[Mohawk73]

Update:
In the meantime i had some e-mail contact with the Luftfahrt-Archiv .
The BMW engine was started with a crank.
The "aussenbordansluss" is an electrical connector Siemens 77 stp 40 b. for external current-supply (= fremde Stromquelle).

If the anlasswagen was used for this or just for starting the engine i don't know yet. Maybe someone does know what kind of startercart was used for this?!