I think hartmann first ditched a plane around the 90 kill mark. Although he feigned injury and escaped from the Soviet troops this would be counted as a ditch in AH.
Hartmann ditched a plane on his very first combat sortie (ran out of gas after running away from his wingman), and another one not long after (ran into wreckage). And many more to follow. In AH, the time he feigned injury would count as a Death seeing as how he was closer to Russian lines than German

I'd rather someone else answer (so I can be lazy and not do the research), but does anyone know the longest streak of Kills Hartmann made without ditching his plane?