What is the primary purpose of a torque link (torque arm) assembly on an oleo-pneumatic landing gear strut?
ACS code: AM.II.E
Correct answer: To keep the piston and axle aligned and prevent the wheel from rotating about the strut
Rationale: The torque links connect the upper cylinder to the lower piston of an oleo strut. They allow the piston to move up and down (telescope) while preventing it from rotating, which keeps the axle and wheel properly aligned with the direction of travel. Fluid metering is done by the metering pin/orifice, not the torque links.
In an oleo-pneumatic (air-oil) shock strut, how is the energy of landing impact primarily absorbed?
ACS code: AM.II.E
Correct answer: By forcing hydraulic fluid through a metering orifice while compressing the air charge
Rationale: An oleo-pneumatic strut absorbs energy in two stages: hydraulic fluid is forced through a small metering orifice (dissipating energy as heat), and the trapped air/nitrogen charge is compressed, acting as a spring. Coil springs and rubber donuts are used in other shock-absorbing designs, not in oleo-pneumatic struts.
An oleo shock strut on a parked aircraft is compressed more than the published exposed-piston dimension. The most likely cause is that the strut is
ACS code: AM.II.E
Correct answer: low on air charge or hydraulic fluid
Rationale: Strut inflation is checked by measuring the exposed (shiny) portion of the piston against the manufacturer's specification. A strut compressed below the correct dimension indicates insufficient air charge and/or low fluid. Over-servicing with air would produce an over-extended strut, not a compressed one.
What is the primary function of the squat switch (landing gear safety switch) in a retractable gear system?
ACS code: AM.II.E
Correct answer: To prevent gear retraction while the aircraft weight is on the wheels
Rationale: The squat (safety) switch is actuated by the compression of a landing gear strut when the aircraft's weight is on the wheels. When compressed (on the ground), it opens the retraction circuit so the gear cannot be inadvertently retracted while on the ground. It does not meter hydraulic pressure or release up-locks.
In a hydraulically operated retractable landing gear system, what is the purpose of the sequence valves?
ACS code: AM.II.E
Correct answer: To ensure the gear doors and gear operate in the proper order during a cycle
Rationale: Sequence valves (timing valves) control the order of operation so that, for example, the gear doors open before the gear extends and close after it retracts. This prevents the gear from striking closed doors. Pressure relief and lock pressure maintenance are performed by relief valves and other components, not sequence valves.
On most retractable-gear aircraft, the landing gear position warning horn is designed to sound when the gear is not down and locked and
ACS code: AM.II.E
Correct answer: the throttle(s) are retarded toward the closed/idle position
Rationale: The gear warning horn typically activates when the throttle is reduced (as during an approach to land) while the gear is not down and locked, alerting the pilot to a possible gear-up landing. It is associated with low power/approach configuration, not with setting the parking brake or retracting flaps for cruise.
What gas is recommended for charging the air chamber of an oleo-pneumatic shock strut when a high-quality charge is required?
ACS code: AM.II.E
Correct answer: Dry nitrogen
Rationale: Shock struts are charged with compressed air or, preferably, dry nitrogen. Nitrogen is inert and dry, which prevents internal corrosion and condensation. Oxygen must never be used near oil because of fire/explosion hazard, and carbon dioxide is not used for strut charging.
What is the diagonal member of a landing gear that reacts fore-and-aft (drag) loads called?
ACS code: AM.II.E
Correct answer: Drag strut (drag brace)
Rationale: The diagonal member that braces the landing-gear leg fore-and-aft and reacts drag loads during taxi, takeoff, and landing is the drag strut (drag brace). The shock absorber is the oleo that cushions vertical loads, and a drag wire is a structural tension member, not the gear's diagonal brace.
What is the primary advantage of a tricycle landing gear arrangement compared to a conventional (tailwheel) arrangement?
