 In November 1916, "Idflieg" banned Windhoff "ear" radiators in operational aircraft because they were at a lower level than the crankcase of the engine they were cooling, and a shot into either radiator was likely to drain the cooling system.Late production D.IIs switched to using a Teves und Braun "airfoil shape" radiator (the Teves company still exists in the 21st century), in the center section of the upper wing.This also proved to be problematic as a leaking or battle damaged radiator could scald the pilot's face.