Here's a crystal-clear video showing what happens when an airplane engine fan blade gets loose
when you fire a chicken at 250 knots into a turbojet using a chicken gun. Result: (Contained) Boom. Update: Corrected.
Update: Sacha, a reader expert in the matter, has wrote to me saying this is not a simulation of a bird striking into a turbo fan, but a simulation of a blade coming loose, which may happen as a result of fatigue or a crack.
...is not a bird test, it's what's called a "blade out" test. Explosive charges are placed on a blade to simulate a blade coming loose — this could happen as a result of fatigue, an unchecked, unseen crack in an engine blade. What you're seeing is essentially "diamond cutting diamond" — and that's why they do the test. Turbo fan blades are extremely strong, and at that speed, they'll chain reaction and destroy each other. You can't really prevent that. But what we don't want is a flying fan blade to hit the fuselage, enter the wing (where fuel is kept), or otherwise leave the engine cowling in any way. That's what this test is for — you want to contain the explosion.
I can hear your confusion: "B-b-b-but, the engine didn't blow up!" — that's because it's not supposed to. We do testing for bird strikes, the engines are built to handle it. They're even designed to continue running, up until a certain size and number of bird ingestions, and beyond that, shut down safely. But they're *never*, ever fragile or brittle enough to be seriously damaged by a hollow-boned soft-bodied bird.
Probably what happened in the US Airways Airbus' engines before its Hudsonlanding.