Indiana CDL — Air Brakes: Safe Driving Practices Practice Test

Question 1

If the safety valve on the air system starts letting air escape, what does that tell you?

Accepted Answer

Something has gone wrong and a mechanic should look at it — A safety valve venting air is a sign something is wrong, and the fault should be corrected by a mechanic.

Answer

The tanks are properly drained

Answer

The parking brakes are set

Answer

The governor has reached its cut-in point

Question 2

What is a 'wig wag' on an air brake vehicle?

Accepted Answer

A mechanical arm that drops into the driver's view when pressure falls below 55 psi — The wig wag is a low-pressure warning that drops a mechanical arm into the driver's view when system pressure falls below 55 psi.

Answer

A gauge that reads application pressure

Answer

A valve that drains the tanks

Answer

A lever that sets the parking brake

Question 3

Before driving a dual air brake vehicle, you should let the compressor build at least how much pressure in both systems?

Accepted Answer

100 psi — Give the compressor time to reach a minimum of 100 psi in both the primary and secondary systems before you drive.

Answer

150 psi

Answer

55 psi

Answer

200 psi

Question 4

What is the purpose of an alcohol evaporator in some air brake systems?

Accepted Answer

To lower the chance of ice forming in the air brake valves in cold weather — The evaporator adds alcohol to the air to cut the risk of ice forming in the valves and other parts during cold weather; daily draining is still required.

Answer

To sober up the driver on long hauls

Answer

To lubricate the air compressor

Answer

To push tank pressure past the governor's setting

Question 5

With the foot brake fully applied, what is the largest acceptable air loss for a combination vehicle?

Accepted Answer

Less than 4 psi per minute — With the brakes applied, a combination vehicle may lose no more than 4 psi in one minute; a single vehicle is limited to 3 psi.

Answer

Less than 1 psi per minute

Answer

Less than 2 psi per minute

Answer

Less than 3 psi per minute

Question 6

Which kind of foundation brake is found most often on air brake vehicles?

Accepted Answer

The s-cam drum brake — The s-cam drum brake is the most common foundation brake; wedge and disc types are seen less often.

Answer

The wedge brake

Answer

The air disc brake

Answer

The hydraulic drum brake

Question 7

Why is it important to drain the air storage tanks regularly?

Accepted Answer

Water and oil gather there and can harm the system - trapped water may even freeze and knock out the brakes — Moisture and compressor oil settle at the bottom of the tanks; the water can freeze and cause brake failure, so the tanks must be drained completely.

Answer

To add oil into the compressed air

Answer

To raise the governor's cut-out setting

Answer

To release the spring brakes for parking

Question 8

What is the main job of the air compressor on an air brake vehicle?

Accepted Answer

To pump air into the storage reservoirs — The compressor, driven off the engine, forces air into the storage reservoirs that feed the brakes.

Answer

To drain moisture out of the tanks

Answer

To warn the driver of low pressure

Answer

To set the parking brakes automatically

Question 9

How do you test the low air pressure warning signal during the final brake check?

Accepted Answer

With the engine off and power on, fan the brake down and watch that the warning trips before 55 psi — With the engine off and the electrical power on, fan the brake to lower the pressure and confirm the warning comes on before pressure drops below 55 psi.

Answer

Rev the engine to build maximum pressure

Answer

Drain both tanks completely first

Answer

Set the parking brake and drive forward

Question 10

In a dual air brake system, what are the two separate circuits called?

Accepted Answer

Primary and secondary — A dual system runs two independent air circuits through one set of controls: the primary circuit and the secondary circuit.

Answer

Upper and lower

Answer

Left and right

Answer

Inner and outer

Question 11

When road-testing the service brakes at about 5 mph, what should you watch for after applying them firmly?

Accepted Answer

Any pulling to one side, an odd feel, or delayed stopping — Rolling slowly and braking firmly can reveal pulling to one side, an unusual feel, or delayed stopping you'd otherwise miss.

Answer

That the engine stalls out

Answer

That the tanks overfill

Answer

That the ABS lamp flashes

Question 12

How are the spring brakes kept in the released position while you drive?

Accepted Answer

By air pressure holding the strong springs back — Air pressure holds the powerful springs back; if that air is lost, the springs apply the brakes.

Answer

By the alcohol evaporator

Answer

By the stop light switch

Answer

By engine oil pressure

Safe Driving Practices

Study questions with answers

1. If the safety valve on the air system starts letting air escape, what does that tell you?

2. What is a 'wig wag' on an air brake vehicle?

3. Before driving a dual air brake vehicle, you should let the compressor build at least how much pressure in both systems?

4. What is the purpose of an alcohol evaporator in some air brake systems?

5. With the foot brake fully applied, what is the largest acceptable air loss for a combination vehicle?

6. Which kind of foundation brake is found most often on air brake vehicles?

7. Why is it important to drain the air storage tanks regularly?

8. What is the main job of the air compressor on an air brake vehicle?

9. How do you test the low air pressure warning signal during the final brake check?

10. In a dual air brake system, what are the two separate circuits called?

11. When road-testing the service brakes at about 5 mph, what should you watch for after applying them firmly?

12. How are the spring brakes kept in the released position while you drive?

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