the SAE Brasil Aerodesign competition. For this, the analytical methods presented in two ways were evaluated, Perkins and Robert (1949) and Nelson (1998), and, for the static margin, the Gyles Aerodesign Pitch Stability Estimator software for longitudinal stability and control was also used. The main differences found between the methods presented in the two bibliographies were in the way of estimating the values of variation of the downwash angle with the wing attack angle and the distinction between lift and drag vectors and those fixed to the reference line of the acting plane on the wing and on the horizontal stabilizer. In this regard, it was possible to assess that the existing differences are negligible for stability calculations. For the variation of the downwash angle, with the methodology presented in Perkins and Robert (1949), minimum values were found 16% lower and maximum values 21.2% higher than those calculated following the method indicated by Nelson (1998), which presents results with greater variation. It was also observed the opportunity to reduce the static margin by 3.1 percentage points, respecting the requirements of the Aerosul team for this variable, which would imply a dimensional reduction of the plane and, consequently, a decrease in mass. With the software applied to the analyses, the static margin results fluctuated between those found with the analytical methods presented by the two bibliographies, with a minimum value of 0.5 percentage point less stable than that calculated with Nelson (1998), a reference currently used by team. Differences of up to 1.1° were also found between the results obtained with both methods for the downwash angle, with consequent variation in the angle of attack acting on the horizontal empennage. For this, it was observed that, for regimes closer to the horizontal empennage stall, a critical region of analysis, the differences in values obtained are small, therefore, the use of both analytical methods was considered satisfactory. [resumo fornecido pelo autor]