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.
Written by the AMTprep editorial team · Published · Last reviewed
Written against the FAA primary sources cited at the foot of this page.
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?
What is the primary function of spoilers on a wing?
During a control cable rigging check, what tool is used to set cable tension to the specified value?
When rigging flight controls, what device is used to hold surfaces in the neutral position?
After rigging is completed, control surface travel is verified using which tool?
In a cable-operated flight control system, what is the function of a turnbuckle?
Extending the wing flaps to the landing position primarily allows the airplane to
Lowering the wing flaps has what effect on the airfoil?
When wing spoilers are deflected asymmetrically (raised on one wing only), they function like which primary flight control?
The ruddervators of a V-tail airplane provide control about which axes?
On a delta-wing or tailless airplane, the trailing-edge surfaces that combine pitch and roll control are called
The primary purpose of a trim tab is to
How does a balance tab move relative to the control surface it is attached to?
An airplane is flying with the left wing low. To correct this, the left aileron trim tab should be moved
When a leading-edge slat is extended, the slot that opens between it and the main wing serves to
With differential aileron control, the up-going and down-going ailerons deflect such that
An airplane is flying with the left wing low. Operating the aileron trim control in the cockpit corrects this by
An elevator trim tab is deflected downward in order to
Apart from wing-mounted spoilers, dedicated speed brakes are most commonly located on the
What is the primary function of a servo tab on a flight-control surface?
How does a spring tab assist the operation of a flight-control surface?
A Krueger flap is a high-lift device that makes up part of the
During a banked turn, wing spoilers may be deployed in order to
What is the main purpose of a Frise aileron?
What are ground spoilers used for after touchdown?
Mass balance weights installed on a flight control surface are used to
What is the purpose of a wing leading-edge slot?
High-lift devices such as flaps and slats are used during
On many airplanes, the spoilers are interconnected with which other flight control to assist in roll?
On a hydraulically powered airplane, aileron droop refers to the condition where the ailerons
An anti-balance (anti-servo) tab is used to
Lowering the wing flaps for takeoff produces what effect on lift and drag?
Wing spoilers deployed fully on landing are used to
Differential aileron travel is designed to
Which group lists only primary flight control surfaces?
An anti-servo tab installed on an all-moving stabilator
When flaps are extended in flight, the resulting change in lift means the
Flight spoilers
If an airplane is flying nose heavy, which way should the elevator trim tab be moved?
Wingtip vortices are strongest when the airplane is
Aerodynamic balance of a flight control surface is used to
A balance tab
Elevons combine the functions of the
Flutter of a control surface can be reduced by using
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.
ACS code: AM.II.C
Correct answer: Disrupt lift and increase drag
Rationale: Spoilers are surfaces raised from the upper wing to disrupt the airflow, decreasing lift and increasing drag; they aid descent and braking, and on some aircraft assist roll control. They do not add lift or serve as pitch trim devices.
ACS code: AM.II.C
Correct answer: A tensiometer
Rationale: A tensiometer measures the tension in a control cable so it can be adjusted to the manufacturer's specified value during rigging. A dial indicator measures small linear movement, and a micrometer measures dimensions; neither reads cable tension.
ACS code: AM.II.C
Correct answer: Rig pins inserted at the rigging fittings
Rationale: Rig pins (rigging pins) are inserted into holes at rigging fittings to hold control surfaces and quadrants in their neutral position while cable tension and travel are adjusted. Bonding jumpers carry static charge across hinges, and fairleads guide cables, neither holds surfaces in neutral.
ACS code: AM.II.C
Correct answer: A universal propeller protractor or travel board
Rationale: Control surface travel is checked against the specified degrees of deflection using a universal protractor or a travel board (rigging board). A tensiometer measures cable tension, not angular travel, and a timing light is used on reciprocating-engine ignition, not control rigging.
ACS code: AM.II.C
Correct answer: Adjust the length and tension of the cable
Rationale: A turnbuckle is a fitting placed in a cable run to adjust its length and thereby set cable tension during rigging; it must be safetied after adjustment. Pulleys change cable direction, and fairleads or pressure seals guide cables through structure.
ACS code: AM.II.C
Correct answer: approach and land at a lower airspeed
Rationale: Lowering the flaps to the landing position increases both wing camber and effective area, raising the maximum coefficient of lift. The wing can then support the airplane at a lower speed, which reduces the stalling speed and the safe approach and landing speed.
