Crow is a method of computer radio mixing on a model with flaps and ailerons using 4 servos, one on each surface. When the programed "Crow" switch is activated both ailerons go up and both flaps go down, Wallah "air brakes". The model I had this set up on (a Dynaflite 80" Chipmunk) would react just like it had hit a stiff head wind, really slowed it down.