what happened is you "stalled" the plane. the rate of climb got to great, the speed dropped, and then the turn just added to the difficulty the wings were having keeping the thing up.

the firebirds will climb at level flight in a straight line. but in a turn they will stall if climbing... you have to back off the throttle (so it levels off) then proceed with your turn. during your turn you can then add throttle to keep the nose up (I also found that they turn better when the throttle is on due to the extra air over the controls.)

if you get into that situation again stop turning (or turn the opposite of what you are banked to level the wings) and add power... then when its about level back off the throttle or it will pitch up and stall. (if you get good enough to can enter a "spiral dive" to gain speed then give it throttle all the way around for a loop) dont try to turn to tight with these or any "fancy moves" until you get used to them as they are not aerobatic machines.

later on you will be bored and wanting a "full" RC plane, then I suggest you seek out an instructor for advice and training.