ACS code: AM.II.E
Correct answer: It allows more forceful braking without nosing over and improves ground stability
Rationale: FAA-H-8083-31 states that tricycle gear provides better forward visibility on the ground, allows more forceful application of the brakes without nosing over, and improves directional stability during ground operations because the center of gravity is forward of the main gear.
In an oleo (air-oil) shock strut, what fluid action provides the primary shock-absorbing and damping function during compression?
ACS code: AM.II.E
Correct answer: Hydraulic fluid is forced through a metering orifice, absorbing the impact energy
Rationale: Per FAA-H-8083-31, when an oleo strut compresses, hydraulic fluid is forced through a metering orifice from the lower chamber into the upper chamber. This restricted flow of fluid absorbs and dissipates the shock energy, while the compressed air (or nitrogen) acts as a spring.
What gas is normally used to service the air side of an oleo shock strut?
ACS code: AM.II.E
Correct answer: Dry nitrogen
Rationale: FAA-H-8083-31 specifies that oleo struts are serviced with compressed air or, preferably, dry nitrogen. Nitrogen is an inert gas that will not support combustion, which is important given the presence of hydraulic fluid under pressure.
What is the function of the torque links (scissors) on a landing gear shock strut?
ACS code: AM.II.E
Correct answer: They keep the piston and wheel aligned with the cylinder while allowing strut travel
Rationale: According to FAA-H-8083-31, the torque links (also called scissors or torque arms) connect the upper cylinder to the lower piston of the strut. They allow the strut to extend and compress while preventing the lower piston and wheel from rotating out of alignment with the upper cylinder.
A shock strut is found to be flat (fully compressed) when the aircraft weight is on the gear. What is the most likely first step in troubleshooting?
ACS code: AM.II.E
Correct answer: Service the strut with the proper fluid level, then inflate to the correct air pressure
Rationale: FAA-H-8083-31 indicates that a strut at improper extension is usually caused by low air charge or low fluid. The correct procedure is to check and service the strut with the proper amount of hydraulic fluid and then inflate it to the correct air pressure per the manufacturer's instructions.
What component within a shock strut meters the rate of fluid flow during both compression and extension to control rebound?
ACS code: AM.II.E
Correct answer: The metering pin and orifice
Rationale: Per FAA-H-8083-31, the metering pin (or a metering tube with an orifice) regulates the flow of fluid through the orifice as the strut compresses and extends. On the rebound (extension) stroke, the restricted flow controls the rate of recoil so the aircraft does not bounce.
On a retractable landing gear system, what is the purpose of the downlock mechanism?
ACS code: AM.II.E
Correct answer: To hold the gear securely in the extended position so it cannot collapse
Rationale: FAA-H-8083-31 explains that the downlock (often an over-center linkage or locking pin) holds the landing gear securely in the extended position so it cannot collapse under the loads of landing and ground operation. An uplock performs the equivalent function for the retracted position.
What is the function of an uplock in a retractable landing gear system?
ACS code: AM.II.E
Correct answer: It holds the gear in the retracted position in the wheel well
Rationale: Per FAA-H-8083-31, the uplock holds the landing gear in the fully retracted position in the wheel well. This prevents the gear from inadvertently extending due to gravity, air loads, or loss of hydraulic pressure while in flight.
Which device, commonly a squat switch on the shock strut, prevents inadvertent gear retraction while the aircraft is on the ground?
ACS code: AM.II.E
Correct answer: A ground safety (squat) switch
Rationale: FAA-H-8083-31 describes the ground safety switch, commonly called a squat switch, mounted on the landing gear shock strut or torque links. When the strut is compressed by the aircraft's weight, the switch opens the gear-retraction circuit so the gear cannot be retracted on the ground.
What is the purpose of a landing gear safety mechanical lock, such as a ground lock pin, installed during maintenance?
ACS code: AM.II.E
Correct answer: To physically prevent accidental gear retraction during ground servicing
Rationale: Per FAA-H-8083-31, ground locks (such as pins with red flags) are installed to physically prevent accidental retraction of the gear while the aircraft is on the ground and being serviced. They must be removed before flight, which the attached warning flags help ensure.
