Private Pilot · Unit 1 · 25 min
Before you preflight an airplane, follow a lesson, or talk shop with a mechanic, you need the names of the parts. This lesson labels every major piece of a Cessna 172, the airplane you will most likely train in.
Every training airplane breaks down into five groups of parts. Learn these as a set; the knowledge test, your instructor, and every FAA handbook use them constantly.
PHAK Ch 3, "Aircraft Construction"
Run a hand along a 172's fuselage and you are touching structure: the skin itself helps carry the loads of flight. Most modern training airplanes use semi-monocoque construction: a skeleton of frames and stringers under a thin aluminum skin, with the skin itself carrying a large share of the flight loads. The older approach is the truss fuselage, a welded frame of steel tubes with fabric or thin metal stretched over it; the frame carries the loads and the covering just gives the airplane its shape. Classic taildraggers like the Piper Cub are built this way, and a growing number of new designs use molded composite shells instead of aluminum.
This matters to you for a practical reason: if the skin is structure, a wrinkle, crease, or dent you find during preflight is a question for a mechanic, not a cosmetic flaw. It also matters for the knowledge test, which likes the word semi-monocoque.
PHAK Ch 3, "Fuselage"
Inside each wing, one or two beams called spars run from the fuselage out toward the tip. The spars carry most of the wing's bending load, which is why the wing attach points get so much attention at inspection time. Ribs sit across the spars like slices, giving the wing its curved cross-section, and the skin wraps over everything. Many trainers also carry their fuel inside the wings; on a 172 the filler caps sit on top of each wing, and checking that fuel visually is part of every preflight.
Wings mount high or low, and both arrangements need support. The 172's high wing uses a strut to share the load between wing and fuselage. Low-wing trainers like the Piper Cherokee are usually cantilever wings: no strut, with all the support built into heavier internal structure. Neither design is better. A high wing gives you a clear view of the ground and shade on a hot ramp; a low wing gives you a clear view in the direction of a banked turn and easier fuel checks.
PHAK Ch 3, "Wings"
The 172's arrangement, two main wheels plus a steerable nose wheel, is called tricycle gear. It is the standard for trainers because the airplane sits level, you can see over the nose while taxiing, and it forgives less-than-perfect landings. The older arrangement, two mains plus a small wheel under the tail, is called conventional gear, or a taildragger. Taildraggers are more demanding on the ground and require specific training and a logbook endorsement to fly.
Gear is also either fixed or retractable. Trainers keep it fixed: simpler, cheaper, and one less thing to forget on final.
PHAK Ch 3, "Landing Gear"; 14 CFR 61.31(i)
Under the cowling of a 172 sits a four-cylinder, horizontally opposed, air-cooled engine turning a fixed-pitch propeller. "Horizontally opposed" means the cylinders lie flat, two per side, which keeps the engine short and the cowling slim. A firewall, a fire-resistant bulkhead, separates the engine compartment from the cabin. Unit 3 opens the cowling properly and follows the fuel, oil, and electricity around; for now the vocabulary is enough.
PHAK Ch 3, "The Powerplant"; PHAK Ch 7
Most of the airframe is bolted in place. Four surfaces are hinged, and moving them is how you fly the airplane (PHAK Ch 6):
Why deflecting a surface moves the airplane comes back to lift and angle of attack. The next lesson, The Four Forces of Flight, starts that story, and the rest of Unit 2 completes it.
PHAK Ch 6, "Flight Controls"
Answer from memory, without scrolling back up. Recalling it yourself is what makes it stick.
Which control surface rolls the airplane into a bank?
The ailerons, on the outboard trailing edges, deflect in opposite directions to roll the airplane. (PHAK Ch 6)
That surface lives on the tail. Rolling is the ailerons' job: they sit on the outboard trailing edge of each wing and move in opposite directions.
What does the empennage include?
Empennage means the whole tail assembly: vertical stabilizer with rudder, horizontal stabilizer with elevator. (PHAK Ch 3)
The empennage is the tail. It includes the fixed vertical and horizontal stabilizers plus their hinged surfaces, the rudder and elevator.
What are flaps for?
Flaps extend downward together, adding lift and drag so you can fly a slower, steeper approach to landing. (PHAK Ch 6)
Flaps do not steer, and extending them adds rather than reduces lift and drag. That lets you fly a slower, steeper approach to landing.
What does the rudder do?
The rudder, hinged to the vertical stabilizer, swings the nose left and right. That motion is called yaw. (PHAK Ch 6)
Pitch belongs to the elevator and roll to the ailerons. The rudder yaws: it swings the nose left and right.
Which of these are all movable control surfaces?
Those three are the primary flight controls, each hinged to a fixed surface. Flaps move too, but as a high-lift device rather than a steering control.
Those parts are all fixed structure. The hinged, movable surfaces are the ailerons, elevator, and rudder (plus the flaps, which add lift rather than steer).
Most modern training airplanes use which kind of fuselage construction?
Semi-monocoque construction splits the load between a light internal skeleton and the aluminum skin itself. That is why skin damage found on preflight matters. (PHAK Ch 3)
Trusses live on under older fabric-covered airplanes, but modern trainers are semi-monocoque: frames and stringers under a load-carrying skin.
Which parts inside the wing carry most of its bending load?
The spars are the wing's main beams, running from fuselage to tip. Ribs shape the wing; the spars hold it up. (PHAK Ch 3)
Those shape the wing or change its lift, but the bending load rides on the spars, the beams running from fuselage to tip.
What makes landing gear "tricycle"?
Mains plus a steerable nose wheel: the airplane sits level, you can see to taxi, and landings are more forgiving. (PHAK Ch 3)
Mains plus a tail wheel is conventional gear, the taildragger. Tricycle gear puts the third wheel under the nose.
Go deeper (primary source): skim PHAK Chapter 3, "Aircraft Construction", then the first pages of Chapter 6, "Flight Controls." Together they take about fifteen minutes and cover every part in this lesson.