Help please: What would explain this ball flight?

I have a natural fade to my ball flights, this increases the larger the club. So my PW is fairly true but my 3 iron fades.

Anyway, this is true exept for my 4 iron. I can get around 180 with my 4 iron but it flies off to the right after going striaght for the first 120.

It's not a gentle fade as with the other clubs. it's a striaght bullet for 120yards then a sharp handbrake-turn to the right.

If it's a slice, why does it go striaght for the majority of the flight? 

Shouldn't that be out to in for a fade Jonny?

Ray have your lies checked out.