What defines a complex aircraft according to the FAA?

A complex aircraft is specifically defined by the Federal Aviation Administration (FAA) as one that is equipped with retractable landing gear, flaps, and a controllable pitch propeller. This definition is crucial because these features contribute to the aircraft's advanced performance and handling characteristics, requiring pilots to have additional training and experience to operate them safely.

Retractable landing gear helps improve aerodynamic efficiency and performance by reducing drag when the gear is retracted during flight. Flaps increase lift and provide better control at lower speeds, particularly during takeoff and landing. A controllable pitch propeller allows the pilot to adjust the blade angle, optimizing engine efficiency for various phases of flight, including takeoff, cruise, and descent.

This combination of features necessitates a higher level of pilot proficiency, making it essential for commercial pilots to understand the operation and management of complex aircraft systems thoroughly. Other options do not meet the FAA's criteria for complexity in aviation, as they relate to different aspects of aircraft design and operation that do not inherently define a complex aircraft.