How does an oleo-pneumatic shock strut work?

The strut is a cylinder and piston containing hydraulic fluid with a charge of compressed air or nitrogen above it. Landing impact drives the piston up and forces fluid through a metered orifice, often varied through the stroke by a tapered metering pin, and that restriction absorbs the energy as heat. The gas charge acts as a spring: it holds the aircraft at rest and extends the strut again.

Why is nitrogen used instead of shop air in a shock strut?

Dry nitrogen is inert and carries essentially no moisture. Shop air brings water vapor into the strut, which corrodes the chrome piston and the cylinder walls and can freeze in the metering orifice at altitude. Oxygen is worse than either, because under pressure and in contact with hydraulic fluid or oil it creates a serious fire and explosion hazard, so it is never used for servicing struts.

How do I tell whether a strut needs air or fluid?

Measure the exposed piston against the dimension in the maintenance manual, with the aircraft at normal weight on level ground. If the strut is low, add air and recheck. A strut that comes up to the correct dimension and then settles again over hours or days is losing fluid or gas past a seal, and it has to be deflated, serviced with fluid, and recharged.

What does the landing gear squat switch do?

It tells the aircraft whether it is on the ground. Mounted on a main gear strut or torque link, the switch changes state when the strut compresses under weight and it opens the landing gear retract circuit, so the gear cannot be raised while the aircraft rests on its wheels. On larger aircraft the same ground-air signal switches other systems between ground and flight modes.

When does the landing gear warning horn sound?

When the gear is not down and locked and the aircraft is configured for landing. Depending on the model, the trigger is the throttle retarded below a set position, the flaps extended to a landing setting, or both. It is a warning only. It does not prevent a gear-up landing, and it is the squat switch, not the horn, that blocks retraction on the ground.

What is the primary purpose of a torque link (torque arm) assembly on an oleo-pneumatic landing gear strut?

To keep the piston and axle aligned and prevent the wheel from rotating about the strut

To hold the strut in the extended position when the aircraft is on jacks

To meter hydraulic fluid flow as the strut compresses during landing impact

In an oleo-pneumatic (air-oil) shock strut, how is the energy of landing impact primarily absorbed?

By forcing hydraulic fluid through a metering orifice while compressing the air charge

By the deformation of rubber donut blocks stacked in the strut housing

By the flexing of the coil spring located inside the strut cylinder

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

low on air charge or hydraulic fluid

over-serviced with air pressure

leaking air past the metering pin orifice

What is the primary function of the squat switch (landing gear safety switch) in a retractable gear system?

To prevent gear retraction while the aircraft weight is on the wheels

To release the gear up-locks once the aircraft is airborne

To meter hydraulic pressure to the gear actuators during taxi

In a hydraulically operated retractable landing gear system, what is the purpose of the sequence valves?

To ensure the gear doors and gear operate in the proper order during a cycle

To relieve excess system pressure back to the reservoir

To maintain constant pressure on the down-lock actuators in flight

On most retractable-gear aircraft, the landing gear position warning horn is designed to sound when the gear is not down and locked and

the throttle(s) are retarded toward the closed/idle position

the parking brake is set during taxi operations

the flaps are fully retracted for cruise flight

What is the primary advantage of a tricycle landing gear arrangement compared to a conventional (tailwheel) arrangement?

It allows more forceful braking without nosing over and improves ground stability

It eliminates the need for any wheel brakes during landing

It permits a steeper climb angle immediately after takeoff

In an oleo (air-oil) shock strut, what fluid action provides the primary shock-absorbing and damping function during compression?

Hydraulic fluid is forced through a metering orifice, absorbing the impact energy

A coil spring compresses against the torque links

Compressed air alone bottoms out against the cylinder head

What is the function of the torque links (scissors) on a landing gear shock strut?

They keep the piston and wheel aligned with the cylinder while allowing strut travel

They meter hydraulic fluid between the upper and lower chambers

They hold the gear in the locked-down position during flight

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?

Service the strut with the proper fluid level, then inflate to the correct air pressure

Disconnect the squat switch and re-rig the gear actuator

Replace the torque links and packing immediately

On a retractable landing gear system, what is the purpose of the downlock mechanism?

