A flying change is where the horse changes the leading leg within the canter. The hind legs and fore legs should change at the same time; if not, they are either late behind, the most common fault where the hind legs change a stride after the forelegs, or late in front where the fore legs change a stride after the hind legs.
The FEI requirements for a flying change are;
The most commonly used way to build your horse up to a flying change is to ride across the diagonal and make a simple change through walk at the end of the diagonal. When your horse is familiar with this exercise, the flying change is asked for in the same place. Another common way of teaching a flying change, is to ride true canter down the long side of the school and then make a small 10m half circle, returning to the track on a sharp diagonal line and ask for the change.
Whilst both these methods have a degree of success, horses tend to make the change because they are off balance and this technique can also lead to horses refusing to counter canter because it’s easier to make a change of lead. Horses trained this way can become difficult to keep straight through the change particularly in sequence changes.
Asking for flying changes on the long side produces straighter flying changes in the horse. Begin by riding around the end of the school in counter canter and make a simple change through walk to true canter at the beginning of the long side. When your horse is well balanced and light in the simple change, ask for the flying change in exactly the same place.
Canter on for a few strides and then walk and reward him. Don’t be tempted to immediately repeat the flying change. Go back to counter canter and canter to the same place that you asked for the change and remain in a calm counter canter.
The aids should be light; think of it as a canter transition, exactly as you would from walk or trot. Many riders give a very big aid which surprises the horse and then they become anxious during flying changes.
Don’t be tempted to pull the reins back as this will block the change and the horse will make a big movement. A flying change should feel as though it is sliding through underneath you more than jumping in the air. Keep your seat moving forward; the temptation is to fold from the waist and tip you upper body forward.
Due to the nature of a flying change, it is hard to find a good example in a still photo, but this video has a good example of one time changes at 3.38 https://www.youtube.com/watch?v=F_QlKdNrzAU
In the pictures below the horses have made the flying change but the riders have blocked the movement with their hands and given an aid that was much too big and surprised the horse.
Diane Followell Classical Dressage Trainer