What is the function of a shimmy damper on a nose landing gear?
ACS code: AM.II.E
Correct answer: To dampen and control nosewheel oscillation about the steering axis
Rationale: FAA-H-8083-31 explains that a shimmy damper is a hydraulic (or sometimes a steer-damper) unit that controls and reduces the tendency of the nosewheel to shimmy, by dampening the rapid oscillation about the steering axis caused by ground forces.
In a typical aircraft disc brake, what part is keyed to and rotates with the wheel?
ACS code: AM.II.E
Correct answer: The rotor (rotating disc)
Rationale: FAA-H-8083-31 explains that in a disc brake the rotor (rotating disc) is keyed or bolted to the wheel and rotates with it. The stationary brake assembly applies pressure through the stators/linings against this rotating disc to create friction and slow the wheel.
Which type of brake uses multiple rotating discs and stationary discs (plates) stacked alternately and is commonly found on larger aircraft?
ACS code: AM.II.E
Correct answer: Multiple-disc brake
Rationale: Per FAA-H-8083-31, multiple-disc brakes consist of several rotors (keyed to the wheel) and stators (keyed to the axle) stacked alternately. This design provides a large friction area needed to stop the high energy of heavy aircraft, and is typical of large/transport-category aircraft.
What is the primary purpose of an aircraft anti-skid (anti-lock) brake system?
ACS code: AM.II.E
Correct answer: To prevent wheel lock-up and skidding while maximizing braking effectiveness
Rationale: FAA-H-8083-31 describes that an anti-skid system detects when a wheel is about to skid (decelerating too rapidly relative to others) and reduces brake pressure to that wheel to prevent it from locking up. This maximizes braking effectiveness and prevents tire blowouts from skidding.
A spongy feel in the brake pedals of a hydraulic brake system most commonly indicates what condition?
ACS code: AM.II.E
Correct answer: Air trapped in the brake hydraulic system
Rationale: Per FAA-H-8083-31, a spongy brake pedal is typically caused by air trapped in the hydraulic brake system. Because air is compressible, it must be bled from the system to restore firm, positive braking action.
When bleeding aircraft brakes by the gravity (top-down) method, fluid is introduced at the reservoir and allowed to flow downward and out at the brake bleeder. Why is bleeding required?
ACS code: AM.II.E
Correct answer: To remove entrapped air so the system contains only incompressible fluid
Rationale: FAA-H-8083-31 explains that brake bleeding removes entrapped air from the hydraulic brake system. Air in the lines compresses under pedal pressure, producing spongy and ineffective brakes; bleeding purges the air so the system contains only incompressible fluid.
What is the function of a brake debooster valve in some aircraft brake systems?
ACS code: AM.II.E
Correct answer: It lowers the high system pressure to the brakes while increasing fluid volume delivered
Rationale: Per FAA-H-8083-31, a debooster valve reduces the high pressure from the main hydraulic system to a lower pressure suitable for the brakes, while increasing the volume of fluid delivered. This provides faster brake response and protects the brake assemblies from excessive pressure.
What is the purpose of a fusible plug installed in some aircraft wheels?
ACS code: AM.II.E
Correct answer: To melt and deflate the tire in a controlled manner if brake heat becomes excessive
Rationale: FAA-H-8083-31 states that fusible (thermal) plugs are installed in wheels equipped with high-pressure tires. If brake heat becomes excessive, the plug's core melts and deflates the tire in a controlled manner, preventing a dangerous tire/wheel explosion from over-pressurization.
Aircraft brake linings that are worn to or beyond their service limit should be handled in what manner?
ACS code: AM.II.E
Correct answer: Replaced in accordance with the manufacturer's wear limits
Rationale: Per FAA-H-8083-31, brake wear is commonly checked by measuring the wear pin extension or lining thickness against the manufacturer's limits. When the linings are worn to the minimum allowable, the brake assembly must be removed and the linings replaced to maintain braking effectiveness.