ACS code: AM.II.C
Correct answer: It increases both lift and drag
Rationale: Lowering the flaps adds camber and, on most types, wing area, which raises the coefficient of lift. The same change increases both profile and induced drag. Flaps therefore increase lift and drag together, which is why they help shorten takeoff and steepen the approach.
ACS code: AM.II.C
Correct answer: Ailerons
Rationale: Raised on one wing only, spoilers reduce lift and increase drag on that wing, rolling the airplane in that direction. This is a roll function, so asymmetric spoilers assist or replace the ailerons. Deflected symmetrically instead, spoilers act as speed brakes or lift dumpers.
ACS code: AM.II.C
Correct answer: Pitch and yaw
Rationale: Ruddervators are the two movable surfaces of a V-tail and combine the functions of the elevator and rudder. Moving them together provides pitch control like an elevator, while moving them differentially provides yaw control like a rudder. They control pitch and yaw, not roll.
ACS code: AM.II.C
Correct answer: Elevons
Rationale: A delta or tailless airplane has no separate elevators and ailerons, so the trailing-edge surfaces act as elevons. Deflected together they control pitch like elevators, and deflected differentially they control roll like ailerons. Combining both functions in one set of surfaces defines an elevon.
ACS code: AM.II.C
Correct answer: relieve the control force the pilot must hold
Rationale: A trim tab is set so its aerodynamic load holds the main control surface in the position needed for the desired attitude, removing the steady force the pilot would otherwise hold. It eases or eliminates control loading but does not move the center of gravity or increase the surface's maximum authority.
ACS code: AM.II.C
Correct answer: Opposite to the surface, in proportion to the surface's deflection
Rationale: A balance tab is linked so it deflects automatically in the direction opposite the main control surface, by an amount proportional to that surface's movement. The tab's aerodynamic force then assists in moving the surface, reducing the stick force the pilot must apply to overcome the hinge moment.
ACS code: AM.II.C
Correct answer: up, which drives the left aileron down
Rationale: To raise a low left wing, the left aileron must move down to add lift on that side. A trim tab deflects opposite to its control surface, so to drive the left aileron down the tab is moved up. The tab's aerodynamic force then holds the aileron in the wing-raising position.
ACS code: AM.II.C
Correct answer: re-energize the boundary layer to delay airflow separation
Rationale: When the leading-edge device extends, it opens a slot to the main wing. High-energy air from below is ducted through the slot onto the upper surface, re-energizing the boundary layer so it stays attached at higher angles of attack. This delays separation and stall rather than directly generating extra lift.
ACS code: AM.II.C
Correct answer: the down-going aileron moves through a smaller angle than the up-going aileron
Rationale: Differential aileron rigging deflects the up-going aileron through a larger angle than the down-going one. This raises drag on the descending wing to balance the extra induced drag on the rising wing, reducing adverse yaw. The down-going aileron therefore travels through the smaller angle.
ACS code: AM.II.C
Correct answer: moving the trim tab up, causing the left aileron to move down
Rationale: If the left wing is low it must be raised, which requires the left aileron to move down to increase lift there. Driving the trim tab upward produces an aerodynamic load that moves the left aileron down, correcting the wing-low condition without the pilot holding the control.
ACS code: AM.II.C
Correct answer: counteract a nose-heavy condition
Rationale: A trim tab deflects opposite to its surface, so an elevator tab moving down forces the elevator up. An up elevator produces a nose-up pitching moment, which corrects a nose-heavy tendency, holding the elevator in the nose-up position so the pilot need not maintain a steady pull force.
ACS code: AM.II.C
Correct answer: sides or rear of the fuselage, or on the wing
Rationale: Speed brakes are surfaces deployed to raise drag without changing lift greatly, slowing the airplane or steepening the descent. Besides wing-mounted spoilers, dedicated speed brakes are often fitted on the sides or rear of the fuselage, so they may be located on either the fuselage or the wing depending on the type.
ACS code: AM.II.C
Correct answer: It moves to help drive the main control surface, reducing pilot effort.
Rationale: On a servo-tab system the pilot's input moves only the tab, not the main surface directly. The tab's aerodynamic load then drives the much larger control surface, greatly reducing the effort required. The tab moves so as to help move the control surface, which is the defining action of a servo tab.
