Split S

The split S is contrasted with the Immelmann turn, which is an ascending half-loop that finishes with a half-roll out, resulting in level flight in the opposite direction at a higher altitude.

The split S, being a descending maneuver, means that the pilot must ensure that it is started high enough to complete the half-loop; the exact minimum altitude depends on factors like the aircraft's speed, weight and maneuverability, likewise the terrain below the plane.

The reasons for starting the split S maneuver from the inverted position include the fact that people tolerate acceleration ("g-force") applied from head to feet several times better than the reverse direction, as much as 9g versus 3g.

The split S without the beginning half-roll was a standard maneuver in early World War II by German pilots seeking to evade British fighters.

The beginnings of a solution was provided by "Miss Shilling's orifice", a fuel-flow restriction device, and was finally solved by changing from the original S.U.