Flat Swing = Hook?

In general is a backswing falling below the plane going to promote a draw (or even a smothered low hook)?

If so what are the basic mechanics of this?

Not necessarily. Look at Hogan's move from the top. The clubface position is far more important. It's right on plane. If the clubface was pointing toward the sky....lookout left.

**EDIT** oops you said "below the plane". Again not necessarily. It could lead to you having to use hands to get the face to square though. Obviously not the most consistent.

There's many "fixes" to get the club on plane on the way down; shafts in the ground, range bucket (use plastic ones only) place opposite right toe for a right-hander. I would recommend working with a profesional. The reason I say that is that they will be able to direct you better. I have seen many go from too far under the plane to too far over the plane and visa versa. The 'ole one asprin is good, so I'll take 10.

Is there at least a significant correlation between the two?

Not being a professional like RNF, I can only be speculating.

I could imagine that coming from a very flat position at the top could easily get your arms trapped on the way down unless your timing is superb. This would lead to a flipping of the hands in order to get the clubface to the ball. This can cause some hooks. Do you have any problems with fat shots? Do you take a a divot? is it in front or after the ball?

Right now I have no noticable tendency to hit fat shots. In fact, I am not sure that I am even coming back below plane, though I think I might be getting a little lazy and getting flat. I am hitting low hooks with all my woods (to the point that it's hardly worth pulling them out of my bag) and drawing my irons a good amount. The longer the club the worse. My straightest shots lately are the ones that I am hitting off the toe. But overall my contact with the irons is pretty dang good for my standards, I would just prefer to be hitting them a little straighter and understand the mechanics of a fault like this better.

Well, if you are catching your shots fat, I suppose you have a casting issue. I think you lose the angle created between shaft and left arm somewhere in the the downswing. Casting always closes the clubface and results in fat shots and hooks. You might want to take a look at your swing on video, if you see yourself casting the club, you know what you have to work on.

As I tried to explain above, this casting motion could result from your arms being trapped behind your body.

Flat Swing will create a path more from inside the target line...

It will generally engage your trailing forearm/hand to pronate a little more, creating a draw/hook...

If the forearm/hand does not engage, you will leave your shot out to the right...(Right Handers)...

Had a video lesson this morning. My problem was combo of shoulder tilt and closed shoulders but no casting problem. The tilt was getting me a little under plane resulting in too much hand release to compensate. The closed shoulders were screwing up my swing path. Niether problems were that bad alone but together the results were disasterous.

The remedy was to hit a bunch of cut shots with open feet and shoulders just to get the feeling of the ball fading right again. I am glad I got the lesson because I was really getting frusterated with my game. Now I can move forward again.