In this the defender rolls inverted and dives away vertically, pulling out in a direction opposite to that of his opponent.
Most defensive maneuvers are designed to counter an attack coming from astern, mainly by forcing an attacker to overshoot. What are the attacker's needs? Much depends on whether he is planning a missile or gun attack. As we saw in the attack phase, a missile attack should be fast, deadly, and conclusive. But, as World War I German Chief of Staff von Moltke observed many years ago: plans rarely survive contact with the enemy. The fighter pilot should be prepared for his attack to fail and know precisely what he will do next, either disengage or enter into manoeuvring combat.
If his attack is from head-on, much will depend on the maneuver potential of the two opponents. The more manoeuvrable fighter will have the edge in a turning fight. (The more manoeuvrable fighter at this stage is frequently the one travelling slowest rather than the most aerodynamically capable.) If this is the attacker he should endeavour to pass wide of his opponent to give himself turning room. If there is any doubt about relative maneuver potential he should pass close to deny his adversary turning room, then pull high in the turn. In either case he should pass down-Sun so that his next change of direction forces his opponent to look into the dazzle. If after a head- on pass both aircraft pull high a vertical ascending scissors may result.
A missile attack from astern is normally made at a high closing speed. If the attack fails the attacker must zoom climb to dissipate his excess speed if he wishes to continue the fight, although it is easier and probably safer to disengage at this point. A gun attack should be made with an overtake speed of about 50 knots (just under 90 feet, 2 7m) per second). This gives time to track the target in the sight, minimises the risk of overshooting and retains an energy advantage for manoeuvring combat.
The defensive maneuvers described earlier place much stres on forcing an attacker to overshoot It is obviously important to avoid overshooting, so how is it done?
An overshoot is caused by one or two factors. The first is an excessively large angle subtended between the fuselages of the respective aircraft. The second is excessive closing speed. This is difficult for the attacker to spot until he is fairly close in. Either way the attacker is faced with overshooting. His first remedy is the high-speed yoyo.
The Split S is a time-honoured method of disengaging from combat. Known to the Royal Air Force as the Half Roll and the Luftwaffe as the Abschwung, it uses maneuver in the vertical plane to evade attack.