ACS code: AM.II.C
Correct answer: It deflects to help move the control surface, with more assist at high airspeed.
Rationale: A spring tab behaves like a balance tab but with a spring in the linkage, so at low airspeeds it acts little and at high airspeeds, where hinge loads are large, it deflects more to assist the pilot. In all cases it moves so as to help move the control surface, easing the stick force without removing all feel.
ACS code: AM.II.C
Correct answer: wing lower-surface leading edge.
Rationale: A Krueger flap is a leading-edge high-lift device that normally lies flush in the lower surface of the wing's leading edge. When deployed it hinges forward and down to increase the camber and effective leading-edge radius, raising the maximum lift for takeoff and landing. It is therefore part of the lower-surface leading edge.
ACS code: AM.II.C
Correct answer: assist the up-going aileron on the inside wing.
Rationale: In a turn the spoiler on the inside (descending) wing rises to spoil lift and add drag on that side, working with the up-going aileron on the same wing to roll and bank the aircraft. By spoiling lift in concert with the aileron, it improves roll response and helps counter adverse yaw, rather than acting symmetrically as a speed brake.
ACS code: AM.II.C
Correct answer: To increase drag on the up-going aileron and reduce adverse yaw.
Rationale: A Frise aileron is hinged so that when it deflects up, its leading edge protrudes into the airflow beneath the wing, increasing drag on the up-going aileron (the rising-wing side). This added drag balances the higher induced drag on the descending wing, reducing the adverse yaw that would otherwise oppose the turn.
ACS code: AM.II.C
Correct answer: To dump lift so weight transfers onto the wheels.
Rationale: Ground spoilers are large panels raised fully on touchdown to destroy (dump) the wing's lift. With lift spoiled, the aircraft weight transfers onto the main wheels, which makes wheel braking effective and increases drag. Assisting braking and reducing ground speed are consequences of dumping the lift, not the primary aerodynamic function.
ACS code: AM.II.C
Correct answer: counteract flutter of the control surface.
Rationale: Per FAA-H-8083-31, mass balance weights move the control surface center of gravity forward, onto or ahead of the hinge line. This breaks the inertial coupling between bending and torsional vibration that drives flutter, a destructive self-exciting oscillation. They do not balance trim tabs or balance the trailing edge; their sole purpose is dynamic balance to prevent flutter.
ACS code: AM.II.C
Correct answer: To re-energize the boundary layer over the upper wing surface.
Rationale: Per FAA-H-8083-31, a fixed slot is a gap that channels high-energy air from below the wing up over the upper surface. This re-energizes the boundary layer, delaying separation to a higher angle of attack and so increasing the maximum lift and stall angle. It does not itself change the wing angle of attack.
ACS code: AM.II.C
Correct answer: both takeoff and landing operations.
Rationale: Per FAA-H-8083-31, high-lift devices increase the wing lift coefficient so the airplane can fly safely at lower speeds. This benefit is needed for takeoff (shorter ground run) and for landing (lower approach speed), so they are used in both phases rather than only one.
ACS code: AM.II.C
Correct answer: The ailerons.
Rationale: Per FAA-H-8083-31, on many airplanes the spoilers provide a roll-augmentation function and are interconnected with the aileron control. During a roll, the spoilers on the down-going wing rise to spoil lift and assist the ailerons. They are not cross-linked to the elevators or flaps for this purpose.
ACS code: AM.II.C
Correct answer: hang downward under their own weight when hydraulic pressure is removed.
Rationale: Per FAA-H-8083-31, aileron droop describes how the ailerons hang down under their own weight when hydraulic power is removed and they are no longer held in the faired position. It is a normal indication on the ground after shutdown, not a leading-edge droop function or a single surface reaching its travel stop.
ACS code: AM.II.C
Correct answer: increase control feel and prevent over-controlling of the surface.
Rationale: Per FAA-H-8083-31, an anti-servo tab moves in the same direction as the control surface, increasing the aerodynamic load the pilot feels. This adds feel and stability to a surface that would otherwise be over-sensitive, such as an all-moving stabilator. Because it adds load rather than relieving it, it does not reduce hinge loads or act primarily as a trim device.
ACS code: AM.II.C
Correct answer: Both lift and drag are increased.
