Complex sentence: The Immelmann turn refers to two quite different aircraft maneuvers-the maneuver nowadays usually called an "Immelmann" has, in fact, no connection with the World War I German flying ace Max Immelmann.
Split into simpler sentences: The Immelmann turn refers to two quite different aircraft maneuvers. The maneuver nowadays usually called an "Immelmann" has, in fact, no connection with the World War I German flying ace Max Immelmann.