Originally Posted by Vicizmax
If that happens, then you are doing it wrong.
That is the way I learned to get a horse to gallop correctly if it keeps starting in the wrong gallop.
I guess maybe you shouldn't use this advice since I can't explain how to do this correctly in words. I could make a video explaining this, but if there's other advice that helps, then I couldn't be bothered.. :)
But its something about "shifting" the weight on the horses outside leg, so the inside leg gets "lighter" and the horse automatically goes in the right gallop, as the head is turned on the outside, but the body is still going in a circle/corner to the inside. Confusing, I'm sorry.. xD
So never mind, good luck though!
What you are explaining is putting the horse in a crooked position to attain the canter. Any method to attain the canter (gallop) can be considered correct as long as the horse's balance is not compromised.
In dressage no trainer of quality will ever use crookedness to achieve a specific goal.
Initially on a young horse where a canter aid is not understood the outside leg will be used to PREVENT the haunches from swinging out (also called crookedness). The haunches swinging out will overload the inside shoulder and while the horse will probably canter on the correct lead he will do so simply because the weight/balance forces the inside lead to be picked up. This would be natural for a horse to do since its balance at this stage is weak. A rider may at this stage even lean forward and increase the weight on the inside shoulder to do exactly this also. To prolong an aggressive outside leg once the horse has learned the aid can result in a horse that will now go crooked to the inside with the haunches bent inwards. I have seen this too many times and have marked down horses that exhibit this fault in compititions.
As the horse gets stronger the rider should try to use the outside leg less and only if the horse exhibits a haunches out desire. This type of horse wants to go crooked and the rider should prevent this. If training is progressing well then the utilization of the outside leg becomes less and less and the rider will come to a point that the closing and "scooping up" of the inside hip leg will be all that is required to attain the canter on the lead desired.
The correct aids for the half pass is the ourside leg against the horse where it will move away from that pressure and along with a correct bend will cross its legs and move over. The problem I had with one student is that she continued to use the outside leg aid for the canter and the horse cantered every time she wanted the half pass. She had to go to the lesser aid (insidehip/leg) at the canter and after she did she had no problems with the half pass.
If a problem arises in a canter lead the rider could try to attain the canter through the shoulder in position and via turning.