 The five aircraft modified by the factory were given the <unk> <unk> @-@ 45 engine , the Soviet unlicensed copy of the Nene engine , and all six aircraft , used by the VVS for aircrew <unk> and training . The aircraft completed were later relegated to test duties . One aircraft was used for drone tests and another , redesignated as the Tu @-@ <unk> , mounted various pulse jet engines on a <unk> above the fuselage . 