Rationale: Per FAA-H-8083-31, lowering the flaps increases the wing camber and so raises its lift coefficient, allowing flight at lower speeds. The increased camber and frontal area also increase drag. Both rise together; flaps never reduce drag, which is why a small flap setting is selected for takeoff to keep the drag penalty acceptable.
ACS code: AM.II.C
Correct answer: act as ground spoilers that destroy lift for effective braking.
Rationale: Per FAA-H-8083-31, wing spoilers can be deployed fully on landing as ground spoilers, destroying lift so the airplane weight settles onto the wheels for effective braking. They oppose, rather than assist, lift, so they cannot increase wing lift or supplement elevator pitch authority.
ACS code: AM.II.C
Correct answer: reduce adverse yaw during aileron deflection.
Rationale: Per FAA-H-8083-31, differential aileron travel makes the up-going aileron deflect farther than the down-going one. This balances the drag produced by each wing, countering the adverse yaw that would otherwise swing the nose away from the intended turn. It is a built-in geometry feature, not a rudder-linked or pitch-producing device.
ACS code: AM.II.C
Correct answer: Elevators, ailerons, and rudder.
Rationale: Per FAA-H-8083-31, the primary flight controls are the elevators (pitch), ailerons (roll), and rudder (yaw), which control the airplane about its three axes. Spoilers, tabs, and trim tabs are secondary or auxiliary surfaces, so any list including them is not a list of primary controls.
ACS code: AM.II.C
Correct answer: moves in the same direction as the surface, increasing control feel.
Rationale: Per FAA-H-8083-31, an anti-servo tab moves in the same direction as the control surface, increasing the aerodynamic load felt by the pilot. This added feel helps return the control toward neutral and prevents over-controlling of a very effective surface such as an all-moving stabilator. It therefore increases, not reduces, pilot effort.
ACS code: AM.II.C
Correct answer: nose should be lowered, reducing the angle of attack.
Rationale: Extending the flaps increases the wing's lift coefficient, so to keep lift equal to weight the angle of attack must be reduced and the nose lowered. Raising the nose would add lift on top of the flap increase and risk a stall.
ACS code: AM.II.C
Correct answer: can be used to decrease lift, allowing a controlled descent without a loss of airspeed.
Rationale: Flight spoilers raise partially to decrease lift and add drag, letting the aircraft descend or slow without reducing engine power or building excess airspeed. They spoil lift rather than increase it, so they cannot raise lift on a down-going wing.
ACS code: AM.II.C
Correct answer: Down, which moves the elevator up.
Rationale: A nose-heavy airplane needs up elevator to raise the nose. Moving the trim tab down produces an aerodynamic force that drives the elevator up, holding the corrected attitude without continuous control input; a tab always moves opposite to the surface it deflects.
ACS code: AM.II.C
Correct answer: flying slowly at a high angle of attack.
Rationale: Wingtip vortices are driven by the pressure difference between the upper and lower wing surfaces, which is greatest when the lift coefficient is high. That occurs at low speed and high angle of attack, such as during takeoff and approach.
ACS code: AM.II.C
Correct answer: reduce the aerodynamic loading on the control system.
Rationale: Aerodynamic balance places part of the control surface area ahead of the hinge line, so airflow on that forward portion helps drive the surface and reduces the hinge moment the pilot must overcome. It eases control forces rather than increasing flutter.
ACS code: AM.II.C
Correct answer: assists the pilot in moving the flight controls.
Rationale: A balance tab is geared to move automatically in the direction opposite the control surface, producing an aerodynamic force that helps deflect the surface and so reduces the pilot's effort. It does not increase surface area or trim the aircraft, which is the role of a trim tab.
ACS code: AM.II.C
Correct answer: elevator and aileron.
Rationale: Elevons combine the functions of elevators and ailerons on tailless or delta-wing aircraft. Moving them together gives pitch control like an elevator, while moving them differentially gives roll control like ailerons. They do not perform the rudder's yaw function.
ACS code: AM.II.C
Correct answer: mass balancing of the control surface.
Rationale: Flutter is suppressed by mass balancing, which moves the control surface center of gravity onto or ahead of the hinge to decouple the bending and torsional vibration that drives it. Horn balances and servo tabs reduce control forces but do not address the inertial coupling that causes flutter.
That is a free sample of the 263 questions tagged to ACS AM.II.C. The rest, the adaptive engine that serves you more of whatever you keep missing, and the timed exam simulator come with a free account.
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