To hold the gear securely in the extended position so it cannot collapse

To meter hydraulic pressure to the brake assemblies

To dampen shimmy in the nose gear during taxi

What is the function of an uplock in a retractable landing gear system?

It holds the gear in the retracted position in the wheel well

It releases nitrogen pressure during emergency extension

It centers the nosewheel before retraction

Which device, commonly a squat switch on the shock strut, prevents inadvertent gear retraction while the aircraft is on the ground?

A shuttle valve in the brake line

A centering cam in the nose strut

What is the purpose of a landing gear safety mechanical lock, such as a ground lock pin, installed during maintenance?

To physically prevent accidental gear retraction during ground servicing

To bleed trapped air from the brake hydraulic system

To electrically isolate the gear position indicator

What is the function of a shimmy damper on a nose landing gear?

To dampen and control nosewheel oscillation about the steering axis

To absorb vertical landing shock in place of the oleo strut

To lock the nosewheel centered before gear retraction

What is the primary purpose of an aircraft anti-skid (anti-lock) brake system?

To prevent wheel lock-up and skidding while maximizing braking effectiveness

To increase brake pressure proportionally to airspeed

To heat the brakes for cold-weather operation

A spongy feel in the brake pedals of a hydraulic brake system most commonly indicates what condition?

Air trapped in the brake hydraulic system

Over-torqued axle nut on the wheel

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?

To remove entrapped air so the system contains only incompressible fluid

To adjust the parking brake ratchet tension

To recharge the accumulator with nitrogen

What is the function of a brake debooster valve in some aircraft brake systems?

It lowers the high system pressure to the brakes while increasing fluid volume delivered

It boosts system pressure above normal for parking brake hold

It vents all brake pressure to atmosphere after each application

What is the purpose of a fusible plug installed in some aircraft wheels?

To melt and deflate the tire in a controlled manner if brake heat becomes excessive

To indicate when the wheel bearing needs lubrication

To ground static electricity from the tire to the axle

Aircraft brake linings that are worn to or beyond their service limit should be handled in what manner?

Replaced in accordance with the manufacturer's wear limits

Sanded smooth and returned to service indefinitely

Reversed and reinstalled to expose unworn surfaces

Why must the correct type of hydraulic fluid always be used when servicing an aircraft brake system?

Using the wrong fluid can cause seals and components to swell and deteriorate

All hydraulic fluids are interchangeable, so it does not matter

Different fluids change the air pressure in the strut

Aircraft tire inflation pressure should be checked under what condition for the most accurate reading?

When the tire is cold, before flight

Immediately after landing while the tire is hot

After the brakes have been applied repeatedly to warm the tire

An aircraft tire that has been operated significantly underinflated is most likely to show wear in what pattern?

Excessive wear on both tread shoulders (outer edges)

Wear concentrated only on the sidewall

Excessive wear only in the center of the tread

Why should aircraft tires be protected from prolonged exposure to fuel, oil, and hydraulic fluid?

These petroleum products deteriorate and soften the rubber

They cause the tire to overinflate at altitude

They increase the rolling resistance during taxi only

What is the proper procedure for inspecting and lubricating tapered roller wheel bearings during a wheel servicing?

Clean, inspect for defects such as spalling or corrosion, then repack with approved grease

Replace bearings only if the tire is also being replaced

Apply oil to the outside of the bearing without removing it

What type of damage to a magnesium or aluminum alloy wheel half generally requires the wheel to be removed from service?

Normal discoloration of the anodized finish

Light surface scratches in the protective paint

On a light aircraft without power steering, how is the nosewheel typically steered during taxi?

By mechanical linkage from the rudder pedals to the nose gear

By electrically driven actuators in the wheel hub

By a dedicated hydraulic steering tiller only

What is the function of a sequence valve in a retractable landing gear hydraulic system?

It ensures gear and door operations occur in the correct order

It meters fluid to the wheel brakes during anti-skid operation

It relieves excess pressure back to the reservoir

How does a typical landing gear position indicating system inform the flight crew that the gear is down and locked?

