The Immelmann Turn:
Named after the German WWI fighter ace Max Immelmann, this aerobatic maneuver is a modified and simplified version of his attack maneuver that he used during dogfights.
How to fly it: Commence the maneuver as if performing a standard inside loop i.e. enter the maneuver from straight and level flight at point A in the picture above, with full power. Let the airplane complete its vertical climb and roll over onto its back, then at point C use aileron to roll through 180 degrees.
Level the airplane out once it has rolled over, and exit the maneuver on a straight and level course, higher than and in the opposite direction to your initial entry course.
Above is the Immelmann Turn on video (on the RealFlight G4 rc flight simulator), including close-ups of the Tx stick inputs and the airplane’s response.