Under federal aviation regulations, the complex aircraft definition covers any airplane with retractable landing gear, flaps, and a controllable pitch propeller. An airplane equipped with a Full Authority Digital Engine Control (FADEC) also qualifies. If you want to act as pilot in command of one, you need a one-time logbook endorsement from an authorized flight instructor certifying you’re proficient in its systems and procedures.1eCFR. 14 CFR 61.1 – Applicability and Definitions
The Three Systems That Make an Airplane Complex
The definition sits in 14 CFR § 61.1, and all three components have to be present. An airplane with retractable gear and flaps but a fixed-pitch propeller doesn’t qualify. Neither does one with a controllable propeller and flaps but fixed landing gear. The classification is deliberately narrow so that the endorsement targets a specific combination of systems rather than any single feature.
Retractable Landing Gear
Retractable gear is the system most responsible for the “complex” label. Unlike fixed gear that just sits there, retractable gear has to be raised after takeoff, lowered before landing, and verified at multiple points in between. A gear-up landing damages the propeller, engine, and belly of the airplane. Premature retraction on the ground during a rejected takeoff can be even worse. Gear-related accidents remain one of the most common mishaps in retractable-gear airplanes, and nearly all of them come down to the pilot forgetting a step or getting distracted.
Flaps
Flaps might seem routine since even basic training airplanes have them, but in a complex airplane, flap management interacts with the other two systems. Raising flaps too aggressively after a go-around while simultaneously managing gear retraction and propeller settings can overwhelm a pilot who hasn’t practiced the coordination. Endorsement training covers how to sequence these actions so they don’t stack up during high-workload moments.
Controllable Pitch Propeller
A controllable pitch propeller, usually called a constant-speed propeller, lets you adjust the blade angle during flight. You select a high-RPM, low-pitch setting for takeoff (maximum power) and transition to a low-RPM, high-pitch setting for cruise (better fuel efficiency). This adds a propeller control lever alongside the throttle and mixture controls, and mismanaging it can cause engine damage. Running high RPM with low manifold pressure, or the reverse, stresses the engine in ways a fixed-pitch setup simply can’t. Pilots transitioning from fixed-pitch airplanes often find the relationship between the throttle and the propeller lever is the steepest part of the learning curve.
FADEC Airplanes
The definition also covers airplanes equipped with a Full Authority Digital Engine Control, a digital computer system that manages the engine and propeller electronically rather than through traditional manual controls.1eCFR. 14 CFR 61.1 – Applicability and Definitions A FADEC-equipped airplane is treated as complex under the rule even if the traditional three-system checklist isn’t the reason.
The Seaplane Version of the Definition
Seaplanes get a modified definition. A complex seaplane needs only flaps and a controllable pitch propeller. Retractable landing gear isn’t part of the equation, which makes sense since many seaplanes use floats with no retractable wheel system at all. If you fly a seaplane with flaps and a controllable-pitch prop, you still need the complex endorsement even though the airplane lacks retractable gear.1eCFR. 14 CFR 61.1 – Applicability and Definitions
The Endorsement Required to Fly One
Under 14 CFR § 61.31(e), you cannot act as pilot in command of a complex airplane unless you’ve received and logged both ground and flight training from an authorized instructor in a complex airplane (or a representative simulator or flight training device), and the instructor has found you proficient in the airplane’s operation and systems.2eCFR. 14 CFR 61.31 – Type Rating Requirements, Additional Training, and Authorization Requirements
The endorsement is a one-time logbook entry. Once an authorized instructor signs you off, you don’t renew it or get re-endorsed periodically. It carries forward for the rest of your flying career. Training typically covers normal and emergency gear operation, constant-speed propeller management, flap procedures, and how all three systems interact during takeoff, landing, and go-arounds. There is no FAA-mandated minimum number of flight hours. Most pilots complete the training in roughly two to three hours of flight time plus ground instruction, though pilots with limited retractable-gear experience may need more.
Who Doesn’t Need the Endorsement
Two groups are exempt. If you logged PIC time in a complex airplane before August 4, 1997, the endorsement requirement doesn’t apply to you. Pilots who completed an approved training program and passed a competency check under 14 CFR § 135.293 in a complex airplane (or representative simulator) are also exempt, provided the training is documented in their logbook or training record.2eCFR. 14 CFR 61.31 – Type Rating Requirements, Additional Training, and Authorization Requirements
Complex vs. High-Performance
Pilots frequently confuse these two endorsements because many airplanes require both. A high-performance airplane is one with an engine producing more than 200 horsepower. The high-performance endorsement is a separate one-time logbook entry under 14 CFR § 61.31(f), with its own ground and flight training requirement.2eCFR. 14 CFR 61.31 – Type Rating Requirements, Additional Training, and Authorization Requirements
A Piper Arrow is complex (retractable gear, flaps, constant-speed prop) but produces only 200 horsepower, so it doesn’t require the high-performance endorsement. A Cessna 182 with a fixed-pitch propeller and fixed gear isn’t complex, but its 230-horsepower engine makes it high-performance. A Beechcraft Bonanza with retractable gear, a constant-speed propeller, and a 285-horsepower engine requires both endorsements. The two classifications are independent, and each airplane has to be evaluated against both definitions.
Why the Definition Matters for the Commercial Certificate
If you’re working toward a commercial pilot certificate with a single-engine airplane rating, you need 10 hours of training in a complex airplane, a turbine-powered airplane, or a technically advanced airplane (TAA), or any combination of those. For a multiengine rating, the 10-hour requirement applies to a multiengine complex or turbine-powered airplane.3eCFR. 14 CFR 61.129 – Aeronautical Experience
The TAA option matters because it changed the economics of commercial training. A TAA doesn’t need retractable gear or a constant-speed propeller. Instead, it must have an electronic Primary Flight Display (with airspeed, attitude, altitude, heading, turn coordination, and vertical speed indicators), a Multifunction Display with a GPS-based moving map showing the aircraft’s position, and a two-axis autopilot integrated with the navigation system. Both displays must be continuously visible.4eCFR. 14 CFR 61.129 – Aeronautical Experience
Many modern training airplanes like glass-cockpit Cessna 172s qualify as TAAs, so single-engine commercial applicants can build their 10 hours without renting a more expensive complex airplane. Complex airplanes are less central to commercial training than they once were, but the complex endorsement itself remains a separate requirement if you ever want to fly one as PIC.