Flight controls is a heavily tested subject area on the airframe side of the A&P written. The FAA tests it in two halves: what each surface and tab does aerodynamically, and how you rig, balance and inspect the cables, rods and bellcranks that move them. Most questions are recall, naming a surface, an axis or a tab, but the wording is precise enough that a loose grasp of the tab families will cost you points you should not lose.
AM.II.C follows the flight control chapters of FAA-H-8083-31. Start with the three axes, because the wording of the questions depends on them. An airplane rolls about its longitudinal axis, pitches about its lateral axis, and yaws about its vertical axis. Ailerons, elevator and rudder are the primary controls, one for each axis. Everything else, including flaps, slats, spoilers, speed brakes and tabs, is secondary or auxiliary, and the test expects you to sort them into the right group. Flaps and spoilers come up constantly. Flaps increase the camber of the wing, and Fowler flaps also increase its area, raising both lift and drag so the airplane can approach more slowly and more steeply. Spoilers do the opposite, disrupting lift and adding drag, and on many airplanes they also assist roll. The tab family is where the questions get picky. A trim tab is set to hold a surface where the pilot wants it and relieve control pressure. A balance tab is linked to move opposite the control surface, so airflow on the tab helps drive the surface and lowers stick force. A servo tab is driven directly by the cockpit controls and moves the surface for you. An anti-servo tab moves in the same direction as the surface and increases the force the pilot feels, which is why a stabilator, a one-piece pitch surface that is sensitive by nature, carries one. The maintenance half covers cable construction and tension, turnbuckle safetying, fairlead and pulley limits, travel checked against the manufacturer's rigging data, and static balance of a surface after repair or paint.
ACS AM.II.C is tested on the FAA Airframe written test, one of 1,748 ACS-tagged questions in the Airframe bank. Every question tagged to this area carries a worked rationale and its FAA handbook reference, so you can drill the code itself rather than the whole test.
On a conventional fixed-wing airplane, which primary flight control surface controls movement about the longitudinal axis?
Which set of surfaces is classified as the primary flight controls of an airplane?
What is the primary purpose of wing flaps when they are extended?
What is the main function of a trim tab on a control surface?
A balance tab is connected so that it moves in which direction relative to the control surface it is on?
On an airplane equipped with a stabilator, what surface is used as the primary pitch control?
What is the main purpose of an anti-servo tab installed on a stabilator?
ACS code: AM.II.C
Correct answer: The ailerons
Rationale: The ailerons control roll, which is movement about the longitudinal axis (the axis running nose to tail). The rudder controls yaw about the vertical axis, and the elevator controls pitch about the lateral axis. The three primary controls each govern one of the three axes of flight.
ACS code: AM.II.C
Correct answer: Ailerons, elevator, and rudder
Rationale: Primary flight controls are the ailerons, elevator, and rudder, which provide control about the three axes. Flaps, slats, and spoilers are secondary (auxiliary) controls, and trim tabs are devices used to relieve control pressures rather than to maneuver the aircraft directly.
ACS code: AM.II.C
Correct answer: Increase lift and drag for lower-speed flight
Rationale: Flaps increase the camber of the wing, raising both lift and drag, which permits flight at lower airspeeds for takeoff and landing. They do not control roll (that is the ailerons), and they increase rather than reduce camber.
ACS code: AM.II.C
Correct answer: Relieve control pressure and hold a set attitude
Rationale: A trim tab allows the pilot to relieve the control force needed to hold a desired flight attitude, reducing fatigue. It does not extend control travel limits, and it is not a gust lock; surface locks are separate devices used on the ground.
ACS code: AM.II.C
Correct answer: Opposite to the control surface deflection
Rationale: A balance tab is mechanically linked to move opposite the control surface, producing an aerodynamic force that assists the pilot in moving the surface and reduces the effort required. It is not tied to autopilot engagement and does not move with the surface.
ACS code: AM.II.C
Correct answer: The one-piece movable horizontal tail
Rationale: A stabilator is a one-piece horizontal tail surface that pivots as a unit to provide pitch control, replacing the separate fixed stabilizer and movable elevator. The vertical fin and rudder provide yaw control, not pitch.
ACS code: AM.II.C
Correct answer: Increase control feel and prevent overcontrol
Rationale: An anti-servo tab moves in the same direction as the stabilator, increasing the force the pilot feels and helping to prevent overcontrolling the sensitive one-piece surface. It increases rather than reduces feel, and it is not a stall-recovery device.
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