Wind-Tunnel Testing of Otto Lilienthal’s Production Aircraft from 1893

Abstract

A full-scale wind-tunnel test of a replica of Otto Lilienthal’s Normalsegelapparat from 1893 was conducted in a closed low-speed wind tunnel. The goal was to determine the flight performance and characteristics of this glider for the first time. It is of particular interest to this investigation to resolve the open question about the design’s static stability and to clear up whether Lilienthal treated the cloth covering the wings. Therefore, tests were performed both with an impermeable, sealed cloth as well as with untreated, permeable wings. Forces and moments were measured at freestream velocities between 5 and at angles of attack from the linear lift interval up to fully stalled conditions. The recorded data are used to investigate the flight performance and characteristics of the glider with an emphasis on its static stability. The impact of the permeability of the cloth in comparison to the impermeable configuration is discussed.