Landing Gear Systems practice questions

Answer: A) Brake chatter or squeal as the linings grab unevenly on the disc

A warped brake disc makes the linings contact the disc unevenly as it turns, which causes brake chatter, squeal or vibration. A spongy or sinking pedal points to hydraulic faults, and fade comes from overheating.

• ACorrect. A warped disc does not run true, so the linings grab and release unevenly as it turns. The result is chatter, squeal or vibration when the brakes are applied.
• BIncorrect. Fade comes from overheated or glazed linings and discs that lose friction. It is not the typical symptom of a warped disc.
• CIncorrect. A spongy pedal usually means air in the hydraulic system, which is fixed by bleeding the brakes. Disc shape does not cause it.
• DIncorrect. A slowly sinking pedal points to fluid leaking past seals, for example inside the master cylinder. It is not caused by a warped disc.

Answer: D) Controls fluid flow through the orifice

• AIncorrect. Steering is separate.
• BIncorrect. The air valve and seals do that.
• CIncorrect. Downlocks do that.
• DCorrect. This sets the strut's damping as it compresses.

Answer: A) Stand them upright on tire racks in a cool, dry, dark room away from electric motors and fluorescent lights

Spare tires should be stored vertically on racks in a cool, dry, dark place. Keep them away from ozone sources (electric motors, battery chargers, fluorescent lights), heat, sunlight and petroleum products.

• ACorrect. Tires should be stored vertically on racks so they don't deform. A cool, dry, dark area limits damage from heat and UV light. Keeping them away from ozone sources such as electric motors, battery chargers and fluorescent lights prevents ozone cracking.
• BIncorrect. Hanging a tire from one point concentrates its weight on a small area of the bead and distorts it. Racks that support the tread are recommended.
• CIncorrect. Battery chargers produce ozone, and heat speeds up rubber aging. Both shorten tire life.
• DIncorrect. Sunlight (UV) and the heat it brings degrade rubber. If tires are wrapped, opaque wrapping in a dark area is preferred.

Answer: A) At reduced power or with flaps down and gear not locked

• ACorrect. It warns of a gear-up landing.
• BIncorrect. The horn warns when the gear is not down.
• CIncorrect. It is tied to gear position.
• DIncorrect. The horn sounds at reduced power.

Answer: B) The cut extends deep enough to expose or penetrate the cord body

A tire with a cut that exposes or penetrates the cord body must be removed. Shallow tread cuts within the manufacturer's limits are acceptable.

• AIncorrect. A shallow tread cut that does not reach the cord and is within the manufacturer's limits can stay in service and be monitored.
• BCorrect. Once the cord body is exposed or cut, the tire has lost structural strength and must be replaced before further flight.
• CIncorrect. Having been retreaded does not by itself make a minor tread cut a reason for removal. The depth of the damage relative to the cord body decides it.
• DIncorrect. A cut's position in a groove, plus normal pressure retention, is not a removal criterion. Removal depends on whether the cord body is reached.

Answer: A) To purge trapped air from the lines; the brake pedal feels firm, not spongy, when applied

Brakes are bled after line maintenance to remove trapped air, which compresses and makes the brakes spongy. A successful bleed gives a firm, non-spongy brake pedal or lever.

• ACorrect. Air compresses but hydraulic fluid does not, so trapped air makes the brakes spongy and weak. Bleeding continues until fluid with no bubbles comes out and the pedal or lever is firm.
• BIncorrect. Extra pedal travel or a soft pedal means air is still in the system. A successful bleed gives a firm pedal with normal travel.
• CIncorrect. Bleeding after line maintenance is done to remove air, not mainly to flush fluid. A reservoir above the full mark means it is overserviced, not that the bleed worked.
• DIncorrect. A wheel that spins freely is a dragging-brake check, not a check on the bleed. The purpose of bleeding is to remove air that makes the brakes spongy.

Answer: B) Hydraulic fluid metered through an orifice and compressed nitrogen or dry air

An oleo-pneumatic strut combines hydraulic fluid metered through an orifice, which absorbs landing energy, with compressed nitrogen or dry air, which supports the load. Servicing the strut means checking both the fluid and the gas.

• AIncorrect. Rubber discs belong to rubber or bungee shock absorbers. An oleo-pneumatic strut uses a gas charge to support the load, not rubber.
• BCorrect. Fluid forced through the metering orifice absorbs and spreads out landing energy. The compressed nitrogen or dry air acts as a spring that supports the aircraft's weight.
• CIncorrect. Gas alone would only bounce like a spring. Without fluid metered through an orifice, the landing energy would not be absorbed.
• DIncorrect. 'Pneumatic' means a gas charge. In an oleo-pneumatic strut, compressed nitrogen or air carries the load and sets the extension, not a coil spring.

Answer: A) Mechanically releasing the gear uplocks so the gear free-falls by gravity

Regulations require an emergency means of gear extension. A common one is releasing the uplocks so the gear free-falls by gravity until the downlocks engage; hand pumps and stored-gas bottles are also used.

• ACorrect. In a common emergency method, the crew pulls a handle or cable to release the uplocks. The gear then falls by gravity, helped by airflow and sometimes springs, until the downlocks engage. Other common backups are a hand pump or a stored-gas bottle.
• BIncorrect. The selector valve only directs fluid; it does not produce pressure. If the normal pressure source has failed, moving the selector back and forth cannot extend the gear.
• CIncorrect. Venting the reservoir does not create enough pressure to move the actuators, and it is not an approved emergency extension method.
• DIncorrect. Downlocks hold the gear once it is extended. It is the uplocks that hold a retracted gear up, so those are what must be released for free-fall extension.

Answer: D) To let trapped casing air escape and prevent ply separation

• AIncorrect. Wear limits are shown in grooves.
• BIncorrect. They do not indicate pressure.
• CIncorrect. Valve stems are on the wheel.
• DCorrect. Vent marks show where trapped air can bleed out.

Answer: A) The flat spot has worn down to the outermost casing ply or outermost belt

A skid flat spot that has worn down to the outermost casing ply (bias tire) or outermost belt (radial tire) calls for removing the tire. Shallow flat spots with tread rubber remaining are judged by depth, not by how visible or long they are or how the skid happened.

• ACorrect. FAA tire guidance (AC 20-97B) says tires worn or flat-spotted to the outermost casing ply (bias) or outermost belt (radial) should be removed from service. At that depth the tire's structure has been exposed and weakened.
• BIncorrect. A shallow flat spot with tread rubber remaining does not by itself require removal. The deciding factor is how deep it goes into the tire structure.
• CIncorrect. No such length rule exists. Flat-spot removal is based on depth into the casing ply or belt, not on how long the spot is.
• DIncorrect. How the skid happened does not set the removal criterion. The tire is judged on the damage itself, mainly whether the flat spot reaches the casing ply or belt.