Thank you, Achim!
Hi, hi - I had already expected that this question will raise many technical implications!
I was simply reading in one of von Koerbers "adventure books" (Feldflieger and der Front). He reported - and at least he was aviator himself - a not named plane type would be able to sail a distance 13 times bigger than its altitude if the motor is out.
I was searching for a technical term for this ratio and fell over this text at a homepage dealing with modern gliders:
"Ein weiteres wichtiges Stichwort im Segelfluß ist die Gleitzahl. Sie gibt an, wie weit ein Segelflugzeug gleiten kann. Heute werden Gleitzahlen über 60 erreicht (60 bedeutet, daß ein Segelflugzeug aus 1000m Höhe über Grund 60 km weit gleiten kann). Diese Gleitzahlen sind allerdings der Offenen Klasse vorbehalten. Die 15m-Segler der Renn- und Standardklasse erreichen eine Gleitzahl von ca. 43 - Tendenz langsam steigend."
I don´t know about the correctness of the use of the term "Gleitzahl" on this page but I am interested in just this ratio. It is of some importance because the traditional claim is that Fokker-Eindeckers was not allowed to cross the lines. Different to this claim I saw some drawings showing the so-called "Fokker-Linie" and this line was not the same as the front line. In an altitude of 2000+ or so meters the Fokker was allowed to cross the lines a bit because a gliding back to the own front was implied there.
VBR
Rammjaeger