Research activities on light aircraft analysis and optimization at University of Naples

ABSTRACT The present paper deals with research activities performed by the authors on light aircraft analysis and optimization. The research group has worked for more than 15 years on research programs addressed to the aerodynamic analysis and aerodynamic optimization of light , ultralight (ULM) aircraft and sailplanes. 1.Experimental investigation on tip device for induced drag reduction Deep research activities have been carried out on tip shape and tip device to reduce induced drag and to improve aircraft drag characteristics at high angles of attack (typical of climbing in thermal of sailplanes and hang-gliders). An elliptical wing has been used to perform aerodynamic measurements in the main wind-tunnel belonging to Aerospace Department at University of Naples. The elliptical wing semi-model was made in such a way to be tested with different span (Total or Short wing) and was also tested with the addition of multiple winglets (remiges) (see fig. 1) to test the influence of such device and to verify the capability to reduce induced drag. Configurations with 5 remiges and with 3 remiges were both tested. The aspect ratio of the Short wing with multiple winglet added was about the same of that one of the original elliptical wing(Total wing). Similar tests have been performed on the same model with several classical winglets. The Short wing with a rounded tip added was compared with the same configuration with some winglet added. The Aspect ratio of the wing with wadded winglet was slightly higher of that without. The goal was again to check the gain in Oswald factor. Four different winglet with different chord position and with different sweep angles have been tested. In fig. 2 the pictures show the Short wing with tip (WING_TIP) and two different winglet (WING_TA-W1 and WING_TB-W1) obtained with the same winglet in different chord position. The tested winglet were carefully designed through the use of aerodynamic calculations (panel methods). 2. Design and analysis of high-lift system for light STOL aircraft An high-lift airfoil has been designed for a STOL ultralight aircraft. Deep numerical activities have been carried out for the design and optimization of a 3-component airfoil, named G1-3F. MSES code has been used for the numerical aerodynamic analysis. A model with main, flap and a slat made in carbon fiber has been built and tested in the main wind-tunnel belonging to DIAS. The figure 5 below show the geometries and the experimental lift coefficient curve obtained with slat extended and with 3 different flap deflections. A maximum lift coefficient of about 4.0 has been obtained with full flap (39°) and at a Reynolds number of about 1.3 million