Why must the correct type of hydraulic fluid always be used when servicing an aircraft brake system?
ACS code: AM.II.E
Correct answer: Using the wrong fluid can cause seals and components to swell and deteriorate
Rationale: FAA-H-8083-31 emphasizes that mixing or using the wrong hydraulic fluid (for example, using a petroleum-based fluid where a phosphate-ester type is required) can cause the seals and components to swell, deteriorate, and fail. Only the fluid specified by the manufacturer may be used.
Aircraft tire inflation pressure should be checked under what condition for the most accurate reading?
ACS code: AM.II.E
Correct answer: When the tire is cold, before flight
Rationale: Per FAA-H-8083-31, tire pressure should be checked when the tire is cold, before flight, because heat from operation and braking raises the pressure and would give a falsely high reading. Checking cold ensures the tire is serviced to the correct pressure.
An aircraft tire that has been operated significantly underinflated is most likely to show wear in what pattern?
ACS code: AM.II.E
Correct answer: Excessive wear on both tread shoulders (outer edges)
Rationale: FAA-H-8083-31 explains that an underinflated tire causes the shoulders (outer edges) of the tread to carry more load than the center, producing excessive wear on both shoulders. An overinflated tire conversely wears excessively in the center of the tread.
Why should aircraft tires be protected from prolonged exposure to fuel, oil, and hydraulic fluid?
ACS code: AM.II.E
Correct answer: These petroleum products deteriorate and soften the rubber
Rationale: Per FAA-H-8083-31, petroleum products such as fuel, oil, grease, and hydraulic fluid deteriorate rubber. Spills should be wiped off promptly because prolonged contact softens and breaks down the tire rubber, shortening its service life and creating a safety hazard.
What is the proper procedure for inspecting and lubricating tapered roller wheel bearings during a wheel servicing?
ACS code: AM.II.E
Correct answer: Clean, inspect for defects such as spalling or corrosion, then repack with approved grease
Rationale: Per FAA-H-8083-31, wheel bearings should be removed, cleaned with an approved solvent, inspected for defects such as galling, spalling, brinelling, or corrosion, and then repacked with the specified grease before reinstallation. Defective bearings must be replaced.
What type of damage to a magnesium or aluminum alloy wheel half generally requires the wheel to be removed from service?
ACS code: AM.II.E
Correct answer: Cracks found in the wheel half
Rationale: FAA-H-8083-31 states that wheel halves must be inspected for cracks, and any cracked wheel must be rejected. Cracks (often found by dye-penetrant or eddy-current inspection, especially in the bead seat area and bolt holes) compromise the wheel's structural integrity.
On a light aircraft without power steering, how is the nosewheel typically steered during taxi?
ACS code: AM.II.E
Correct answer: By mechanical linkage from the rudder pedals to the nose gear
Rationale: FAA-H-8083-31 explains that many light aircraft use direct mechanical linkage from the rudder pedals to the nose gear (often through push-pull rods or a steering bungee/collar) so that pressing the rudder pedals turns the nosewheel left or right for ground steering.
What is the function of a sequence valve in a retractable landing gear hydraulic system?
ACS code: AM.II.E
Correct answer: It ensures gear and door operations occur in the correct order
Rationale: Per FAA-H-8083-31, sequence valves (timing valves) ensure that operations occur in the proper order during gear retraction and extension. For example, a sequence valve ensures the gear doors fully open before the gear extends, and that the gear is up before the doors close, preventing interference and damage.
How does a typical landing gear position indicating system inform the flight crew that the gear is down and locked?
ACS code: AM.II.E
Correct answer: Position switches illuminate green indicator lights when each gear is down and locked
Rationale: FAA-H-8083-31 describes that gear position indicators use switches actuated by the gear and its locks to illuminate cockpit lights — commonly three green lights indicating each gear is down and locked, and an unsafe/red light or warning horn when the gear is in transit or not locked for the throttle/flap configuration.