Position switches illuminate green indicator lights when each gear is down and locked

A pressure gauge reads zero when the gear is locked down

The shock strut air pressure rises to indicate lock

Landing Gear Systems — FAA A&P Test Questions (ACS AM.II.E)

Landing gear is a systems area, and the airframe written test treats it as one: how an oleo-pneumatic shock strut absorbs a landing, what the structural members are called, and how a retraction system knows what to do and when. Every AMTprep question tagged to AM.II.E comes with a rationale and a handbook reference. The strut questions carry the most weight, and nearly all of them come back to one idea, which is that fluid absorbs the impact while air carries the static load. Get that straight and a whole cluster of questions falls into place.

Written by the AMTprep editorial team · Published July 27, 2026 · Last reviewed October 21, 2026

Written against the FAA primary sources cited at the foot of this page.

What ACS AM.II.E covers

AM.II.E follows the landing gear material in FAA-H-8083-31, and the oleo-pneumatic strut sits at the center of it. On touchdown the piston drives up into the cylinder and forces hydraulic fluid through a metered orifice, and that restriction, not the air, absorbs the impact and turns it into heat. The compressed air or nitrogen above the fluid behaves as a spring: it supports the parked weight of the aircraft, sets how far the piston stays extended, and returns the strut after compression. The servicing questions follow from that. A strut sitting lower than the exposed-piston dimension in the maintenance manual is usually low on air, but a strut that settles again after charging has lost fluid, and dry nitrogen is the specified charging gas. Structure is mostly naming. Torque links keep the piston aligned with the cylinder so the wheel tracks straight, and they also limit how far the strut extends. The drag brace reacts fore-and-aft loads, the side brace reacts side loads, and a shimmy damper controls nosewheel shimmy. The retraction half is about sequence and safety. Sequence valves make doors and gear move in the correct order by holding pressure until the previous step finishes. The squat switch, also called the safety or ground-shift switch, senses that the strut is compressed and interrupts the retract circuit so the gear cannot be raised on the ground. A position warning horn sounds when the gear is not down and locked and the aircraft is configured to land, and every retractable system has downlocks, uplocks, and an emergency extension method independent of normal power.

Where this sits on the test

ACS AM.II.E is tested on the FAA Airframe written test, one of 1,739 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.

FAA handbook references

FAA-H-8083-31

Three traps candidates fall into

The most common wrong answer about struts is that the compressed air absorbs the landing shock. It does not. Fluid forced through the metering orifice absorbs and dissipates that energy as heat, while the air charge supports the static weight, sets strut extension, and pushes the strut back out.
A low strut gets more air and the technician moves on. If it settles again, the problem is fluid rather than air, and topping off with nitrogen only hides a leaking seal until the strut bottoms out on a hard landing. Service to the exposed-piston dimension the maintenance manual gives.
Shop air seems close enough for charging a strut, and it is not. Compressed air carries moisture that corrodes the strut internally and can freeze in the metering orifice at altitude, and oxygen under high pressure in contact with hydraulic fluid is a fire hazard. Dry nitrogen is specified.

