▁new ▁ 3 4 6 ▁prototype ▁was ▁constructed , ▁incorpor ating ▁ref in ements ▁suggested ▁by ▁the ▁tests . ▁This ▁was ▁designated ▁ 3 4 6 - P ▁(" P " ▁for ▁plan er ▁- ▁" gl ider "). ▁No ▁provision ▁was ▁made ▁for ▁a ▁power plant , ▁but ▁ball ast ▁was ▁added ▁to ▁simulate ▁the ▁weight ▁of ▁an ▁engine ▁and ▁fuel . ▁This ▁was ▁carried ▁to ▁alt itude ▁by ▁a ▁B - 2 9 ▁Super fort ress ▁captured ▁in ▁Vlad iv ost ok ▁and ▁successfully ▁flow n ▁by ▁Wolfgang ▁Z iese ▁in ▁a ▁series ▁of ▁tests . ▁This ▁led ▁to ▁the ▁construction ▁of ▁three ▁more ▁pro tot ypes , ▁intended ▁to ▁lead ▁to ▁power ed ▁flight ▁of ▁the ▁type . ▁ ▁First ▁acc idents ▁ ▁New ly ▁built ▁ 3 4 6 - 1 ▁incorpor ated ▁minor ▁aer od ynamic ▁ref in ements ▁over ▁the ▁ 3 4 6 - P , ▁and ▁was ▁first ▁flow n ▁by ▁Z iese ▁on ▁September ▁ 3 0 , ▁ 1 9 4 8 , ▁with ▁dummy ▁engines ▁installed . ▁The ▁gl ider ▁was ▁released ▁at ▁an ▁alt itude ▁of ▁ 9 7 0 0 ▁m , ▁and ▁the ▁pilot ▁real ised ▁that ▁he ▁hardly ▁could ▁maintain ▁control ▁of ▁the ▁aircraft . ▁Con sequently , ▁while ▁attempting ▁to ▁land , ▁he ▁desc ended ▁too ▁fast ▁( his ▁speed ▁was ▁later ▁estimated ▁at ▁ 3 1 0   km / h ). ▁After ▁first ▁touch ing ▁the ▁ground ▁he ▁b ounced ▁up ▁to ▁a ▁height ▁of