Helicopter splits in half

 

This is fatigue failure.  It's like wings falling off planes in the 50's.  We get massive failure with buildings in earthquakes due to this.  It happens when metal or concrete is stressed to about 60% of strength numerous times.  It was the failure mechanism of that Titanic sub, although nobody ever mentions it.

That's because it isn't supposed to happen.  Main metal parts should only go to 10 or 20% strength, with allowance for emergencies.  Engine parts for aircraft may go to 60% but have to be changed out regularly.

An airframe splitting from fatigue indicates a poor understanding of the stresses.  Of course, that isn't the case here, where, for legal purposes, and my protection, we must say the polar vortex fairies hit it.

ps an old office chair in the house just split in half with perfect fatigue failure fractures.  Neat.

ps the classic patterns of fatigue.  

You would find them, most likely, on the helicopter.