[BerntR]

Most good swings happens on one or two planes, or somewhere inbetween:

The elbow plane: That's the plane you have the club on if you keep your right forearm on the clubshaft plane at address and your right elbow very close to your hip. This plane is often used in combination with a planeshift in the down swing.

The turned shoulder plane: Draw a straight line from the ball to the right shoulder when you've completed your back swing. That's the turned shoulder plane. This plane is slightly steeper than the elbow plane, but it still goes throug the middle of your core. You can still have the right forarm on plane at address & impact, but now there will be more air between your right elbow and your hip.

In any case the left shoulder will be way above the plane at all times, except, perhaps far into the follow through. Therefore the left arm is moving on a very different path than the swing plane (even though the left hand may be on plane). So trying to swing on the left arm plane is a dead end.

Right elbow plane: Yes, but remember that the right elbow is only on plane at address and impact. It goes under the swing plane early in the downswing, gets back to plane at impact and gets over the plane in the finish and follow thru.

Also remember that both shoulders are far above the plane at address and usually at impact too. I haven't measured but I would guess that the swing revolves around the belly button or perhaps a point slightly above it, of course depending on the swing plane you use.