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CDL Class A/B Louisiana 2019 > CDL Class B Airbrakes > Flashcards

CDL Class B Airbrakes Flashcards

1
Q

What does an air compressor do in an air brake system?

A

It pumps air into the air storage tanks.

In an air brake system, the air compressor pumps air into the air storage tanks. The air compressor is controlled by the air compressor governor.

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2
Q

The air storage tanks:

A

Hold enough air for the brakes to be used several times if the compressor stops working.

The air storage tanks in an air brake system store compressed air to be used for braking. They hold enough air for the brakes to still be used several times if the compressor stops working.

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3
Q

To ensure normal stopping power, drivers of vehicles equipped with a front brake limiting valve
should:

A

Set the control to normal.

Some older vehicles have front brake limiting valves with “normal” and “slippery” settings. Setting a brake limiting valve to “slippery” reduces the vehicle’s stopping power, so a driver should make sure the valve is in its “normal” position. Front wheel braking has proven to be effective in all driving conditions.

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4
Q

If the spring brakes are on, you should:

A

Not use the brake pedal.

Do not use the brake pedal when the spring brakes are on. This could damage the brakes by subjecting them to the combined forces of springs and air pressure.

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5
Q

Vehicles equipped with Anti-Lock Braking Systems (ABS) have ____ malfunction lamps to
indicate when the ABS is not working.

A

Yellow

Vehicles with ABS have yellow malfunction lamps to alert drivers when the braking systems are not working. Be sure you know where the malfunction lamp on your vehicle is before beginning a trip.

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6
Q

A dual air brake system:

A

Consists of two separate air brake systems that share a single set of controls.

A dual air brake system is made up of two separate air brake systems. The systems share a single set of brake controls, but each has its own air tanks, hoses, and lines. One system typically operates the regular brakes on the rear axle or axles while the other system
operates the regular brakes on the front axle.

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7
Q

If an air compressor is belt-driven, the belt should be routinely checked to ensure that it is:

A

Properly tightened.

If your vehicle has air brakes, the air compressor drive belt should be checked before each drive. Check the tightness of the belt and verify that it is in good condition.

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8
Q

Having ABS on only one axle:

A

Still allows you additional control when braking.

If you have an Anti-Lock Braking System (ABS) equipped on only the tractor, only the trailer,
or only one axle, you will still have more control over the vehicle when braking than you would without ABS. You should brake normally.

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9
Q

The air compressor is connected to the:

A

Engine.

The air compressor of an air brake system is connected to the engine through gears or a
v-belt. The compressor may be air-cooled or cooled by the engine cooling system.

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10
Q

A safety valve is set to open at ____ pounds per square inch (psi).

A

› 150

The safety valve protects air tanks and the rest of an air brake system from accumulating
too much air pressure. The safety valve is usually set to open at 150 psi.

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11
Q

An application pressure gauge shows:

A

› How much air pressure is being applied to the brakes.

If a vehicle is equipped, an application pressure gauge shows how much air pressure is being
applied to the brakes. This gauge can help a driver identify if their brakes

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12
Q

A wig wag is:

A

› A low pressure warning device.

Vehicles with air brakes are required to be equipped with a low pressure warning device. A
wig wag is a type of low air pressure warning device. This device drops a mechanical arm
into the driver’s view if the pressure in the tanks drops to a level between 55 and 75 psi.

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13
Q

The parking brake in a newer vehicle is applied by:

A

› Pulling a yellow, diamond-shaped knob.

In newer vehicles with air brakes, the parking brake is controlled by a yellow,
diamond-shaped knob.
The driver should pull the knob outward to apply the parking brakes
and push the knob inward to release them.

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14
Q

In a dual air brake system, if one air system is very low on pressure:

A

Either the front or rear brakes will not be fully operable.

In a dual air brake system, either the front or rear brakes will not be fully operable if one of
the air systems gets too low on pressure. If the air pressure in either tank gets too low while
you are driving, you should exit the road and park as soon as possible.

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15
Q

Air pressure should build up in a single air system within:

A

Three minutes.

In single air systems, air pressure should build from approximately 50 to 90 psi within three
minutes.

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16
Q

What is brake lag?

A

The time required for the brakes to work after the brake pedal is pressed

Because air takes time to flow through the air lines to the brakes, air brakes cannot begin
working instantly. There is often a brake lag of at least one-half of a second between the
moment the brake pedal is pressed and the moment the brakes begin to work.

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17
Q

If using spring brakes when hauling a heavy load, a complete stop will:

A

Take a long time.

