▁Following ▁wind - t unnel ▁testing ▁of ▁the ▁ram jet ▁and ▁the ▁coal ▁basket , ▁modifications ▁were ▁incorpor ated ▁to ▁provide ▁more ▁efficient ▁comb ust ion . ▁ ▁The ▁coal ▁was ▁to ▁take ▁the ▁form ▁of ▁small ▁gran ules ▁instead ▁of ▁irregular ▁l umps , ▁to ▁produce ▁a ▁controlled ▁and ▁even ▁burn , ▁and ▁the ▁basket ▁was ▁alter ed ▁to ▁a ▁mesh ▁drum ▁revol ving ▁on ▁a ▁vertical ▁axis ▁at ▁ 6 0 ▁r pm . ▁A ▁jet ▁of ▁fl ame ▁from ▁t anks ▁of ▁bott led ▁gas ▁would ▁fire ▁into ▁the ▁basket ▁once ▁the ▁P . 1 3 a ▁had ▁reached ▁operating ▁speed ▁( above ▁ 3 2 0   km / h ), ▁whether ▁by ▁using ▁a ▁ro cket ▁to ▁assist ▁take off ▁or ▁by ▁being ▁to wed . ▁ ▁The ▁air ▁passing ▁through ▁the ▁ram jet ▁would ▁take ▁the ▁f umes ▁from ▁the ▁burning ▁coal ▁towards ▁the ▁rear ▁where ▁they ▁would ▁mix ▁under ▁high ▁pressure ▁with ▁clean ▁air ▁taken ▁from ▁a ▁separate ▁int ake . ▁The ▁resulting ▁mixture ▁of ▁gas ▁would ▁then ▁be ▁directed ▁out ▁through ▁a ▁rear ▁no zz le ▁to ▁provide ▁thrust . ▁A ▁burn er ▁and ▁drum ▁were ▁built ▁and ▁tested ▁successfully ▁in ▁Vienna ▁by ▁the ▁design ▁team ▁before ▁the ▁end ▁of ▁the ▁war . ▁ ▁It ▁is ▁not ▁known ▁what ▁arm ament ▁would ▁have ▁been ▁carried ▁by ▁the ▁P . 1 3 a ; ▁the ▁M K ▁ 1 0 3 ▁can non ▁would ▁have ▁been ▁too ▁heavy ▁and ▁large ▁for ▁such ▁a ▁small ▁aircraft ▁and