Loss of a FFS C 12 aircraft
 

Hello! I'm searching for details of the following loss, any help is appreciated!

Date 10 Aug 1940, crash location Hradek about 10km east of Plzeň/Pilsen, unit FFS(C) 12 (Prag-Rusin).
Crew all perished: Flugzeugführer/Schüler Gefr. Otto Bittermann, Fluglehrer Leutnant Fritz Kaiser, Obergefr. Alfred Egle, Gefr. Hermann Deppe.
No further infos, aircraft maybe Ju 52 or 86.

Thanks in advance!