In order to do a flying change, that is, switch leads in the canter without breaking stride, the horse has to be straight and in balance. The horse should not move to the side and the change should happen in the same rhythm and length as the normal canter stride. Canter-walk transitions and simple changes are the preparation for the flying change.
The aids need to occur early enough to give the horse a chance to switch leads while all four feet are off the ground. Since it is easier for most horses to go from the right to the left lead in the beginning, we will use this as our example. From the right canter, the rider sits a little more on the right seat bone and engages the right hind. The horse is then carefully led to a left bend and the rider drives with the left leg. When the horse lifts his right hind leg, the rider puts his right leg behind the girth and cues for the change. This aid is given in the same driving rhythm as before, only the leg is farther back. The right hind is off the ground when the rider feels the barrel swing towards the left, the horse's withers are also at the highest point in the stride. (Note: if the horse is accustomed to cantering off of the rider's inside leg, then give the aid for the new canter lead with what will be the new inside leg. For example, when changing from the right lead to the left, aid with your left leg at the girth).
The rider maintains the pressure on the right rein in order to allow the horse to put his new outside (right) hind leg down. The momentary pressure on this rein will let up and the rider can then gather the horse softly with the new inside (left) rein. The left leg stays at the girth. After the change, the rider sits more on the left seat bone and continues the aids for the left canter.
There are several ways to teach the horse the change. One is from counter canter into the correct canter lead. Once the horse has switched leads correctly, he should be ridden forward into the new canter so that he knows he's done it right. Another method is to do a figure eight of two 20 meter circles. Canter left on one circle and change to the right circle on the right lead by trotting a few steps. The trot period should be made ever shorter until the horse figures out that the rider wants to do a flying change. Another method is to canter across the diagonal and to change when he changes direction at the corner. The horse is bent slightly in the new direction about two strides before the change. Another way is to begin in right haunches-in and then ride forward-sideways to the left. With practice, the flying change can be made on a straight line.
Remember not to "throw" the horse onto the new lead. The change onto the new inside rein should be soft; he should stay on the new outside rein. The rider shouldn't be too quick about sitting on the new inside seat bone because it makes it difficult for the horse to raise that side in order to put his new inside leg-pair forward.
Common mistakes the rider can make are: being tense in the waist, leaning forward, putting the new outside leg back too late, sitting too fast and too heavily on the new in side seat bone, and using too powerful leg aids.
If the horse changes late behind, the rider should go back to trot haunches-in to get the horse more obedient to the outside leg.
Leopold von Heydebrand und der Lasa writes this in his 1898 book Der Reitkunst hohe Schule mit besonderer Ruecksicht auf ihren Betrieb
in der k.u.k. Hofreitschule in Wien und ihren Wert fuer die anderen Zweige der Reitkunst. (Source: http://www.classicaldressage.com/articles/heydebrand.html, Thomas Ritter).
pp. 44ff.:
"Gebhardt (the author is referring to the famous Oberbereiter Franz Gebhardt who served at the Spanish Riding School 1865-1897, and who was succeeded by the legendary Johann Meixner) gives the following instruction for the lead changes in the canter:
'Before I even start with the changes, the horse must have learned to strike off willingly and reliably on both leads, and the transitions to the halt must be executed very softly, with the hind legs placed well underneath the body. The horse also must not step back with his hind legs after the transition to the halt, because only then is it possible to strike off again willingly and swiftly. - Horses who have learned the piaffe and the levade in the pillars will always execute the flying changes and the transitions to the halt better. They will also learn these movements more easily than other horses who have not been trained this way, because sensible work in the pillars has made their hindquarters flexible and step under.
'Now, if I want to begin practicing the changes, I ride a passade in the right lead canter, coming out of a corner. I pay attention that the lively jump and the tempo are not lost in the turn (this is usually forgotten). In the early stages, I lead the horse's head to the wall a little sooner, so that his body is positioned at an angle - (this position greatly facilitates the change) - and I use the opposite shoulder at the same time, apply a pressure with the right calf - the left leg has to rest on the horse - but I must not omit to keep my left hip and shoulder well forward. This relieves the left seat bone. The right one is consequently loaded more, and the horse will change easily and reliably, if these movements (which constitute the aids) are executed in accord with the horse's temper. Once the horse has changed leads, the inside calf must immediately become active to ensure a lively jump and the straight position of the haunches.
'When the horse has understood the lead change in both directions in this fashion, I have to begin the following: I ride a passade out of a corner again, but, as soon as I have passed the corner, I push the quarters more sideways. After having completed the turn, I shift the shoulder that is closest to the wall forward, ride forward in very lively strides, guide my horse alongside the wall, and try to keep it parallel with it. I continue on the same lead for another five or six strides, and then I try to gain the lead change in the manner described above, because this is the only way in which the horse will not change out of habit, - (which would be a grave mistake) - but he will learn to await the aid for the change. 'Once I have achieved this, reliable lead changes, whether two or three tempo changes, have never been a problem with any horse. My students have also been able to execute lead changes anywhere this way, when they asked for them.'
Von Heydebrand und der Lasa continues after the quote with his own observations:
"The rider should ride flying changes only with horse with truly strong haunches, for whom the lead change is not too difficult, when he uses the correct aids at the moment in which the inside hind leg is about to step down, and if he pays attention to the correct distribution of his own weight. The flying changes are easier to execute on straight lines than out of demi-voltes, since the latter require not only a more pronounced lateral poll position, but the weight shift must be precisely timed, so that the horse does not change too early. The shift in the rider's weight must be done so discreetly under any and all circumstances that an observer never notices it. Just as a spectator should never be able to see with which aids the rider is communicating with his horse. It must always appear as though both were of one mind.
"The most difficult thing in the canter is the transition to the halt, because in this gait the weight is not transferred alternatingly from one hind leg to the other, as in the walk and trot, but as result of the jump-like strides the weight has to be supported by the haunches, so that the raised forehand can be lowered to the ground softly and quietly. In order for the hindquarters to be able to carry the load long enough, it is necessary to bend them more during a transition to the halt than during a transition from the walk or trot to the halt. The rider must consequently encourage his horse with his calves, or his spurs, to step under lively during the last canter strides before the transition to the halt. Then, he gives the aid for the halt with his reins at the moment when the outside hind leg is about to touch down.
"The transition from the canter to the halt in one tempo is decidedly easier alongside the wall than in the interior of the arena, since a lateral deviation of the haunches is easier to prevent when the wall is on one side, especially if the teacher supports the student with the longe whip, if necessary. In the interior of the arena, on the other hand, the rider has only his two legs and the inside rein to keep the croup straight.
"As soon as both hind legs have stepped underneath and are flexing, and the transition has succeeded by a half halt on the reins, the hand has to yield again, but never so much that the rein contact is lost. If the horse leans onto the reins too much, one asks for a few strides of reinback after the transition to the halt, in order to regain the correct posture."
References
Brandl, Albert. Perfekter Reiten - Dressur, Springen, Military. BLV Verlagsgesellschaft, München, 1974.
Hedlund, Gunnar. REITEN Dressur, Springen, Geländeritt. Mosaik Verlag, München, 1979.
von Heydebrand und der Lasa, Leopold. Der Reitkunst hohe Schule mit besonderer Ruecksicht auf ihren Betrieb in der k.u.k. Hofreitschule in Wien und ihren Wert fuer die anderen Zweige der Reitkunst. 1898
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