Thank you Duggy for this link. So the flight instructor sits out. But for which reason? To easier bail out if the student pilot is learning too slowly? Although, jumping out from this position means almost inevitable contact with one, probably running, airscrew…

The link further suggests that the USB trainer was used for frontline service too… Has there been such a desperate need of aircraft within the VVS?

Thanks once more for every answer, and regards,
RT