Definition
An airplane equipped with a retractable landing gear, flaps, and a controllable-pitch propeller, including airplanes equipped with an engine control system consisting of a digital computer and associated accessories that perform the functions of a controllable pitch propeller. A complex airplane designation requires all three features to be present.
Plain English
A small airplane with three features that make it more demanding to fly: wheels that fold up into the airplane, wing flaps the pilot can extend or retract, and a propeller whose blade angle the pilot can adjust in flight.
Context Anchor
You may see this term in takeoff and rejected takeoff discussions, where aircraft configuration and quick cockpit decisions matter.
Derivation
Complex' comes from the Latin 'complexus,' meaning 'woven together' or 'made up of parts.' The FAA uses it here in that original sense -- an airplane made up of more systems the pilot must manage -- rather than the everyday sense of 'complicated' or 'hard to understand.'
Why Pilots Care
A pilot must hold a complex aircraft endorsement before acting as pilot in command, and understanding these systems directly affects procedures such as gear retraction timing and propeller control during a rejected takeoff.
Intuition Check
Complex does not mean the aircraft is automatically unsafe or too difficult to fly. Here it means the aircraft has additional systems or controls that must be managed correctly.
Example Sentence 1
Before flying the Piper Arrow solo, the student needed a complex aircraft endorsement because the airplane had retractable gear and a controllable-pitch propeller.
Example Sentence 2
During the rejected takeoff drill the instructor reviewed the gear and propeller procedures unique to complex aircraft.