A remarkable high altitude flight over the Cologne-Bonn area

Abstract

On Sunday the 16th May 1954 a Condor IV glider conducted a flight in the Cologne-Bonn area that reached a height of about 4,000m (12,000ft) in a nearly cloudless airmass.... It may be asked, to what height is soaring possible in a cloudless airmass?... Firstly: weather conditions with such an unstable structure of the atmosphere and without the formation of any convection clouds are very rare, and secondly: unstable layers only prevail for a short period......