How is a complex airplane defined?

A complex airplane is specifically defined as one that includes a controllable pitch propeller, retractable landing gear, and wing flaps. This definition is important because these features enhance the aircraft's performance and safety in various flight conditions, allowing for greater control and efficiency.

The controllable pitch propeller allows pilots to adjust the blade angle for optimal thrust at different speeds and altitudes. Retractable landing gear improves aerodynamic efficiency by reducing drag during flight, and wing flaps increase lift during takeoff and landing phases by altering the wing's shape. These characteristics require additional training and skill to operate safely, hence the designation of "complex."

While advanced avionics, multiple engines, and aerobatic designs might add complexity, they do not fit the official definition of a complex airplane as used in pilot training and certification contexts. Understanding this definition is crucial for pilots in training, as it is linked to the requirements for obtaining relevant aircraft endorsements and ensuring safe operational practices.