Open AccessINFLUENCE OF MINIFLAPS ON SAILPLANE FLIGHT CHARACTERISTICS
Author(s) -
Peep Lauk,
Karl-Eerik Unt
Publication year - 2015
Publication title -
aviation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.239
H-Index - 13
eISSN - 1822-4180
pISSN - 1648-7788
DOI - 10.3846/16487788.2015.1104793
Subject(s) - wing , trailing edge , chord (peer to peer) , lift coefficient , climb , wing loading , airfoil , leading edge , lift to drag ratio , structural engineering , physics , materials science , chemistry , geometry , aerodynamics , mechanics , aerospace engineering , mathematics , angle of attack , engineering , turbulence , computer science , reynolds number , distributed computing
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.