originally developed by g & a aircraft with the co-operation of the united states army air forces' air technical service command, the g & a model 45b (designated xr-9 "rotocycle" by the army) was a design for a single-seat helicopter of pod-and-boom configuration. it had a fixed tri-cycle landing gear and three-bladed main and tail rotors. power would have been supplied by a 126 hp (94 kw) avco lycoming xo-290-5 engine. the model 45c (xr-9a) was the same helicopter with a two-bladed rotor. neither of the two helicopters were built. g & a aircraft was purchased by firestone in 1943,