Spring brakes do not work on all axles. If your vehicle’s spring brakes activate due to low
pressure in an air brake system, your vehicle will need a longer distance to stop than usual,
especially if you are carrying a heavy load.

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18
Q

When parking, you should not use the parking brake if:

A

The brakes are very hot.

If your brakes are hot after coming down a steep grade, you should not use your parking
brake when parking. Let your brakes cool before applying the parking brake or risk damaging
the brakes.

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19
Q

How is water and compressor oil removed from the bottom of an air storage tank?

A

› A drain valve is opened to remove the water and oil from the tank.

Water and compressor oil are removed from air storage tanks through a drain valve. The
water and oil can damage the brakes if left to accumulate in the system. Manually operated
tanks must be drained every day to remove this build-up.

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20
Q

Some air brake systems use alcohol:

A

To reduce the risk of ice forming in air brake valves.

Some air brake systems contain an alcohol evaporator. This device introduces alcohol into
the braking system to inhibit the formation of ice.

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21
Q

What color is the low air pressure warning light?

A

› Red

A low air pressure warning signal is required in vehicles with air brakes. The warning light is
usually red and may be accompanied by a buzzer.

22
Q

A low air pressure warning signal should activate:

A

When tank pressure falls below 60 psi.

In an air brake system, a low air pressure warning signal must come on if air pressure in the
tanks falls below 60 psi. This warning signal may come in the form of a light, a buzzer, or a
wig wag.

23
Q

Spring brakes come on:

A

When too much air pressure is lost.

Spring brakes come on automatically when air pressure drops to an unsafe psi level. Instead
of waiting for the spring brakes to automatically activate, you should safely exit the road as
soon as you notice the low pressure warning signal and bring your vehicle to a stop while
you are still able to control the brakes.

24
Q

On trucks and buses, where are ABS malfunction lamps located?

A

On the instrument panel

Tractors, trucks, and buses with Anti-Lock Braking Systems (ABS) have yellow malfunction
lamps located on their instrument panels. Trailers have yellow ABS malfunction lamps on
their left side, either on the front or rear corner.

25
Q

Before driving a vehicle with a dual air brake system, you must wait for the air compressor to
build a minimum of ____ in both the primary and secondary systems.

A

100 psi

Before driving a vehicle with a dual air brake system, you should wait for the air compressor
to build up at least 100 psi in both the primary and secondary systems.

26
Q

What does ABS do?

A

Prevent wheel lockup

The purpose of an Anti-Lock Braking System (ABS) is to prevent wheels from locking up
during hard applications of the brakes, especially on slippery surfaces.

27
Q

If your tractor is equipped with ABS but your trailer is not, the ABS:

A

Will still improve your steering control.

In a tractor-trailer combination, if the tractor is equipped with an Anti-Lock Braking System
(ABS) but the trailer is not, the ABS will still improve the driver’s steering control. The driver
should keep an eye on the trailer and let up on the brakes if the trailer begins to swing out.

28
Q

What kind of force must emergency brakes use?

A

Mechanical

Because air pressure can eventually leak away, the emergency brakes in an air brake system
must be held on by mechanical force.

29
Q

Anti-Lock Braking Systems (ABS):

A

Are equipped in addition to other braking systems and do not reduce normal braking
power.

ABS is equipped in addition to a vehicle’s normal braking system and it neither increases nor
decreases the vehicle’s braking capability. ABS activates during hard applications of the
brake pedal in order to prevent wheels from locking up.

30
Q

If using air tanks with manually operated drains, how often should you drain the tanks?

A

› Every day

To prevent the build up of oil and water in a vehicle’s air tanks, manually operated air tank
drains should be used at the end of each day of driving.

31
Q

Pressing and releasing a brake pedal unnecessarily can:

A

› Release air faster than it can be replaced.

In an air brake system, pressing and releasing the brake pedal unnecessarily can release air
from the braking system faster than the compressor can replace it.

32
Q

The parking brake should be:

A

Used whenever you park your vehicle.

The parking brake in a vehicle with air brakes should be used every time the vehicle is
parked.

33
Q

When using the controlled braking method in an emergency situation, you should:

A

Apply the brakes as hard as possible without locking the wheels.

The controlled braking method for emergency stops involves applying the brakes as hard as
you can without locking the wheels. Keep steering wheel movements small when braking in
this way.

34
Q

To use the stab braking method in an emergency situation, you should:

A

Apply the brakes completely until the wheels lock up, release the brakes until the wheels
start rolling, then repeat the process.

