ith the engine operating at full speed, the cannon uses compressed air to shoot chicken carcasses (or sometimes duck or turkey carcasses) into the turbine at 180 mph (not 500 mph). This is the approximate speed a plane would be traveling if it encountered a bird during takeoff or landing, when most such incidents occur. The chickens are bought not from the corner grocery but from a game farm; the engineers apparently figure that for maximum realism they'd better use birds with feathers. Bird disintegration occurs only after the chick hits the fan. If the turbine disintegrates too, or if the engine can't be operated safely for another twenty minutes after impact, the design fails the test.
Other stress tests involve water and ice. The most pyrotechnic test of all requires that dynamite charges be strapped to the compressor blades and detonated while the engine is going full blast. (Needless to say, this is the last test of the day.) If the exploding blades aren't completely contained by the fan case, it's back to the drawing board. Better to have pieces of engine embedded in the concrete walls of the test building than in some poor passenger's skull.