Influence of Miniflaps on Sailplane Flight Characteristics

Abstract

The effect of miniflaps for increasing the L/D ratio and the lift coefficient has been studied on airliners as well as on UAV-s and wind turbines. For sailplanes the lift when Cl > 1.0 is of main interest. As the maximum wing loading of racing sailplanes reaches 60–62 kg/m2, it is necessary to achieve a high Cl max (1.7–1.8) in thermals. In this case the decrease in TAS caused by a high Cl max even compensates for the drop of the L/D ratio to a certain extent, as the climb speed will increase when the spiral flight radius diminishes in thermals. To bring the L/D to Cl > 1.0, a 2% chord miniflap at a 30° deflection angle was attached to the trailing edge of a Jantar-Standard 3 type sailplane wing (airfoil NN-8). In flight tests it was found that the miniflap increased the sailplane‘s Cl max to 1.35–1.66, i.e. by 23% (Re 1.0–0.92×106). At the same time the L/D ratio Cl increased by over 1.0. Especially good L/D improvement was noted with Cl at 1.13–1.19. In thermal Cl of 1.57–1.65 the roll control was good. At lower Cl < 1.0 values, the miniflap reduced the L/D ratio in comparison with a normal configuration.

Analisis karakteristik aerodinamika telescopic wing dengan konfigurasi sayap flying wing dan glider menggunakan metode pendekatan simulasi CFD

“…Untuk model penerbangan dengan kecepatan terbang rendah, pesawat model jenis glider sangat relevan untuk diaplikasikan. Pesawat glider memiliki coefficient lift (C L ) yang tinggi hingga mampu terbang dengan kecepatan rendah dan efiesiensi penggunaan motor penggerak lebih baik [8].…”

Impact of Variable Geometry Miniflaps on Sailplane Flight Characteristics

“…At landing, the best miniflap deflection angle was +90 degrees, due to the biggest drag that this angle helped to generate. The author of this paper ran flight tests with 2% length of the chord fixed deflection angle miniflaps on the Jantar-Standard 3 sailplane (Lauk, Unt 2015) (Fig. 2).…”