Setting the stage:

You are approaching an enemy aircraft from behind with a low Angle Of the Tail (AOT) and high closer rate. If this bogey does not turn it is a pretty easy kill. But this is not to be and the pilot sees you coming in and breaks to the left.

Simply relaxing the turn may not slow your closure fast enough to prevent overshooting. Should the defender reverse in this situation, the attacker could be in real trouble. The picture below illustrates this case.

Here, the attacker's high closure causes him to fly out in front of the target after the reversal. Technically, any time the attacker crosses behind the target an overshoot has occurred; but this is usually not dangerous unless the target is moving at a slower speed or has a tighter turn radius. Such a situation often results when a missed gunshot is pressed to minimum range with high closure,

Position "1" in the picture assumes that the attacker cannot pull sufficient lead for a gunshot. To avoid a dangerous overshoot in such a situation it is necessary to stop the closure rapidly. This may be accomplished by a speed reduction, by a hard turn away from the target (reducing the component of velocity in the direction of the target), or by an out-of-plane maneuver. A speed reduction may not be desirable since a speed

advantage often provides a maneuverability advantage (particularly below corner speed), and the attacker may lose maneuvering potential. A hard turn away from the target (pulling toward its extended six o'clock region) in the bogey's plane of turn may cause the attacker to lose sight of the bogey, and also may bleed off valuable energy (speed). Additionally, such a maneuver would make it unlikely that lag pursuit could be reinitiated, and it probably would result in loss of the offensive.

An out-of-plane maneuver is often the best alternative in this situation.

The above picture illustrates one such maneuver, called the lag roll. At point "1" the attacker, in lead pursuit at close range, levels his wings and pulls nose-up out of the defender's plane of turn.

The resulting climb reduces speed and the component of velocity in the defender's direction (reducing closure). The attacker continues to pull up, possibly also pulling somewhat toward the bogey's flight path in a rolling-pull maneuver, to ensure that he passes above and behind the defender as he crosses the bogey's flight path. A slow, continuous roll toward the bogey (here to the right) during this phase of the maneuver enables the attacker to maintain sight throughout, and he passes above and behind the defender essentially inverted, as depicted at point "2." Trading airspeed for altitude in this maneuver allows the attacker to maintain his total energy better than if he had simply pulled more G in a level turn, and low-G conditions once the climb is established may even allow energy addition. From position "2” the attacker benefits from a gravity assist in the nose-low turn, allowing him to pull the bogey closer to the nose and position offensively in lag pursuit.

After the foregoing description of the lag roll, the following narrative by Colonel Robin Olds, USAF, should have a familiar ring.

I had another [MiG] in sight at my 10 o'clock, in a left turn … I pulled sharp left, turned inside him, pulled my nose up about 30 [degreesl above the horizon … barrel rolled to the right, held my position upside down above and behind the MIG until the proper angular deflection and range parameters were satisfied, completed the rolling maneuver, and fell in behind and below the MIG-21 at his seven o'clock position at about .95 mach. Range was 4500 feet, angle off 15. The MIG obligingly pulled up well above the horizon and exactly down sun. I put the pipper on his tailpipe, received a perfect [missile] growl, squeezed the trigger once, hesitated, then once again. The first Sidewinder leapt in front and within a split second, turned left in a definite and beautiful collision course correction … Suddenly the MIG-21 erupted in a brilliant flash (of] orange flame.'

One of the common mistakes made in the employment of lag roll attack is attempting to use it without sufficient initial lead pursuit. Returning to picture of the lag roll, note that the attacking and defending aircraft are aligned nearly parallel at time "1" Visualize what would happen if the attacker's nose at time "1" were pointed at, or only slightly ahead of, the bogey, First, as the attacker started his pull-up, the bogey would disappear beneath the nose, requiring the attacker to perform a very quick roll just to maintain sight, and greatly reducing any altitude advantage which may be achieved over the bogey. Without the climb between times "1" and "2, " the attacker's forward velocity component may cause him to overshoot the bogey's flight path grossly, or force him to pass too far behind the target, allowing nose-tail separation to increase greatly. The lack of sufficient altitude advantage at time "2" also reduces the gravity assist available to the attacker for pulling his nose back toward the bogey to maintain an angular advantage.

Another common error is beginning the pull-up too late. In order for the attacker to gain the required vertical separation in this case, he must attain a rather high nose attitude. This situation may allow the defender to dive away and gain separation before the attacker can pull back down. Or the bogey may wait until about time "2' and pull sharply up toward the attacker, meeting him on the way down with high AOT, and causing a vertical overshoot.

The attacking fighter may also need a speed advantage over the defender for lag displacement roll to work well. If the pull-up is begun in the bogey's rear hemisphere as depicted in picture above, the attacker must cover considerably more distance than the defender to arrive at position "Y' and therefore needs a considerable speed advantage. But if at time "1" the attacker was closer to the target's beam or even slightly into its forward hemisphere, then the attacker would require less speed to complete the maneuver.

One of the effective defenses against the lag displacement roll attack is to dive away in an extension maneuver as the attacker approaches his maximum climb attitude. The defender should simply unload while maintaining his original bank angle, as though he were still turning, during the early part of this extension. Otherwise, the attacker may recognize the tactic and pull back down before sufficient separation can be achieved. The extension may generate enough separation for escape, or it may provide room for a hard turn back into the attacker to negate his position advantage.