There are three forms of pursuit – lead, pure, and lag – are technically defined by the orientation of the attacking aircraft’s velocity vector (flight path marker) ahead of, directly toward, or behind the target aircraft, respectively. Since a pilot does not always have an indication of the precise direction of his velocity vector, his nose position is usually substituted as a reference. I personally use the center of the Revi gun sight as my reference in determining pursuit.

Lead Pursuit

A lead-pursuit path is followed by positioning the aircraft’s nose ahead of the target, or “bogey.” The practical maximum lead when you are maneuvering near the target’s plane of turn is often limited by your over-the-nose visibility and the requirement that you maintain sight of the bogey. “Blind” lead turns may be appropriate under some circumstances, but they are inherently dangerous, both because of the possibility of a collision and because of the potential for losing sight of the bogey and allowing it to gain a more threatening position or to escape. Larger amounts of lead can often be generated by turning in parallel plane with the target, so that sight may be maintained over the side of the attacker’s nose.

The purpose of lead pursuit is primarily to increase closure on the target by use of geometry. The ideal lead angle for greatest closure depends on relative aircraft positions, relative speeds, and target maneuver. A proportional-navigation course usually maximizes closure, and can be estimated visually as the lead angle that causes the target to appear to remain stationary against the distant horizon. If the target’s drift appears to be toward the attacker’s nose, more lead is called for, and vice versa.

The lead-collision or lead-pursuit curve may even allow an attacker to close on a much faster target, particularly if that target turns toward the attacker at a rate that places the attacker at a large angle off the targets tail.

You must be able to pull lead pursuit in a turn fight to get rounds on target!

Pure Pursuit

Holding your nose directly on the target also provides closure, unless the target has a significant speed advantage and AOT (angle off tail) is very small. Although pure pursuit does not generate as much closure as lead pursuit under most conditions, neither does it cause AOT to increase as rapidly.

Lag Pursuit

In lag pursuit you place your nose at an angle behind the target aircraft. This tactic is useful in slowing or stopping closure to maintain a desired separation from the target while simultaneously maintaining or decreasing AOT. Using lag pursuit, even a faster fighter can maintain a position in the rear hemisphere of a maneuvering target.