Basic Fighter Maneuvers - BFM Concepts - Circle Flow

Circle Flow

Aircraft can turn either towards or away from each other. How the opponent turns in relation to the other determines the flow of the fight. If two fighters meet head-on, they will usually make a very close, neutral pass, called a "merge." After the pass, both fighters may turn to engage. If the two fighters turn in the same direction, (i.e.: both turn to the north), they will be traveling towards each other along the same turn circle. This type of engagement is known as "one circle flow." If the aircraft turn in opposite directions, (i.e.: one turns north but the other turns south), they will move away from each other, flying around to engage each other on separate turn circles. This is called "two circle flow."

One circle flow will result in another merge, unless an angular advantage can be obtained. During one circle flow, the fighter with the smaller turn radius will have the advantage. Pilots will often pitch-up out-of-plane while increasing thrust, to help minimize turn radius. Since turn rate is of little importance during one circle flow, it is often called a radius fight. An out-of-plane maneuver, such as a displacement roll, is a viable option for reducing turn radius.

Two circle flow will also result in another merge. Two circle flow is a turn rate fight, and the angular advantage usually goes to the aircraft with the higher turn rate at its corner speed. Pilots will often slice turn in order to maximize their turn rate.

A third option is called vertical flow, in which one or both fighters turn toward the vertical plane. If both fighters go up or down, the fight becomes one circle flow. If one fighter goes up or down, while the other turns horizontally, it is really a modified version of one-circle flow. However, if one fighter goes up while the other goes down, it becomes two circle flow.

In both types of flow, the closest possible merge is desirable to keep the enemy at an angular disadvantage. Although circle flow is often described using neutral merges, the concept applies anytime two aircraft maneuver in relation to each other and the horizon. For instance, the "flat scissors" is an example of one circle flow, while the "rolling scissors" is an example of two circle flow.