36 free sample questions from ACS AM.II.E

AM.II.ETap an answer
What is the primary purpose of a torque link (torque arm) assembly on an oleo-pneumatic landing gear strut?
Show the answer and explanation
Answer: To keep the piston and axle aligned and prevent the wheel from rotating about the strut
Why: 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.· FAA-H-8083-31 — Landing Gear Systems (oleo strut components)
AM.II.ETap an answer
In an oleo-pneumatic (air-oil) shock strut, how is the energy of landing impact primarily absorbed?
Show the answer and explanation
Answer: By forcing hydraulic fluid through a metering orifice while compressing the air charge
Why: 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.· FAA-H-8083-31 — Shock Absorbing Landing Gear
AM.II.ETap an answer
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
Show the answer and explanation
Answer: low on air charge or hydraulic fluid
Why: 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.· FAA-H-8083-31 — Shock Strut Inspection and Servicing
AM.II.ETap an answer
What is the primary function of the squat switch (landing gear safety switch) in a retractable gear system?
Show the answer and explanation
Answer: To prevent gear retraction while the aircraft weight is on the wheels
Why: 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.· FAA-H-8083-31 — Landing Gear Safety Devices
AM.II.ETap an answer
In a hydraulically operated retractable landing gear system, what is the purpose of the sequence valves?
Show the answer and explanation
Answer: To ensure the gear doors and gear operate in the proper order during a cycle
Why: 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.· FAA-H-8083-31 — Hydraulic Gear Operation (sequence valves)
AM.II.ETap an answer
On most retractable-gear aircraft, the landing gear position warning horn is designed to sound when the gear is not down and locked and
Show the answer and explanation
Answer: the throttle(s) are retarded toward the closed/idle position
Why: 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.· FAA-H-8083-31 — Landing Gear Warning Systems
AM.II.ETap an answer
What gas is recommended for charging the air chamber of an oleo-pneumatic shock strut when a high-quality charge is required?
Show the answer and explanation
Answer: Dry nitrogen
Why: 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.· FAA-H-8083-31 — Servicing Shock Struts (charging medium)
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What is the diagonal member of a landing gear that reacts fore-and-aft (drag) loads called?
Show the answer and explanation
Answer: Drag strut (drag brace)
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What is the primary advantage of a tricycle landing gear arrangement compared to a conventional (tailwheel) arrangement?
Show the answer and explanation
Answer: It allows more forceful braking without nosing over and improves ground stability
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
In an oleo (air-oil) shock strut, what fluid action provides the primary shock-absorbing and damping function during compression?
Show the answer and explanation
Answer: Hydraulic fluid is forced through a metering orifice, absorbing the impact energy
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What gas is normally used to service the air side of an oleo shock strut?
Show the answer and explanation
Answer: Dry nitrogen
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What is the function of the torque links (scissors) on a landing gear shock strut?
Show the answer and explanation
Answer: They keep the piston and wheel aligned with the cylinder while allowing strut travel
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
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?
Show the answer and explanation
Answer: Service the strut with the proper fluid level, then inflate to the correct air pressure
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What component within a shock strut meters the rate of fluid flow during both compression and extension to control rebound?
Show the answer and explanation
Answer: The metering pin and orifice
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
On a retractable landing gear system, what is the purpose of the downlock mechanism?
Show the answer and explanation
Answer: To hold the gear securely in the extended position so it cannot collapse
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
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What is the function of an uplock in a retractable landing gear system?
Show the answer and explanation
Answer: It holds the gear in the retracted position in the wheel well
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
Which device, commonly a squat switch on the shock strut, prevents inadvertent gear retraction while the aircraft is on the ground?
Show the answer and explanation
Answer: A ground safety (squat) switch
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What is the purpose of a landing gear safety mechanical lock, such as a ground lock pin, installed during maintenance?
Show the answer and explanation
Answer: To physically prevent accidental gear retraction during ground servicing
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
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What is the function of a shimmy damper on a nose landing gear?
Show the answer and explanation
Answer: To dampen and control nosewheel oscillation about the steering axis
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
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In a typical aircraft disc brake, what part is keyed to and rotates with the wheel?
Show the answer and explanation
Answer: The rotor (rotating disc)
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
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Which type of brake uses multiple rotating discs and stationary discs (plates) stacked alternately and is commonly found on larger aircraft?
Show the answer and explanation
Answer: Multiple-disc brake
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
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What is the primary purpose of an aircraft anti-skid (anti-lock) brake system?
Show the answer and explanation
Answer: To prevent wheel lock-up and skidding while maximizing braking effectiveness
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
A spongy feel in the brake pedals of a hydraulic brake system most commonly indicates what condition?
Show the answer and explanation
Answer: Air trapped in the brake hydraulic system
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
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?
Show the answer and explanation
Answer: To remove entrapped air so the system contains only incompressible fluid
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What is the function of a brake debooster valve in some aircraft brake systems?
Show the answer and explanation
Answer: It lowers the high system pressure to the brakes while increasing fluid volume delivered
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What is the purpose of a fusible plug installed in some aircraft wheels?
Show the answer and explanation
Answer: To melt and deflate the tire in a controlled manner if brake heat becomes excessive
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
Aircraft brake linings that are worn to or beyond their service limit should be handled in what manner?
Show the answer and explanation
Answer: Replaced in accordance with the manufacturer's wear limits
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
Why must the correct type of hydraulic fluid always be used when servicing an aircraft brake system?
Show the answer and explanation
Answer: Using the wrong fluid can cause seals and components to swell and deteriorate
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
Aircraft tire inflation pressure should be checked under what condition for the most accurate reading?
Show the answer and explanation
Answer: When the tire is cold, before flight
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
An aircraft tire that has been operated significantly underinflated is most likely to show wear in what pattern?
Show the answer and explanation
Answer: Excessive wear on both tread shoulders (outer edges)
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
Why should aircraft tires be protected from prolonged exposure to fuel, oil, and hydraulic fluid?
Show the answer and explanation
Answer: These petroleum products deteriorate and soften the rubber
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What is the proper procedure for inspecting and lubricating tapered roller wheel bearings during a wheel servicing?
Show the answer and explanation
Answer: Clean, inspect for defects such as spalling or corrosion, then repack with approved grease
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What type of damage to a magnesium or aluminum alloy wheel half generally requires the wheel to be removed from service?
Show the answer and explanation
Answer: Cracks found in the wheel half
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
On a light aircraft without power steering, how is the nosewheel typically steered during taxi?
Show the answer and explanation
Answer: By mechanical linkage from the rudder pedals to the nose gear
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
What is the function of a sequence valve in a retractable landing gear hydraulic system?
Show the answer and explanation
Answer: It ensures gear and door operations occur in the correct order
Why: 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.· FAA-H-8083-31 — Landing Gear Systems
AM.II.ETap an answer
How does a typical landing gear position indicating system inform the flight crew that the gear is down and locked?
Show the answer and explanation
Answer: Position switches illuminate green indicator lights when each gear is down and locked
Why: 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.· FAA-H-8083-31 — Landing Gear Systems

