when you pick up poo and lob it in a fan and it sprays everywhere -

An expression that which a horrible disaster or something big has happened, or just going out of control

When an action takes place bringing about a number of undesiarable consequences.

The point at which "the shit hits the fan" is the point at which an already unstable situation devolves into utter chaos, often in spite of--or even due to--a higher authority's attempt to control it.

Expression - A derivative of the original: "The excrement made physical contact with a hydro-electric powered oscillating air current distribution device". Used primarily to describe a set of circumstances where events became inflamed to a point that control was lost.

Basically, this is when emotions break loose and people get hurt. A literal meaning would be that shit gets on everybody due to the intrinsic nature of the fan.

1. When the critical moment occurs, usually involves the culmination of some sort of crisis or scandal.

2. When shit is literally slung into a fan. (See the movie Airplane.)