The stab braking method for emergency stops involves fully applying the brakes until they
lock up. The brakes are then released until the wheels start rolling, then the process is
repeated.

35
Q

What can happen if a parking brake is used in very wet weather when temperatures are below
freezing?

A

› The brakes may freeze so the vehicle cannot move.

If you use the parking brakes when the weather is very wet and the temperature is below
freezing, the brakes may become frozen, preventing the vehicle from moving.

36
Q

When only the tractor is equipped with an Anti-Lock Braking System (ABS):

A

› There is a decreased risk of jackknifing.

If a tractor is equipped with an Anti-Lock Braking System (ABS) but the trailer is not, the risk
of jackknifing will be reduced and the driver should still be able to maintain steering control.
If only the trailer is equipped with ABS, it is less likely that the trailer will swing out to one
side.

37
Q

When traveling down a steep downgrade, the best way to use your brakes is to:

A

Apply the brakes for a few seconds, then release the brakes for a few seconds. Continue
to repeat these steps as you travel down the hill.

On a long or steep downgrade, brakes should only be used to supplement the braking effect
of the engine. Apply the brakes just enough to feel a definite slowing down, then release
them once you are about five mph below your target “safe” speed. Once your vehicle
reaches its safe speed again, repeat this process.

38
Q

If the safety relief valve in an air brake system is releasing air:

A

There is something wrong with the brakes.

The safety relief valve in an air brake system releases air if necessary to prevent pressure in
the system from becoming too high. If the valve starts releasing air, there is something
wrong. Have a mechanic fix the problem.

39
Q

When parked on a flat surface, you should:

A

Use wheel chocks to prevent your vehicle from moving.

When parking on a level surface, you should use wheel chocks. If the vehicle is not equipped
with spring brakes, this is essential to prevent the trailer from moving.

40
Q

If the brake pads rub against the brake drums and create too much heat:

A

The brakes may stop working.

Brakes heat up with use. If they are overused and become too hot, expansion and chemical
changes will make them less effective and eventually cause them to stop working
altogether. This is known as “brake fade.”

41
Q

If the low air pressure warning signal comes on, you should:

A

Pull over and inspect the brakes.

If the low air pressure warning signal comes on while you are driving a vehicle with air
brakes, you should immediately bring the vehicle to a safe stop while you are still able to
control the brakes. Inspect and repair the brakes as soon as possible.

42
Q

Brake linings should be:

A

Free of oil.

Brake linings should not be loose or soaked with oil or grease. They shouldn’t be dangerously
thin.

43
Q

Test the low pressure warning signal:

A

› Before every trip.

It is essential that your low pressure warning light function properly. After allowing the
system to charge, you can test the warning signal by rapidly applying and releasing the
brake pedal. This will release air from the braking system and the warning signal should
come on when pressure drops to a dangerous level.

44
Q

The brake pedal is part of which braking system?

A

The service brake system

The service brake system applies and releases the brakes when a driver presses the brake
pedal while driving normally.

45
Q

Foundation brakes are used:

A

At each wheel.

Foundation brakes are used at each wheel. The most common type is the S-cam drum
brake.

46
Q

The air compressor governor controls:

A

› When the air compressor pumps air into the air storage tanks.

In an air brake system, the air compressor governor controls when the air compressor pumps
air into the air storage tanks.

47
Q

When traveling down a steep downgrade:

A

Shift into a lower gear, then use brakes to supplement the braking effect of the engine.

On a downgrade, the braking effect of the engine should be your primary method of
controlling speed. Shift down to a lower gear before starting down the hill and save the
brakes for additional slowing or stopping that may be required by road or traffic conditions.

48
Q

To confirm that a trailer has ABS, you can:

A

Look under the trailer for wheel speed sensors coming from the back of the brakes.

If you are unsure if a trailer is equipped with an Anti-Lock Braking System (ABS), look under
the vehicle for the electronic control unit and wheel speed sensor wires coming from the
back of the brakes.

49
Q

How is the parking brake released?

A

› By pushing in the brake control knob

In newer vehicles with air brakes, the parking brakes are controlled by a diamond-shaped
yellow knob. Pull the knob out to activate the parking brakes and push it in to release them.

50
Q

Dollies equipped with ABS are required to have malfunction lamps located where?

A

› On the left side

A dolly equipped with an Anti-Lock Braking System (ABS) is required to have a yellow
malfunction lamp located on its left side.

CDL Class A/B Louisiana 2019 (3 decks)

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