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Related subject areas

The areas that share the most ground with AM.II.E — study them alongside it.

Hydraulic and Pneumatic Systems (AM.II.F)
Airframe Inspection (AM.II.D)
Ground Operations and Servicing (AM.I.F)

Frequently asked questions

How does an oleo-pneumatic shock strut work?: The strut is a cylinder and piston containing hydraulic fluid with a charge of compressed air or nitrogen above it. Landing impact drives the piston up and forces fluid through a metered orifice, often varied through the stroke by a tapered metering pin, and that restriction absorbs the energy as heat. The gas charge acts as a spring: it holds the aircraft at rest and extends the strut again.
Why is nitrogen used instead of shop air in a shock strut?: Dry nitrogen is inert and carries essentially no moisture. Shop air brings water vapor into the strut, which corrodes the chrome piston and the cylinder walls and can freeze in the metering orifice at altitude. Oxygen is worse than either, because under pressure and in contact with hydraulic fluid or oil it creates a serious fire and explosion hazard, so it is never used for servicing struts.
How do I tell whether a strut needs air or fluid?: Measure the exposed piston against the dimension in the maintenance manual, with the aircraft at normal weight on level ground. If the strut is low, add air and recheck. A strut that comes up to the correct dimension and then settles again over hours or days is losing fluid or gas past a seal, and it has to be deflated, serviced with fluid, and recharged.
What does the landing gear squat switch do?: It tells the aircraft whether it is on the ground. Mounted on a main gear strut or torque link, the switch changes state when the strut compresses under weight and it opens the landing gear retract circuit, so the gear cannot be raised while the aircraft rests on its wheels. On larger aircraft the same ground-air signal switches other systems between ground and flight modes.
When does the landing gear warning horn sound?: When the gear is not down and locked and the aircraft is configured for landing. Depending on the model, the trigger is the throttle retarded below a set position, the flaps extended to a landing setting, or both. It is a warning only. It does not prevent a gear-up landing, and it is the squat switch, not the horn, that blocks retraction on the ground.

All 40 ACS areas

General

Airframe

Powerplant

Primary sources

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