The Yo-Yo is very difficult to explain. It was first perfected by the well known Chinese fighter pilot Yo-Yo Noritake.

Just like the lag-roll is used to prevent overshooting the flight path of a maneuvering target or to reduce AOT under various conditions. The high yo-yo is also useful for preventing overshoots and reducing AOT, and it is best suited to conditions of moderate AOT (about 30º to 60º), when the attacker is more nearly co-speed with the defender and lacks the excess lead required for lag rolls. As with the lag displacement roll, the high yo-yo uses three-dimensional maneuvering rather than increased load factor to reduce horizontal turn radius, thereby allowing the attacker to retain greater energy. The image below depicts this maneuver.

At position "1" the attacker is turning in the bogey's plane of maneuver in pure pursuit with rapidly increasing AOT and closure (this means the enemy is out turning him), If this course is continued it could result in an overshoot of the bogey's flight path and loss of the offensive. Therefore, the attacker rolls his wings level and pulls up, out of the defender's plane of turn. This climb reduces the component of the attacker's velocity, which is oriented toward the bogey, eventually stopping the closure, and if it is begun soon enough, it will prevent an overshoot. As the closure slows to nearly zero, the attacker should be high in the defender's rear hemisphere in a nose-high attitude. At point "2' the attacker rolls toward the bogey to place his lift vector ahead of, on, or behind the defender to establish lead, pure, or lag pursuit, respectively.

The choice depends primarily on the present nose-tail separation and the desired range once the attacker's nose is pointed back toward the defender. In the case depicted the attacker wishes to close the range for a guns pass at point "3, " so he pulls for a point ahead of the target's position at point "3' and keeps his nose ahead of the defender throughout the remainder of the rolling, nose low turn toward point "3”

The lead-pursuit option depicted generally results in the attacker reaching a higher peak altitude, losing more airspeed, and approaching the bogey in a rather steep dive across the circle at point "3." Choosing lag pursuit at point "2' usually will result in the attacker maintaining greater speed but scooping out below the bogey's altitude. The result of this option is usually a lag-pursuit position looking up at the defender across the circle.

A common error in most out-of -plane offensive maneuvers is to generate excessive pitch attitudes relative to the defender, either nose-up or nose-down. Excessive nose-high pitch may result from beginning a high yo-yo too late. The short range then requires greater pitch attitude to avoid a horizontal overshoot. Once the attacker is very nose-high in the bogey's rear hemisphere, range begins to open very rapidly, affording the defender an opportunity to dive away and gain separation in an extension maneuver.

The excessive nose-down situation usually results from greed on the part of the attacker, when he chooses the lead-pursuit option from the top of a high yo-yo or lag-roll attack in an attempt for a quick gun shot. If the defender pulls hard up into the plane of this high-side attack after the attacker is committed to being excessively nose-low, the bogey can often generate a vertical overshoot, with the attacker losing the offensive after he passes through the target's altitude. It is important to note that out-of-plane maneuvers generally will prevent an overshoot and often will improve the attacker's offensive position; but without a significant turn performance advantage the attacker should not expect an immediate lethal firing position.

I use this maneuver quite a bit when I’m in a turn fight. As soon as I see that the enemy is starting to out turn me I immediately pull up into a high yo-yo. This allows me to keep my speed advantage and maintain my position behind him in his plane of maneuver.

The hard part with this maneuver is knowing how high you have to pull up. All I can say is it comes with experience because it will be different every time.

Overall this is an outstanding maneuver to learn if you fly a Bf109 because it really highlights its superior climb rate at slow speeds.