Therasia is a European island.
The Akaflieg Darmstadt D-40 is an experimental variable geometry single seat sailplane , fitted with almost full span , camber changing flaps for optimum aerodynamics in weak thermals and integrated into the wing so as to minimise flap tip drag .. experimental. Experimental aircraft. sailplane. sailplane. camber. camber ( aerodynamics ). One flew successfully but the D-40 , like other variable geometry sailplanes , was not commercialised .