Complex sentence: At the time, the formation was 30 to 40 km southwest of Ischia when Hauptmann Schiess's wingman was forced away by two Lightnings and lost sight of his "Staffelkapitän".
Split into simpler sentences: At the time the formation was 30 to 40 km southwest of Ischia. It was at this time that Hauptmann Schiess wingman was forced away by two Lightnings and lost sight of his "Staffelkapitän".